2. SOILS AND TOPOGRAPHY
3. CLIMATE AND AGRO-ECOLOGICAL ZONES
4. RUMINANT LIVESTOCK PRODUCTION SYSTEMS
5. THE PASTURE RESOURCE
5.2 GRASSLANDS IN US HUMID REGIONS
6. OPPORTUNITIES FOR IMPROVEMENT OF GRAZING RESOURCES
7. RESEARCH AND DEVELOPMENT ORGANIZATIONS AND PERSONNEL
Authors: David B. Hannaway, Peter J. Ballerstedt, Henry A. Fribourg, and Rex D. Pieper
The United States of America (also referred to as the United States, the US, the USA, or America) is a federal constitutional republic comprising fifty states and a federal district. The country is situated mostly in central North America, where its forty-eight contiguous states and Washington, D.C., the capital district, lie between the Pacific and Atlantic Oceans, bordered by Canada to the north and Mexico to the south. The state of Alaska is in the northwest of the continent, with Canada to the east and Russia to the west across the Bering Strait. The state of Hawaii is an archipelago in the mid-Pacific (see Figure 1.1). The country also possesses several territories in the Caribbean and Pacific (Wikipedia). The 48 contiguous states lie between about latitudes 24–49oN and longitudes 67–125oW. The population estimate for July 2011 was 313 232 044 with a growth rate of 0.963% (World Factbook). The largest city is New York – Newark with a population of 19.3 M; other major cities are Los Angeles, Chicago, Miami and Washington DC. With an area of 3.79 million square miles (9.83 million km2) the USA has land boundaries with Canada of 8 893 km (including 2 477 km with Alaska), and with Mexico of 3 141 km. In terms of total area, the USA is third in the world in size behind Russia and Canada with China fourth.
The Great Plains (or Prairie in Canada) rightly comes to mind when one thinks of North American grasslands. The term “grassland” is all-inclusive and refers to any vegetated land that is grazed or has the potential to be grazed by domestic or wild animals; it includes many different kinds of grazing lands, as opposed to croplands or forestlands. It includes pasturelands, rangelands, meadows, and grazable other lands, whether temporary, permanent, natural or created by humans (Allen et al., 2011).
The rich grassland resources of the US, however, include far more than the vast Great Plains. Temperate grassland, savanna, and shrubland biomes exist across the continent; their distribution and the degrees to which they were anthropogenically managed, are demonstrated by the observations that bison (Bison bison), the quintessential animal of the Great Plains, once roamed along the east coast from New York to Georgia (Mann, 2006) on west to the Rocky Mountains and that elk (Cervus canadensis), now largely confined to the Rocky Mountain region, have been observed in every continental state except Florida (Manning, 1997).
The popular impression of North America as a “wilderness” and the Great Plains as devoid of trees is not accurate, but rather reflects a lack of understanding of pre-Columbian North American conditions and practices (Mann, 2006), European farming mindset typical of the eighteenth and nineteenth centuries (Manning, 1997), and a modern environmentalist ethic (Mann, 2006). “The post-Columbian abundance of bison”, was largely due to “Eurasian diseases that decreased [Indian] hunting”, according to Geist (1998). The huge herds of bison that were described by early European settlers were a symptom of the destruction of the human-animal-environment system that the Native Americans had operated for centuries before European contact, rather than an example of the “natural”, undisturbed grassland/wildlife system.Thus, the massive, thundering herds were pathological, something that the land had not seen before and was unlikely to see again (Mann, 2006). The grasslands of imagination have, for the most part, disappeared (USGS, 2006). They have been displaced by agricultural and urban development. The majority of the economically important grassland species now present are not native to the US. This displacement began, by accident, with the initial European contact. Evidence of how early this process began and how rapidly it progressed is provided by the fact that the first English settlers to reach what became known later as Kentucky found Kentucky bluegrass (Poa pratensis) and white clover (Trifolium repens) already established there (Mann, 2006).
The physical health and condition of the plains-dwelling Native Americans were far more robust than those of contemporary Europeans. Explorers who first contacted the Kiowa and other bison-dependent nations documented that the diet of these people was almost exclusively meat-based. Observations made during the 1830s record that it was rare to find a male of the Cheyenne tribe less than six feet (183 cm) tall, while among the Osage people in the Kansas area few were shorter than that and some of them were seven feet (213 cm) tall (Catlin, 1844). In addition, there was no evidence of the chronic diseases already observed in European populations (Taubes, 2008).
When European settlers first moved into the central portion of what is now the US, they encountered extensive, unbroken grasslands from the prairies of Canada to the Gulf of Mexico, from the boreal forest of Canada to Mexico, and from the western edge of the eastern forests to the Rocky Mountains (Figure 1.2). These grasslands were generally free of woody plants, existing as a dynamic ecotone between the mountains and deserts to the west and the eastern deciduous forests neighbouring the central and northern portions (Bazzaz and Parrish, 1982; Gleason, 1913; Transeau, 1935). The general impression held by many observers of the time was that conditions in this vast grassland area prior to European settlement were pristine and little modified by humans (Deneven, 1996; Leopold et al., 1963). However, Flores (1999) presented persuasive arguments that Native American populations were relatively large in the Great Plains and that they probably exerted considerable influence on many components of these grassland ecosystems.
Native American Influence
The popular image of pre-Columbian North America is of a pristine paradise. However, when Europeans first arrived in North America, they found anything but a primeval landscape. Instead, they encountered a land significantly altered by humans through the use of fire, sophisticated agricultural techniques, mining, and road and mound building (Gartner, 1998).
From fire-maintained prairies and altered forests to earthworks and settlements, the American landscape by the time of European contact had already endured thousands of years of modification by large Native American populations. The pristine view, according to Gartner and others, to a large extent is the invention of nineteenth century romantic and primitivist writers like Henry David Thoreau and Henry Wadsworth Longfellow. The reality is that the impact of native peoples was nearly ubiquitous, even in areas with comparatively sparse Indian populations.
Many scholars now believe there were 40–80 million inhabitants of the New World when Christopher Columbus first set sail for the Indies. "Indigenous peoples routinely cleared the ... landscape with fire”, Gartner explained. "They burned to facilitate hunting and game drives, to clear village and agricultural lands, to assist in fuel-wood cutting, to improve visibility and overland travel, to manage pests, and to facilitate warfare”.
As an example, the climate responsible for the eastward extension of the tall grass prairies disappeared thousands of years ago, but native-set fires preserved those prairies in some areas such as southern Wisconsin, Illinois, Indiana, and parts of Ohio. Moreover, forest disturbances resulting from the use of fire and the creation of encroaching habitat may have resulted in the large numbers of wildlife, especially the deer and elk (Cervus sp.), beaver (Castor canadensis), turkey (Meleagris gallopavo), and quail (Colinus sp. and related genera) that so impressed English colonists in North America.
The prehistoric human imprint on the North American landscape, to a large extent, was masked by the decimation of Amerindian populations as a result of exposure to Old World diseases, for which they had no immunities. This allowed the landscape to recover until about the late eighteenth century, when white colonists, pushing into interior regions, re-imposed a human influence on the land. [The preceding five paragraphs on Native American Influence were adapted from USA Today (Society for the Advancement of Education), 1998 and original sources for that article.]
This use of fire to create and maintain grasslands for bison grazing extended into regions classified as savanna, a grassland characterized by precipitation between 375 and 1 500 mm/year, variable proportions of trees or large shrubs, especially in tropical and sub-tropical regions, and which is often a transitional vegetation type between grassland and forestland (Allen et al., 2011). These savannas were created and maintained by Native Americans until the seventeenth-century deaths of most natives (Brown and Smith, 2000; Earley, 2006; Stanturf, 2009; Williams, 2003). Surviving indigenous inhabitants continued using fire to clear savannas until European colonists began settling the eastern Seaboard 200 years later. Many colonists continued the practice of burning to clear underbrush, reinforced by their similar experience in Europe, but some land reverted to forest (Brown and Smith, 2000).
Location and General Description of US Grasslands
The extent of areas classified as grasslands in North America in the latter part of the twentieth century is shown in general terms in Figure 1.3. At coarse scales, the Great Plains grassland commonly is divided into tall-grass (true prairie), mixed (or mid)-grass, and short-grass prairies (Bazzaz and Parrish, 1982; Gleason and Cronquist, 1964; Lauenroth et al., 1994; Laycock, 1979; Sieg et al., 1999; Sims, 1988).
Figures 1.4A-C show examples of the three major grassland types from North Dakota to New Mexico.
A transect from the Pacific Ocean to the Atlantic Ocean at 37° N latitude, the northern boundary of Arizona and New Mexico, is shown in Figure 1.5.
This diagram shows short-grass prairie occupying the area between 105° and 101°W longitude, the mixed prairie from 101° to 98°, and the tall-grass prairie from 98° to 93°. The map in Lauenroth et al. (1994) shows that the northern mixed prairie forms a broad band in Canada, eastern Montana, the Dakotas, and eastern Wyoming. The southern mixed-grass prairie is constricted between the tall-grass prairie to the east and the short-grass prairie to the west, and found in southern Nebraska, central Kansas and Oklahoma, and Texas (Lauenroth et al., 1994; 1999). The estimated past area, current area, and percent decline of tall-grass, mixed-grass, and short-grass prairies are detailed in the USGS web segment on “Prairie Past and Present” (USGS, 2006). Decline ranges from 20 to almost 100%, with little native grassland remaining from the past, grassland-dominated central North America.
Semi-arid and Arid Rangeland Forage Resources
Rangeland is found predominantly in arid and semi-arid regions. The indigenous vegetation, climax or sub-climax, is mostly grasses, grass-like plants, forbs or shrubs that are grazed or have the potential to be grazed, and which is used as a natural ecosystem for the production of grazing livestock and wildlife. Predominant forages used in these systems include a variety of native warm and cool-season grasses, forbs, and shrubs. Marked seasonal and year-to-year variation in forage availability and quality, in addition to spatially uneven distribution of resources, are the hallmarks of rangeland forages.
Grasses in the genera Bouteloua, Bromus, Buchloe, Elymus, Festuca, and Pascopyrum are among the most prominent native forage resources for domesticated grazers. Woody browse and cool-season forbs are critical winter and spring forages for wild ungulates. A few Eurasian and African exotic grass species introduced either accidentally or for reclamation purposes in the early and mid-1900s pose challenges throughout the region. Cheatgrass (Bromus tectorum) and crested wheatgrass (Agropyron cristatum) in the cold deserts of the Great Basin, and Lehman lovegrass (Eragostis lehmaninana) in the hot deserts of the Southwest are the most prominent of such species. Their invasion has caused detrimental impacts on fire regimes and native plant diversity which in most cases have outweighed their initial perceived value as forages or erosion control tools.
In recent decades, US rangelands are managed for multiple uses, which include livestock production, mining, timber production, wildlife management, and recreation. The major regions of the western continental US, the focal point of US rangelands, are described in Section 5.1 on Native Grasslands. Characteristic features are therein described for each region and type (Northern and Southern Great Plains, California annual grasslands, Great Basin, Desert Southwest, woodlands and forested rangelands), including climate, soils and vegetation, goods and services, and key aspects envisioned for the future.
Humid Region Forage Resources
Eastern portions of the US having sufficient rainfall to support forest vegetation (see Figures 1.5 and 1.6A, B, C), and sections of the Pacific coastal states, often are managed in highly productive forage-livestock systems. Predominant forages used in these systems are cool-season (C3 physiology) grasses (Poa, Dactylis, Festuca, Lolium, Agrostis, and other genera) in the northern and eastern portions of the region and warm-season (C4 physiology) grasses (Cynodon, Sorghum, Paspalum, and other genera) in the southern portions of this region. Several leguminous forages also are important, grown singly or in mixtures with grasses (Medicago, Trifolium, and other genera). The landscape, predominant forage and livestock species, and the forage-livestock system managements imposed in humid regions are described in section 5.2, Humid Pastures.
Maps that show the mean annual precipitation of the conterminous US, Alaska, and Hawaii are presented in Figures 1.6A, 1.6B, and 1.6C.
Summary of the Importance of US Grasslands, Rangelands, Pasturelands, and Cropland Forages.
Grassland, rangeland, pastureland and cropland forage resources of the conterminous US include far more than the central Great Plains region. They also include intensively managed pasturelands and croplands throughout the country, and the extensively managed arid and semi-arid regions of central and western US.
Rangelands, pasturelands, and meadows, together comprise about 55% of the land surface of the US, ~405 million ha. Privately owned lands constitute about 45% of this total (~260 million ha). These lands represent the largest and most diverse land resources in the US. Rangelands and pasturelands include the annual grasslands of California, the tundra rangelands of Alaska, the hot arid deserts of the Southwest, the temperate deserts of the Pacific Northwest, the semi-arid cold deserts of the Great Basin, the prairies of the Great Plains, the humid native grasslands of the South and East, the pastures and meadows (natural or semi-natural grasslands often associated with the conservation of hay or silage) within all 50 states from Hawaii to Maine and Alaska to Florida.
These grasslands are the primary forage base for the livestock grazing industry in the US. They are utilized by >60 million cattle and 8 million sheep and support a livestock industry that contributes >$60 billion/year in farm sales to the US economy. The estimated value of hay production alone is $11 billion, the third most valuable crop in US agriculture, behind only corn (Zea mays) and soybeans (Glycine max). The publicly-owned rangelands in the western US are also important, providing forage on 105 million ha for 3 million beef cattle and sheep. Nearly 70% of dietary protein and 40% of dietary calories for the US inhabitants are of animal origin, and forage resources are vital for sustained production of animal-based products.
The functions of these lands are of increasing importance as watersheds and as habitats for biologically diverse plants and animals, for maintaining adequate supplies of clean water for urban areas and irrigated agriculture, and to meet environmental needs, critical functions of grassland ecosystems. Grasslands also provide forage and habitat for numerous wildlife species, including 20 million deer, 500 000 pronghorn antelope (Antilocapra americana), 400 000 elk, and 55 000 feral horses (Equus ferus caballus) and burros (Equus africanus asinus). Associated with these functions is an array of additional demands placed on these natural resources, such as camping, hiking, fishing, hunting, and other sometimes deleterious recreational activities involving motorized vehicles.
Harvested and conserved forages provide a dietary resource for continuity of livestock sustenance. This is especially important during periods of cold temperatures or drought when grazable forage is not available. Harvested and conserved forages also provide an important source of fibre (and cellulose) and nutrients for dairy cattle in confined animal feeding operations. To meet this demand, nearly 200 million metric tonnes of forage crops are harvested each year from 30 million ha, 24% of the US cropland. The value of forage crops harvested as hay or silage is $16 billion annually, of which about half provide the forage requirements of dairy cattle. The remainder, along with rangeland and pastureland, supplies the forage needs of beef cattle, sheep, horses, and other livestock (USDA-ARS, 2007).
Authors: Joel R. Brown, David B. Hannaway, Henry A. Fribourg, and Rex D. Pieper
Grasslands are areas where grass or grass-like vegetation is the dominant form of plant life; they are widely distributed in the US. Grazing lands are vegetated lands that are grazed or have the potential to be grazed by domestic and wild animals and include grasslands, pasturelands, rangelands, and meadows (Allen et al, 2011). These areas, which can range from <1 ha to 106 km2, are the result of the combination of a wide variety of physiographic, topographic, soil, and climatic factors. Within broad climatic regions, topography and soils can have a great influence on the extent and patterns of grasslands. In this section, a broad overview is presented of the spatial distribution of topographic and soil features and their influences on grassland development within the continental US.
The US has a varied topography (Figure 2.1), with relatively predictable and consistent influences on grazing land extent and types. A broad, flat coastal plain lines the Atlantic Ocean and Gulf of Mexico from the Texas-Mexico border to the Hudson River at New York City, and includes the Florida peninsula. Grasslands of these coastal plains range from the extensive sawgrass (Cladium sp.) marshes of the Everglades to small meadows surrounded by deciduous forests.
Areas farther inland feature rolling hills and temperate forests. The Appalachian Mountain Range forms a line of low (up to ~2 000 m) mountains separating the eastern Seaboard from the Great Lakes and the Mississippi Basin. The five Great Lakes are located in the north-central portion of the country, four of them forming part of the border with Canada. Grasslands within these regions are typically small, open meadows or park-like savannas, within a forest matrix associated with shallow dry soils or conditions too wet for tree growth, or interspersed with farmlands.
The Southeast US originally contained subtropical forests. Near the Gulf coast are mangrove wetlands, especially in Florida. West of the Appalachians lie the Mississippi River basin and two large eastern tributaries, the Ohio and the Tennessee Rivers. The Ohio and Tennessee Valleys and the Midwest consist largely of rolling hills and productive farmland, stretching south to the Gulf Coast. The Mississippi River Delta extends from the southern tip of Illinois, where it is a few km wide, to the Gulf, with varying widths that in some places approximate 200 km. Grasslands have limited extent within these areas, but the western portion of this region is a transition zone to the tall-grass prairies, savannas and open woodlands of the eastern Great Plains (Figure 2.2).
The Great Plains lie west of the Mississippi River and east of the Rocky Mountains, rising gradually from about 30 m above sea level to over 1 600 m at the foot of the mountains. A large portion of US agricultural products is grown in the Great Plains. Before their general conversion to farmland, the Great Plains were noted for their extensive grasslands, from tall-grass prairie in the east to short-grass prairie in the western High Plains. The generally low relief of the plains is broken in several places, notably by the Ozark and the Ouachita Mountains, which form the Interior Highlands, the only major mountainous region between the Rocky Mountains and the Appalachian Mountains.
The Great Plains come to an abrupt end at the Rocky Mountains, which form a large portion of the western US from Canada nearly to Mexico. The Rocky Mountain region is the highest region of the US. The Rockies generally contain slopes which are not as steep as those of other great mountain ranges, and wider peaks, with a few exceptions such as the Teton Mountains in Wyoming and the Sawatch Range in Colorado. The highest peaks of the Rockies are found in Colorado, the tallest being Mount Elbert (4 400 m), with many smaller, intermittent mountain ranges forming numerous basins and valleys. This topography usually features basin and valley grasslands, mixed shrub and dwarf tree-grasslands on slopes, and forests with open meadows at the higher elevations (Figure 2.3).
West of the Rocky Mountains, and east of the Cascades and Sierra Nevada ranges, lie the Intermontane Plateaus (the Intermountain West), a large, arid desert. The southern portion, known as the Great Basin, consists of salt flats, drainage basins, and many small north-south mountain ranges. The Southwest is predominantly a low-lying desert region, and has extensive desert grasslands that occupy all but the highest elevations. A portion known as the Colorado Plateau is centred near the Four Corners region (where Colorado, Utah, New Mexico, and Arizona share a corner), accentuated by national parks, such as the Grand Canyon. Grasslands are a ubiquitous feature within this region, but usually are small and mixed with shrubs and small trees on lower slopes or on areas with shallow soils (Figure 2.4).
The Intermontane Plateaus abut the Cascade Range and the Sierra Nevada. The Cascades consist of largely intermittent, volcanic mountains, many rising prominently from the surrounding landscape. To the south of the Cascades, the Sierra Nevada is a high, rugged, and dense mountain range. It contains the highest point in the contiguous 48 states, Mount Whitney (4 421 m). West of the Cascades and Sierra Nevada is a series of valleys, including the Central Valley of California and the Willamette Valley in Oregon. Along the coast are low mountain ranges known as the Pacific Coast Ranges. Much of the Pacific Northwest coast is covered by some of the densest vegetation outside of the tropics-- a temperate rain forest -- and also has the tallest trees in the world, the redwoods (Sequoioideae). The foothills of the Sierra Nevada and Cascade ranges are dominated by open grasslands, oak savannas, and conifer woodlands with a grass understorey (Figure 2.5).
The temperate rainforest extends into southeastern Alaska, where prominent mountain ranges rise up sharply from the coast or from broad, flat tundra plains. On the islands off the south and southwest Alaskan coasts are many volcanoes and faults. The state of Hawaii, far to the south of Alaska in the Pacific Ocean, is a chain of tropical, volcanic islands; the summit of the Earth's most massive volcano, Mauna Loa, is at 4 169 m.
Within a climatic, physiographic region, or topographic unit, different soil properties can have a major influence on the dominant vegetation. In the absence of a major disturbance regime, soil properties can be used to accurately predict the vegetation relationships. The systematic classification and mapping of soil properties are the basis for a credible system that can predict vegetation distribution.
Soils are classified into various levels of categories to understand relationships among different ones and to determine the usefulness of each for a particular use. One of the first classification systems was developed by Dokuchaev, ca. 1880. It was modified several times by other European and American pedologists, and developed into the system commonly used until the 1960s, based on the concept that the morphology of soils depends on the materials and factors that formed them. In the 1960s, a different classification system began to be developed, primarily in the US, based on the morphology of a soil instead of just its parent materials and soil-forming factors. Since then, numerous modifications have led to the World Reference Base (WRB) for Soil Resources (IUSS, 2007), an international reference base for soil classification (Wikipedia).
US Soil Classification System
In the US, soil orders are the highest hierarchical level in the USDA Soil Taxonomy classification system. There are 12 soil orders with names that end with the suffix “-sol” (Mills, 2009):
1. Entisols - recently formed soils that lack well-developed horizons, commonly found on unconsolidated sediments like sand; some have an A horizon on top of bedrock.
A map of the distribution of the 12 soil orders in the US is provided in Figure 2.6. This map and additional information on each order is provided on a University of Idaho web segment (McDaniel, 2011).
Soil Surveying and Mapping
Soil surveys are conducted to provide a detailed report on the soils of an area, including maps with soil boundaries and photos, descriptions, and tables of soil properties and features (http://soils.usda.gov/survey/how_to/). Soil surveys are of potential value to farmers, real estate agents, land use planners, engineers, disposal technicians, and others who desire information about the soil resource. Soil surveys in the US are conducted and information managed according to protocols defined as part of the National Cooperative Soil Survey program (http://soils.usda.gov/partnerships/ncss/).
The soil maps contained in soil surveys show the distribution of soil types and/or soil properties (soil pH, textures, organic matter, depth of horizons, etc.) in the area of interest. Soil maps are most commonly used for land evaluation, spatial planning, agricultural extension and research, environmental protection, and similar projects. Traditional soil maps show only the general distribution of soils, accompanied by the soil survey report. Newer soil maps use aerial and remote sensing images as a base and digital soil mapping techniques. These maps are rich in context and show high spatial detail.
Currently, soil maps are being developed in digital format and used for various applications in geosciences and environmental sciences. In this context, soil maps are only visualizations of the soil resource inventories commonly stored in a Soil Information System (SIS), of which the major part is a Soil Geographical Database. A SIS is a combination of polygon and point maps linked with attribute tables for profile observations, soil mapping units, and soil classes. Different elements of a SIS can be manipulated and then visualized against the spatial reference (grids or polygons). For example, soil profiles can be used to make spatial prediction of different chemical and physical soil properties. Information, both spatial and tabular, can be accessed via the Web Soil Survey (http://websoilsurvey.nrcs.usda.gov/app/HomePage.htm).
It is important to distinguish primary soil attributes (those described or measured in the field) from the inferred attributes, also called secondary soil information (the properties of the soils in the context of the soil use, such as soil production capacity, soil reaction to certain uses, soil functions, soil degradation measures, and many other traits) (http://en.wikipedia.org/wiki/Soil_map).
Digital Soil Mapping (http://en.wikipedia.org/wiki/Digital_soil_mapping)
Digital Soil Mapping (DSM) in soil science, or "predictive soil mapping", is the computer-assisted production of digital maps of soil type and soil properties. Digital Soil Mapping involves the creation and population of spatial soil information by the use of field and laboratory observational methods coupled with spatial and non-spatial soil inference systems (McBratney and Lagacherie, 2004; Rossiter, 2004). It applies pedometrics, the use of mathematical and statistical models that combine information from soil observations with information contained in correlated environmental variables and remote sensing images. The international Working Group on Digital Soil Mapping (WG-DSM) defines DSM as "the creation and population of geographically referenced soil databases generated at a given resolution by using field and laboratory observation methods coupled with environmental data through quantitative relationships."
Digital Soil Mapping can rely upon, but is distinct from, soil mapping involving manual delineation of soil boundaries by field soil scientists. Digitized and geo-referenced soil survey information does not become a DSM product until the Geographic Information System (GIS) layer is used to derive other soil-related information within a GIS or similar information software application. The DSM technique makes extensive use of technological advances, including GPS receivers, field scanners, remote sensing, and computational advances, including geostatistical interpolation and inference algorithms, GIS, digital elevation models (DEMs), and data mining. Semi-automated techniques and technologies are used to acquire, process, and visualize information on soils and auxiliary information, so that the end result is obtained at cheaper costs. Products are commonly assessed for accuracy and uncertainty, and can be updated easily when new information becomes available (McBratney et al., 2003; Scull et al., 2003).
Soil Influence on Grasslands (and vice versa)
Grassland soils have developed over centuries along with regional vegetation and according to local climatic conditions, as parent materials allowed. Tropical grassland soils, like tropical forestland soils, are highly leached by abundant rainfall and have moderate to poor nutrient and humus contents. In temperate grasslands, however, generally light precipitation allows nutrients to accumulate in thick, organic upper soil layers. Lacking the acidic leaf or pine needle litter of forests, these soils tend to be basic (pHs of ~6.5 to 8) and fertile. Such conditions historically supported the vigorous growth of grasses on which herbivores fed. They can likewise provide good grazing lands and croplands. Through crops and domestic herbivores, humanity has relied for millennia on grasslands and their fertile, loamy soils for the majority of its food.
Along a moisture gradient, the margins of grasslands gradually merge with moist savannas and woodlands or with drier, desert conditions. As grasslands extend into higher latitudes or altitudes, and the climate becomes too cold for grasses to flourish, grasslands grade into tundra, which is dominated by mosses (Bryophyta), sedges (Cyperaceae), willows (Salix sp.), and other cold-tolerant plants (http://science.jrank.org/pages/3127/Grasslands.html).
Grassland soils are derived from a wide variety of parent materials: limestone, sandstone, shale, metamorphic and igneous outwash (soil deposited by flowing water), and loess (Pieper, 2005). In the central portion of the country, the dominant soils are Mollisols, deep soils with dark A horizons and high (>50%) base saturation, especially Ca (Figure 2.7); the clay content is evenly distributed throughout the A and B horizons. The translocation of clays from the B to the A horizons occurs by a variety of processes, including a common prairie ant (Formica cinerea). The development of these dark, relatively fertile soils occurs via the process of “melanization” involving (1) penetration of plant roots into the soil profile and their subsequent death, (2) decay of organic material, (3) mixing by soil microorganisms, (4) movement of organic and some inorganic colloids within the soil by water (eluviation and illuviation), and (5) formation of resistant "ligno-protein" residues producing the dark colour in the soil. These soils generally support prairie vegetation. In the eastern, more humid portion of the Great Plains, grassland soils are dominated by Alfisols. These soils have developed in higher rainfall environments and have undergone moderate leaching and have subsurface accumulation of clay and ≥35% base saturation. These soils are generally occupied by forests, savannas, and open prairies.
In the semi-arid portions of the western United States, Aridisols (desert soils) are commonly found in association with desert grasslands and shrub savannas. These soils typically have low concentrations of organic matter and are characterized by low soil moisture. Calcification (accumulation and hardening of calcium) is an important process in these soils and they often develop CaCO3 (caliche) layers at varying depths below the surface (Monger and Martinez-Rios, 2001). These subsoil horizons may become cemented and can form layers that restrict root growth and water infiltration.
Soil factors that influence forage production
Landscape and soil properties from soil survey information that have a significant and direct effect on forage plant production and their management nationally include: slope; drainage class; available water capacity; frequency and duration of flooding and ponding; soil reaction, acidity and alkalinity as measured by pH; salinity; cation exchange capacity (CEC), and organic matter content, describing fertility; frost heaving potential; trafficability as characterized by the Unified Soil Classification; surface rock cover fragments; drainage class; shrink-swell; and depth to restrictive layers.
Other measurable soil properties that help define or modify other soil characteristics have an indirect effect on forage production and management. Soil texture is an example; it influences plant growth by affecting soil aeration, water intake rate, available water capacity, CEC, permeability, erodibility, trafficability and, in the case of surface stones, the amount of surface soil area upon which plants can grow. For forage suitability groups, texture is an important soil property, but not precise enough to be used alone for defining soil capability groups. This is because a soil textural class may have some good as well as some negative features, making it impossible to evaluate it properly; for example, a sandy loam may have great permeability and trafficability, but also low water holding capacity and native fertility.
Summary. The great diversity in geological history, topography, and climates in the US is reflected in the soils that mantle the country. The grasslands which occupy a large portion of the country similarly have a wide spectrum of climatic, soil, and topographic attributes. Most grasslands in non-arid climates grow on Mollisols; Aridisols, Alfisols, and other soil orders are found where grasslands occur. This wide range in defining conditions naturally results in considerable variability in ecological processes. The Mediterranean grasslands of California are dominated by cool-season annual grasses and forbs, whereas the mixed-grass prairies of the eastern Great Plains are dominated by warm-season perennials. Although there are few grasslands with a complete absence of woody vegetation, the appearance and role of trees and shrubs vary greatly among grasslands. Desert grasslands of the Southwest demonstrate the delicate balance that exists between perennial grasses and several species of native shrubs; these can dominate if the grass layer is disrupted. Tall-grass prairie of the upper Mississippi Valley contains an extensive variety of native hardwood trees, which can expand from drainages into uplands in the absence of frequent, low-intensity fires. Thus, the many different situations engendered by these varying conditions, and their accompanying ecological processes, result in many diverse management opportunities and challenges. Ranchers, advisors, and policymakers must not assume that a uniform management approach for all grasslands can be successful in maintaining the unique ecology of each grassland type; such an assumption has been shown to be disastrous in the past, and could be catastrophic in the future. The grassland goods and services valued by society also vary a great deal, as they are influenced by different soils, topographies, climates, and managements, and their interactions. A quantitative, fine-scale understanding of all these interacting factors and processes is essential for the development of strategies, tactics, and practices that ensure both the provision of services from grasslands and the continued sustainability of these ecosystems. Comprehension of these realities will support the development of principles that can be employed to achieve sustainable grassland management.
Authors: Christopher Daly, George H. Taylor, David B. Hannaway, Henry A. Fribourg
The eastern US has somewhat similar latitudinal patterns, but they are mediated by elevational and coastal influences. A combination of latitudinal and coastal influences allows for extremely mild winter minima that average nearly 15 ºC in southern Florida. Winter temperature patterns in the western US are dominated by relatively mild marine influences along the West Coast, elevational effects in the mountains, and cold-air pools in many interior valleys. The Cascade Range in the Pacific Northwest and the Sierra Nevada in California serve as effective barriers to the eastward flow of mild Pacific air, creating sharp temperature contrasts along their crests. The Rocky Mountains act as a barrier to arctic outbreaks that occasionally move southward from Canada during winter, resulting in milder temperatures west of the Rockies than to the east. The coldest winter temperatures in the western US are located not at the highest elevations, but rather in interior valleys where persistent cold-air pooling occurs.
As with winter temperatures, summer temperature patterns in the conterminous US are controlled by latitude, elevation, and proximity to oceans (Figure 3.1C). However, the latitudinal pattern is not as strong. Summer temperatures drop rapidly with elevation, decreasing at a rate of approximately 6.5 ºC per km. This results in large horizontal temperature gradients in the mountainous areas of the US. Along the West Coast, the cold waters of the Pacific Ocean moderate summer temperatures but not the hot, inland areas. At low elevations and away from coastlines, July maximum temperatures in the conterminous US generally range from 25 ºC in the north to 35 ºC in the south.
In the conterminous US to the east of the 100th meridian, the climate is humid continental in the north to humid subtropical in the south (Figure 3.1D). The southern tip of Florida is tropical. The Great Plains west of the 100th meridian are semi-arid. Much of the Rocky Mountains, the Sierra Nevada, and the Cascade Range are alpine. The climate is arid in the Great Basin, desert in the Southwest, Mediterranean in coastal California, and maritime in coastal Oregon and Washington, according to the Köppen Climate Classification System (Wikipedia [Climate classification], 2011; Ritter, 2006).
The two states outside of the conterminous US are Alaska and Hawaii. Alaska is situated at the northwest corner of the North American continent, separated by Canadian territory from the conterminous 48 states. Alaska’s climate falls into five major zones (Figure 3.1E): (1) a maritime zone which includes southeastern Alaska, the south coast and southwestern islands; (2) a maritime-continental zone (not shown on the figure) which includes the western portions of Bristol Bay and west-central zones. In this zone the summer temperatures are moderated by the open waters of the Bering Sea, but winter temperatures are more continental in nature due to the presence of sea ice during the coldest months of the year; (3) a transition zone between the maritime and continental zones in the southern portion of the Copper River zone, the Cook Inlet zone and the northern extremes of the south coast zone; (4) a continental zone made up of the remainders of the Copper River and west-central divisions, and the interior basin; and (5) an arctic zone (NCDC, 2011).
The State of Hawaii is an island group situated in the northern Pacific Ocean, about 3 900 km WSW of San Francisco. The outstanding features of Hawaii's climate include mild temperatures throughout the year, moderate humidity, persistent northeasterly trade winds, significant differences in rainfall within short distances and elevations, and infrequent severe storms. For most of Hawaii, there are only two seasons: "summer," between May and Oct. and "winter," from Oct. to April (NOAA, 2011). Seven climatic sub-regions are recognized for Hawaii. These are defined chiefly by the major physiographic features of the state and by location with reference to windward or leeward exposure (Western Regional Climate Centre, 2011). These patterns can be seen from the mean annual precipitation maps (Figure 1.6C; Daly, 2006).
Relationship of Grassland Type Distribution to Climate
The precipitation gradient east of the Rocky Mountains in the central part of the Great Plains (Figure 3.2) results from the rain-shadow effect of the Rocky Mountains and access to moisture from the Gulf of Mexico. Annual precipitation increases from about 320 mm at Greeley, CO, to nearly 900 mm at Kansas City, MO. Seasonal precipitation patterns also vary from south to north in the central plains (Trewartha, 1961), depending on proximity to the Gulf of Mexico, especially in warmer months. In southern portions of the short-grass prairie, summer maxima are the rule, while farther east there is one peak in the late spring-early summer and another in late summer-early autumn (type 3b in Trewartha, 1961). In the northern Great Plains, spring peaks are common (type 3c in Trewartha, 1961) while in the upper Mississippi Valley-Great Lakes region, summer and autumn peaks occur (Trewartha, 1961).
The major temperature gradient is from warm temperatures in southern grasslands to cooler temperatures in the north (Figure 3.3). The gradient is steeper for January temperatures than for July temperatures. Colder winter temperatures in the north have many implications for both plants and animals. However, snow cover in the north moderates extremely cold air temperatures at the soil surface. Winter temperatures in southern locations allow cool-season plant growth almost any time that there is adequate soil moisture (Smeins, 1994; Holechek et al., 2001).
As described in the Introduction, the three grassland types in the central portion of the continent, prior to European settlement, reflected the gradient of precipitation: tall-grass species in the higher rainfall eastern portions and short-grass species located in the rain shadow of the Rocky Mountains, with mixed-grass prairies between them. The areas covered by these grassland types were fairly comparable: short-grass prairie covered 615 000 km2, mixed prairie extended over 565 000 km2, and tall-grass prairie area was 570 000 km2 (Van Dyne and Dyer, 1973). Today, the tall-grass prairie is much constricted, not due to climate changes, but because of conversion to intensive agriculture. Originally, it extended eastward into southern Minnesota, most of Iowa, northern Missouri and northern Illinois, and western Indiana (Lauenroth et al., 1999). There were also isolated patches within the eastern deciduous forests further east, such as in cedar barrens, usually on very shallow soils (DeSelm and Murdock, 1993). Currently, the tall-grass prairie occurs mostly as isolated tracts, such as in the Osage Hills in Oklahoma and the Flint Hills in Kansas.
Ecoregions denote areas of similarity in ecosystems and in the type, quality, and quantity of environmental resources (http://www.fs.fed.us/rm/ecoregions/products/map-ecoregions-united-states); they are designed to serve as a spatial framework for the research, assessment, management, and monitoring of ecosystems and ecosystem components (http://www.epa.gov/wed/pages/ecoregions/reg3_eco.htm). Ecoregions have been used to assist in the development of biological criteria and water quality standards and the establishment of management goals for nonpoint-source pollution. They are also relevant to integrated ecosystem management, an important goal of most federal and state resource management agencies.
A Roman numeral hierarchical scheme has been adopted for different levels of ecological regions. The approach used to compile maps representing US ecoregions is based on the premise that ecological regions can be identified through the analysis of the spatial patterns and the composition of biotic and abiotic factors that affect ecosystem quality and integrity (Wiken, 1986; Omernik, 1987, 1995). These include geology, physiography, vegetation, climate, soils, land use, wildlife, and hydrology. Explanations of the methods used to define the USEPA’s ecoregions are given in Omernik (1995), Griffith et al. (1994), and Gallant et al. (1989). Level I (Figure 3.4) is the coarsest level, dividing North America into 15 ecological regions.
Level II (Figure 3.4) divides the continent into 52 regions (Commission for Environmental Cooperation Working Group 1997). For the Great Plains designation of Level I, Level II divides this one region into the following 5 subregions:
9.1 Temperate Prairies
At level III (Figure 3.5), the continental US contains 104 regions (United States Environmental Protection Agency [USEPA], 2003). For example, the Temperate Prairies is divided into 4 subsections: (1) Aspen Parkland/Northern Glaciated Plains, (2) Lake Manitoba and Lake Agassiz Plain, (3) Western Corn Belt Plains, and (4) Central Irregular Plains.
Level IV (Figure 3.6) is a further subdivision of level III ecoregions.
Work on ecoregions subdivision has been completed for all but 3 states (New Jersey, California, and Arizona) as of January 2011. State maps are available from a clickable map on this EPA webpage: http://www.epa.gov/wed/pages/ecoregions/level_iii_iv.htm.
For example, the Ecoregions of Oregon map (Figure 3.7) provides 9 primary divisions and 64 secondary divisions.
Ecoregion-based strategies for managing the grassland resources of the US are described in sections 4 and 5 of this publication (Ruminant Livestock Production and Native and Introduced Grassland Resources, respectively).
Summary. The climate types of the US vary greatly due to its large size, range of geographic features, and non-contiguous arrangement. In the contiguous US, to the east of the 100th meridian, the climate ranges from humid continental in the north to humid subtropical in the south. The southern tip of Florida is tropical. The Great Plains, west of the 100th meridian, are semi-arid. Much of the Rocky Mountains, the Sierra Nevada, and the Cascade Range are alpine. The climate is arid in the Great Basin, desert in the Southwest, Mediterranean in coastal California, and oceanic in coastal Oregon and Washington.
The three grassland types in the central portion of the continent, prior to European settlement, reflected the gradient of precipitation: tall-grass species in the higher rainfall eastern portions and short-grass species located in the rain shadow of the Rocky Mountains, with mixed-grass prairies between them. The areas covered by these grassland types were fairly comparable: short-grass prairie covered 615 000 km2, mixed-grass prairie extended over 565 000 km2, and tall-grass prairie area was 570 000 km2. Today, the tall-grass prairie is much diminished and constricted, not due to climate changes, but because of conversion to intensive agriculture. Originally, it extended eastward into southern Minnesota, most of Iowa, northern Missouri and northern Illinois and western Indiana. There were also isolated patches within the eastern deciduous forests further east, as over the cedar barrens, on very shallow soils. Currently, the tall-grass prairie occurs mostly as isolated tracts, such as in the Osage Hills in Oklahoma and the Flint Hills in Kansas.
Authors: Edward B. Rayburn and Steven P. Washburn
Ruminant livestock production is a major segment of US agriculture. Income from beef cattle and calves, milk products, sheep, and goats totalled about $93 700 million in 2007, compared to $77 200 million income from grain crops and $50 300 million income from horticultural crops (Table 4.1). This is a reflection of land use in the country. In 2007 there were 373 million ha in farms, of which 165 million ha were in permanent pasture and rangeland (44%), 14.5 million ha of cropland used only for pasture (4%), 12 million ha in pastured woodland (3%), and 164 million acres in cultivated crops (44%).
The 2007 Census of Agriculture counted 2 204 792 farms in the US. Thus, the average value of products sold was $135 000 per farm.
Beef production is the major ruminant livestock enterprise on pasturelands in the US. In 2007 there were about 798 300 farms with 59.9 million beef cattle and another 4.5 million head in feedlots. The cow herd comprised 33.7 million cows and heifers that had calved. In that year 34.9 million cattle were sold with a gross income of $24 900 million. Most US herds are small: 90% of the farms have less than 100 head and do not provide the main farm or family income. The highest density of beef cattle occurs in the central part of the nation from Texas to North Dakota, in the Appalachian Mountains and Plateaus, and in Florida (Figure 4.1).
Beef production is divided into three main enterprises: cow-calf (Figure 4.2), backgrounding/stocker (Figure 4.3), and finishing. These three enterprises may be combined on a farm but more commonly are separate over different farms and a feedlot.
The cow-calf enterprise provides the basic production of calves that ultimately will be grown out, finished, and slaughtered for meat. “Backgrounding” is the term used to describe the growing of weaned calves, often under a health management protocol to reduce the risk of diseases occurring when the animal goes into a feedlot. Backgrounding is most often done on pasture but may be accomplished in drylot on harvested feed. Stocker cattle are weaned calves or yearlings grown on pasture to allow them to grow to a heavier weight before grain feeding in a feedlot. Raising stocker cattle on pasture is especially worthwhile when grain prices are high relative to the value of finished cattle and feedlots want to finish the animal quickly using a limited amount of grain.
Most cattle are finished in commercial feedlots on a ration containing a high proportion of grain or grain by-products from the ethanol and processed-corn industry. The highest density of beef feedlots is in the High Plains east of the Rocky Mountains and in the western part of the Corn Belt (Figure 4.4). However, there is a growing interest in finishing cattle on pastures to increase the content of omega-3 fatty acids and conjugated linoleic acids (CLA) in the meat.
Pasture is the primary feed not only for steers (castrated males grown for meat) but also for beef cows and replacement heifers. Some pastures are managed with continuous stocking (grazing) while others are managed according to one of the several methods of deferred stocking of paddocks within a grazing system.
Conserved forage is preserved as hay or haylage, sometimes as grass silage, for feeding in winter and times of drought. These conserved forages are used in the South when transitioning in autumn from pastures of warm-season species to cool-season pastures, if forage production is not expected to meet the feed requirements of the grazing animals. Most hay is made into large round bales (200 kg or heavier) to reduce labour requirements. Haylage for beef cattle is made most often from bales wrapped in plastic bags extruded and cut from continuous sheets and sealed at periodic intervals to produce ensiled baleage.
Beef cows are bred to calve to maximize the sale size of calves or in consideration of anticipated pasture production and weather. The alternative chosen to reduce production costs and risks depends on the manager’s preferences. Some managers prefer to calve in winter, with the goal of producing larger weights at weaning and sale time. Others prefer to synchronize calving with pasture growth in the spring, since pasture plants will grow at the same time as the calves or, in the South, in early autumn when high quality pasture becomes available; this avoids having to breed cows in hot summer weather.
Cross breeding is used in beef cattle herds since it improves animal performance, vigour, and economic productivity. The foundation genetics for US beef production are the British cattle breeds (Bos taurus). These cattle are crossbred with one of the European continental breeds or, in the Deep South, with one of the Zebu cattle breeds (B.indicus).
Beef cattle usually are kept on pasture without housing, although shade from trees or artificial structures is often provided. Sheltering the animals from winter wind, driving rain, and snow, is accomplished in woods or in deep valleys. In intensively managed herds, cows or especially first-calf heifers may be brought into a barn for calving. On many farms, cows calve without major assistance on pasture, although superior managers inspect their cow herds frequently during each day of the calving season.
Herd health in beef cattle is an important management focus. Many progressive beef producers are involved with the Beef Quality Assurance program (National Cattlemen’s Beef Association, 2011; http://www.bqa.org). This is a national program that provides guidelines for beef cattle production, including teaching about proper use and administration of vaccines. These vaccines promote cow breeding health and, in preparation for shipping to feedlots, ensure calf respiratory health. Vaccination programs are tailored to local health issues. Under good management and depending upon local problems, animals are wormed (made to swallow a bolus of nematocidal medication) and treated for external parasites by dipping, brushing or spraying. Both pastures and conserved feed may have to be supplemented with protein and/or energy, as well as needed mineral nutrients.
Dairy production in the US follows one of two models. One is the confined feeding of harvested crops to lactating cows in large herds, with relatively little if any use of pasture. The second is the greater use of pasture accompanied with supplemental feeding of harvested crops at certain times of the year, and adherence to a management program. The pasture-based model is used on farms having smaller herds as well as on some farms with herds of more than 400 milking cows. In both cases, dry cows and growing heifers graze pasture to reduce feed costs and benefit animal health.
In 2007 there were 69 890 farms reporting 79.1 million dairy cattle and growing heifers. These cows produced 31.7 million dollars in dairy sales, as reported by the US Census of Agriculture (2007). The greater density of dairy farms occurred in California, the Upper Midwest, and the northeastern States (Figure 4.5). In recent years, as fuel and other inputs have become more expensive, the profitability of pasture-based dairies has increased (Figure 4.6).
A typical pasture-based dairy in the eastern US will have 0.1–0.25 ha of pasture/cow within a km of the milking facility. Additional land is required to support dry cows, replacement heifers, and bulls, and for growing stored feed. Labour is provided by the family, supplemented with some hired labour. Interest in large-scale pasture-based dairies has been stimulated by New Zealand investors who recently have established seasonal pasture-based dairy farms mostly in Missouri, Georgia, and Mississippi.
Typically, these farms include 120–200 ha of pasture with or without irrigation, about 500 cows, a 40 to 50 unit swing milking system, and employ 2 or 3 labourers in addition to the herd manager. Swing milking is set up with milking units above the middle of the parlour pit; all milking units are placed on 40 to 50 cows on one side and then swung to the other side to milk the next line of cows.
Seasonal calving is an attractive option for pasture-based dairy producers. Even though seasonal calving is not essential to have a successful pasture-based dairy farm, management is simplified when cows are bred to calve in compact seasons (<60 days).The use of two calving seasons leads to even month-to-month milk production either for cash flow or if it is a marketing requirement. Potential advantages of seasonal calving also include the matching of animal nutrient needs to forage availability, resulting in lower feeding costs; having fewer animal-management groups; allowing the manager to concentrate on specific tasks for short periods; and spreading the farm workload over the year.
There are also potential disadvantages to seasonal calving. Matching forage availability to the calving season may not result in the highest milk prices, since milk prices in the US are counter-cyclical to cool-season perennial pasture production, and also subject to government mandates. Thus, farm net income may not be enhanced even with lower feeding costs. Management of cash flow can be an issue when milk income fluctuates during the year. In seasonal herds, the considerable work demand from the start of calving through rebreeding can add to family stress levels; some producers prefer a uniform workload for themselves and their employees. There is risk involved when having to breed all the cows within a short period: low conception rates (Washburn et al., 2002a), untimely disease outbreaks, or a nutritional crisis can lead to failure to get cows bred within a reasonable period, thereby disrupting the seasonal calving strategy.
Typically, seasonal dairy graziers try to have 80–90% of the cows bred to calve within 9–12 weeks, using a combination of artificial insemination (AI) and natural service. Pasture-based dairy producers use cross breeding (bull and dam from different breeds or genetic history) to increase reproductive performance and animal vigour. Two research studies found only 70–85% of Holstein cows were detected in oestrus when compared to Jerseys (90–95%) or crossbred cows (85%) (Washburn et al., 2002b; Williams, 2007). Fewer Holsteins were cycling early after calving and they had smaller first-service conception rates. In general, US seasonal calving graziers obtain, by combining AI and natural service, breeding rates of 80–90% pregnancy after 8–to12-week breeding seasons. Such herds often have crossbred cows or a significant influence of Jersey or New Zealand Friesian genetics. To rank bulls used in AI, the USDA Animal Improvement Programs Laboratory (AIPL) uses an economic index: Net Merit $. This index summarizes traits of many daughters of bulls to determine a weighted economic value of milk production along with fitness traits such as daughter pregnancy rate, productive life, conformation, body size, calving ability, and udder health (http://aipl.arsusda.gov/reference/nmcalc.htm). Daughter pregnancy rate (DPR) data have been available from the USDA AIPL since 2003, thus enabling graziers interested in seasonal calving to avoid using bulls which have had daughters with insufficient fertility, without losing much in Net Merit $ (Norman et al., 2006).
When seasonal breeding is used, it needs to be done in concert with forage production, rebreeding, and seasonal milk prices. In the cool environments of the Northeast, late winter or early spring calving is used so that cows can have access to abundant high quality cool-season pastures when they reach peak milk production and approach rebreeding. In the South and lower Midwest, breeding cows in June-October subjects cows to heat stress. Elevated air temperatures accompanied by high humidity lead to low conception rates, reducing the proportion of cows successfully bred within the desired period. In such areas, compact calving seasons during cooler months are planned (mid-August until late-January). To even forage availability, combinations of warm- and cool-season annual and perennial forages are used.
Different management strategies will be optimal for different producers, depending upon available resources and ultimate goals. Although milk production/cow often is less with seasonal grazing than with confined feeding, lower costs for facilities, equipment, and feed, and improved animal health allow well-managed seasonal pasture-based dairy systems to be economically competitive.
Calves group-fed and started on pasture at an early age
Calves on seasonal pasture-based farms often are group-fed. Group feeding is efficient and, when done on pasture, induces calves to learn to graze prior to weaning. On farms using confinement feeding, calves are prevented from being in direct contact with each other until after weaning. With seasonal calving, there is a break in any disease cycle, since calf rearing areas are not inhabited continuously during the year. When two calving seasons are used, care is needed to ensure that calf-rearing areas are not contaminated from an earlier use: there should be distinct calf-rearing areas for each season. Without seasonal calving, group feeding is less advantageous because many smaller groups are needed during the year.
Many graziers use whole milk, including waste milk, for calf feeding; others use a high-quality milk replacer. Neither colostrum nor milk should be pasteurized before feeding. Calf health in group feeding ranges from satisfactory to excellent; this is related to the ability of managers to quickly spot calves that are weak, not competitive, or need attention. Such calves can be separated from the group and placed with a younger, smaller, and less aggressive group to enable them to more easily compete and achieve adequate growth rates.
Young calves are started in small groups so that each calf can learn to nurse effectively before being placed into successively larger groups. As many as 100 calves in a pasture may feed from two 60-nipple milk feeders; these feeders are used by multiple groups, and relocated periodically with a small utility tractor. Graziers that use nipple feeders feed calves twice daily, transitioning to once-daily feeding before weaning. Other farms train calves to drink milk out of an open pail, then place them in groups and feed milk in a trough. Calves are fed about 4 L of milk/calf once a day in the trough, and have access to a calf starter grain ration and fresh water. Calves fed from troughs grow similarly to calves that are fed individually or from nipple barrels or nipple tanks, but may have more sucking of the ears of other calves (cross sucking) after feeding. However, this behavior seldom persists after weaning (Jackson and Washburn, 2008), although an occasional calf may either require a nose guard to prevent sucking of the mammary areas of other calves or have to be culled from the herd. Some graziers choose to let dairy calves nurse their mothers or specific nurse cows through weaning. This practice usually gives calves a very good start but it can be tricky to manage: calves may use more valuable milk than needed for growth, may get too fat, and the development of their mammary glands may be arrested.
Crossbreeding in pasture-based systems
Dairy genetic selection in the past has emphasized high milk production, resulting in the occurrence of traits detrimental to fitness. Selection within breeds can address needed genetic improvements. However, crossbreeding can provide a more immediate solution for some traits, under certain production systems and pricing structures. Holstein dairy cattle maintain a substantial advantage over other breeds in fluid milk production/cow. However, crossbred dairy cattle can be economically competitive when multiple traits are evaluated within a production system. Continued within-breed selection together with the use of crossbreeding is an optimal approach for maintaining genetic diversity and improving future production efficiencies in various systems.
Jersey and Holstein crosses are used most commonly in the US, but many other breed combinations are of interest. A research comparison of the economic implications of breeding strategies using Holstein-Friesians (H), Jerseys (J), and Ayrshires (A) found that crossbred groups had relative net income/unit area ranked as follows: HJ>HJA>JA>J>HA>H>A. Changing values for beef and ratios of milk fat and protein affected the relative rankings (Lopez-Villalobos et al., 2000). Another study, in Australia, using data from 14 commercial herds, found a substantial operating profit advantage for Jersey x Holstein-Friesian crossbred cattle over pure Holstein-Friesians (Pyman, 2007).
Using USDA data on breed differences, heterosis, and net economic merit of purebred and crosses (VanRaden and Sanders, 2003), Holsteins excelled for Fluid Merit $, based on milk volume. However, average F1 crosses of Brown Swiss or Jerseys with Holsteins had an advantage over elite crossbreds for fluid milk. Mating of elite animals within the Holstein breed had an advantage over elite crossbreds for fluid milk production. Changes in the economic weighting of Net Merit $ index from the USDA with the addition of daughter pregnancy rate and calving ability may favour crossbred cattle in the future, especially in pasture-based systems.
Labour efficiency is important
Two different philosophies have evolved regarding milking systems. Since investment in the milking system is substantial, one approach maintains that it is important to keep the system active, to dilute fixed costs. This philosophy has resulted in large dairy farms where cows are milked three times/day, with each milking shift lasting about 7 hours. Under this system, the milking parlour operates nearly around the clock. In contrast, many graziers believe that there are activities which they prefer to do other than milking cows; therefore, they design systems to milk the herd quickly and only twice/day. Some dairy herds are even going to once-a-day milking, as a lifestyle choice of the manager. When providing milk to a solids or cheese market, once-a-day milking has some advantages, since the volume of milk is reduced more than is the production of solids production.
Swing-type milking systems are very common on pasture-based dairy farms which have up to about 600 cows. Swing systems may have 8–10 milking units for herds of 100 cows or less, up to 50 milking units for herds of up to about 700 cows. Swing parlours are typically at about a 1.225 rad angle (70 degree angle) with about 71 cm between adjacent units. Large rotary milking systems with 60 or more stalls are more commonly used for very large herds with more than 700 cows.
Cows on pasture spread about 85% of the manure
Less manure storage is needed and cows recycle manure nutrients well in properly-managed pastures (White et al., 2001). The amount of manure storage and handling needed is about the same for 7 pastured cows as for 1 confinement cow. Thus, there is less cost for constructing and managing manure handling facilities on pasture-based dairy farms than where confinement feeding is practiced.
Location of water sources and shade determine manure deposition within a paddock. Moving watering troughs, avoiding use of shade except when necessary, and having designated shade paddocks with good shade coverage, can improve manure distribution. In a healthy pasture system, there is abundant activity of dung beetles (Scarabaeoidea family), earthworms (Oligochaeta class), and other biological agents that help to break manure piles down and redistribute nutrients. In North Carolina pastures, 28 species of dung beetles have been identified, with varying species activity across the year (Bertone et al., 2005). In summer, it is not unusual for dung beetles to land on a fresh dung pat within seconds after it is dropped. Within a few days, soil has been worked up through the dung pat and its exterior surface is only a dried-up shell.
Lower investments in equipment
Typical family dairy farms in the South have 150–300 cows. Most of their forages, including corn (Zea mays) and small grains (Triticum, Avena, Hordeum, and Secale sp.) are used for silage and hay crops. Some farms produce corn for grain but many purchase grain supplements. To plant crops and harvest them in a timely manner, farmers often own the needed planting and harvesting equipment. Family members typically have designated areas of responsibility. If debt load is small, farms may be able to survive a turbulent economic situation, but if debt load is large the enterprise may be vulnerable. On farms where annual tilled crops are major enterprises, the work is hard, rest periods are few, and there is little to generate excitement in the next generation.
Pasture-based dairies often hire custom harvesting, emphasizing grazing management and efficient milking systems rather than field work. Such pasture-based systems function without a full complement of equipment. Cows do most of the forage harvesting as well as most of the manure disposal. Cows reproduce and generate wealth over time whereas equipment depreciates.
Investments in housing typically are very low on pasture-based farms, with most new start-ups not providing any. Housing is often an open shed with a bedded pack rather than a freestall barn, unless freestalls were carried over from a converted confinement system, where they are the common system.
Cold weather is not a major issue when cows are fed well. Many graziers in northern states out-winter their cows, particularly if they are not lactating. However, some precautions may be needed for cows lactating during cold winter months to avoid chapped and frozen nipples.
Dealing with heat stress varies with farms and the potential severity of the problem. For smaller herds, rotational use of 3- or 4-shade paddocks with many trees is adequate when temperatures and humidity are high. Larger pasture-based herds use a combination of shade paddocks or spray irrigation to keep cows cool in the summer. Fall calving also is used to reduce heat stress, because cows in that breeding system will be either in late lactation or dry at the hottest times of the year.
Grazing cows get more exercise than those in confinement feeding, usually have fewer health problems, and typically live longer. Cows in a pasture-based system spend a relatively small proportion of their time on concrete and, unless large amounts of concentrates are fed, usually consume a ration that is favourable to rumen health. In pasture-based systems, cows rarely need hoof trimming, would rarely have a displaced abomasum, and have fewer cases of clinical mastitis. However, there may be increased risk of milk fever, grass tetany, and perhaps bloat. Contagious mastitis, such as that caused by Staphylococcus aureus, can be a problem in pasture-based dairy farms if horn flies (Haemato biairritans) are not controlled as a potential vector.
Discussion groups, pasture walks, and electronic media
Dairy graziers often participate in discussion groups and usually are willing to share production and financial information within those groups. Discussions may be facilitated by agricultural extension agents, veterinarians, farm consultants, or farmers. The groups function best when there are common interests among the participants, and if some producers exert leadership. General grazing discussion groups that try to include beef, sheep, goats, and dairy graziers usually do not have enough focus to be successful over time. Discussion groups can be fairly local or they can function when graziers from many states are involved. Groups who have members from several states usually meet 3–4 times/year, with one of the members serving as a host. A subject matter theme is used at each session and an outside speaker may be invited to lead the discussion on a specific topic. In addition to discussion groups, many dairy graziers also stay in touch with each other regularly via telephone calls, e-mail, other social communication means, and many subscribe to and/or contribute to grazing magazines.
Economic returns, positive outlook, and importance of lifestyle
Participants at training events for dairy industry professionals have commented on the positive outlook of dairy graziers. This attitude is reflected in the children of successful dairy graziers who return to the home farm or start a pasture-based farm of their own with the help of their family. A positive and optimistic attitude can be seen on other types of dairy farms but it seems to be prevalent among graziers. Dairy grazing systems, requiring lower capital investment than confined-feeding systems to get started, provide an easier path to entering dairy production and future farm ownership. Many dairy graziers look for opportunities to assist young people to become involved in the dairy industry.
Because most dairy graziers are cost conscious, it is not unusual for many of them to do well financially when milk prices are low, and examples of successful graziers abound at different levels of milk production. Some successful graziers may have a system where few external inputs are used, just a few kg of purchased grain/cow/day, even though they sell less than 5 000 kg milk/Jersey cow in a seasonal-calving herd. Others have profitable pasture-based Jersey herds among the top in the country with production of over 9 500 kg milk/cow/year.
Successful pasture-based dairy systems are able to grow rapidly from within because of more efficient reproduction. In some cases that increased equity is used to start up additional grazing farms for other graziers or family members. In other cases, these resources have been used for off-farm investments or to fund retirement accounts, in which cases the farm will not have to be sold to fund retirement. A more detailed discussion of the learning experiences of pasture-based dairy producers can be found in Washburn (2009) and at http://dairy.ifas.ufl.edu/dpc/2009/Washburn.pdf.
The US sheep (Ovis aries) industry is based primarily around meat production, due to the low price for wool. There are niche markets for specialty spinning wool, sheep milk, and sheep cheese. Due to the low price of wool and the lack of contract shearers to clip sheep, many new small-scale producers are choosing to reduce labour needs by herding hair-sheep breeds. In 2007 there were 83 134 farms reporting 5.8 million sheep and lambs with 3.5 million ewes 1-year old or older (Figure 4.7). The majority (>91%) of farms have less than 100 head of sheep. Only 42 494 farms (51%) sold wool, producing 15.3 million kg of wool. Seventy-two percent of farms with ewes >1-year old or older sold 4.4 million sheep and lambs. The primary region of sheep production is in the western states where climate reduces the risk of internal parasitic worms (Figure 4.8).
There is growing interest among new and small land-owners for raising sheep, since they are more productive/unit area and more valuable/unit weight than cattle. There is often a strong market for lamb near urban areas with populations of some ethnic backgrounds. This market is driven by immigrants from countries where sheep meat is commonly eaten, especially during holidays and for religious observances. Some small land-holders are also interested in co-grazing sheep with other livestock for controlling pasture weeds.
In contrast, in areas where sheep once were common, there has been a decline in sheep numbers due to problems with predators such as coyotes (Canis latrans) and stray dogs (Canis lupus familiari), because of immigration of coyotes from western areas, and due to the increase of feral stray dogs from escaped pets. Predators can be controlled by guard dogs, llamas (Lama glama), donkeys (Equus africanus asinus), and appropriate fences. Another issue is that internal round-, tape-, and other worm parasites (Nematoda) are developing resistance to some nematocidal wormer medications, making it more difficult for grazing lambs to remain healthy.
Ewes are bred to lamb, depending on the manager’s preferences, concurrently with the demands of a specific marketing system or in synchronization with pasture production and weather conditions. Some managers prefer to produce for the seasonal religious holidays that yield the highest market price. Others prefer to breed according to anticipated weather conditions and pasture production, to reduce cost and produce slaughter lambs that are larger than those preferred in the religious holiday markets. Cross breeding is used for sheep meat production since it improves animal performance, vigour, and economic productivity. In small flocks, sheep often are provided housing, whereas the majority of sheep that are kept on pastureland and rangeland are not. Herd health is maintained using vaccination programs tailored to local health issues, worming animals against local parasite problems, and using protein, energy, and mineral supplements as needed.
Other livestock production
Other livestock produced in the US that are fed and maintained on pasture include horses (Equus ferus caballus) and ponies (E. f. caballus), goats (Capra aegagrus hircus), whitetail deer (Odocoileus virginianus and other Odocoileus sp.), elk (Cervus canadensis), alpacas (Vicugna pacos), llamas, and American bison (Bison bison).
Horses and ponies
Horses and ponies, most of which are used for recreational purposes in the eastern US, are owned by many families on small rural and suburban areas, as well as on farms. In 2007 there were 575 942 farms reporting 4 million horses and ponies, and 99 745 farms reporting a total of 283,806 mules, burros (small donkeys in western US), and donkeys. Gross sales of horses and ponies totaled $2 062 million (Table 4.1).
The density of horses is highest in areas of the West with working ranches, such as Texas, Oklahoma, and Missouri; around urban areas; in the “Bluegrass” area of Kentucky in summer; and in northern Florida, a major training and competition area (Figure 4.9) in winter.
In addition to family-owned recreational pets (Figure 4.10), horses are kept at boarding stables for owners without the land to maintain them, and at commercial stables where people can hire rides on bridle trails. Important local activities involve horses bred, reared, housed, and trained on farms for competition at race tracks.
Meat, milk, and wool goats
In the US, goats are used primarily for meat, but also for milk and angora wool production. In 2007 there were 123 278 farms with 2.6 million meat and other goats, 27 481 farms with 334 754 milk goats, and 7,215 farms with 204 106 Angora goats. Meat goats are most prevalent in Texas, Oklahoma, Missouri, Middle Tennessee, Kentucky, and the Appalachian Mountains and Plateaus (Figure 4.11). Most milk goats are in the northern Midwest and in California (Figure 4.12), while Angora goats are found in southwestern Texas, northeastern Arizona and northwestern New Mexico (Figure 4.13). Goat populations vary, declining in some areas but increasing on new small farms. They are especially useful for weed control when reclaiming old pastures which have grown up with brush (Figures 4.14 and 4.15) and have been used in some cities to substitute for mowing or clearing land from undesirable brush and other cover.
The introduction of Boer goats from South Africa has led to increasing interest in meat goat production. As is the case for sheep, some immigrant groups in large cities traditionally purchase and eat goat meat for religious holidays.
Deer and elk farm enterprises are relatively new in the US. Until recently, all deer and elk had been owned in common by the people through the state governments and managed by state wildlife management agencies. With changes in game laws, these animals now can be produced by individuals in some states. In 2007 there were 5 654 farms reporting 269 537 deer and 1 917 farms reporting 68 251 elk. Captive deer include American whitetail deer (Figure 4.16), European deer species (Cervus sp.), and red deer (C. elaphus), a close relative of American elk (Figure 4.17). A concern among these cervid producers is chronic wasting disease, a transmissible spongiform encephalopathy (TSE) disease similar to bovine spongiform encephalopathy (BSE) in cattle. Deer and elk are produced for meat, hides, and for their antlers, harvested in the velvet stage and sold for their purported medicinal properties.
Alpacas and llamas also are relatively newly farmed species in the US. Alpacas are used for their wool, while llamas are employed as pack animals, especially in fragile environments, and as guard animals with sheep. In 2007 there were 8 708 farms reporting 121 904 alpacas and 26 060 farms reporting 122 680 llamas.
American bison (Figure 4.18) are the original bovine species of North America. In 2007 there were 4 499 farms reporting 198 234 bison, in addition to bison herds maintained at several federal and state parks. Bison are raised for their meat, buffalo robes (hides with winter haircoats), and horns.
Production of these species and types differs across the US due to regional climate, soils, and social culture. Where climate and soils are suitable for cropping, pasture-based livestock production is limited to areas marginal for crop production. Where climate and soils are not appropriate for tilled cropping systems, livestock are used on a greater proportion of the land. Historically, as the US was developing, dairy cattle were raised mostly in the cool northern climates where milk could be chilled in water springs, and butter and cheese could be produced. Beef cattle and hogs were more common in the southern states where they could graze unencumbered in the forests and woods, many of which had been native savannas. In the West, beef cattle were common after their introduction by the early Spanish settlers, who also brought in sheep and goats, which were adapted to the dry western environment. Early producers had little of the technology that we have today to assist them in their livestock management; they had to rely on animals and management that were adapted to the climate and plants of the region. Management and economic considerations have changed over the centuries, but the original environment and culture are still reflected in current livestock systems. Over the long run, the balance among animal adaptation, environmental factors, animal science, and market economics will determine agricultural land use and livestock production.
Summary. Grasslands in the US are utilized primarily by ruminant livestock for the production of meat, milk, and wool. The value of ruminant livestock production ($93 700 million) is greater than that of all grain crops ($77 200 million) or horticultural crops ($50 300 million) in the country and is based primarily on grazing and harvested forages from permanent pasturelands and rangelands.
Beef production is the major ruminant livestock enterprise on grazinglands and encompasses cow-calf production, backgrounding and stockers rearing, and finishing. In 2007 there were about 798 300 farms with 60 million beef cattle. Most herds are small: 90% of the farms have less than 100 head, and do not provide the main farm or family income. The cow-calf enterprise provides the basic production of calves that ultimately will be grown out, finished, and slaughtered for meat. Most cattle are finished in commercial feedlots on a ration containing a high proportion of grain or grain by-products from the ethanol and processed-corn industry. However, there is a growing interest in finishing cattle on pastures to increase the content of omega-3 fatty acids and conjugated linoleic acids in the meat. Grazed forages are the primary feed not only for steers (castrated males grown for meat) but also for beef cows and replacement heifers. Many grazinglands are managed with continuous stocking but an increasing number of others are managed according to one of the several methods of deferred stocking of paddocks within a grazing system.
Dairy production is practiced either with confined feeding of harvested crops to lactating cows in large herds, with relatively little use of pasture, or with pastureland grazing accompanied by seasonal supplemental feeding of harvested crops. The pasture-based model is used on farms having smaller herds as well as on some farms with herds of more than 400 milking cows. In both cases, dry cows and growing heifers graze to reduce feed costs and benefit animal health. In 2007 there were nearly 70 000 farms reporting 79 million dairy cattle and growing heifers. A typical pasture-based dairy in the eastern US has 0.1–0.25 ha of pasture/cow within a km of the milking facility. Additional land is required to support dry cows, replacement heifers, and bulls, and for growing stored feed.
Sheep production is mostly for meat, and for wool, milk, and cheese niche markets. In 2007 there were approximately 83 000 farms reporting 5.8 million sheep and lambs, with 3.5 million ewes 1-year old or older. More than 90% of farms that raise sheep have less than 100 head. The primary region of sheep production is in the western states where climate reduces the risk of internal parasitic worms. There is growing interest among new and small land owners in raising sheep, since they are more productive/unit area and more valuable/unit weight than cattle.
Other livestock produced in the US that are fed and maintained on grazinglands include horses and ponies, goats, deer, elks, alpacas, llamas, and American bison. Most equines are owned by families for recreational purposes on small rural and suburban areas, as well as on farms, but horses are used also on working ranches and in the racing community. In 2007 there were nearly 576 000 farms reporting 4 million horses and ponies.
5.1 NATIVE GRASSLANDS (RANGELANDS)
Authors: Joel R. Brown, Rex D. Pieper, Andrés Cibils, Kris Havstad, Debra Peters, Barbara Allen-Diaz, Brandon Bestelmeyer, David Briske, Jeff Herrick, Patricia Johnson, Linda Joyce, Tony Svejcar, Jin Yao, James Bartolome, and Lynn Huntsinger*
* Much of the material in this section was taken from Havstad et al. (2009), edited by Brown, Pieper and Cibils.
Rangeland is found predominantly in arid and semi-arid regions, on which the indigenous vegetation, climax or sub-climax, is mostly grasses, grass-like plants, forbs or shrubs that are grazed or have the potential to be grazed, and which is used as a natural ecosystem for the production of grazing livestock. In recent decades, US rangelands are managed for multiple uses, which include livestock production, mining, timber production, wildlife management, and recreation. There are approximately 308 M ha of rangeland in the United States, about 31% of the total land area. This land type is characterized by four features: 1) limited water and nutrient availability, primarily nitrogen (N), 2) large temporal and spatial variability in vegetative production, 3) highly interspersed areas of public and private ownership, and 4) culturally sensitive use histories. Rangelands produce a multitude of ecosystem services for society, which include water, energy, food, recreation, critical minerals, and open space.
This native grassland section describes the major regions of the western continental US, the predominant area of US rangelands, and the biophysical and socio-demographical characteristics of each region. The concluding section describes important conservation practices that are now available to today’s land owners and stewards.
The physiography of the Great Plains consists of an enormous piedmont that flanks the eastern slope of the Rocky Mountains. The Northern Great Plains are vast grasslands occupying most of the states of North Dakota and South Dakota and substantial areas of Montana, northeastern Colorado, and northern Nebraska (Figure 5.1.1).
This region is flat to rolling, with features such as the Black Hills, badlands, and rivers providing sharp breaks in the gentle topography. The Southern Plains are situated between the Rocky Mountains and the central lowlands and encompass portions of six states.
The climate is continental and is characterized by dominant north-south temperature and east-west precipitation gradients. These climatic gradients and physiographic features define the ecological attributes of these ecosystems (see Section 3 – Climate for additional details).
Native vegetation is dominated by short, mid-height, and tall perennial grasses that evolved with natural disturbance regimes characterized by grazing, drought, and fire.
Soils of the Great Plains region are predominantly Mollisols, characterized by a thick, dark surface (A) horizon, and a high base saturation. The dark surface horizon results from the process of melanization -- darkening via the addition of organic matter. Mollisols form as a result of long-term accumulations of plant material and are high in organic matter content. Biological activity is important in Mollisols, where soil fauna such as earthworms and rodents help break down and incorporate organic matter. These soils characteristically form under grassland or prairie vegetation in climates that have moderate to pronounced seasonal moisture deficits - but under a wide range of temperature regimes. The typical topography associated with Mollisols is flat or gently rolling to undulating. The parent material is associated with unconsolidated material resulting from glaciation, aeolian deposits (loess) high in calcium, and/or sedimentary rocks. Mollisols are characteristic not only of North America, but also of the steppes of Europe, Asia and South America. They are fertile and productive soils and, in areas with higher rainfall, have been converted extensively to cropland (see section 2 for more details on topography and soils).
At the time of European settlement of the Southern Great Plains, woody plants, including eastern red cedar (Juniperus virginiana), Ashe juniper (J. ashei), Pinchot or redberry juniper (J. pinchotii), Rocky Mountain juniper (J. scopulorum), and honey mesquite (Prosopis glandulosa), were restricted primarily to riparian or deeply dissected areas that seldom experienced fire. However, beginning early in the twentieth century, woody plant encroachment became a substantial land management issue that continues to occur at a rapid rate.
Although there is considerable cropland in the Northern Great Plains, most remains in rangeland, as a result of farming limitations, including the semi-arid climate, soil restrictions (e.g. texture, rockiness, restrictive layers), and topography. Livestock use of the northern mixed-, short-grass, and tall-grass prairies is predominantly cow/calf, with some sheep and a growing population of bison. Livestock production is a major component of the economies of each of the states in the region and relies heavily on the native prairies for forage. Recreation is a major contributor to the economies of all of the states in the Northern Great Plains. Each state has been able to capitalize on the open spaces and beautiful scenery associated with the prairies through active tourism industries.
The goods and services that could be sustainably provided by Southern Plains ecosystems, primarily beef cattle and small grains, with some irrigated cotton in the southern portion, were clearly defined by the drought of the 1930s. Only minimal amounts of rangeland have been converted to cropland since that period and substantial areas of marginal cropland have been replanted to perennial grass cover. The Conservation Reserve Program (CRP), instated by a provision of the 1985 Food Security Act, provided land owners with incentives to take erosive, marginal land out of cultivation to promote ecological sustainability by establishing perennial grassland species. The number of beef cattle has remained relatively high, but it has declined 18% from 4.4 million in 1950 to 3.6 million in 2002.
The rangelands of the Northern Great Plains function as huge watersheds funneling moisture into streams and rivers, with much of it flowing into the Missouri River and ultimately the Mississippi River to the east of the region (Figure 5.1.2). There is concern over the amount of sediment carried by the streams which ultimately accumulates behind dams in the Missouri River. Prairie watersheds also are important in aquifer recharge. Agriculture and urban areas in the region are dependent on both surface and subsurface sources to meet their water needs.
The Ogallala Aquifer underlies much of the Southern Great Plains and it is the single most important source of water in the province. The aquifer supplies irrigation water to 5.5 M ha of agricultural land, with Nebraska, Texas, and Kansas extracting the largest amounts. Substantial aquifer depletion has occurred in the past 60 years, especially in the Texas and Oklahoma Panhandles and southwestern Kansas, and it continues to be depleted at approximately 0.8 m/year. Recharge occurs slowly because of the semi-arid climate and the limited permeability of substrates overlying much of the aquifer.
The Northern Great Plains states are mostly rural and sparsely populated. Montana, South Dakota, North Dakota, and Wyoming are among the ten least populated states in the United States, each having a population of less than one million. Wyoming is the least populated state in the country with just over 0.5 million citizens. While Nebraska supports over 1.7 million people, the majority live in population centres south and east of the Northern Great Plains region. The vast majority of land in the Southern Great Plains is in private ownership and use patterns are characterized by a combination of intensive agriculture, primarily in the more mesic eastern portion of the province, grading to extensively managed rangelands in the semi-arid western portion (Figure 5.1.3). The Southern Plains has remained decidedly rural, but several large population centres are located on the periphery of the province. These include the Front Range Corridor in Colorado (4 million), the interstate highway I-35 San Antonio-Austin Corridor in Texas (4 million people), and the Dallas-Fort Worth Metroplex (6.4 million) southeast of the province. The population of the Southern Plains has increased about 114% from 5.7 million in 1950 to 12.2 million in 2000 (excluding the Dallas-Fort Worth metroplex). The majority of this growth can be attributed to several population centres and future population growth is anticipated to be greatest in regions that currently have the highest densities.
California Annual Grasslands
The California Annual Grasslands occupy about 5.5 M ha, primarily in the foothills of the Central Valley and in coastal valleys. The original dominant plants of the California grasslands were bunch type (caespitose) perennial grasses interspersed with native annual grasses and annual and perennial herbs, probably with a higher proportion of annuals in drier areas than in more humid ones. Conversion of this grassland to an ecosystem dominated by exotic annuals began with the introduction of livestock, cultivation, and seed dispersal of Mediterranean-origin annual plants in the late eighteenth century, and increased dramatically with a series of severe droughts in the late 1800s.
The dominant soils in the California Annual Grassland region are predominantly Alfisols and Entisols. Alfisols are characterized by distinct periods of high soil moisture and high soil temperature (Mediterranean climate). Alfisols typically develop on relatively flat slopes or floodplains. The parent material is primarily clay minerals. The highly variable temperature and moisture regime favours the translocation of clay particles and the formation of argillic horizons, which can restrict water infiltration and plant root penetration. Because of these processes, Alfisols are typically low in organic matter and have poorly developed granular structure.
Entisols are soils formed on relatively young land surfaces or areas that have been recently disturbed. They are found on relatively steep slopes or where soil formation is inhibited. In addition, harsh environments or inherent infertility may limit plant growth and the accumulation of organic matter. These soils often are subject to mass movement, which may inhibit further development. The primary feature of California Annual Grassland Entisols is their shallowness (<50 cm).
The California annual grasslands harbour rich floristic diversity at multiple scales, with ten or more species/m2 not uncommon, and considerable patch-level heterogeneity linked to edaphic and topographical variation (Figure 5.1.4). There are altogether more than 500 grassland plant species, with many wildlife species dependent on grassland, including birds, lagomorphs, other small mammals, carnivores and reptiles. The endangered San Joaquin kit fox (Vulpes macroitis) is found in and adjacent to this habitat. Grasslands are critical foraging grounds for raptors and numerous other species. Several prominent native and non-native game species include deer (Cervus sp.), turkeys, and feral pigs (Sus scrofa). Whereas the water supply in California is generated largely in montane regions, most of it flows through grasslands, and is augmented by overland flow and grassland seeps and springs.
Ranch owners have long been termed lifestyle “consumers”, because the ranching lifestyle and beautiful environment are ecosystem services supported by annual grasslands and consumed by ranchers, such that ranch land prices are well above those of land with value for agricultural production. In recent decades, with the increasing popularity of “ranchette” type developments, more of the grassland has been devoted to the grazing of horses and other recreational stock, as well as “used” for viewing landscapes and wildflowers, hiking, picnicking, mountain-biking, and other recreational pursuits. On coastal grasslands, small scale speciality dairy and niche meat operations have increased in number in response to consumer demand, often supported by the high productivity and long growing season.
Grazing will continue to be a service provided by these grasslands, though the grazing animal will increasingly be recreational or niche-market livestock. Understanding the effects of grazing on vegetation in the California grassland is complicated by a large climatic gradient, pronounced inter-annual variation in precipitation, strong variation in topography and land-use history, and regional variation in the species pool. At any one site, the impact of grazing arises out of the interaction of land use history, the current and recent grazing management schemes, the abiotic environment, and the species pool in the local plant community.
California has one of the most rapidly growing human populations in the world: from less than 160 000 people in 1850, to over 36 million people today, for an average annual rate of growth of 3.4 percent. The population is projected to reach 63 million in the next 50 years. The ecosystem goods and services consumed from California grasslands have changed dramatically over time, as the grasslands, peoples, and industries of the state have changed. The grasslands have been valued as a source of sustenance and homesteading, for livestock forage, as real estate, and increasingly for a diverse array of tangible and intangible services.
The region designated as Great Basin (Figure 5.1.1) includes the area which is internally drained (hydrologic definition), but also includes additional areas of shrub steppe to the north and east. Much of the Great Basin is in the Basin and Range Province, with isolated mountain ranges separated by valleys. The mountain ranges are a result of fault activity (the meeting of the Pacific and North American tectonic plates), and generally have a north-south orientation. The Basin and Range geography results in rain shadows and steep elevation gradients, which create high temporal and spatial variability in both climate and vegetation.
A complex topography and variable climate have produced an interesting mixture of soils in the Great Basin. The dominant soils in the region are Aridisols, soils formed in arid climates. Aridisols are defined based on their soil moisture regime, which is dry in all parts more than 50% of the time and lacks sufficient moisture for plant growth for as much as 90 consecutive days when temperatures are adequate for growth. In most years, little or no water percolates through the soil and potential evapotranspiration greatly exceeds precipitation. Soil organic matter, microbial populations and nutrient availability are low. They can form a variety of landforms, slopes and parent materials, and are found on relatively stable landscapes. Because of limited plant productivity, there is little organic matter accumulation. In the US, many Aridisols are high in CaCO3, which may form petrocalcic layers (horizons), further restricting water infiltration and plant root penetration. Some soil features associated with Aridisols present substantial management challenges: surface formations can include crusts and desert pavement, and subsurface formations include nitric, calcic, and argillic horizons. All of these characteristics make Aridisols vulnerable to degradation and extremely difficult to remediate.
Many of the northern, central, and western portions of the area defined in Figure 5.1.1 are sagebrush steppe. There are many species of sagebrush (Artemisia sp.), and a wide variety of grasses and forbs found in the region. Some salt desert communities, often dominated by species of saltbush (Atriplex sp.) and winterfat (Krascheninnkovia lanata), occur in the northern portion of the Great Basin, but they are much more common in the central and southern portions. At the southern end, the sagebrush and salt desert vegetation types give way to communities dominated by creosote bush (Larrea sp.).
Part of the diversity of Great Basin vegetation is a result of moisture accumulation in small localized riparian or wetland areas. These areas may be along streams, lakes, springs, or meadows that are supplied with water from runoff and snowmelt from higher elevations. These areas occupy 0.5 to 1.0% of the landscape but are important to a host of fish and other wildlife species, for recreation, and for domestic livestock.
There are several major issues which currently influence vegetation patterns in the Great Basin. The most significant is the spread of invasive non-native annual grasses. The most abundant invader is cheatgrass (Bromus tectorum), which by some estimates dominates 25% of the sagebrush steppe. In recent years there has also been rapid invasion by medusahead (Taeniatherum caput – medusae) in the northern reaches of the Great Basin and red bromegrass (Bromus rubens) to the south. These annual grasses (especially cheatgrass) can drastically alter historic fire cycles. The combination of more frequent and earlier fires can have negative impacts on native plant species including sagebrush; these changes also result in loss of critical habitat for sage grouse (Centrocercusuro phasianus).
In the more productive mountain big sagebrush (Artemisia tridentata ssp. vaseyana) communities there has been increasing conversion from shrub steppe to conifer woodlands [dominated by species of juniper (Juniperus sp.) and/or pine (Pinus sp.) depending on location] (Figure 5.1.5). Ironically, the conversion to woodlands is thought to be largely a result of a reduction in frequency of fires. The paradox of fire in the Great Basin is that there are more frequent fires at the lower elevation sites where cheatgrass has invaded, and less frequent fires at the higher elevation sites where woodlands now dominate, although some instances of woodlands with cheatgrass understorey also exist.
Much of the region is public land, with Oregon having >50% public land, Idaho and Utah >60%, and Nevada >80%. During the past 40+ years there has been a multiple-use mandate for most public lands. The emphasis of land management depends on the agency involved, and the specific authorizations associated with the land (national parks, wildlife refuges, grazing permits, wilderness areas, etc.). There has been a shift in emphasis on public land from producing economic returns to seeking a balance among economic production, environmental needs, and recreational uses. Public lands are valued for the open space and recreational opportunities provided to a growing human population.
In the faster-developing portions of the Great Basin, ranches are often purchased for development into suburban housing tracts or small acreage “ranchettes”. Although the concept is not new, there has been a trend toward the purchase of agricultural water rights for either residential use or to enhance in-stream flow. If temperatures continue to increase in the region, projections suggest that future water resources could become more limiting. Less snowpack, earlier snow-melt, and higher evaporative demand could combine to limit the availability of surface water, especially during late summer and autumn.
The Great Basin will continue to provide clean air and water, diverse plant and animal populations, an array of recreational opportunities, open space, and a sustainable harvest of livestock forage. However, excessive development pressure, inappropriate land management, resource-damaging recreation, and some extractive industries will place a strain on the sustainability of the ecosystem services listed above. The need for appropriate rangeland management in the face of changes in vegetation, climate and human populations will create challenges for everyone involved.
The desert rangelands in the southwestern US, sometimes known as hot deserts, are the driest, hottest, and least productive rangelands in North America. Desert rangelands consist of three subtypes: Chihuahuan, Sonoran, and Mojave (Figure 5.1.1).
Most of the Chihuahuan Desert - the largest desert in North America covering more than 500 000 km2 - lies in Mexico, however it also extends into parts of New Mexico, Texas, and Arizona. The Sonoran Desert covers 310 000 km2 in southwestern Arizona and southeastern California. The Mojave Desert, the smallest of the three hot deserts, occupies more than 65 000 km2 in parts of California, Nevada, Arizona and Utah. These three desert rangelands share a number of common characteristics related to climate, vegetation, and land-use dynamics related to human activities, yet differ in elevation, rainfall seasonality, and plant species composition. Despite the differences among these three deserts, the goods and services provided to human populations are remarkably similar.
Current landscapes in the Desert Southwest are part of the Basin and Range Physiographic Province. Landscapes are complex mosaics of soils of highly variable age formed from diverse parent materials modified by extensive redistribution by wind and water. These complex landforms result in a mosaic of woodland, grassland, shrubland, and savanna vegetation. Grassland, shrubland, and savanna vegetation is dominant in basins and valleys. The soils are predominantly Aridisols, described previously.
Vegetation structure is similar for all three deserts: plant cover and density are low and the percentage of bare ground is high. The same plant species or genera can be found in more than one desert, although each desert is characterized by different species. Two shrub genera or species can dominate large expanses in one or more deserts. Creosote bush is important in all three deserts on coarse, rocky soils primarily on bajadas at foothills of mountains, although the species differ: Larrea divarticulata typically occurs in the Mojave, and L. tridentata dominates in the Sonoran and Chihuahuan. Honey mesquite dominates large areas of sandy soils in basins of both the Sonoran and Chihuahuan. Native perennial grasslands occur in a patchy distribution in all three deserts. In the Mojave, native grasses are C3 and C4 species whereas most native grasses are C4 species in the Sonoran and Chihuahuan (Figure 5.1.6).
Although some areas of the Sonoran and Mojave have been shrub-dominated for 10 000 to 15 000 years, grasslands occurred over parts of the Sonoran as recently as 150 years ago. Widespread expansion of native shrubs (e.g., creosote bush, mesquite) and invasion of exotic grasses (e.g., Lehmann lovegrass, Eragrostis lehmanniana; buffelgrass, Pennisetum ciliare; fountaingrass, P. setaceum; red bromegrass) have fundamentally altered biological diversity, the water, carbon and nitrogen cycles, fire regimes, and land surface-atmosphere interactions. Efforts to return these areas to a previous vegetation state often are unsuccessful or require very long time periods. Reasons for the changes in vegetative composition are varied, but include heavy grazing by domestic livestock combined with periodic drought, cessation of fire, and increase in lagomorph population density. Recent studies show high spatial and temporal variability in rate and extent of shrub increase and grass loss that depend on landscape context (i.e., spatial variation) and the key processes (i.e., climate, disturbances) driving the vegetation change.
Historically, a primary benefit provided by the hot deserts to human populations was beef production on areas used for rangeland (Figure 5.1.7). However, much of this region is public land. As human populations have increased, public land stewards have emphasized management for multiple uses as the rangeland livestock industry has become constrained. Thus, these lands now provide a greater diversity of ecosystem goods and services than previously, including cultural services (e.g., educational value), regulatory services (e.g., waste treatment), supporting services (e.g., water cycling), and provisioning services (e.g., genetic resources). For example, the proportion of the population living in rural areas has declined through time, with the largest decreases since the drought of the 1950s. Increasingly, people are moving to the Desert Southwest in search of open space for recreation and aesthetic value; thus land has been and continues to be converted from large, working ranches often of marginal value for livestock production to small, multi-use areas.
Land previously valued for livestock production is now being sold for housing development at prices that are up to 10 times greater than their value as rangeland. There also is an increasing awareness of the need for natural systems to provide high quality water in sufficient quantities to serve the increasing human population. The combination of already scarce water with human population increases has resulted in competing demands for water among agricultural users, urban users, and wildlife. The increasing urban population throughout the region will likely overwhelm agricultural water needs not only within the region, but also those from other regions.
All of the hot deserts have experienced dramatic increases in human population growth, in particular since 1950 with the development of air-conditioning technologies (i.e., evaporative coolers). A pleasant year-round climate combined with amenities designed to attract a broad range of potential interests (e.g., golf courses, wilderness areas) and inexpensive land have resulted in an influx of people to this region. Most counties in the southwest have increased in population density with the largest changes occurring in southern CA, central AZ, and southern NM-northwestern TX. Human populations continue to increase rapidly in such population centres as Phoenix/Tucson, Albuquerque, and El Paso.
Woodlands and Forested Rangelands
Piñon-juniper (P-J) [Pinus subsection Cembroides and Juniperus sp.] and Juniper woodlands are widely distributed in the Southwest, Intermountain Region, the Pacific Northwest (Oregon and Idaho), as well as in the Great Plains and Texas. Of the Western US states with P-J vegetation, New Mexico has the largest area, and Idaho the smallest. Forested rangelands can produce sufficient understorey vegetation for grazing without significantly impairing wood production and other forest values. Grazed forestland comprises ≤20% of the total area grazed in the US, about 24 M ha in the Rocky Mountains, Great Basin, Pacific Northwest, and California Coastal Range.
Soils within P-J and juniper woodland rangeland vary across the distribution of the type; often they are rocky, shallow, and low in fertility. The dominant soil orders within the region are Inceptisols and Andisols. Inceptisols are similar in their development to Aridisols, but have a more favourable soil moisture regime and a cooler temperature regime. They can form under a variety of climates and are found on relatively steep slopes. They are relatively shallow and may have rock outcrops. The parent material of Inceptisols is relatively young sediments or glacial deposits, highly calcareous or resistant to weathering. They are formed on relatively young landscapes and frequently are susceptible to erosion. Low organic matter and weak development are characteristic. Andisols are formed from volcanic ash and occur in a variety of climatic regimes, topographies, and vegetation types. Andisols form from pyroclastic deposits such as ash, pumice, cinders, and lava and have very low base status. Andisols are low in bulk density, highly porous with rapid drainage, and highly susceptible to both wind and water erosion.
During the last 150 years P-J woodland area has increased at the expense of grassland, and tree density has increased (Figure 5.1.8). Prior to the introduction of livestock onto western rangelands, P-J woodlands were commonly restricted by periodic wildfires. After the American Civil War (1861–65), livestock numbers increased substantially across the West; these heavy livestock concentrations reduced fine fuels, mostly grasses, needed to sustain and help propagate wildfires. In the early 1900s, improved fire detection and suppression reduced the number and severity of wildfires. During the settlement period after the Civil War, mining operations were extensive in many areas of the West and woodland trees were used extensively for mine timbers. In addition, trees were harvested for fuel, wood for homes, and railroad ties. Later the woodlands were re-established on many grassland areas after the trees had been harvested. After World War II, extensive areas of P-J woodlands were cleared mechanically in an effort to improve habitat for livestock and game. During the 1970s, however, high fuel prices sharply curtailed this practice. As a result, woodlands that had been cleared have been re-established. Livestock have grazed on P-J woodlands since they were introduced by early Spanish settlers. Livestock grazing in the Southwest is often continuous through the year, whereas in the Great Basin and Intermountain Region, the woodlands serve as spring and autumn seasonal ranges.
The P-J woodlands have long been valued as wildlife habitat, as more than 70 species of birds and about 50 species of mammals can be found there, but only a few species are unique to the woodlands. Of all the species, deer, elk (Cervus sp.), and turkeys receive the most attention. Fuel wood has been an important by-product of some mechanical control projects, and in some locations there is an economic competition between herbage and fuel-wood. Fuel-wood demand is especially high around large cities in the Southwest such as Phoenix and Albuquerque. Junipers are considered excellent materials for fence posts with the potential to provide over 200 million fence posts in Arizona alone. Christmas trees, solid wood, and extractive-based products such as perlite also offer possibilities for revenue from these woodlands. Native Americans have used piñon nuts as a food source for centuries. Present-day cooks have increased the demand for these nuts and nearly a million kg have been harvested during high-yield years.
Recreational uses of P-J woodlands have continued to increase as populations in the West increase. Several national parks and monuments, including Grand Canyon, Mesa Verde, and Bandelier, are located within or near the woodlands. Along with population increases, the demand for residential developments near or in the woodlands has increased, with the potential for negative effects on wilderness experiences and many animal species.
The woodlands occupy large areas in the West; hence, they are important watersheds. When these watersheds are disturbed, runoff and erosion often increase. Livestock grazing on these lands has often been challenged, because many of the P-J woodlands are public lands under the jurisdiction of the Bureau of Land Management, the Forest Service, or the various State agencies.
Forested rangelands support numerous goods and services, especially a wide diversity of recreational demands. Over much of the western forested ecosystems, precipitation comes primarily as snow; the resulting snowpack is a critical water source for agriculture, energy, and human consumption. This snowpack provides much of the surface water for the demands of the western US living at lower elevations, and may be the most important of all the ecosystem goods and services in the region. Soils have been derived from a variety of parent materials; some are old and others relatively young. Their texture and depth are critical factors influencing vegetation expression. In addition, western forested rangelands support a diversity of wildlife, including large herbivores such as elk, mule deer (Odocoileus hemionus), and moose (Alces alces), and carnivores such as cougar (Puma concolor), lynx (Lynx rufus), and wolverine (Gulo luscus).
The traditional use of forested range for livestock grazing continues in most of the provinces throughout the West. Large areas of federal land (National Forest and Bureau of Land Management) are available for grazing through permits. Much of the National Forest land is at higher elevations, with private land holdings in the valleys. This historical land ownership pattern led to the grazing pattern of summer grazing on federal lands. Grazing numbers on federal lands have remained somewhat steady over the last 20 years. Environmental concerns about the legacy of heavy grazing in parts of the West have resulted in close scrutiny of grazing management and the role of grazing in forested ranges.
In the more mesic provinces, commercial forestland uses are mixed with commercial livestock operations. Forestland grazing provides the opportunity to increase revenue from the landscape, land productivity, and the diversity of plants and animals while reducing the need for chemical or mechanical weed control. Most forested grazing occurs in the summer-autumn season in the West. Livestock grazing in forested lands requires management to minimize the impact on wood production and on riparian ecosystems where livestock can congregate. Ecosystem health on these grazed landscapes can be maintained by utilizing cattle breeds developed for mountainous terrain, and manipulating cattle behaviour through grazing management while on the forested land.
Land classification: Numerous land classification systems have been developed based on various combinations of climate, topography, soils, history, and current and potential vegetation. For long-term land use planning and management, one of the most effective types of systems uses climate and relatively static soil profile properties to stratify rangeland based on its ability to produce particular types and amounts of vegetation. The Natural Resource Conservation Service (NRCS) originally developed these site potential-based units as ‘range sites’. At the end of the twentieth century, the land use classification system employed was modified to emphasize processes and properties. The basic land classification unit is an ‘ecological site’ defined as a distinctive kind of land with specific soil and physical characteristics that differs from other kinds of land in its ability to produce distinctive kinds of vegetation and in its responses to management. Descriptions of ecological sites are readily available through the NRCS Ecological Site Information System at http://esis.sc.egov.usda.gov/ESIS/.
Conceptual models: Conceptual ‘state and transition’ models are now used in much of the US for integrating and communicating the evolving understanding of rangeland dynamics. These models are developed from existing information for each ecological site. To the extent possible, these models are based on long-term observational and experimental data, supplemented by expert knowledge of historical dynamics and both general and site-specific ecosystem processes. The level of detail in these models is far greater and involves a greater spectrum of processes than the simple models represented in the original range site descriptions of the mid-twentieth century.
A primary advantage of these models is that they facilitate the development of scenarios based on currently available knowledge. The plant communities and associated soil properties described in a model represent what is possible and therefore the range of options available to managers attempting to define the ‘desired future condition’. Another advantage of these models is that they encourage the development of management hypotheses. Implementation of a particular practice followed by monitoring provides tests of these hypotheses. An additional advantage of these models is that they are open to revision with new information. These descriptions can be improved as more is learned about a particular ecological site, either through experience or research.
Ecological process-based assessment and monitoring technologies: Strategies and methods for rangeland assessment and monitoring have changed rapidly in response to both increased understanding of ecosystem processes and thresholds, and increased ability to acquire and interpret both point-based and spatial data. Recent research has demonstrated the importance of soil and water redistribution at plant-to-landscape scales, leading to the development of vegetation pattern and other resource redistribution indicators in the US as well as in Australia. Other process-based indicators include changes in the soil profile and patterns of plant species invasions. A key challenge for the future is evaluating changes in these processes across multiple spatial scales. This requires standardization of methods across different land management units and the development of increasingly sophisticated sampling strategies.
Remote sensing imagery (including aerial photography), Geographic Information Systems (GIS), and Global Positioning Systems (GPS): High-resolution aerial photography can be used to rapidly detect general changes in vegetation composition and pattern across large areas. Indices of live vegetation generated from multi-spectral sensors on satellites and aircraft are being used to guide short-term management. These and other sensors have the capacity to detect seasonal and inter-annual changes in bare ground. Earlier limitations to the application of these data are being overcome through image analysis automation, integration of land classification information using GIS, and careful calibration using geo-located ground sampling points. High costs and training requirements, along with limited discernment of some specific soil and vegetation attributes limits applications of remote sensing in many rangelands.
Conservation of Western US Rangelands in the Twentyfirst Century
Though conservation practices applied to rangeland have changed very little over the past 60 years, the expectations of land owners and society about the services and products derived from rangelands have changed dramatically. The characteristically low, variable production of rangelands has greatly limited the opportunities for development and deployment of new technologies as the basis for conservation practices. Even though range management emphasis has shifted from food and fibre production to a more multiple-use approach, traditional management practices are largely unchanged. Additionally, the widespread distribution of invasive plant species has forced scientists and managers to view rangeland ecosystem dynamics and management responses very differently.
Relatively cheap fossil fuels heavily influenced economic analyses that justified both federal government-funded cost-share programs on private land and conservation initiatives on public land. As energy prices have climbed steadily, the benefits derived from the application of practices have failed to keep pace with the costs. In addition to the changing economics of energy-intensive conservation practices such as mechanical and chemical vegetation manipulation, fencing and water development (ponds and wells), the emergence of a new concept of rangeland ecosystem behaviour has dramatically altered our views of costs and benefits associated with conservation practice application. As a non-equilibrium view of plant community dynamics has gained favour, the probability of effecting change in a community or landscape where ecological processes have changed drastically is reduced greatly. Reversing changes in soils and vegetation that have occurred over decades and are being driven by global, continental and regional scale processes with one-time intensive application of expensive technologies is increasingly viewed as a risky investment by both private and public sector land managers. Although the same conservation practices are used, they are increasingly deployed in a more holistic context that integrates expanded spatial and temporal scales.
Without doubt, the most influential conservation practice applied to rangelands in the past half century is the large scale conversion of land marginal for tilled crop production to perennial vegetation cover in conservation programs such as the Conservation Reserve Program (CRP). Of the total 14.5 M ha enrolled in CRP in 1985–2007, about 10 M ha are located in the 17 western states, primarily in the Great Plains regions. In many counties, more than one-third of the existing cropland has been converted to perennial grass cover. In addition to the expected benefits of reducing wind and water erosion, substantial increases in wildlife habitat benefited numerous grassland birds and other wildlife species. In conjunction with a host of other land retirement and conservation easement programs, many conservation benefits have accrued to both individuals and the public.
The vast majority of rangeland with native or semi-natural cover in the seventeen western states, whether public or private, is still used as the primary source of forage for commercial livestock operations. Although the emphasis has shifted to other ecosystem services in many public, and some private rangelands, those uses are typically viewed as compatible with existing livestock operations. The fundamental principle of grazing management remains proper stocking rate. Grazing management research and extension organizations have focused on gaining and transferring an improved understanding of the effects of stocking rate and climatic variability on rangeland ecosystem properties, particularly vegetation dynamics. In the 1970s, the adoption of controlled stocking schemes, particularly those with multiple pastures and short grazing periods, was fuelled by claims of an ability to increase carrying capacity and stocking rate by improving harvest efficiency and timing rest periods. However, little experimental or observational evidence has been found to supplant moderate stocking rate as the most influential conservation practice on rangelands used for livestock grazing.
The distribution of disturbance, whether as a result of activities such as livestock grazing, recreation, or fuel harvest remained an important focus for the application of conservation practices. Realization of the importance of riparian areas to wildlife values, water quality, and recreation shifted the emphasis to implementation of existing (fencing, herding) and developing (behaviour modification) technologies to control free-ranging grazers. Benefits from improved riparian management were typically rapid and impressive due to the availability of water and nutrients from the surrounding landscapes. Improved water development as a means of controlling livestock and other grazer distribution continues to be an important tool for rangeland management. However, the effectiveness has become limited as fewer economically viable sites remain to be improved.
Increase of both native and exotic brush species emerged as a significant threat to ecosystem integrity and multiple rangeland ecosystem services in the last half of the twentieth century. The research and development focus of the late 1940s through 1960s was based primarily on new chemical and mechanical technologies. However, widespread application of chemical and mechanical techniques to modify range vegetation on both public and private land produced mixed results, mostly due to the variability in land, operators, and climate. Both chemical and mechanical brush control remain viable technologies for managing undesirable vegetation on rangelands. However, the inconsistent response, increasing costs and awareness of unintended environmental consequences have greatly limited the expansion of these technologies. Conversely, an age-old technology, fire, has resurfaced as a viable alternative for vegetation management. Decades of fire suppression in many rangelands and forestlands allowed fuel to accumulate to unsafe levels and catastrophic wildfires became a common occurrence throughout the 1990s. Prescribed burning to reduce fuel loads in particular and vegetation management in general has become a much more widespread and acceptable practice. However, public perceptions and air quality considerations represent a formidable constraint to increased use. Research in the near-term must expand beyond merely the effects of fire on ecosystems to include reducing the unintended environmental impacts.
The potential of conservation science to contribute to the management of rangeland ecosystems is very promising. As new demands form and new markets are created, rangeland management and the implementation of conservation practices can find new outlets as well as new incentives. However, the ability to realize this potential will depend almost exclusively on the ability of scientists to develop new concepts and technologies for prediction and measurement, the ability and willingness of rangeland managers to implement practices and pursue new objectives, and the willingness of policy makers to provide incentives for creativity and risk-taking that will best serve society.
The emphasis on using rangelands to address national energy security concerns also represents a threat to the conservation of US rangelands. Along with a much more intensive use of landscapes associated with fossil fuel-based energy exploration and extraction, new technologies (solar, wind) will compete for and affect rangeland resources. In particular, the infrastructure supporting energy production, whether traditional or green, on rangeland has affected and will continue to alter ecological processes and require new conservation systems (combinations of practices) to avoid degradation. Road networks and resource extraction infrastructure such as well-pads (areas surrounding an oil or gas well that have been cleared of all vegetation) influence the movement of matter and energy across range landscapes and have been shown to alter soil:vegetation relationships. Continued expansion of energy extracting technologies on rangelands brings new risks and challenges to range managers and policy makers. Future research will need to focus on new and innovative solutions to the problems created by the energy industry to avoid large-scale degradation of rangeland resources.
Climate change will add an additional complex factor to future rangeland decision-making processes. In addition to increased demand for ecosystem services from rangelands, a changing climate will complicate land management decision-making and implementation. Climatic variability has always played a role in long-term range management. The impact of periodic droughts on range production and vegetative composition has been well documented. Global warming is predicted to bring a new level of climatic variation to US rangelands. This additional climatic variability will require range managers to develop long term plans that will take into account how changing temperatures and atmospheric carbon dioxide levels may affect rangeland ecosystems. New opportunities and potential pitfalls will be created. Research continues on conservation systems and management practices that will be best suited to a changing climate.
Given the changes in fundamental economic, ecological, and social processes faced by rangeland managers, the potential of conservation science to contribute to the management of rangeland ecosystems is not just promising, but absolutely necessary. As new demands form and new markets for rangeland-based goods and services are created, rangeland management and the implementation of conservation practices can find new outlets as well as new incentives. However, the ability to realize this potential will depend almost exclusively on the ability of scientists to develop new concepts and technologies for prediction and measurement, on the ability and willingness of rangeland managers to implement practices and pursue new objectives, and on the willingness of policy makers to provide incentives for creativity and risk-taking that will best serve society.
Summary. Rangeland is a grassland found predominantly in arid and semi-arid regions, on which the indigenous vegetation, climax or sub-climax, is mostly grasses, grass-like plants, forbs or shrubs that are grazed or have the potential to be grazed, and which is used as a natural ecosystem for the production of grazing livestock and wildlife. In recent decades, US rangelands are managed for multiple uses, which include livestock production, mining, timber production, wildlife management, and recreation. The major regions of the western continental US, the focal point of US rangelands, are described in this section on Native Grasslands. Characteristic features have been described for each region and type (Northern and Southern Great Plains, California Annual Grasslands, Great Basin, Desert Southwest, Woodlands and Forested Rangelands), including climate, soils and vegetation, goods and services, and key aspects envisioned for the future. Emerging technologies seen as keys to sustainable management of this land under current and future conditions, such as land classification systems, the development of conceptual models, the use of remote sensing imagery, Global Information Systems and Global Positioning Systems are described. Important conservation practices for future application and amplification are highlighted, and the potential of science to contribute to the management of rangelands in addressing issues of future uses and national energy security is stressed.
Authors: Edward B. Rayburn, Steven Washburn, David B. Hannaway, Henry A. Fribourg, Yoana C. Newman, and Glen K. Fukumoto
Eastern Humid Region Landscape
Adapted forage species and cultivars, and their productivity and general management requirements, depend on the climate and soils of each local area (see Section 2: Topography and Soils, and Section 3: Climate, for greater detail on the influence of these factors on US grasslands). The main factors that affect these in the US humid region are latitude, elevation, geology and age, and longitude as modified by proximity to the Great Lakes, the Atlantic Ocean, or the Gulf of Mexico. In the northern latitudes, summers are relatively cool with short hot periods and winters are cold. Soils were developed from glacial till and outwash, old glacial lakebed or marine deposits, and recent alluvial sediments. In the southern latitudes, summers are longer and hot but winters are relatively warm. Soils developed from rock residuals, and colluvial and alluvial sediments. At any latitude, temperatures typically decrease with increasing elevation. Late spring and early autumn frosts are affected by position within the landscape, with deep valleys receiving cold air drainage from surrounding hills and becoming frost pockets.
The eastern humid region in the conterminous US extends from about 25o to 49o N latitude and from 66o to 99o W longitude. Mean temperatures range from -18o to 21o C in January and from 18o to 28oC in July (see Figures 3.1B and 3.1C). Annual precipitation ranges from about 500 to over 2 100 mm (see Figure 3.1A). Even though the entire region is considered humid, precipitation is highly variable and may vary up to 50% within 80–160 km at certain times of the year, due to site locations relative to the Allegheny Plateau, the Great Lakes, and the Gulf of Mexico, and with the paths of prevailing winds in each season. On the western side of the Allegheny Plateau, precipitation increases as elevation increases. There is less precipitation on the eastern side of the Allegheny Front (the eastern escarpment where the Allegheny Plateau meets the Ridge and Valley region of the Allegheny Mountains) because of the rain shadow effect from the Plateau. Areas near to and west of the Great Lakes, or north of the Gulf of Mexico, tend to have higher precipitation than on the eastern side of the Allegheny Front. Due to the effect of elevation on precipitation and temperature, high elevation areas have deeper snow accumulation and longer periods of snow cover than low elevations. In addition, evapotranspiration increases from the Atlantic Ocean to the Mississippi River areas, and from the north toward the Gulf of Mexico.
Pasture-based livestock producers need to have management practices that reduce production and economic risks, especially in view of probable inconsistent precipitation patterns. These practices include moderate stocking rates, adequate supplies of stored forage, and occasional irrigation in specific localities.
The geological provinces of the eastern humid region, extending west from the Atlantic Ocean, include the Coastal Plain; the Piedmont; the Appalachian Province, consisting of the Blue Ridge Mountains, the Great Valley and Ridge region, and the Appalachian Mountains; and the stable interior, made up of the Allegheny and Cumberland Plateaus, and the central lowlands (Roberts, 1996) (Figure 5.2.1).
From the Gulf of Mexico north, they include the Coastal Plain; the Piedmont; the Ouachita Mountains, an extension of the Appalachian Ridge and Valley region; the Ozark Plateau, a part of the central lowlands in Arkansas and Missouri; and intruding onto the Interior Plains, the delta of the Mississippi River, forming a triangle with its apex near Cairo, IL, and a base of about 200 km at the Gulf of Mexico.
The Coastal Plain extends from New Jersey south to Georgia and Florida, then west into Texas, lying between either the Atlantic Ocean or the Gulf of Mexico, and the Piedmont, meeting the Piedmont along a line called the ‘fall line’. Here the hard metamorphic rocks of the Piedmont are more resistant to erosion than the soft sedimentary rocks of the Coastal Plain; thus, waterfalls and river rapids occur on the rivers as they descend from the Piedmont onto the Coastal Plain. Major urban areas developed along the fall line, which marked the upper end of flat-water river transportation from the interior to coastal markets and provided water power for early industrial development. The Coastal Plain soils vary considerably in texture, depending upon whether they originated from either shallow or deep water, from wind deposits (loess), from unconsolidated sediments, or from one of several sedimentary rocks, such as limestone or shale. Parent material laid down in deep still water resulted in fine clayey soils. Soils derived from windblown sand dune parent material resulted in deep sandy soils, whereas loess from glacial lacustrine deposits is mostly silty. The better silty-clay loam, silt loam, and sandy loam soils in the Coastal Plains are used as croplands. The drier, wetter, heavier or more drought-prone soils are used for pasture, hay, or forest production (Figure 5.2.2). Many of the sandy soils are too droughty for forage production and are covered with pine (Pinus sp.) forests, especially in the southern part of the Coastal Plain.
The Piedmont lies between the Coastal Plain and the Blue Ridge Mountains, extending from Pennsylvania south to Georgia and west into Alabama. The Piedmont soils are derived from metamorphic rocks and can be deep, sometimes clayey. They are well adapted to grow cultivated crops, pasture and hay (Figures 5.2.3 and 5.2.4); some have high natural fertility but most need fertility amendments (Helms, 2000).
The Blue Ridge Mountains and the Northern Highlands extend from Maine to Georgia and Alabama. Due to their mountainous landscape, agriculture is limited largely to pasture, hay and forestry on the slopes (Figures 5.2.5, 5.2.6, 5.2.7). The flat river bottoms often are used for alfalfa (Medicago sativa), hay, and annual crops such as corn (Zea mays) for grain or silage. Shallow rocky soils on slopes and river bottom soils unsuited to tillage are used for pasture.
The Great Appalachian Valley spreads from the Champlain Valley in New York and Vermont south through the Shenandoah Valley (Great Valley) in Virginia (Figure 5.2.8) and on south to the Tennessee Valley in Tennessee and Alabama (Figure 5.2.9). This valley system has many soils derived from limestone in karst topography interspersed with soils derived from shales and sandstones. The landscapes within the valley systems range from level to rolling and include small hills.
To the west of the Great Valley lie the folded Ridge and Valley Appalachian Mountains. These relatively steep mountains (over 1 800 m) often are used for pasture or forest production where they have not been included within extensive national and regional parks and preserves. Ridge tops may be used for tree fruit production, such as apples. Large valley bottoms contain pastures, meadows, and tilled annual crops (Figure 5.2.10).
The Allegheny Front extends from Pennsylvania to West Virginia, followed to the south by the Cumberland Escarpment. These escarpments mark the end of the Ridge and Valley Appalachian Mountains to the east and the beginning of the Allegheny and Cumberland Plateaus to the west.
The landscape of these plateaus is typified by hilltops of fairly uniform elevation, and rolling land with deep valleys cut by creeks and rivers (Figure 5.2.11). In the northern Allegheny Plateau the deep valleys were filled in by glaciers, leaving less deep broad valleys covered by soils derived from glacial outwash, till and recent alluvial deposits. These plateaus are the beginning of the large Stable Interior region of the eastern United States.
The Ozark Plateau also is part of the Stable Interior region and lies north of the Ouachita and Boston Mountains in Arkansas (Figures 5.2.12 and 5.2.13). The Stable Interior is an extensive area comprising much of the heartland of the US, including valuable cropland interspersed with pastureland (Figure 5.2.14).
The northern part of the area, south to about the latitude of the Ohio River, was mostly glaciated (Figure 5.2.15) while native prairies, a very few of which still exist, are found to the west (Figure 5.2.16).
The Mississippi River Delta, which extends from southern Illinois to the Gulf of Mexico, has few grazinglands, and is devoted primarily to annual cash crops, such as cotton (Gossypium sp.), rice (Oryza sativa), and soybean (Glycine max).
Western Humid Region Landscape (Pacific Northwest and Alaska)
The Pacific Northwest (PNW) is a region in northwestern North America, bounded by the Pacific Ocean to the west and the Rocky Mountains on the east. A common concept of the PNW includes the US states of Oregon and Washington and the Canadian province of British Columbia (Coates, 2002; http://en.wikipedia.org/wiki/Pacific_Northwest#Climate ). Definitions based on the historic Oregon Country reach east to the Continental Divide, thus including nearly all of Idaho and part of western Montana (Fig. 5.2.17; http://upload.wikimedia.org/wikipedia/commons/3/35/PacNWComparison.PNG ).
The PNW is a diverse geographic region, dominated by several mountain ranges, including the Coast Mountains, the Cascade Range, the Olympic Mountains, the Columbia Mountains, and the Rocky Mountains. The highest peak in the PNW is Mount Rainier, in the Washington Cascades, at 4 392 m. Immediately inland from the Cascade Range there is a broad plateau, narrowing progressively northwards, only a few miles wide in Canada, and also higher in elevation. In the US, this semi-arid and often entirely arid region is known as the Columbia Plateau, while in British Columbia it is the Interior Plateau, also called the Fraser Plateau. The Columbia Plateau, including the Snake River Plain, was the scene of massive ice-age floods; as a consequence there are many coulees, canyons, and plateaus. Much of the Plateau, especially in eastern Washington, is irrigated farmland. The Columbia River cuts a deep and wide gorge around the rim of the Columbia Plateau and through the Cascade Range on its way to the Pacific Ocean. More water flows through the Columbia than in any other river in the lower 48 states, except for the Mississippi River.
The humid portions of the PNW are west of the Cascade Range (Figure 5.2.18). Due to the proximity of the range to the Pacific Ocean and the prevailing westerly winds, precipitation is substantial (http://en.wikipedia.org/wiki/Cascade_Range) (see Figure 3.1A). In general, the entire region has dry summers and wet winters.
Climate extremes result from large differences in latitude and elevation. Mountain ranges are parallel to the coast and include valleys of different sizes and elevations. Hay and pasture are produced from sea level to over 1 800 m. Growing seasons vary from a couple of months at high elevations to nearly the entire year at low elevations near sea level. Precipitation decreases and temperature increases from Washington to California along the coast, and from the coast toward the east where the Cascade Range of Washington and Oregon captures most of the rainfall. Annual rainfall extremes range from over 4 500 mm in the mountainous areas of Oregon to 200–500 mm in interior valleys (http://www.prism.oregonstate.edu/state_products/index.phtml?id=OR).
Soil conditions including depth, texture, infiltration rate, drainage, and pH, influence land use and choice of species for forage production. Irrigated pastures generally are confined to heavy-textured, shallow soils with imperfect internal or external drainage, or rocky alluvial fans in mountain valleys with adequate irrigation water sources nearby. Cultivated forages such as alfalfa, oat, sudangrass, and silages, occupy the more productive croplands, all in competition with cash cropping systems (Marble et al., 1985). Similar forage-livestock systems are found from British Columbia, Canada to northern California and from the coastal zone to the Cascade Mountains. East of the Cascade Range, native rangeland and irrigated forage systems are found.
Geographic description and land ownership.
Alaska is situated in the northwest extremity of the North American continent, with Canada to the east, the Arctic Ocean to the north, the Pacific Ocean to the west and south, and Russia farther west across the Bering Strait (Figure 5.2.19; http://en.wikipedia.org/wiki/File:Map_of_USA_AK_full.svg).With a land area of 1 518 800 km2, Alaska is the largest state in the US. It is over twice the size of Texas, the next largest state (Figure 5.2.20; http://en.wikipedia.org/wiki/File:Alaska_area_compared_to_conterminous_US.svg).
Approximately 65% of Alaska is owned and managed by the US federal government as public lands, including numerous national forests, national parks, and national wildlife refuges. Of these, the Bureau of Land Management manages 350 000 km2, or 23.8% of the state. The Arctic National Wildlife Refuge is managed by the US Fish and Wildlife Service; it is the world's largest wildlife refuge, comprising 65 000 km2.
Of the remaining land area, the state of Alaska owns 410 000 km2, its entitlement under the Alaska Statehood Act. The University of Alaska, as a land grant university, also owns substantial areas which it manages independently.
Another 180 000 km2 are owned by 12 regional, and scores of local, Native corporations created under the Alaska Native Claims Settlement Act (ANCSA). Effectively, the corporations hold title (including subsurface title in many cases, a privilege denied to individual Alaskans) but cannot sell the land. Individual Native-American allotments, however, can be sold on the open market.
Various private interests own the remaining land, totalling about 1 % of the state. Alaska is, by a large margin, the state with the smallest percentage of private land ownership when Native corporation holdings are excluded (material in this section edited from http://en.wikipedia.org/wiki/Alaska).
Climate and geographic features.
Climate Zones. The geographical features of Alaska have a profound influence on its climate, which falls into five major zones (Figure 3.1E). The climate zones are: (1) a maritime zone which includes southeastern Alaska, the south coast, and southwestern islands; (2) a maritime continental zone which includes the western portions of Bristol Bay and west-central zones. In this zone the summer temperatures are moderated by the open waters of the Bering Sea, but winter temperatures are more continental in nature due to the presence of sea ice during the coldest months of the year; (3) a transition zone between the maritime and continental zones in the southern portion of the Copper River, the Cook Inlet, and the northern extremes of the south coast;(4) a continental zone made up of the remainders of the Copper River and west-central divisions, and the interior basin; and (5) an arctic zone.
Precipitation. In the maritime zone a coastal mountain range coupled with plentiful moisture produces annual precipitation amounts up to 5 000 mm in the southeastern panhandle, and up to 3 800 mm along the northern coast of the Gulf of Alaska. Amounts decrease to near 1 500 mm on the southern side of the Alaska Range in the Alaska Peninsula and Aleutian Island sections. Precipitation amounts decrease rapidly to the north, with an average of 300 mm in the continental zone and less than 150 mm in the arctic region.
Snowfall makes up a large portion of the total annual precipitation. For example, Yakutat averages 5 500 mm of snow annually and has a total annual precipitation (rain plus water equivalent of snow) of about 3 300 mm. Along the arctic slope, Barrow receives an average of 740 mm of snow annually and a total annual precipitation of slightly more than 100 mm. Total snow depths on the ground are controlled by the temperature of an area. Most of the areas of heavy snow have relatively mild temperatures which prevent total depths from becoming excessive. Present-day snow removal equipment is able to keep highways and airports operational.
Temperature. Mean annual temperatures in Alaska range from about 5 degrees under the maritime influence in the south to 12 degrees along the Arctic Slope north of the Brooks Mountain Range. The greatest seasonal temperature contrast between seasons is found in the central and eastern portion of the continental interior. In this area summer heating produces average maximum temperatures of 20 to 25 degrees with extreme readings of about 30 to 35 degrees. The highest recorded temperature for the state is 38 degrees at Fort Yukon in June 1915. In winter the lack of sunshine lowers temperatures to –45 degrees and occasionally colder for two or three weeks at a time. Average winter minimums in this area are –28 to –34 degrees. The coldest temperature ever recorded in Alaska was –62 degrees at Prospect Creek on January 23, 1971.
Elsewhere in the state, temperature contrasts are much more moderate. In the maritime zone the summer to winter range of average temperatures is from about 15 to –5 degrees. In the transition zone, temperatures range from about 15 to –18 degrees; in the maritime-continental zones the range is from about 15 to –23 degrees. The arctic slopes have a range extending from about 7 to –29 degrees.
Winter temperatures play a principal role in the flow of most of Alaska’s rivers. Beginning in late October and extending into May, thick layers of ice form. Several rivers cease to flow during the coldest months. In many areas construction work and oil exploration is done in winter because both the ground and the streams are frozen hard enough for the use of the heaviest of equipment.
Wind. A normal storm track along the Aleutian Island chain, the Alaska Peninsula, and all of the coastal area of the Gulf of Alaska exposes these parts of the state to the majority of storms crossing the North Pacific, resulting in a variety of wind problems. Direct exposure results in the frequent occurrence of winds in excess of 80 km/h during all but the summer months. Shemya, on the western end of the Aleutian Islands chain, has experienced winds in excess of 200 km/h. Wind velocities approaching 160 km/h are associated with mountainous terrain and narrow passes.
An occasional storm will either develop in or move into the Bering Sea then move north or northeastward, creating strong winds along the western coastal area. Because of the low flat ground in many places along the coast, these winds will cause flooding during the time the winds are blowing onshore. Winter storms moving eastward across the southern Arctic Ocean cause winds of 80 km/h or higher along the arctic coast. Except for local strong wind conditions, winds are generally light in the interior sections (this section edited from http://www.wrcc.dri.edu/narratives/ALASKA.htm).
Ecosystems and species diversity.
The 1 518 807 km2 area and the 54 718 km of tidal shoreline of Alaska, as well as its 3 million lakes, countless rivers, and multiple mountain ranges form a rich mosaic of landscapes with 32 different “ecoregions” (Figure 5.2.21; http://www.hort.purdue.edu/newcrop/cropmap/alaska/maps/AKeco3.html; ftp://ftp.epa.gov/wed/ecoregions/ak/Gallant_p1567pt01_front.pdf). These serve as year-round or seasonal havens for fish and wildlife. Many of these habitats are found nowhere else in the US and some occur very few other places in the world (http://www.adfg.alaska.gov/index.cfm?adfg=ecosystems.list).
Over 1 000 vertebrate species are found in the state, sometimes in huge numbers. More than 900 000 caribou (= reindeer, Rangifer tarandus) roam in 32 herds across vast tundra landscapes. On the Copper River Delta alone, five to eight million shore birds stop to forage and rest each spring on their way to arctic breeding grounds. Alaska has 32 species of carnivores, more than any other state.
Most of Alaska’s fish and wildlife populations are considered healthy. In the rest of the nation, more than 400 species are listed as threatened or endangered. In Alaska, only 20 species are listed this way (except as noted, other paragraphs in this section edited from http://www.adfg.alaska.gov/index.cfm?adfg=species.main).
Forages and other crops, livestock, and wildlife.
Due to the northern climate and steep terrain, relatively little farming occurs in Alaska; although Alaska is the largest state (nearly 148 million ha), fewer than 405 000 ha are farmed. Most farms are in either the Matanuska-Susitna Valley (Figure 5.2.22; http://en.wikipedia.org/wiki/File:Matanuska-Susitna_Valley.jpg ), about 64 km northeast of Anchorage, or on the Kenai Peninsula, about 97 km southwest of Anchorage.
The short 100-day growing season limits the crops that can be grown, but the long sunny summer days allow productive growing seasons. The primary crops are potatoes, carrots, lettuce, and cabbage.
The Delta Junction area, about 160 km southeast of Fairbanks, also has a sizable concentration of farms, which mostly lie north and east of Fort Greely. This area was largely set aside and developed under a state program spearheaded by Hammond during his second term (1978–1982) as governor. Delta-area crops consist predominantly of barley and hay. Barley was planted on about 1 660 ha in 2008, with production for grain at about 2 695 000 kg. The largest areas are devoted to grass crops for hay, silage, and pasture. Hay is planted on the largest agricultural land area, 7 284 ha.
Rangelands are widespread in the Alaska mainland. Herds of wild caribou forage on portions of these lands, consist of hundreds of thousands of animals, and are an important source of protein in many Alaska villages. Cattle and sheep are raised in areas of the Kenai Peninsula, the Alaska Peninsula, and the Aleutian Islands, and small herds of reindeer are raised on the tundra lands of the Seward Peninsula (http://www.wrcc.dri.edu/narratives/ALASKA.htm).
Hunting for subsistence, primarily caribou, moose, and Dall sheep, is still common in the state, particularly in remote communities in the bush. An example of a traditional native food is Akutaq, the “Eskimo ice cream,” which typically consists of reindeer fat, seal oil, dried fish meat, and local berries. Alaska's reindeer herding is concentrated on the Seward Peninsula where wild caribou can be prevented from mingling and migrating with the domesticated reindeer.
Greenhouse and nursery crops are the fastest-growing segment of Alaska’s agricultural industry. Also, in 2007, Alaska accounted for over 62% of the volume of the commercial seafood harvested in the United States.
Land Grant University.
The Alaska Agricultural and Forestry Experiment Station (AFES) was established in 1898 in Sitka, Alaska, also the site of the first agricultural experimental farm in what was then Alaska Territory. Today the station is administered by the University of Alaska Fairbanks through the School of Natural Resources and Agricultural Sciences. Facilities and programs include the Fairbanks Experiment Farm (est. 1906), the Georgeson Botanical Garden, the Palmer Research and Extension Center, the Matanuska Experiment Farm, and the Reindeer Research Program.
Research at the AFES has concentrated on introducing vegetable cultivars appropriate to Alaska and developing adapted cultivars of grains, grasses, potatoes, and berries (for example, strawberries and raspberries). Animal management was important in early research, with studies on sheep, yaks (Bos grunniens), cattle, dairy cows, poultry, and swine. Modern animal husbandry study at AFES is focused on reindeer and muskox (Ovibos moschatus), with some research on fisheries. Other research is on soils (cryosols and carbon cycling studies, for example) and climate change, re-vegetation, forest ecology and management, and rural and economic development, including energy and biomass research (except as noted with other references, above paragraphs edited from http://en.wikipedia.org/wiki/Alaska and http://www.agclassroom.org/kids/stats/alaska.pdf).
Forage species and cultivar selection.
Perennial plants in Alaska are exposed to a variety of stresses during the winter: low temperatures, fluctuating temperatures, desiccation, long dormant period, ice sheets, and disease. If these plants are to survive, they must store an adequate amount of reserves, develop internal cold hardiness, and become dormant. Adapted plants use signals from daylength and ambient temperature to initiate winter preparations. The ability to recognize the daylength signal is related to the latitude of origin for a variety. Northern adapted varieties generally begin to make the necessary changes earlier than varieties from lower latitudes. In addition to the above physiological adjustments for winter, plant morphology and snow cover can be important factors in plant survival. When perennial plant parts are protected by the soil and snow, survival is enhanced. The general recommendation with regard to limiting winter-kill losses is to avoid importing plants from lower latitudes (Panciera, 2010).
More specific information related to characteristics and site adaptation of forage grasses and legumes is found in Jahns and Quarberg (2009). Grasses recommended for various sites include alpine (Poa alpina), glaucous (P. glauca) and Kentucky bluegrass, smooth bromegrass, reed canarygrass, hard and red fescues, creeping (Alopecurus arundinaceus) and meadow foxtails (A. pratensis), Bering (Deschampsia beringensis) and tufted hairgrass (D. cespitosa), polargrass (Arctagrostis arundinacea), bluejoint reedgrass (Calamogrostis canadensis), American sloughgrass (Beckmannia syzigachne), timothy, beach wildrye (Elymus mollis), and Siberian wildrye (Elymus sibiricus). Suitable forage legumes listed include alfalfa, alsike, red, sweet, and white clovers. Recommended cultivars are provided as well as qualitative information on yield potential, winter hardiness, and longevity.
Klebesadel (1994) compared four traditional forage grasses with five species native to Alaska. Traditional forage grasses included ‘Polar’ hybrid bromegrass (predominantly Bromus inermis x B. pumpellianus), ‘Engmo’ timothy (Phleum pratense), ‘Garrison’ creeping foxtail, and a non-cultivar, commercial meadow foxtail. Native Alaskan species were Siberian wildrye, slender wheatgrass (Agropyron trachycaulum), arctic wheatgrass (A. sericeum), bluejoint, and polargrass. Grasses were compared for responses to management variables that included different frequencies and schedules of forage harvests and the effects of five different rates of nitrogen fertilization on yield and quality of forage. All experiments were conducted at the University of Alaska’s Matanuska Research Farm (61.6 oN) near Palmer in south central Alaska. Results showed that the least winterhardy of the nine grasses were Engmo timothy and meadow foxtail. The other two cultivated grasses, Garrison creeping foxtail and Polar bromegrass, were much more winterhardy. The native grasses showed no evidence of winter injury in any of the experiments. Total annual forage dry-matter yields of all grasses generally were highest with two cuttings per year and became progressively less as the number of cuttings per year increased. Yields of digestible dry matter of all grasses were increased with increasing rates of applied N up to 242 kg/ha. The increases generally were due to the combined effect of higher forage yields and enhanced digestibility with increasing rates of N. Native polargrass was generally highest in yield of digestible dry matter at all N rates; at the highest N rates bluejoint was second to polargrass and surpassed other grasses.
Tropical Climate Regions Landscape
Climatic zones of the conterminous US are shown in Figure 3.1D. Tropical climates are found in the southernmost portion of Florida, in Hawaii, and in Puerto Rico, an unincorporated territory associated with the US. In the Köppen climate classification, tropical climate is a non-arid climate in which all 12 months have mean temperatures above 18 °C (64°F) (Fig. 5.2.23; http://en.wikipedia.org/wiki/Tropical_climate).
In the conterminous US, tropical forage production is limited to the southernmost region of Florida where growing conditions are frost-free. Florida has a mainly subtropical climate. However, most areas below latitude 27º experience very late frost and are suitable for production of tropical forages from May (spring) to October (late fall) (Orlando, FL is located approximately in the centre of the state at 28°25'N 81°19'W). Land in these tropical areas is devoted almost exclusively to beef cattle production supporting the cow-calf industry in the state, which contributes to the supply of calves utilized by feedlots in the Central Plains.
A few tropical forages can be grown in south Florida where pasture production is dominated by stoloniferous grasses with creeping growth habits. These include bahiagrass (Paspalum notatum) (Figure 5.2.24), digitgrass (Digitaria sp.), stargrass (Cynodon nlemfuensis), hybrid bermudagrasses (Cynodon sp.), limpograss (Hemarthria altissima) (Figure 5.2.25), Rhodes grass (Chloris gayana), to a lesser extent St. Augustine (Stenotaphrum secundatum) grown on the organic soils of the Everglades, and the brachiaria group represented by paragrass (Brachiaria mutica). Although paragrass exists in extensive areas in south Florida, it is considered invasive and not recommended for new plantings.
Bahiagrass is originally from South America in latitudes similar to portions of Florida and is well suited to the infertile soils of the Peninsula. It is popular in Florida because of its tolerance of low soil fertility and its low input requirements. Bahiagrass can be established by seed, an easy dissemination procedure in contrast to the labour- and machine-intensive vegetative propagation required by most improved hybrid bermudagrasses and limpograss. Bahiagrass is used primarily for pasture and hay production. It has moderate production and acceptable animal performance. Whereas dry matter production is lower than that of other species, this grass has the advantage of tolerating poor soil conditions and severe defoliation. Most of the production occurs during summer, and while most producers use it for pasture, some harvest it for hay. Additional uses include seed production and sod to supply the turf industry in Florida.
Bermudagrasses and stargrass are more productive than bahiagrass but have relatively high soil fertility and management requirements. Many producers favour stargrass when high yields and good nutritive value are required.
Hawaii is the most unique and environmentally diverse region of the US. The Hawaiian Islands are located in the middle of the North Pacific Ocean, more than 2 400 miles away from the nearest continental land mass (Figure 5.2.26). The geo-spatial location in the tropics, between 18º and 22 ºN latitudes, the buffering complex of the large ocean surrounding the islands, and the prevailing northeasterly trade winds drive the mild and stable weather conditions. The land area of the seven human-inhabited islands totals 16 510 km2, with the island of Hawaii accounting for nearly two-thirds of the total. The island of Hawaii continues to grow in land area due to active lava flows from the Kilauea volcano; more than 91 ha of new land have been added to the island since 1983.
Important climatic and environmental features
There are no extreme weather variations in the Hawaiian Islands that would typify the 4-season annual cycle. Temperature, humidity, solar radiation, and rainfall are relatively stable over the ocean waters that surround the islands. However, variations of the landscape throughout the islands create diverse microclimates which influence temperature, rainfall and soil types within very short distances.
Elevation, landscape features, and land orientation significantly affect the weather patterns and climate in Hawaii. In general, the windward (eastern) sides of the islands receive higher rainfall than the leeward (western) sides, as the warm and moisture-laden ocean air currents rise over the coast and upland slopes, causing precipitation; the leeward sides receive less moist air. Most of the moisture that encounters the islands with taller and massive mountains is dissipated on the windward side, resulting in an arid leeward environment (Figure 5.2.27).
The landscape features of each island are unique, due to the effects of geologic time and the spatial location within the island archipelago. The islands are progressively older from the southeast end of the island chain toward the northwest. The youngest, Hawaii, encompasses 11 climatic zones, from tropical conditions in the lowland, to humid forests, to sub-arctic extremes at the summit of Mauna Kea, 4 194 m above sea level. There are 551 separate watersheds and 144 different soil types in the state of Hawaii.
Rainfall distribution patterns differ drastically from watershed to watershed within very short elevation gradients. For example, Mount Wai’ale’ale on the island of Kauai is known as the wettest spot on earth, with an average annual precipitation of 1 168 cm and a record annual of 1 692 cm. However, within a distance of 21 km to the west, annual rainfall averages only 25 cm per year at sea level (Juvik and Juvik, 1998).
Forages and other crops
The environmental diversity of Hawaii has a large impact on the growing period of plant and animal species. Prime agricultural lands have been developed in the relatively level coastal lands and the low alluvial plains near the coastal perimeters of the islands, allowing nearly year-round cropping. To expand their operations, large-scale sugarcane and pineapple enterprises in the dry leeward regions of the islands have developed sophisticated irrigation infrastructures. Pasturelands and rangelands with extensive grazing management were developed in the upslope regions. No irrigation, other than stock water infrastructure, was installed in these regions. The growing periods in these areas are short due to the higher elevation and the poorer soil conditions. However, since the downsizing of both the sugar and pineapple industries within the past decade, the prime agricultural lands formerly devoted to these crops have become available for pastoral operations. There are currently about 400 000 ha of grazinglands in Hawaii. Forage and range types are listed in Table 126.96.36.199.
1 The vegetative zones of Hawaii have been described by Ripperton and Hosaka (1942) as follows:
Zone A. Low elevations on the leeward sides of the islands. Rainfall is less than 25–50 cm annually. This is the hottest and driest zone. Rainfall is principally of Kona (southwest) origin, most of which comes in the winter. Kona rainfall is subject to greater variation from year to year than trade-wind rainfall. It is often torrential, so that the proportion of the rainfall utilized by the plant is small. The natural vegetation is sparse; it consists largely of drought-resistant shrubs except on the coastal flats, where the roots of certain trees and shrubs penetrate to ground water and support good growth. Certain annual grasses are able to develop and seed during the short intervals of sufficient rainfall. The annual legumes are conspicuously absent.
Zone B. Principally on the leeward sides of the islands from sea level to 900 m. The annual rainfall, which measures about 50–100 cm, comes principally in the winter from the southwest. Much of what has been said of zone A applies to zone B. The natural vegetation is drought-resistant shrubs, quite dense in places, with a considerable growth of annuals during the rainy season. The heavier rainfall of this zone permits the development of numerous deep-rooted leguminous shrubs, especially in small gullies and depressions, which concentrate the moisture. A number of desirable herbaceous legumes develop during the winter months.
Zone C1. Found on both leeward and windward sides of the island; from sea level to about 760 m. The annual rainfall is about 100–150 cm. Since much of the rainfall is of trade-wind origin, it is less variable than in zones A and B and is sufficient in amount to support a dense and varied plant population. Most of the zone was probably once forested. Cleared lands support a vigorous growth of perennial grasses, as well as numerous perennial and annual herbs. Many of the herbaceous legumes, which are annuals in zone B, are short-lived perennials in this zone. The summer months are normally dry enough to permit normal ripening of the seeds, which germinate the following winter or spring. Both temperate and tropical species are adapted. Most of the temperate species make seasonal growth in the winter and spring, while the tropical species tend to be perennial in growth.
Zone C2. Occurs only on the islands of Hawaii, Maui, and Kauai from 760 to 1 200 m altitude. Rainfall is similar in amount and distribution to the low phase of this zone. In this high phase, though many of the more temperature-sensitive tropical legumes are not adapted, a number of the most common temperate species are found. These species develop in the early spring and summer. In moist areas bordering zone D, the moisture-loving types such as white clover are found, while in the dry sections the distinctly annual types grow such as black medic, bur clover, and Indian yellow clover.
Zone D1. Lies principally on the windward side of the islands from sea level to 460 m or less. With 150 cm or more of annual rainfall, this zone is not conducive to growth of desirable legumes because the soils are generally quite acid, leached, and poorly aerated. This zone has probably the greatest need for good forage legumes to balance the grass forage, which is commonly low in protein, minerals, and total dry matter.
Zone D2. Lies above the low zone and receives 250 cm or more of rainfall annually. Limited sunshine and very acid, often boggy, soils preclude the growth of most legumes. Normally this zone is used as a forest reserve.
Zone D3. Found on the islands of Hawaii, Maui, and Kauai where it lies between 1 200 and 2 100 m altitude with an annual rainfall varying from 125 cm in the upper to 250 cm in the lower elevations. Its climate is moist and cool, and there is considerable fog. The porous ash soil, common to much of this zone, is well adapted to legumes. The annual types like black medic, bur clover, and Indian yellow sweetclover (Melilotus indicus) normally do not persist, probably because of lack of sunshine and absence of a dry season, which are necessary for the seed to cure. Wherever the ash soil is of sufficient depth and proper grazing methods are used, a mixture of white clover and low hop clover (Trifolium campestre) with Kentucky bluegrass, orchardgrass, and ryegrass is possible.
Zone E1. Occurs from1 200 to 2 100 m on the islands of Maui and Hawaii. It has an annual rainfall of 125 cm or less, with dry periods during the summer months. Those parts on the windward side-adjoining zone D3 contain the moisture-loving legumes such as white clover, but growth is often seasonal. Many of the annual legumes like black medic, bur clover, and Indian yellow sweetclover (Melilotus indicus), which are common to zone C2, are also found in the leeward areas above it. In this high, cool climate, growth begins late in the spring. Where the loose, ashy soil is of sufficient depth, excellent, although seasonal, legume growth can be developed. Over much of the phase, the soil is too coarse-textured and thin for pasture development.
Zones E2 and E3. Extend from 2 100 m to the summits of the high mountains. Continuous low temperatures preclude growth of most species; practically none of the land in these zones is used for pasture.
Kikuyugrass (Pennisetum clandestinum) is the most important forage grass in the state (Figures 5.2.28, 5.2.29). However, this grass is listed by the USDA as a noxious weed in the conterminous 48 states. In 2003, a petition requesting the USDA to remove this particular grass from the Federal noxious weed list was not successful.
Other important grasses include pangolagrass (Digitaria decumbens), guineagrass (Panicum maximum syn. Urochloa maxima), paragrass (Brachiaria mutica), buffelgrass (Cenchrus ciliaris), bahiagrass (Paspalum notatum) and other Paspalum species, stargrass (Cynodon nlemfuensis) and other Cynodon species, and banagrass or napiergrass (Pennisetum purpureum).
Temperate grasses, such as ryegrasses, were evaluated in the past with low success rate due to the highly aggressive nature and competitiveness of kikuyugrass.
Important legume forages include: white clover (Trifolium repens), trefoils (Lotus species), Desmodium sp., perennial soybean (Neonotonia wightii (Am.) Lackey), common vetch (Vicia sativa), pinto peanut (Arachis pintoi), and leucaena (Leucaena leucocephala). The latter two legumes are being evaluated by the College of Tropical Agriculture and Human Resources at the University of Hawaii.
Most of the pastures in Hawaii consist of mixtures of grass and legume species. The most common mixture involves kikuyugrass and white clover in the moderate elevation zones and combinations of guineagrass and desmodium in the pastures at lower elevations.
Virtually no annual pasture or range planting is done by producers in the counties of Hawaii, Maui, Oahu, and Kauai. Most of the grasses and legumes are tropical and subtropical perennials. On occasion a producer may overseed a pasture to develop a mixture or bank of different forages. Some of this kind of seeding establishment is being done at the Hawaii Agricultural Research Station. The University of Hawaii, College of Tropical Agriculture and Human Resources recently purchased a no-till pasture seed drill with which to evaluate the benefits of pasture forage diversification and to encourage strategic no-till seeding practice by producers.
Pasture pests and their management
The isolation and environmental diversity of the Hawaiian Islands has had a profound effect on the evolutionary development and history of endemic plant and animal communities, leading to a considerable number of unique species. The rate of introduction of a new species prior to human contact was very low, estimated at one new species per several thousands of years. Since the discovery of the islands by explorers, more than 20 new species per year have been introduced. In recent times, Hawaii has seen the unintended consequences of an abundant variety of plant and insect introductions from all over the world. As a consequence of its position as a major intersection of air and ocean transportation, and of both civilian and military traffic, it has been estimated that up to 200 new species per year are introduced into the Hawaiian ecosystems and become serious economic and social problems. The introduced species, with their competitiveness against endemic species community and the absence of effective natural enemies, have led to a very high pest establishment rate and led to Hawaii being labelled as the “endangered species capital of the world.”
Pasture and range insect pests include yellow sugarcane aphid (Sipha flava); grass webworm (Herpetogramma licarsisalis) in late spring to mid-summer and early winter; stinging nettle caterpillar (Darna pallivitta), a potentially new pest in mid-spring to late summer; and seed weevils.
Weeds are the major pest management concern for pastoral systems in Hawaii. The publication by Motooka et al. (2003) is an excellent reference for the weeds in Hawaii; species with the notation “bio” are those selected by the Hawaii Department of Agriculture as candidates for investigation of biological control agents for their control or eradication.
The major weed species are the trees guava (Psidium guajava), Christmas berry (Schinuster binthifolius), and faya tree (Myrica fava); the shrubs lantana (Lantana camara), apple of Sodom (Solanum linnaeanum), yellow Himalayan raspberry (Rubus ellipticus), sourbush (Pluchea carolinensis), downy rosemyrtle (Rhodomyrtus tomentosa), gorse (Ulex europaeus), and blackberry (Rubus argutus); the herbs and vines Madagascar fireweed (Scenecio madagascariensis) (Figure 5.2.30) and Koster's curse (Clidemia hirta); and the grasses fountaingrass (Pennisetum setaceum), tufted beardgrass (Schizachrium condensatum) and broomsedge (Andropogon virginicus).
There are rust fungi (species unknown) that affect grasses, but they do not constitute a serious pest for the adapted subtropical and tropical forage plants. They have, however, been observed to affect imported temperate grasses, such as sorghum. Slugs also can become a pest.
In summary, the control and management of weeds in pasturelands and rangelands in Hawaii is the most significant and costly pest concern, followed by insect pests as a secondary problem. Forage-based industries in Hawaii are continually interested in the introduction, investigation and evaluation of new forage species that potentially could adapt to the diverse environment niches and the management strategies required to increase the productivity of tropical pastoral systems. Critical needs include the biological control of Madagascar fireweed and grass webworm, the continued evaluation of new herbicide chemicals and formulations for weed control in tropical environments; the exploration for improved warm-season grasses and legumes adaptable to subtropical and tropical environments; and the delisting of kikuyugrass from the USDA Federal Noxious Weed List.
Forage production on the island includes many more tropical species than those in the southern portion of Florida, including a mixture of tropical forage grasses, shrubs, and trees, some native and some introduced. Pastures are composed of a diversity of species in contrast to the single species focus observed in most south Florida pastures. Pasture legumes are abundant but they are not planted. The main forage legumes are clitorea (Clitorea ternatea) (Figure 5.2.32), velvet bean (Mucuna sp.), perennial peanut (Arachis sp.), acacia blanca (Albicia procure), leucaena (Leucanea sp.), and many native legumes. Tree legumes such as mata de ratón (Gliricidia sp.) are used as live fencing and protein banks.
The predominant grasses occurring in planted pastures in the northern humid area of Puerto Rico are digitgrass (pangola), guineagrass (Panicum maximum), and stargrass. Dairies in this region are small and use guineagrass as their staple forage, as well as some stargrass pastures under rotational stocking (Figure 5.2.33).
In the drier areas of the island, pastures are mainly buffelgrass (Cenchrus sp.) and bluestems (Dichanthium sp.). Preferred grasses for hay are digitgrasses, buffelgrass, and bluestems due to their fine stems (Figure 5.2.34).
Forage crops in the conterminous US Humid Region
Preference for particular forage species depends on local precipitation amount and distribution, soil drainage and texture, desired use, length of growing season, summer and winter temperature regimes, and snowfall depth and cover duration.
Northern Humid Region
In the northern portion of US humid regions, cool-season grasses such as Kentucky bluegrass (Poa pratensis) and other bluegrasses, orchardgrass (Dactylis glomerata), redtop (Agrostis alba) and other bentgrasses, timothy (Phleum pratense), smooth bromegrass (Bromus inermis), and reed canarygrass (Phalaris arundinacea) are used commonly or found naturalized in pastures and meadows. In the central portion of the eastern US (Mid-South or transition zone), tall fescue (Lolium arundinaceum, formerly known as Festuca arundinacea) is the predominant grass (Figure 5.2.35), with some bluegrass, bentgrass, and orchardgrass. Much of the tall fescue is infected with Neotyphodium coenophialum, an endophytic fungus (Fribourg et al., 2009) which causes tall fescue toxicity in consuming herbivores. The main tall fescue cultivar, ‘Kentucky 31’, was planted extensively throughout the transition zone, starting in the 1950s. Recently, with increasing understanding of the toxicity issue, new cultivars are available with nontoxic novel endophytes and are recommended for use in new or replacement plantings. Other grasses used to a limited extent for forage within the region include perennial ryegrass (Lolium perenne), meadow fescue (Festuca pratensis), creeping foxtail (Alopecurus arundinaceus), and meadow brome (Bromus riparius).
Southern Humid Region
In the southern half of the eastern US, temperatures and evapotranspiration are high enough for warm-season grasses to outcompete cool-season grasses in summer. Perennial warm-season grasses used in this zone include numerous indigenous strains of bermudagrass (Cynodon sp.) as well as improved genotypes and cultivars such as ‘Coastal’ and ‘Midland’, and johnsongrass (Sorghum halepense); in the deeper South, bahiagrass (Paspalum notatum) and dallisgrass (P. dilatatum) occur widely. In Florida, several subtropical species are prevalent, including limpograss (Hemarthria altissima), Desmodium and Pennisetum species, and perennial peanut (Arachis glabrata). Some of the improved genotypes of grass forage species need to be established vegetatively by sprigging, rather than with seed.
Many legumes (Fabacea) are important in pastures and meadows; in symbiosis with Rhizobium bacteria in root nodules, they fix atmospheric N and improve forage quality through their lower cell wall fibre content than grasses at similar maturity stages. Several different genotypes of white clover (Trifolium repens) (Figure 5.2.36) constitute the primary legume mixed with grasses in pastures from Maine to Minnesota south to Georgia, eastern Texas, and Arkansas. Other perennial cool-season legumes used include red clover (T. pratense) (Figure 5.2.37), birdsfoot trefoil (Lotus corniculatus) (Figure 5.2.38), and alsike clover (T. hybridum).
On well-drained soils, alfalfa (Medicago sativa) is the main legume used in hay fields, some of which are grazed at times. In the South, the semi-endemic annual lespedezas, striate (Lespedeza striata) and Korean (L. stipulacea) are used frequently, as well as perennial sericea lespedeza (L. cuneata).
Deep South Humid Region
In the Deep South, annual legumes are important in combination with annual grasses for winter grazing. Winter annual legumes include crimson clover (T. incarnatum) (Figure 5.2.39), berseem clover (T. alexandrinum), and arrowleaf clover (T. vesiculosum). The winter annual grasses include rye (Secale cereale) (Figure 5.2.40), annual ryegrass (Lolium multiflorum), and wheat (Triticum aestivum). Various Brassica species are used as annual crops in cool-season grazing systems. In central and north Florida, recommended winter legumes include red, crimson, and white clovers. The southern Florida window for production of winter legumes allows for using white clover in the humid conditions of the Flatwoods.
An important perennial warm-season legume for south Georgia and Florida sandy soils is perennial peanut (coined the ‘Alfalfa or Queen of the South’) because of its nutritive value equivalent to that of alfalfa (Figure 5.2.41). It forms a dense ground cover and canopy.
Summer annual grasses are used on tillable land to provide summer feed, especially in dairy enterprises, and as a smother crop in preparation for new forage plantings. These include several types of grain and forage sorghums (Sorghum bicolor) and sudangrass (S. bicolor), sorghum-sudangrass hybrids, pearlmillet (Pennisetum glaucum) (Figure 5.2.42), and foxtail millet (Setaria italica). Warm-season annual legumes such as forage soybean (Glycine max) and the annual lespedezas are used; the southern adaptation limit for lespedezas is in southern Georgia. In Florida, other annual legumes such as deer vetch (Aeschynomene americana), alyce clover (Alysicarpus vaginalis), and carpon desmodium (Desmodium heterocarpon) are grown increasingly.
Pacific Northwest (PNW)
Alfalfa is the principal hay crop in the Pacific Coast states, being produced primarily under irrigation (Figure 5.2.43). In 2010, over 9 million metric tonnes of alfalfa hay were harvested from the region on 832 000 ha (4.75 million metric tonnes from 460 000 ha in Idaho, 2.46 million metric tonnes from 202 000 ha in Washington, and 1.8 million metric tonnes from approximately 170 000 ha in Oregon) for a value of over $1 billion ($111 per metric tonne in 2010, approximately $180 per tonne in 2011; http://hayandforage.com/marketing/quality-hay-alfalfa-prices/).
In Idaho, alfalfa was almost 77% of the “all hay” harvested (http://www.nass.usda.gov/Statistics_by_State/Ag_Overview/AgOverview_ID.pdf). For Washington and Oregon, larger areas of “other hay” are harvested, but lower yields and lower prices per tonne make the value of other hay somewhat less than that of alfalfa.
Corn for silage is important for dairy rations but, although yields are high (60.5 metric tonnes/ha average for Oregon), it is grown on a much smaller area than hay crops and is used close to the areas of production. [http://www.nass.usda.gov/Statistics_by_State/Washington/Publications/Annual_Statistical_Bulletin/2010/ab65.pdf]; [http://www.nass.usda.gov/Statistics_by_State/Ag_Overview/AgOverview_OR.pdf]
Development of pastures on PNW hill lands has had a major impact on livestock production in recent decades (Figure 5.2.44). Transition has been from open areas of numerous indigenous species and from brushlands and cutover timberlands. Nearly 600 000 ha have been developed into legume-based, productive pastures, often referred to as hill pastures. Typical annual grasses include species of bromegrass (Bromus inermis), oat (Avena sativa), and fescue (Festuca and Lolium sp.). Forbs include numerous native legumes [clover (Trifolium sp.), medic (Medicago sp.), and birdsfoot and big trefoils (Lotus corniculatus and L. pedunculatus Cav.)], several species of filaree (Erodium sp.), and many weedy forbs. Most of the annual grasses and legumes and a few forbs are preferred and nutritious while vegetative, but they lose nutritive value rapidly as they mature (Marble et al., 1985).
Much of the development, especially on hills, has been based on winter annual legumes - mostly subterranean clover (T. subterraneum) - used alone or in combination with rose clover (T. hirtum). Some use is made of alfalfa and birdsfoot trefoil in interior areas, and big trefoil and white clover on wet coastal areas. Production of winter annuals in a summer-dry situation results in a marked seasonality of production. There is some grass growth during the winter, a grass-clover spring flush, and drying of the pasture in early summer (Marble et al., 1985).
Productivity is a function of annual rainfall patterns, modified locally by factors such as slope, aspect, and soil water-holding capacity. Early fall rains followed by good growing weather can result in the production of 1 000 kg/ha or more of forage prior to winter. Some of the spring surplus forage may be conserved as hay if slopes are not too steep for mechanical harvest, with the remainder providing dry feed for livestock during the summer. Because of steep slopes, much of the early development was by aerial application of seed and fertilizer, requiring high rates of legume inoculum and lime-pelleted seed. With annual application of P and S and full utilization, deficient P conditions are corrected and only S needs to be applied. In more acid soils, Mo is required for best clover growth. It is made available for plant use by liming the soil or by application of small amounts with the other fertilizer (Marble et al., 1985).
Most of the irrigated pastures in the region are used for beef production. Some are used for dairy cows or fattening lambs and flushing ewes. Irrigated pastures frequently are based on cool-season grasses (perennial ryegrass, orchardgrass, and tall fescue) and white clover, but a number of other species are used including birdsfoot trefoil and alfalfa. Irrigated pastures on better cropland are usually rotation pastures for a few years. Using white clover or alfalfa as the legume component, these mixtures have produced 1 100 kg/ha beef during the pasture season. Production is correspondingly less with shorter seasons at higher elevations (Marble et al., 1985).
Oregon is the largest producer in the world of cool-season forage seed. Grass seed production is one of the leading agricultural crops in the state (Figure 5.2.45). Over half of the Willamette Valley is sown to grass seed production fields. The northern end of the Willamette Valley produces tall fescue and perennial ryegrass seed, the southern end is dominated by annual ryegrass (Lolium multiflorum), and fine fescues (Festuca sp.) are grown in the hills of Silverton. Almost all of the grass seed produced in Oregon is of cool-season turf and forage seed crops (slightly modified from http://www.oregongrassseed.com/).
The value of grass and legume seed crops in 2010 was $252 million. Of this total, grass seed crops accounted for 90.6% ($228 464 000) and legume seed crops were valued at $23 707 000 (9.4%) (http://cropandsoil.oregonstate.edu/seed-ext/sites/default/files/wcy022111.pdf).
Cattle and calves are the largest domestic livestock category for the Pacific Northwest, with 1.26 million head in Oregon in 2010 (with sales valued at $800 million and value of nearly $1 000 per head), 1.08 million head in Washington (sales value of $581 million, total value of $1 123 million), and 2.14 million head in Idaho (valued at $2 119 million) (http://www.idahocattle.org/agstatistics.aspx).
Idaho dairy product receipts were $1 430 514 000 in 2009, leading cattle and calves, potatoes, wheat, and hay (http://www.ers.usda.gov/StateFacts/ID.htm#TCEC). Washington state milk production was valued at $684 million in 2009, second only to the value of apples and slightly ahead of potatoes, cattle and calves, and wheat (http://agr.wa.gov/AgInWA/). In Oregon, 2009 milk value was nearly $308 million, fifth among agricultural commodities, behind greenhouse and nursery products, hay, cattle and calves, and grass seed.
Livestock inventories for sheep, lambs, and goats numbered 225 000 in Oregon, 60 000 in Washington, and 220 000 in Idaho (http://www.nass.usda.gov/Statistics_by_State/Idaho/Publications/Special_Reports/pdf/sheepfeb10.pdf).
The PNW has rich and varied landscapes which are home to a diversity of wildlife providing extensive opportunities for fishing, hunting, and wildlife viewing. National and state government agencies have responsibilities for protecting and enhancing the fish and other wildlife and their habitats for use and enjoyment by present and future generations. (http://www.fs.fed.us/r6/nr/wildlife/)
Pasture systems and management in humid regions
Pastures are used in various livestock enterprises in the region, including cow-calf, growing stocker cattle, finishing beef cattle, developing replacement dairy heifers, and feeding milking dairy cows, sheep, goats, and horses. Pastures are found predominantly on land that is not well suited for tillage. These sites often have limitations, such as having low water-supplying power or being poorly drained, having rocky or shallow soil, or being on steep hill and mountain slopes. Some of the best pastures in the region are found on good cropland soils; in such areas, pastures are found also on the less desirable cropland or on untillable neighbouring hillsides (Figure 5.2.46).
The natural undisturbed climax vegetation in most locations of the US humid region is temperate hardwood forest. Prior to the 1600s, however, along the Atlantic coast, as much as 16 % of the area was kept as open grassland by Native Americans using fire (Rountree et al., 2007). Some of these areas extended as much as 260 km2 (Lawson, 1709; Byrd, 1728). In the western Piedmont, a greater percentage may have been maintained by Native American burning as grassland, with many areas 16–19 km long by 5–8 km wide (Pyne, 1982). These burned areas were found on the flanks of the Appalachian Mountains, in the Piedmont along the James River, and in the Coastal Plain. In the Southeast there were large areas of longleaf pine (P. palustris) savannahs with grassland understories of native little bluestem (Schizachyrium scoparium) and pineland threeawn or ‘wiregrass’ (Aristida stricta). The western part of the region in Missouri, Iowa and Minnesota was a native prairie, again maintained by Native Americans with fire (Pyne, 1982). Both in the eastern and western portions of the humid region, numerous occurrences of patches of varying sizes provide testimony to the extent of these native former grasslands: wild growing indiangrass (Sorghastrum nutans), eastern gamagrass (Tripsacum dactyloides), big bluestem (Andropogon gerardii), switchgrass (Panicum virgatum), and other Paspalum species.
In pasture systems, livestock do most of the harvest, limiting the need for expensive equipment, fossil fuel, and labour, for feeding and cleaning up after livestock. Under good management pasture is managed to optimize both forage yield and quality. Optimum management varies with livestock species and breeds, forage species and cultivars, soil conditions and local environments, and economic considerations. Stored forages and supplements are available and can be used as needed. In pasture-based systems, optimal milk or meat production per unit land area and overall farm profitability are the best measures of success.
Good pasture management requires an understanding of plant and animal production principles, enabling the manager to adapt to changing environmental and market conditions, during each year and from year to year. The goal is to match the available feed resources to the nutritional needs of all animals during the entire year without compromising future capabilities. Because of varying soils, weather patterns, and animal production stages, management decisions and adjustments in pasture stockings, rotation methods, and stocking densities, supplements are needed regularly. At the same time, it is desirable for graziers to keep the pasture-livestock system relatively simple.
With the high price of nitrogen (N) fertilizer, pastures that include legumes often are more desirable than grasses alone, but amendments with phosphorus (P) and potassium (K) fertilizers are needed for legume longevity and productivity. Pastures with high percentages of legumes may occasionally cause bloat under certain conditions, therefore attention must be given to this potential risk. One option is to allow animals to adapt slowly to legume pastures, to limit the time of their exposure, to avoid wet lush pastures when grazers are hungry, and to use a bloat-preventing additive administered in a supplement or water source. These are much preferred to emergency surgical procedures.
A typical system for cattle grazing in the northern portion of the humid region uses mixtures of cool-season grasses and legumes (Figure 5.2.47) in pastures and meadows. Hay (Figure 5.2.48) or haylage (Figure 5.2.49) for supplemental feed is made in late spring and early summer. A second cutting may be taken from some meadows, or they can be grazed in summer. Late in the season, usually all pastures and meadows are grazed. The cool weather in this region provides a desirable balance between rainfall and evapotranspiration, leading to relatively little reduced summer production. Spring forage growth is high, gently tapering throughout the summer into early autumn. Pasture growth occurs for 6 to 7 months/yr, and conserved feed is needed during the 5- to 6-month winter period. Where tillable soils are available, perennial cool-season pasture may be supplemented with annual warm-season grasses, and corn or grass silage. In the case of dairy cows, this general pasture system is modified with the addition of supplemental grains and additional stored forage to ensure adequate nutrient intake during lactation. In the transition zone of the humid region, approximately delineated by the northern boundary of Maryland and the southern border of Tennessee, basic pasture systems are similar to those farther north, with some modifications. In this zone, warmer summer temperatures may cause heat stress, and a “summer slump” in production develops during hot and dry periods. There is also a long cool period in autumn and relatively little or intermittent snow cover in winter. Tall fescue, tolerant of heat and soil moisture stresses, dominates pastures; this grass also tolerates frosts well, especially when fertilized with N or mixed with legumes. Tall fescue quality improves during cool fall weather because its sugar content increases at that time, leading to better digestibility and acceptability to cattle. These characteristics combine to increase the potential length of the grazing season.
“Stockpiling” is a practice used to take advantage of this potential, whereby tall fescue fields are subdivided and grazing is suspended in late summer and early fall in some paddocks. When the area has little or no legume in the stand, N fertilization is advisable before allowing the grass to grow until the forage is needed in late autumn, usually reaching peak yield and quality in November-December. This stockpiled forage is then grazed during the dormant season (Figure 5.2.50). Its quality decreases from late December through the winter until forage growth commences in the spring, depending on frequency and amount of precipitation, but the residual forage often has greater nutritional value than the needs of nonlactating cattle.
At elevations above 600 m at these latitudes, cooler temperatures and higher precipitation reduce the risk of a summer slump. These areas also are subject to longer snow and ice cover periods, thus reducing the need for stockpiled tall fescue because conserved forage has to be employed. However, even in these environments, stockpiling tall fescue can increase the grazing season by 30–60 days.
Perennial or annual warm-season grasses, and stockpiled tall fescue being grazed after first snowfall, are used to reduce the effects of the cool-season forage summer slump in this zone. These grasses grow well in hot weather and tolerate drier conditions than cool-season forages. Warm-season grasses used include the native grasses such as switchgrass, big bluestem, eastern gamagrass, and indiangrass, as well as the exotic bermudagrasses. In the southern portion of this area, endemic bermudagrass often volunteers in tall fescue pastures. During summer, bermudagrass dominates, whereas tall fescue predominates in the stand during spring and autumn. This mixed stand has little summer slump due to the complementary growth patterns of the two forages, but careful management is essential to maintain a good and persistent balance. Where adapted, this tall fescue-bermudagrass grazing system can provide near year-round grazing from South Carolina to Arkansas.
In the Deep South, summer heat is inhospitable to cool-season perennials and emphasis is placed on the warm-season perennials -- bermudagrasses, dallisgrass, and bahiagrass constitute the major pastures. Cows usually are bred for fall calving to avoid the heat stress that spring calving cows and calves experience. To provide winter grazing, these sods frequently are overseeded with a winter annual, such as annual ryegrass. Cropland can be pastured with a rotation of winter annuals, such as annual ryegrass for winter and spring grazing, followed by summer annuals such as sudangrass, pearlmillet, and crabgrass (Digitaria sanguinalis) for summer grazing. The challenge with this system is that there is often a lack of feed during the transitions between grazing crops; it may be necessary to feed hay at those times.
The pasture systems described above are generalized; livestock managers will need to modify them according to local soils, weather, and elevation. For example, in the Great Valley in Virginia, and east of the Allegheny Plateau, droughts can occur at any time, because the Plateau catches much of the rain, leaving relatively dry air entering the valley. In contrast, this area has milder winters and little snow cover when compared to the Plateau. Consequently, Valley managers must deal with different limitations than managers only 80 km to the west – they need to develop grazing systems that reduce drought risks and capitalize on mild winter conditions. On the Plateau, there are fewer droughts, but snow cover may reduce the availability of stockpiled tall fescue for winter feeding.
In the southern part of the region, where pine forests are well adapted and grown as a farm enterprise, grazing of silvopastoral areas can be a major part of a year-round pasture system. Even though winter conditions are milder here than in more northern areas, management must no less carefully maintain animal health. In all regions, supplemental feed may provide a major supplement when gleaned by grazing field crop residues, such as from corn, soybean, grain sorghum, peanut, or cotton (Gossypium sp.).
In Hawaii, the beef cattle industry is supported by applied research conducted at the Mealani Research Station and by on-ranch field plot projects conducted by the Hawaii Cooperative Extension Service, the outreach arm of the College of Tropical Agriculture and Human Resources (http://www.ctahr.hawaii.edu/ctahr2001/InfoCenter/Forages/overview.html). One aspect of the applied research conducted by the research station is the collection and evaluation of grass and legume germplasm. Kikuyu grass genetic material (Pennisetum clandestinum) makes up nearly 85% of the grass collection, as it is the main pasture and range forage in Hawaii. Other grasses in the collection are comprised of new introductions and grasses that are resistant to the yellow sugarcane aphid (Sipha flava). Research information includes yield, nutritional data, and aphid resistances scores for the various grasses in the collection. Germplasm materials are made available to the forage-based industries for their pasture and range improvement programs.
Cooperative work with other land grant institutions and federal research agencies has led to the introduction of new pasture legumes, such as perennial peanut (Arachis pintoi) and trefoil (Lotus sp.). These species are being evaluated under local environmental conditions for introduction into forage-livestock systems. In addition, faculty and students have developed lines of high-elevation- and psyllid-tolerant Luecaena luecocephala (a woody species known as haole koa in Hawaii) as a valuable addition to grasses and legumes.
Increasing demand for Hawaii-grown grass-fed beef is based on its growing reputation for high quality, as well as its year-round availability. The goal of research and extension programs is to help create a livestock industry that is ecologically, economically, and socially sustainable. This has given rise to evaluations of various forage production systems and technologies, market development opportunities and incentives, and consumer education about the benefits of forage-based animal production.
Due to the highly varied topography, climate, and soil conditions, Hawaii has one of the most diverse ecosystems in the world. From the fiery lava fields on the coast of the big island to the alpine regions on the upper slopes of the world's largest mountain masses to the unique marine habitats of the northwestern Hawaiian Islands, species adaptations have developed over the millennia. Combined with new "alien" introductions to these islands, forage-livestock systems have been developed which effectively utilize these environmental niches. The following photographs illustrate the grass-fed beef industry in various island locations (Figures 5.2.51, 5.2.52, 5.2.53, 5.2.54).
Current situation, economic considerations, and future prospects
Pastures provide low cost feed for livestock and are the primary feed for beef cattle, dairy heifer, sheep, and goat production systems. Under good management they often generate greater net income/unit area than crops, even on good tillable soils. Small dairies frequently use pasture for lactating cows. Large pasture-based dairies have been developed and maintained by progressive managers for several decades. Government farm program payments and, in recent years ethanol subsidies have had a major impact on crop prices and cropping system incomes, affecting producers’ interest in cropping over pasture-based livestock production.
Pastures and harvested perennial forage crops are the most productive crops in cool, moist, northern climates where corn and soybean are not well adapted (Figure 5.2.55). In all regions, well-managed pastures provide soil and water conservation benefits by reducing soil erosion, maintaining water quality through less runoff of P and N applied to tilled crops, and providing carbon sequestration from land no longer cultivated. Pastures provide a profitable, environmentally safe means of producing nutritious meat and milk products for human consumption on steep and shallow soils not suited to tillage. Where interspersed with woodlands and other habitats, pastures are a major food supply for wildlife, such as whitetail deer (Odocoileus virginianus) and wild turkey (Meleagris gallopavo). Pastureland also provides openings that protect landscape views for travellers through the countryside. Much of the confinement livestock industry depends on pastureland for the usually gratis disposal of dairy, poultry, and hog manures (Figure 5.2.56). The forage produced on this disposal land is then either grazed or harvested for hay or haylage, but the livestock producer may have to pay a fee for the manure or its spreading. The rationale for this fee includes the value of the nutrients supplied from the manure to the forage plants, particularly P, and by the incurred transportation and spreading costs.
New farmers, some of whom wish to produce organic milk and meat products, find that pasture-based production has lower entry cost than does production of harvested crops: there is less need for machinery, and land can be rented from absentee and rural resident owners who do not use the land but want it to be kept open. Unfortunately, new producers have limited understanding of pastureland and livestock management, and the educational infrastructure for this knowledge is increasingly thin due to retrenchments in funding from state and federal governments. Nonetheless, where producers need pasture management information, state Land Grant University Extension Service staff at the state and county levels, and USDA/NRCS staff and local personnel, provide educational programs and technical services through formal and informal training at pasture schools and conferences, field days, and pasture walks (Figure 5.2.6). These educational activities often use the knowledge and experience of local pasture-based producers.
Many producers today are old, and they are retiring and going out of business. In most parts of this region, land prices are not driven by the profitability of agriculture. Much cropland and pastureland within a few km of cities and towns is being bought by speculators who then subdivide the land into house lots or small hobby-farms. In other areas, farmland is being purchased by urban residents for recreational hunting. Where there is tillable soil at a distance from urban areas, competition for field crops such as corn and soybean occurs when prices are high.
Other factors can discourage pasture-based producers. Regulations established by the US Department of Agriculture (USDA) and the Food and Drug Administration (FDA) to target the needs of large packers and export markets are stressing small meat packers, driving them out of business. Thus, the slaughter infrastructure, needed by small-scale producers interested in diversified production of grass-fed meat, milk, and poultry products, is decreased. The lack of processing facilities then has a deleterious impact on the local marketing of these products. The ongoing challenge for pasture managers is to manage pastureland, livestock and farm infrastructure economically, in view of the relatively high prices for essential supplies, such as fences, water and water distribution systems, fertilizers, and agricultural limestone. Global trade also has led to the introduction of new invasive weeds into the country. Fortunately, scientists and producers have determined that cows can be trained to eat many weeds, but managers have lagged in putting this information into practice. Other challenges include those brought about by climate change and the resulting increase in weather variability, and the political and social issues between states and agricultural, urban, and industrial demands for increasingly limited water supplies.
Summary. In spite of the challenges that pasture managers in the humid region of the US have to face -- just like managers everywhere else in the world – whether these challenges originate in the physical environment (droughts, floods, frosts, heat, or cold), the market (high prices for inputs and low ones for products), or society (family, state and federal government regulations) - the humid region pastures have many advantages and strengths. Pasture-based livestock producers are generally literate, intelligent, resourceful, and independent-minded. The humid pasture region provides a beautiful place to live. In most years, the region has sufficient, well-distributed precipitation to produce abundant forage without needing irrigation. Livestock in pasture systems harvest their own feed and recycle plant nutrients, helping to keep machinery, fuel, and fertilizer costs at a minimum. Legumes within the system reduce and can eliminate the need for purchased N fertilizer. Most soils have structural characteristics that allow for proper nutrient management. Improved knowledge of genetics is providing plants and animals that are more efficient in pasture systems. As fuel, fertilizer, and grain prices increase, pastures become more economically competitive for producing meat and milk products for human consumption than confined feeding enterprises. All these factors, with a positive attitude among pasture-based livestock producers, bode well for the continued use and good management of this important resource.
Authors: Henry A. Fribourg, David B. Hannaway, and Peter J. Ballerstedt
Widespread need to apply current knowledge
There are numerous possibilities for improvement of US feed resources and great potential for increasing the personnel and funding devoted toward grassland management. Even though many advances have been identified since the middle of the twentieth century, and many of those have been applied to varying extents within regions, countries, and producer economic classes, much remains to be done. The ability and willingness of grazing enterprises with extensive infrastructure and financial resources to implement advances in knowledge are much larger than those of small or marginal producers. Thus, Extension efforts often target these producers and the approximate 10% of all producers who are recognized as “early adopters”.
In the US, many farmers have yet to implement practices known to improve performance of grazinglands and livestock. For instance, it has been known since the early twentieth century that adjusting the pH of acid soils in the humid regions of the US is the single most effective means of improving plant nutrition. While agricultural limestone has been used for most cultivated crops, very few pasturelands have been limed where needed. Few have received fertilizers other than N, although it is well known that P is widely limiting, that K and B, and sometimes S, are essential for optimal growth of legumes, and that periodic fertilization maintains proper fertility levels. Restrictions limiting the adoption of these practices include the advanced age of many farmers, their educational level, the small size of their enterprise, the unavailability of financial resources, and sometimes their cultural environment.
In humid area pasturelands, the introduction of legumes in an adequate proportion in grass stands is known to improve animal performance. The establishment and maintenance of these mixtures require critical inputs and managements. Legumes, and perhaps other plant genera, require acclimated symbiont strains of Rhizobium sp.; other plants, in addition to some trees, also may benefit from a mycorrhizal mutualistic association (Furseth et al., 2010). The need for legumes in the sward is particularly acute in sub-tropical and tropical areas, where competition from aggressive C4 perennial grasses is severe.
Grazing at optimum carrying capacity is a compromise between optimizing intake and individual animal production with animal production per unit area, since intake decreases when available herbage per animal decreases (Figure 6.1).
Because lower grazing pressures, or high forage allowances, allow high levels of animal performance and intake preference, grazing management practices that use lighter grazing intensities should be encouraged, but often is not the case. On rangelands, grazing efficiency can be regulated by having daily herbage allowances <20 kg per animal unit, by using deferred grazing to allow ranges to recover, and to increase the biomass productivity and the frequency of the desirable species for the site.
Managers should recognize that each forage species and cultivar has a characteristic seasonal variation and ability to respond to grazing; that the maximum efficiency is a compromise among plant growth and plant utilization, and animal performance, taking production costs into account. Many characteristics are influential: C4 plants produce more than C3 ones; moderate grazing intensities allow light interception and yield to reach their potential, and desirable mixtures are more easily managed than when intensive grazing intensities are used; some cultivars have greater tolerance or resistance to diseases and pests than others; heavier grazing intensities lead to vegetation with prostrate plant types and decrease organic matter, reduce water infiltration rate, soil cover and biodiversity, and the availability of nutrients; persistency depends on soil fertility and lenient grazing management, and even though lenient grazing is important, it is not enough for pasture sustainability.
Animal production systems rely not only on the ability of the manager to supply sufficient nutritious feed corresponding to the year-round needs of the gender, age, and development of various animals, but also on the traits of the livestock being raised. Different species or hybrids, breeds, even unrecognized different strains adapted to regional climates, and diverse desired end-products, have different requirements. Some species, such as cattle and sheep, are complementary rather than competitive. Genetic selection has been used by some producers for desirable characteristics, such as for feed efficiency, precocity, biological efficiency of carcass or dairy production, and desirable biochemical components of marketed products. Tolerance or resistance to diseases (e.g., brucellosis) and pests, including internal and external parasites, must be considered within a carefully developed calendar of preventive veterinary practices.
Cultural, historical, and social considerations influence grassland resources. Tax structure prevents the storage of hay protected from rain in humid regions where roofs are taxed as if they were buildings; the identification of individual animals with embedded microchips is opposed by operators because it could be used to determine assets and income, even though it would permit rapid determination of problem products in the market chain. Public rangelands are overgrazed when forage utilization and excessive grazing pressure are not discouraged by fee structures. Grain marketers have convinced the US public that beef steers should be fed grain for ~100 days prior to slaughter, in order to eliminate yellow and increase white fat. This marketing strategy is understandable when it is recognized that the marketing of meat is several times more profitable than the marketing of grain. On the other hand, since steers are ruminants that digest cellulose and starch, grain is not needed for their sustenance; much of the fat is trimmed by the butcher; yellow fat is no worse nutritionally than white fat, and both contain saturated fats perceived as undesirable for consumers, when in fact they may be healthy or desired; flavour, enhanced by fat when the meat is cooked rapidly, can be preserved by altering cooking procedures and speed (http://extension.osu.edu/~twig/food/html/112496.html).
In 2007, the per capita meat and poultry consumption in the US was 91.1 kg/yr. A little more than half (55 %) of all meat consumed consists of red meat products – beef, veal, lamb, mutton, and pork (AMI, 2009). The top three meat sources are poultry, beef, and pork. Modern US poultry and swine production systems do not utilize pasture. Forages made up only 15% of the feed fed to swine and none of the US poultry feed in 1980 (CAST, 1980). Per capita beef consumption hit an all-time high of 42.8 kg in 1976 and has been trending downward since. Over the last ten years it has averaged 30 kg. One reason for the decline in beef consumption has been the official dietary recommendation, beginning in 1980, to reduce consumption of red meat in general, and beef in particular (Hite et al., 2010). The scientific basis for these recommendations is being increasingly questioned (Taubes, 2008; Hite et al., 2010). The assimilation of this information by the consumer may lead to an increase in beef consumption.
The majority of beef consumed in the US is from cattle that were brought to final slaughter weight by feeding a ration containing 70–90% grain and protein concentrates (USDA ERS, 2009). Grain feeding to finish cattle, while a long-standing practice in the US, expanded dramatically after World War II. In 1947 only 30% of slaughter cattle were grain fed, by 1973 this practice had increased to 75% (Ensminger and Perry, 1996). Increases in energy costs and grain prices, and changes in government policies, will change the economics of the cattle feeding industry and could favour grass finishing systems. Such changes could also reduce the competitive advantage currently enjoyed by poultry and pork.
The growing interest in sustainable agriculture, and the sustainability of all segments of society, have produced a growing interest in small farms and local food production in many parts of the US. A small, but growing trend in the US meat industry is the grass-finished niche market (Williams, 2006). Similar niche markets are growing for dairy products, eggs and poultry from pasture-based systems. Numerous researchers have reported quantifiable differences between grain-finished beef and grass-finished beef. These differences have been used to promote grass-finished meat to the health-conscious consumer. These benefits, however, are questionable when included as part of the carbohydrate-based diet recommended by the USDA (Taubes, 2008). Some consumers are adopting diets substantially lower in carbohydrates than the USDA recommendation. For these consumers, these quantifiable differences may translate into health benefits.
Research and extension capacity
The prospects for grasslands are linked to the future of an environmentally-conscious, energy-efficient, productive animal agriculture using land that is unsuitable for row crops for the rearing of domestic and other animals, while embracing an increasing role in protecting soil and water, and enhancing the aesthetics of urban and agricultural landscapes. A workshop that gathered many of the leaders in grazingland thinking provided a detailed report as a guideline for future action and consideration (Wedin and Jones, 1995). The report is still valid at this writing. Grassland plants capture solar energy, which can be transformed into human food via animals capable of digesting cellulose and starch. The digestion of cellulose in the rumen of cattle, sheep, and other ruminants, is the biological system that allows these animals to utilize this major component of forages; there is no other known way for cellulose and some other long-chain carbohydrates to be converted for animal or human nutrition. Thus, domestic livestock will remain a viable part of agriculture where soils are too steep, too wet or too dry, too rocky or shallow, too high in elevation or too cold, or too remote for cultivated crops. However, these grazinglands, in both humid and drier US regions, will be competing with the agricultures and grasslands of all other regions in the twentyfirst century flat world described by Friedman (2005). Grassland ecology, which varies from region to region, nevertheless embraces principles which apply to all grazinglands, wherever found, as they respond to changing climatic factors and to pressures arising from rapidly increasing human populations (Gibson, 2009). Should climate change engender hotter tropical areas than at present, it is possible that some grazinglands in such regions may decrease in suitability or productivity areas; however, the converse might happen if animal or plant genotypes are developed which thrive under such changed conditions. Human populations, bound in each region by distinct histories, religions, and cultures, will alter their consumption habits, increasing their intake of animal products as their economic status increases and their secular environments change.
Management practices and systems, developed from sound research in each region while considering factors limiting production efficiency and sustainability, product and environmental quality, and biodiversity, will take into account the status and changes in the financial capital, social capital and even the political aspects of grassland/animal systems for the long-term, while improving the well-being of rural communities. Numerous examples are available of developments where relatively small investments in research have yielded many returns in forage productivity and utilization as the technology was extended to producers, helping them to improve their efficiency or facilitating the change from cash cropping to pastoral agriculture (e.g., Fribourg et al., 2009). In addition, grazing by cattle has been shown to be a viable strategy to rehabilitate millions of US hectares of degraded croplands (Franzluebbers and Stuedemann, 2010).
Urban communities and their leaders will recognize that freedom from want encompasses food as a human right, that better communication between all facets of agriculture and the consumers of agricultural products is essential, and that all citizens have a stake in funding agricultural research and extension. There will be faster adoption of research findings by grazinglands managers and livestock industries, especially complex technologies that are aligned with sustainable production, rather than employing the current trickle-down diffusion approach that is effective with simple technologies (Pannell et al., 2006). It will be recognized that grassland management on the one hand, and livestock management on the other, require different arrows in the knowledge quiver, although a specialist in each area, as well as in the economics of local and international marketing as influenced by governmental policies, could be shared by several neighbouring enterprises.
At present, agriculture research and science, and those dealing with grazinglands and forages, have been relegated to low priorities, except in the role of biomass production from green plants in preference to more efficient systems for capturing solar energy. Expanded effort should be given to communicating to not only forage and livestock producers and managers, but also to the general public and government officials, the considerable contributions that grazinglands can offer to sustainable US food production, security, and biodiversity.
Grassland monitoring and decision support systems
Pasture- and rangeland-monitoring protocol tools have been developed and tested (Ring and Noggles, 2002; West, 2003; Wolfe et al., 2006) to collect basic information on parameters such as cover, botanical composition, biomass productivity, daily growth, and plant populations. Environmental parameters are readily measured and historical trends are available. There is a need for complete and accepted protocols for the management of rangelands and pasturelands, with acceptance of agreed protocols to predict and monitor grazinglands. As super-computers become more generally available and affordable, accurate computer-generated species suitability maps based on these data can be used for predicting the adaptability of various system components to other regions where they can be verified empirically by local scientists.
Although many researchable questions remain to be solved, basic and applied approaches eventually will shed light on these problems. In the meantime, as current knowledge is disseminated and applied to enhance better and more sustainable management practices, science-based applications will play an increasing role in ensuring long-term food and feed sustainability in a fragile world with an increasing population, doing its share to protect soil and water resources while transforming solar energy into feed on lands that should not be tilled. As these practices become more widespread, there will be an integration of cropland and grassland agriculture within a complete system of land use and farm and ranch productivity. The annual crops will generate financial resources for improving the soil fertility, thus reducing the costs of grazingland utilization. There will be increases in daily gain per animal which will reduce animal production costs and increase total animal production, at the same time as grazing intensities and systems are adjusted for optimal long-term animal and grazingland performance. New technologies may affect production costs greatly, or render previously-hostile environments capable of contributing to animal agriculture. For example, cheaper, safer, and more effective means of energy generation than the burning of fossil fuels, with its attendant detrimental environmental effects, will be developed from direct use of solar radiation, wind and tidal movements, geothermal and transuranic sources. Economic desalination of sea water and efficient irrigation practices, already used in places like Israel, will alter both cropland and grazingland possibilities in arid zones; they will also decrease the utilization of fossil water to exhaustion, as may be the case for the Ogallala aquifer in the Great Plains.
Genetic improvement of plants for grazinglands and of consuming ruminants will be an integral part of grassland agriculture. Molecular DNA markers will be used, as traditional breeding is supported by genomics, to provide insight into the genetic bases for traits of interest. Considerable genetic variability exists for many important traits of both plants and animals, facilitating modification of these organisms, as has occurred ever since the dawn of agriculture and its control by early humanity. Desirable traits of C4 plants, such as high productivity, will be incorporated into C3 plants of moderate production, while the latter may provide improvements in feed nutritional composition and preference by herbivores to C4 plants. The persistence under grazing of some perennial grasses may become a new component of the genomes of desirable companion legumes. Biotechnology is justifiable on the basis that it has the potential to achieve what conventional breeding techniques might never achieve (Spangenberg et al., 2001). The irrational and politically erroneous views that pesticides, genetic modification (GM), and irradiation are satanic and to be avoided will yield to better-informed and scientifically-educated persons. However, unrealistic and publicized expectations to achieve targets on-time and on-budget will have to be forsworn in the quest for support and political funding, especially as unresolved conflicts about these issues are delayed by the reluctance of their opponents to learn the sciences involved. Public and private-industry scientists will combine distinct genotypes into novel progeny with enhanced evolutionary potential, as they strive to create, develop, and evaluate novel elite improved forage cultivars with selected symbionts (Furseth et al., 2010) for better-adapted and more efficient genetic strains of animals within and across species and breeds.
As the intricate series of biochemical and physiological processes and interactions among animals, plants, fungi and microorganisms are uncovered, forage plants will have persistence and tolerance to stresses occasioned by extremes of temperature, water availability or surplus, physical and chemical aspects of soils, disease organisms, insect vectors, other pests and nematodes, and additional factors limiting establishment, growth, survival, reproductive efficiency, and feed composition. They will possess biochemical characteristics that will generate desirable animal performance in both favourable and unfavourable growth periods. Unintended consequences will be avoided, as happened when a gene for tolerance to an herbicide engendered undesirable agronomic consequences in the host plant. Some plants also will possess characteristics that will make them valuable for soil cover, erosion control, aesthetic environments, and minimizing environmental quality problems of anthropomorphic origins.
Animal genetic improvement has been impeded by the long time required for the in vivo development of each generation from birth to sexual maturity, e.g., over two years for cattle. Thus, long-term goals and sustained funding will be essential for realizing the great potential that exists within species and breeds, although in vitro technologies – which may shorten the time needed for each generation – will still require realistic evaluation of their products. Distinct strains within breeds that possess superior adaptation to different regional climatic and other stresses will be identified and multiplied. Animal performance will be enhanced for meat, milk, or other products as desired, with accompanying improvements in pregnancy rates, birth weights, efficiency of conversion of nutrient intake influenced only slightly by changes in composition of ingested feeds, and minimal needs for high-energy supplements except in special situations, as in dairy production.
Flexible, science-based, and innovative management strategies will be implemented by most producers as they employ the services of well-trained specialists to supplement the advisory services provided by government, industrial and commercial concerns, and financial institutions. There will be more widespread use of soil and plant tissue testing services, applications of soil amendments, fertilizers of major and minor nutrients in appropriate amounts at optimum frequencies to sustain high grazingland productivity and quality while maintaining environmental quality and ensuring satisfactory animal performance throughout the year. Agricultural enterprises will increasingly combine grazing strategies to utilize both croplands and grazinglands, annual and perennial crops, preserved feeds, and residues, to extend grazing seasons and equalize distribution of production throughout the year. They also will utilize different climatic zones to take advantage of the characteristics of each for a specific facet of their total production, e.g., as the King Ranch of southern Texas has maintained some herds in Montana, transferring animals between the two areas as appropriate for desired results at specific times of the year. Managers will supply appropriate nutritional supplements to grazing animals (e.g., mineralized salt, sulphur, ionophores, medications in molasses), and follow an inclusive veterinary program to ensure healthy animals during marketing and shipping as well as during growing and grazing seasons.
Technology transfer and adoption in grazingland systems, as brainpower (knowledge and its application) substitutes for muscle power, are constrained for several reasons. Capitalized farmers and enterprises that already have reasonable economic outputs have little incentive for adopting more intensive and originally expensive systems. The marketing of animal products is removed from the cost of inputs to the grazing system. Thus, the benefits accruing to grazing systems often are not attributed by producers to the real causes of the benefits they receive from new techniques or equipment, biological improvements, and the numerous other components of science-based agriculture. Animals and land often are used as a capital reserve rather than as a means of production. Producers who have relatively small enterprises may not have the resources necessary to adopt new technology, although there are many techniques that could be adopted with little additional input other than willingness to try something new. The increasing age of US agricultural producers, increasing indebtedness, and difficulties in attracting skilled labour constitute additional impediments in some regions and situations, in addition to the inability of rural environments to surmount the supposed attractiveness of urban living, especially for producers’ spouses and children. Cultural mores may slow down or prevent the rapid adoption of new tools that will be increasingly essential in a future world where competition and the need for collaboration will extend over the entire world; e.g., a producer in the US in the future will not only be competing with his neighbour, but also with producers in China, Brazil, Ukraine, and all over the world.
Extension and other educational organizations will have to develop programs that attract and keep the attention of producers and will permit them to multiply their efficiency and productivity. Demand for livestock products will increase as world population increases, and the increasing numbers of relatively affluent consumers will affect positively the US and global markets for the products of grazinglands. However, potentially negative impacts such as the political environment, climate change, and the potential scarcity or high cost of essential agricultural inputs such as fertilizers, chemicals, machines, energy, and mandated requirements, will require new approaches. As these changes occur, agricultural producers will need to recognize that, although they do not intend to be harmful to the environment and to deplete diversity, it was in the nature of some past practices to do so, and these practices will have to be modified appropriately for the sake of existing and future generations. New understandings by the public and its leaders eventually will lead to more enlightened policies than many currently in effect (Undersander et al., 2009).
Summary. The prospects for grasslands are linked to the future of an environmentally-conscious, energy-efficient, productive animal agriculture using land that is unsuitable for row crops for the rearing of domestic animals and wildlife, while embracing an increasing role in protecting soil and water, and enhancing the aesthetics of urban and agricultural landscapes. There are numerous possibilities for improvement of feed resources in the future and great potential for expanding support for grassland management. Many humid area pasturelands will improve as legumes form an increasingly large proportion of the swards. Grazing efficiency on rangelands will be achieved frequently by controlling daily herbage allowances, obtained by using desirable grazing practices and increasing biomass productivity and frequency of desirable plants adapted to the locality. Traits of livestock will be improved through genetic improvement tools bearing on feed efficiency, precocity, biological efficiency of carcass or dairy production, desirable biochemical components, tolerance to diseases and pests, and preventive veterinary practices.
Management practices and systems, developed from sound research in each region while considering factors limiting production efficiency and sustainability, biodiversity, and product and environmental quality, will improve intake, individual animal production, and animal production per unit area. Concurrently, they will take into account the financial capital, social status, and even the political aspects of grazinglands and animal systems for the long-term, while improving the well-being of rural communities. Public policies, moderated by cultural and social considerations, will be developed and implemented to influence grassland resources positively and beneficially. Scientific realities will be recognized as enhanced influences on marketing strategies and desirable nutritional menus for consumer health.
As standards of living increase all over a fragile world with an increasing population, consumption of meat products will increase, though tempered somewhat by increases in energy prices and changes in government policies. Nevertheless, conversion of solar energy into consumable products will expand as livestock increase their presence on non-tillable land and are increasingly removed from unnecessary dependence on croplands. The irrational and erroneous views about pesticides, genetic modification, and irradiation, will yield to better-informed and scientifically-educated opinions.
As knowledge and its applications substitute for muscle power, the standards of living of rural inhabitants will approach those of urban dwellers, while modern communities and their leaders will recognize that freedom from want encompasses food as a human right while allowing full participation in the world economic life. Eventually, it will be possible for humanity to recognize the validity of the inspiring visions so eloquently expressed by Ingalls in 1948: “Grass is the forgiveness of nature – her constant benediction … sown by the wind … it softens the rude outline of the world. Its tenacious fibres hold the earth in its place … it invades the solitude of deserts … and determines the history, character, and destiny of nations … should its harvest fail for a single year, famine would depopulate the world”.
Authors: Henry A. Fribourg, David B. Hannaway, James Dobrowolski, and Evert Byington
The current landscape
Forage/grazingland plants collectively represent the most extensively-grown crop in the US, occupying more than half of the total area of the 50 states, and responsible for more than one fourth of the total value created in US agriculture. Non-agricultural values associated with these plants, such as aesthetic and environmental contributions to society, also add substantially to their economic importance. The problems facing users of these plants are many, varied, and complex. Yet, the combined state and federal public funding for research and technology transfer for pastureland and rangeland plants is less than that allocated for some minor crops (Wedin and Jones, 1995).
It is not possible to describe accurately the financial resources budgeted in the US which impinge on grazing lands, because both the federal budget and 50 state budgets must be considered. The problem is further compounded by the fact that some issues related to grazinglands are included under different names in other programs. All these budgets are subject to legislative discussions and approvals, and final approval and allocation by different decision-makers. Nevertheless, at the time of this writing, it can be stated that the 2010–11 annual budget for the ARS (USDA-Agricultural Research Service) Pasture, Forages and Rangeland Systems national program is $46 994 606. Several other national programs work on related issues, such as bioenergy, animal disease, and invasive weeds, which are important to the Pasture, Forages and Rangeland federal program carried out at 24 locations in 21 states. The budgets for these related efforts are not included in the $47 million. Typical expenditures for USDA-NIFA’s (National Institute of Food and Agriculture) Rangeland and Grassland Ecosystems research, education, and extension programs (including pasture and forage crops) from both competitive and base level funding averages $12.5 million dollars/yr.
USDA-ARS Federal Research Locations
The US government supports research, teaching, and extension outreach activities related to forage-livestock, pastureland, and rangeland systems through the USDA, with a national system of ARS research locations and partial support of State Agricultural Experiment Stations, State Agricultural Extension Services, and university teaching activities funded through USDA’s extramural funding agency NIFA.
The ARS research is organized into National Programs with four primary areas: (1) Animal Production and Protection; (2) Crop Production and Protection; (3) Natural Resources & Sustainable Agricultural Systems; and (4) Nutrition, Food Safety, and Quality. The national programs within each area are described at the following web link: http://www.ars.usda.gov/research/programs.htm.
Although the Rangeland, Pasture, and Forages national program (http://www.ars.usda.gov/research/programs/programs.htm?NP_CODE=215 is most directly related to US grasslands, with related projects being conducted in 20 states, nearly all of the national programs in each of the four areas have components needed for a system approach to grassland research.
Regional organization of the USDA-ARS involves the regions shown in Figure 7.1.
Many of the research locations in each of the regions have one or more important components of their research related to forage, livestock, pasturelands, and rangelands. Those with the greatest linkage to these systems are listed below. Information on each of the centres can be obtained from the interactive map (http://ars.usda.gov/pandp/locations.htm).
North Atlantic Area: (1) Pasture Systems and Watershed Management Research Unit, University Park, PA; (2) Plant Sciences Institute Soybean and Alfalfa Research Laboratory, Beltsville, MD; (3) Appalachian Farming Systems Research Center, Beaver, WV.
South Atlantic Area: (1) Plant Science Research (Plant-Animal Forage Interactions), Raleigh, NC; (2) Coastal Plains Soil, Water, and Plant Research Center Florence, SC; (3) Richard B. Russell Agricultural Research Center, Athens, GA; (4) J. Phil Campbell Sr. Natural Resource Conservation Center, Watkinsville, GA; (5) Plant Genetic Resources Conservation Unit, Griffin, GA; (6) Tifton Research Center, Tifton, GA.
Midwest Area: (1) North Appalachian Experimental Watershed, Coshocton, OH; (2) National Soil Erosion Research Laboratory, West Lafayette, IN; (3) U.S. Dairy Forage Research Center, Madison, WI; (4) North Central Soil Conservation Research Lab, Morris, MN; (5) St. Paul Research Center, St. Paul, MN; (6) National Laboratory for Agriculture and the Environment, Ames, IA; (7).
Mid South Area: (1) Forage Animal Production Research Unit, Lexington, KY; (2) Animal Waste Management Research Unit, Bowling Green, KY.
Northern Plains Area: (1) Northern Great Plains Research Laboratory, Mandan, ND; (2) Lincoln Research Center, Lincoln, NE; (3) Roman L. Hruska U.S. Meat Animal Research Center, Clay Center, NE; (4) Fort Keogh Livestock and Range Research Laboratory, Miles City, MT; (5) Rangeland Resources Research Unit, Cheyenne, WO; (6) The National Plant Germplasm System, Ft. Collins, CO; (7) Forage & Range Research Lab, Logan, UT; (8) Poisonous Plant Research Laboratory at Logan, UT.
Southern Plains Area: (1) Dale Bumpers Small Farms Research Center, Booneville, AR; (2) Hydraulic Engineering Research Unit, Stillwater, OK; (3) Grazinglands Research Laboratory, El Reno, OK; (4) Southern Plains Range Research Station, Woodward, OK; (5) Jornada Experimental Range, Las Cruces, NM; (6) Conservation and Production Research Laboratory, Bushland, TX; (7) Grassland Soil and Water Research Laboratory, Temple, TX; (8) Southern Plains Agricultural Research Center, College Station, TX.
Pacific West Area: (1) Vegetable and Forage Crop Research Unit, Prosser, WA; (2) Forage Seed and Cereal Research Unit, Corvallis, OR; (3) Range and Meadow Forage Management Research, Burns, OR; (4) U.S. Sheep Experiment Station at Dubois, ID; (5) The Exotic and Invasive Weed Research Unit with locations at Albany, CA, Davis, CA and Reno, NV.
USDA National Institute for Food and Agriculture (NIFA) and State Land Grant Universities
The unique mission of NIFA is to advance knowledge for agriculture, the environment, human health and well-being, and communities by supporting research, education, and extension programs in the Land-Grant University System and other partner organizations (http://www.csrees.usda.gov/). Land Grant Universities (both 1862 and 1890 institutions) (Figure 7.2) are the primary agricultural research entities for addressing local farmer, rancher, and land manager research and extension needs. Each state has at least one Land Grant University.
The top research challenge articulated for 1862 Land Grant Colleges and Universities during a 1993 national workshop was “the development of an economically stable and viable agriculture that is internationally competitive and environmentally sensitive; with multidisciplinary research involving food supply, environmental quality, biotechnology development, and an understanding of living systems”(Wedin and Jones, 1995).
For 1890 schools, the focus has been somewhat different: “strengthening research capacity for socio-economic problems and integration of social and technical research” (Wedin and Jones, 1995). The 1862 schools listed extension outreach priorities as: science, system, policies, and international issues, whereas 1890 schools had greater focus on problems of people and communities. Overall, at the completion of the national workshop, there was recognition of the need to focus on the entire human food system and to restructure accordingly with foci on production, health, safety, energy efficiency, and environmental quality. Links to US Land Grant Colleges and Universities are provided at: http://www.csrees.usda.gov/qlinks/partners/state_partners.html#maps.
To obtain the necessary resources from federal and state public funds in the future, there is an imperative need for all these entities and agencies to become associated with practical problems of a contemporary, large urban and suburban public, rather than just the traditional clientele of agricultural producers and managers. This will involve balancing the needs for basic research on fundamental understanding of plant, animal, soil, and atmospheric systems with more immediate needs for practical, problem-solving kinds of research. The continuing challenge is to develop and implement a plan for creating innovative systems for utilizing grazingland resources that are friendly to the environment and to society, economically sound, and maximize the number of citizens who are benefitted, now and in the future.
The Natural Resource Conservation Service (NRCS), initially established in 1935 as the Soil Conservation Service, “works with landowners through conservation planning and assistance to benefit the soil, water, air, plants, and animals for productive lands and healthy ecosystems. Working at the local level, in field offices at USDA Service Centers in nearly every county in the Nation, NRCS employees’ understanding of local resource concerns and challenges result in conservation solutions for the long term. Since 70% of the land in the US is privately owned, stewardship by private landowners is critical to the health of our Nation’s environment” (http://www.nrcs.usda.gov/about/).
The NRCS succeeds through partnerships, working closely with individual farmers and ranchers, landowners, local conservation districts, government agencies, Amerindian Tribes, Earth Team volunteers, and many other people and groups that care about the quality of natural resources. Administratively, the NRCS is organized into three regions: East, Central, and West. States associated with each of the regions and National Technology Support Centers in each region (Figure 7.3).
National centres for agricultural wildlife; geospatial management; soil survey; water and climate; water management; design, construction, and soil mechanics; information technology, employee development, and agroforestry are distributed around the US and listed at http://www.nrcs.usda.gov/about/organization/cent_inst.html.
Links to state offices are provided at: http://www.nrcs.usda.gov/about/organization/regions.html#state.
The US Forest Service (USFS), established in 1905, is an agency of the USDA. The Forest Service manages public lands in national forests and grasslands, which encompass >78 M ha. The mission of the USFS is “to provide the greatest amount of good for the greatest number of people in the long run" (http://www.fs.fed.us/aboutus/).
“The Forest Service works with a variety of state agencies, other federal agencies, and organizations to manage rangelands use.” http://www.fs.fed.us/rangelands/uses/index.shtml
The mission of the US Department of the Interior (USDOI) Bureau of Land Management (BLM) is to sustain the health, diversity, and productivity of public lands for the use and enjoyment of present and future generations (http://www.blm.gov/).
The BLM administers nearly 100 M ha of public lands and manages livestock grazing on >63 500 000 ha of those lands, as guided by Federal law. The terms and conditions for grazing on BLM-managed lands, such as stipulations on forage use and season of use, are set forth in the permits and leases issued by the BLM to public land ranchers.
The BLM administers nearly 18 000 grazing permits and leases held by ranchers for their livestock, mostly cattle and sheep, at least part of the year, on more than 21 000 allotments under BLM management (Figure 7.4). Permits and leases generally cover ten years and are renewable if the BLM determines that the terms and conditions of the expiring permit or lease were met. The amount of grazing that takes place each year on BLM-managed lands is determined by range conditions (affected by drought and wildfire), and the market situation. (Edited from http://www.blm.gov/wo/st/en/prog/grazing.html)
“In managing livestock grazing on public rangelands, the BLM’s overall objective is to ensure the long-term health and productivity of these lands and to create multiple environmental benefits that result from healthy watersheds. The Bureau administers public land ranching in accordance with the Taylor Grazing Act of 1934, and in so doing provides livestock-based economic opportunities in rural communities while contributing to the West’s, and America’s, social fabric and identity. Together, public lands and the adjacent private ranches maintain open spaces in the fast-growing West, provide habitat for wildlife, offer a myriad of recreational opportunities for public land users, and help preserve the character of the rural West.”
Several American professional societies have programs and activities related to forages and grazinglands.
Forage & Grassland Centers & Foundations
Personnel involved in forage and grazingland research and extension activities
The previously mentioned research organizations, agencies, universities, and foundations have forage, livestock, wildlife, and grazinglands personnel engaged in research, teaching, and outreach activities. Compiling a comprehensive and up-to-date list would be a nearly impossible task.
An alternative approach that should provide useful contact information is to identify web links to searchable personnel databases at the primary centres of activity. The following is a list of many of those primary sources.
Allen, V.G., Batello, C. Berretta, E.J., Hodgson, J., Kothmann, M., Li, X., McIvor, J., Milne, J., Morris, C., Peeters, A.& Sanderson, M. 2011. An international terminology for grazing lands and grazing animals. Grass and Forage Science 66, pp.2–28. onlinelibrary.wiley.com. Retrieved 8 March 2011.
American Meat Institute. 2009. U.S. Meat and Poultry Production & Consumption: An Overview. Washington, D.C.
Barbour, M.G., Burk, J.H. & Pitts, W.D. 1987. Terrestrial plant ecology. 2nd ed. Menlo Park, California, USA: The Benjamin Cummings Pub. Co.
Bertone, M., Green, J., Washburn, S., Poore, M., Sorenson, C. & Watson, D.W. 2005. Seasonal activity and species composition of dung beetles (Coleoptera: Scarabaeidae and Geotrupidae) inhabiting cattle pastures in North Carolina. In: Annals Entomological Society of America 98 (3), pp. 309–321.
Bazzaz, F. A. & J. A. D. Parrish. 1982. Organization of grassland communities. In: Estes, J.R.,Tyrl, R.J. & Brunken, J. N. (eds). Grasses and grasslands: systematics and ecology. Univ. of Oklahoma Press, Norman. pp. 233–254.
Byrd, W. 1728. Histories of the Dividing Line betwixt Virginia and North Carolina. Introduction by Adams, P.G. (1967) Dover Publications Inc., New York, NY.
Catlin, G. 1844. Letters and Notes on the Manners, Customs, and Conditions of the North American Indians, London. Republished in 1973 by Dover Publications, Inc. New York, NY.
Council for Agricultural Science and Technology. 1980. Forages: Resources for the Future. Report. 108. Ames, Iowa.
Daly, C. 2006. Annual Average Precipitation, United States of America. http://www.prism.oregonstate.edu/pub/prism/maps/Precipitation/Total/U.S./us.gif. Retrieved 27 Jan 2011.
Deneven, W. 1996. Carl Sauer and native American population size. The Geographical Review 86, pp. 385–397.
DeSelm, H.A. & Murdock, N. 1993. Grass-dominated communities. In: Martin, W.H., Boyce, S.G. & Echternacht, A.C. (eds). Biodiversity of the Southeastern United States – Upland Terrestrial Communities. John Wiley & Sons, New York. pp. 87–141.
Earley, L.S. 2006. Looking for Longleaf: The Fall and Rise of an American Forest. University of North Carolina Press. pp. 75–77. ISBN 0807856991.
Ensminger, M.E. & Perry, R.C. 1996. Beef Cattle Science. 7th ed. Prentice Hall. Upper Saddle River, NJ.
Flores, D. 1999. Essay: the Great Plains "wilderness" as a human-shaped environment. Great Plains Research, 9, pp. 343–355.
Franzluebbers, A.J. & Stuedemann, J.A. 2010. Surface soil changes during twelve years of pasture management in the Southern Piedmont USA. In: Soil Science of America Proceedings 74, pp. 2131–2141.
Fribourg, H.A., Hannaway, D.B. & West, C.P. 2009. Tall Fescue for the Twenty-first Century. Agronomy Monograph 53. American Society of Agronomy, Madison, WI. 539 pp.
Friedman, T.L. 2005. The World is Flat – A Brief History of the Twenty-first Century. Farrar, Straus & Giroux, New York. 488 pp.
Furseth, B.L., Conley, S.P. & Ané, J.M. 2010. Enumeration of soybean-associated rhizobia with quantitative real-time polymerase chain reaction. Crop Sci. 50: 2591–2596.
Gallant, A.L., Whittier, T.R., Larsen, D.P., Omernik, J.M. & Hughes, R.M. 1989. Regionalization as a tool for managing environmental resources.Corvallis, Oregon, U.S. Environmental Protection Agency.EPA/600/3–89/060, 152 pp.
Gartner, W. 1998. Pre-Columbian North America was no Eden. USA Today (Society for the Advancement of Education). http://findarticles.com/p/articles/mi_m1272/is_n2639_v127/ai_21098145/. Retrieved 28 March 2011.
Geist, V. 1998. Buffalo Nation: History and Legend of the North American Bison. Voyager Press, Stillwater, MN.
Gibson, D.J. 2009. Grasses and Grassland Ecology. Oxford University Press. 305 pp.
Gleason, H.A. 1913. The relation of forest distribution and prairie fires in the Middle West. Torreya 13: 173–181.
Gleason, H.A. & Cronquist, A. 1964. The natural geography of plants. New York, NY, USA. Columbia University Press.
Griffith, G.E., Omernik, J.M., Wilton, T.F. & Pierson, S.M. 1994. Ecoregions and subregions of Iowa - a framework for water quality assessment and management: The Journal of Iowa 101(1), pp.5–13.
Havstad, K.M., Peters, D., Allen-Diaz, B., Bartolome, J., Bestelmeyer, B., Briske, D., Brown, J., Brunson, M. Herrick, J., Huntsinger, L., Johnson, P., Joyce, L., Pieper, R., Svejcar, T. & Jin, Y. 2009. The western United States rangelands: a major resource. In: Wedin, W.F. & Fales, S.L. (eds). Grassland: Quietness and Strength for a New American Agriculture. American Society of Agronomy, Madison, WI. pp. 75–94. (Used with permission)
Helms, D. 2000. Soil and Southern History. In: Agricultural History 74, pp. 723-758.
Hite, A.H., Feinman, R.D., Guzman, G.E., Satin, M., Schoenfeld, P.A. & Wood, R.J. 2010. In the face of contradictory evidence: Report of the Dietary Guidelines for Americans Committee. Nutrition 26, pp. 915–924.
Holechek, J.L., R.D. Pieper & Herbel, C.H. 2001. Range management principles and practices. Upper Saddle River, New Jersey, USA. Prentice Hall.
IUSS Working Group WRB. 2007. World Reference Base for soil resources - A framework for international classification, correlation and communication. FAO.
Jackson, K.A. & Washburn, S.P. 2008. The effect of milk feeding method on cross-sucking behavior in pasture-based dairy calves fed once daily. Journal of Dairy Science 91, E - Supplement 1, p. 190 (Abstr.) http://adsa.asas.org/meetings/2008/abstracts/0189.PDF.
Jahns, T.R. & Quarberg, T. 2009. Selecting Perennial Forage Crops in Alaska. FGV-00245. University of Alaska Extension Service.
Juvik, S.P. & Juvik, J.O. 1998. Atlas of Hawaii. 3rd ed. University of Hawaii Press, Honolulu, HI.
Klebesadel, L.J. 1994. Comparative winterhardiness of cultivated and native Alaskan grasses, and forage yield and quality as influenced by harvest schedules and frequencies, and rates of applied nitrogen. Bulletin 99. Agricultural and Forestry Experiment Station, School of Agriculture and Land Resources Management, University of Alaska, Fairbanks.
Lauenroth, W.K., Milchunas, D.G., Dodd, J.L., Hart, R.H., Heitschmidt, R.K. & Rittenhouse, L.R. 1994. Effects of grazing on ecosystems of the Great Plains. In: Vavra, M, Laycock, W.A. & Pieper, R.D. (eds). Ecological implications of livestock herbivory in the West. Denver, Colorado, USA: Society for Range Management. pp. 69–100.
Lauenroth, W.K., Burke, I.C. & Gutmann, M.P. 1999. The structure and function of ecosystems in the Central North American Grassland Region. Great Plains Research 9, pp. 223–259.
Lawson, J. 1709 (1967 reproduction). A new voyage to Carolina. Edited and with an introduction and notes by Lefler, H.T. The University of North Carolina Press, Chapel Hill, N.C.
Laycock, W.A. 1979. Introduction. In: French, N.R. (ed). Perspectives in grassland ecology. New York, New York, USA: Springer-Verlag. pp. 1–2.
Leopold, A.S., Cain, S.A., Cottan, C.M., Gabrielson, I.N. & Kinball, T.L. 1963. Wildlife management in the National Parks: the Leopold Report. Advisory Board on Wildlife Management, Washington, D.C., USA.
Lopez-Villalobos, N, Garrick, D.J., Holmes, C.W., Blair, H.T. & Spelman, R.J. 2000. Profitabilities of some mating systems for dairy herds in New Zealand. Journal of Dairy Science 83, pp. 144–153.
Mann, C.C. 2006. 1491: New Revelations of the Americas before Columbus. Vintage Books. ISBN 9781400032051.
Manning, R. 1997. Grassland: The History, Biology, Politics and Promise of the American Prairie. Penguin Books. ISBN 0140233881.
Marble, V. L., McGuire, W.S., Raguse, C.A. & Hannaway, D.B. 1985. Hay and Pasture Seedings for the Pacific Coast States. In: Heath, M.E., Barnes, R.F. & Metcalf, D.S. (eds). Forages. 4th ed. Iowa State Press, Ames. pp. 400–410.
May, J. 2001. Noninsured Crop Disaster Assistance Program Forage Program Recommendations. USDA, NRCS, Kamuela, HI 96743.
McBratney, A.B. & Lagacherie, G. 2004. Global Workshop on Digital Soil Mapping, Montpellier. 2004.
McBratney, A.B., Mendonça Santos, M.L. & Minasny, B. 2003. On digital soil mapping. In: Geoderma117 (1-2), pp.3–52. Elsevier B.V., Amsterdam.
McDaniel, P. 2011. The 12 Soil Orders: Soil Taxonomy. http://soils.cals.uidaho.edu/soilorders/index.htm . Retrieved 01 February 2011.
Mills, A. 2009. EVSC 4270: Soil Science. University of Virginia. http://www.evsc.virginia.edu/~alm7d/soils/. Retrieved 31 January 2011.
Monger, H.C. & Martinez-Rios, J.J. 2001. Inorganic carbon sequestration in grazing lands. In: Follett, R.R., Kimble, J.M. & Lal, R. (eds) .The Potential of U.S. Grazing Lands to Sequester Carbon and Mitigate the Greenhouse Effect. CRC Press, Boca Raton FL, USA. pp. 87–118.
Motooka, P.M., Castro, L., Nelson, D., Nagai, G. & Ching, L. 2003. Weeds of Hawaii's pastures and natural areas - An identification and management guide. College of Tropical Agriculture and Human Resources, University of Hawaii, Manoa, Honolulu, HI.
National Cattlemen’s Beef Association.2011. Beef Quality Assurance Program. http://www.bqa.org. Retrieved 06 April 2011.
National Climatic Data Center. 2011. Climate of Alaska. http://www.dec.state.ak.us/AIR/ap/docs/Clim_AK_01.pdf . Retrieved 28 January 2011.
NOAA. 2007. Climate of Hawaii. http://www.prh.noaa.gov/hnl/pages/climate_summary.php. Retrieved 28 January 2011.
Norman, H.D., Wright, J.R., & Powell, R.L. 2006. Is there a need for different genetics in dairy grazing systems? In: Proceedings of the 6thMid-Atlantic Dairy Grazing Conference: Oct 31- Nov 1. Center for Environmental Systems, Goldsboro, NC.
Omernik, J.M. 1987. Ecoregions of the conterminous United States (map supplement): Annals of the Association of American Geographers 77 (1), pp. 118–125 (scale 1:7 500 000).
Omernik, J.M. 1995. Ecoregions - a framework for environmental management. In: Davis, W.S. & Simon, T.P. (eds). Biological assessment and criteria-tools for water resource planning and decision making.Boca Raton, Florida, Lewis Publishers. pp. 49-62.
Panciera, M.T. 2010. Factors affecting cold hardiness development. Crop Production and Soil Management Series, FGV-00143, University of Alaska Extension Service.
Pannell, D.J., G.R. Marshall, N. Barr, A. Curtis, F. Vanclay, and R. Wilkinson. 2006. Understanding and promoting adoption of conservation practices by rural landholders. Australian Journal of Experimental Agriculture. 46:1407–1424.
Pieper, R. D. 2005. Grasslands of central North America. In Suttie, J.M., Reynolds, S.G. & Batello, C. (eds). Grasslands of the World. Plant Production and Protection Series No. 34, pp. 221–263. Food and Agriculture Organization, United Nations, Rome, Italy. ISBN 9251053375.
Pyman, M.F.S. 2007. A comparative study of the productivity, selected health parameters, and reproductive performance of Holstein-Friesian x Jersey crossbred cows in predominantly Holstein or Jersey herds in Victoria. Ph.D. Thesis, University of Melbourne, Victoria, Australia.
Pyne, S.J. 1982. Fire in America, a Cultural History of Wildland and Rural Fire. University of Washington Press, Seattle, WA.
Ring, C. & Noggles, S. 2002. Rangeland Monitoring Fact Sheet. Range and Pasture. Technical Note Number MT-29. USDA-NRCS Plant Materials.
Ripperton, J.C. & Hosaka, E.Y. 1942. Vegetation Zones of Hawaii. Hawaii Agricultural Experiment Station, Bulletin 89. University of Hawaii, Honolulu, HI.
Ritter, M.E. 2006. The Physical Environment: An Introduction to Physical Geography.
Rossiter, D.G. 2004. Global Workshop on Digital Soil Mapping, Montpellier.International Union of Soil Sciences.
Rountree, H.C., Clark, W.E. & Mountford, K. 2007. John Smith’s Chesapeake Voyages, 1607–1609. University of Virginia Press, Charlottesville, VA.
Scull, P., Franklin, J., Chadwick, O.A. & McArthur, D. 2003. Predictive Soil Mapping - a Review. In: Progress in Physical Geography 27(2), pp. 171–197.Sage Publications.
Sieg, C.H., Flather, C.H. & McCanny, S. 1999. Recent biodiversity patterns in the Great Plains: implications for restoration and management. Great Plains Research 9, pp. 277–313.
Sims, P.L. 1988. Grasslands. In: Barbour, M.G. & Billings, W.D. (eds). North American terrestrial vegetation. New York, N.Y., USA. Cambridge University Press. pp. 324–356.
Smeins, F. 1994. Little bluestem-Indiangrass-Texas winter grass - SRM 717. In: Shiflet, T.N. (ed). Rangeland cover types of the United States. Denver, Colorado, USA.Society for Range Management. pp. 65–66.
Spangenberg, G., R. Kalla, A. Lidgen, T. Sawbridge, E.K. Ong & U. John. 2001. Breeding forage plants in the genome era. pp. 1-39. In Spangenberg, G. (ed) Proc. 2nd Int. Symp. Molecular Breeding of Forage Crops. Kluwer Academic Pub., Dordrecht, Netherlands.
Stanturf, J. 2009. Use of Fire by Native Americans. The Southern Forest Resource Assessment Summary Report. Southern Research Station, USDA Forest Service. http://www.srs.fs.fed.us/sustain/report/fire/fire-06.htm. Retrieved 25 January 2011.
Taubes, G. 2008. Good Calories, Bad Calories: Challenging the Conventional Wisdom on Diet, Weight Control, and Disease. Anchor Books, New York, NY.
Transeau, E.N. 1935. The prairie peninsula. Ecology 16, pp. 423–437.
Trewartha, G. 1961. The earth’s problem climates. Madison, Wisconsin, USA. University of Wisconsin Press.
Undersander, D.J., Bouton, J.H., & Massengale, M.A. 2009. The Road Ahead: Policy, Programs, and Progress. In: Wedin, W.F. & Fales, S.L. (eds). Grassland – Quietness and Strength for a New American Agriculture. American Society of Agronomy, Madison, WI. pp. 235–247.
USA Today (Society for the Advancement of Education). 1998. Pre-Columbian North America was no Eden. The CBS Interactive Business Network. http://findarticles.com/p/articles/mi_m1272/is_n2639_v127/ai_21098145/. Retrieved 6 March 2011.
US Census of Agriculture. 2007. http://www.agcensus.usda.gov/Publications/2007/index.asp. Retrieved April 6, 2011.
USDA. 1948. Grass: The Yearbook of Agriculture. U.S. Government Printing Office. Washington, D.C. 892 pp.
USDA-ARS. 2007. National Program 215: Rangeland, Pasture, and Forages. http://www.ars.usda.gov/research/programs/programs.htm?np_code=205&docid=15876. Retrieved 27 January 2011.
USDA-ERS. 2009. Briefing Rooms: Cattle: Background. http://www.ers.usda.gov/Briefing/Cattle/Background.htm. Retrieved 11 January 2011.
U.S. Environmental Protection Agency. 2003. Level III ecoregions of the continental United States (revision of Omernik, 1987). Corvallis, Oregon, U.S. Environmental Protection Agency - National Health and Environmental Effects Research Laboratory Map M-1. (various scales).
USGS. 2006. Regional Trends of Biological Resources – Grasslands. Prairie Past and Present. Fig. 2. http://www.npwrc.usgs.gov/resource/habitat/grlands/pastpres.htm. Retrieved 27 January 2011.
Van Dyne, G.M. & Dyer, M.I. 1973. A general view of grasslands - a human and ecological perspective. In: Analysis of structure, function and utilization of grassland ecosystems. Proposal submitted to the National Science Foundation. Colorado State University, Fort Collins, Colorado, USA. pp. 38–57.
VanRaden, P.M. & Sanders, A.H. 2003.Economic merit of crossbred and purebred US dairy cattle. Journal of Dairy Science 86, pp. 1036–1044.
Washburn, S.P. 2009. Lessons learned from grazing dairies. In: Proceedings 46th Florida Dairy Production Conference, Gainesville, April 28. pp. 57–68. http://dairy.ifas.ufl.edu/dpc/2009/Washburn.pdf. Retrieved 06 April 2011.
Washburn, S.P., Silvia, W.J., Brown, C.H., McDaniel, B.T. & McAllister, A.J. 2002a. Trends in reproductive performance in Southeastern Holstein and Jersey DHI herds. Journal of Dairy Science 85, pp. 244–251.
Washburn, S.P., White, S.L., Green, Jr., J.T., & Benson, G.A. 2002b. Reproduction, mastitis, and body condition of seasonally calved Holstein and Jersey cows in confinement or pasture systems. Journal of Dairy Science 85, pp. 105–111.
Wedin, W.F. & Jones, P.J. 1995. Innovative systems for utilization of forage, grassland, and rangeland resources. In: Proceedings of Workshop on Innovative Systems for the Utilization of Forage/Grassland/Rangeland Resources. Airlie, VA, 22-24 Sept 1993. Published by Minnesota Extension Service, St. Paul, MN. ISBN 1-888440-02-3.
West, N.E. 2003. Theoretical underpinnings of rangeland monitoring. Arid Land Research and Management 17, pp. 333–346. http://www.gis.usu.edu/~doug/frws3710/readings/westtheory.pdf.
Western Regional Climate Center. 2011. Climate of Hawaii. http://www.wrcc.dri.edu/narratives/HAWAII.htm. Retrieved 05 February 2011.
White, S.L., Sheffield, R.E., Washburn, S.P., King, L.D. & Green, Jr., J.T. 2001. Spatial and time distribution of dairy cattle excreta in an intensive pasture system. Journal of Environmental Quality 30: 2180–2187.
Wiken, E. 1986. Terrestrial ecozones of Canada. Ottawa, Environment Canada, Ecological Land Classification Series No. 19. 26 pp.
Williams, A.R. 2006. Niche Beef Marketing: Current Status. The Jacob Alliance, LLC. http://www.csuchico.edu/grassfedbeef/documents/AllanRWilliams%20Leopold%20.pdf. Retrieved 11 January 2011.
Williams, C. M. 2007. Effects of crossbreeding on puberty, postpartum cyclicity, and
fertility in pasture-based dairy cattle. M.S. Thesis. North Carolina State University.
Williams, G.W. 2003. References on the American Indian use of Fire in Ecosystems. http://www.blm.gov/heritage/docum/Fire/Bibliography%20-%20Indian%20Use%20of%20Fire.pdf. Retrieved 25 January 2011.
Wolfe, E.C., J.A. Paul & Cregan, P.D. 2006. Monitoring ley pastures and their response to winter cleaning. Australian Journal of Experimental Agriculture 46, pp. 1023–1033. doi: 10.1071/EA04074.
Additional Reference Resources
Anderson, M.K. 2006. Tending the Wild: Native American Knowledge and Management of California’s Natural Resources. Berkeley: University of California Press.
Anon. 2011. Climates of the United States.Wikipedia. http://en.wikipedia.org/wiki/Climate_of_the_United_States. Retrieved 28 January 2011.
Bailey, R.G., Avers, P.E., King, T. & McNab, W.H. (eds) 1994. Ecoregions and subregions of the United States (map) (supplementary table of map unit descriptions compiled and edited by McNab, W.H. & Bailey, R.G. Washington, D.C., U.S. Department of Agriculture-Forest Service (scale 1:7 500 000).
Birkeland, P. 1999. Soils and Geomorphology, 3rd ed. Oxford University Press. ISBN 9780195078862.
Brady, N.C. & Weil, R.R. 1996. The Nature and Properties of Soil.14th ed. Prentice Hall, Pub.
Brown, J.K. & Smith, J.K. 2000. Wildland fire in ecosystems: effects of fire on flora. In: General Technical Report RMRS-GTR-42, Vol. 2, pp. 40, 56–68. Department of Agriculture, Forest Service, Rocky Mountain Research Station. http://www.treesearch.fs.fed.us/pubs/4554. Retrieved 20 July 2008.
Brown, K.L. & Sorrells, N.T. 2004. Virginia’s Cattle Story. The Virginia Cattlemen’s Foundation and The Dairy Foundation of Virginia. Lot’s Wife Publishing, Staunton, VA.
Coates, K.S. 2002. 1. Border Crossings. In Findlay, J.M., & Coates, K.S. Parallel Destinies: Canadian-American Relations West of the Rockies. University of Washington Press. pp. 3–5. ISBN 9780295982526. http://books.google.com/books?id=4leTYpWOE5UC&pg=PA3. Retrieved 14 December 2010.
Cole, J.B., van Raden, P.M. & Multi-State Project S-1040. 2009. Net merit as a measure of lifetime profit. 2010 revision.
College of Tropical Agriculture and Human Resources, University of Hawaii, Manoa, HI. Hawaii Beef Initiative. 2003. Hawaii Forages.
College of Tropical Agriculture and Human Resources, University of Hawaii, Manoa, HI. 2010. Hawaii Rangelands.
College of Tropical Agriculture and Human Resources, University of Hawaii, Manoa, HI. Hawaii. 2010. Beef Initiative.
Commission for Environmental Cooperation Working Group. 1997. Ecological regions of North America - toward a common perspective: Montreal, Quebec. 71 pp.
Dick-Peddie, W.A. 1993. New Mexico Vegetation: Past, Present and Future. University of New Mexico Press. Albuquerque, NM, USA.
Dokuchaev, V.V. 1879. Short Historical Description and Critical Analysis of the More Important Soil Classifications. In: Transactions Society Natural Sciences Vol. 10, St. Petersburg. pp. 64-67. [In Russian]
Doswell, C. A. 1997. III. Severe Storms. Presentation at III Jornades de Meteorología Eduard Fontsere, sponsored by Catalán Meteorological Society (15-16 Nov 1997), Barcelona, Spain.
Esque, T.C. & Schwalbe, C.R. 2002. Alien annual grasses and their relationships to fire and biotic change. In: Tellman, B. (ed). Invasive Exotic Species in the Sonoran Desert Region. University of Arizona Press, Tucson, AZ, USA. pp. 165-194.
Fenneman, N.M. 1931. Physiography of the Western United States. McGraw-Hill Book Company, New York, NY. 534 pp.
Glinka, K.D. 1927. Dokuchaiev's Ideas in the Development of Pedology and the Cognate Sciences. Russian Pedological Investigations No. 1, USSR Academy of Sciences, Leningrad.
Gottfried, G.J. & Pieper, R.D. 2000. Pinyon-juniper rangelands. In: Jemison, R. & Raish, C. (eds). Livestock management in the American Southwest: Ecology, society and economics. Elsevier, Amsterdam. pp. 153-211.
Griffith, G.E., Omernik, J.M. & Azevedo, S.H. 1998. Ecoregions of Tennessee (Map poster). U.S. Geological Survey, Reston, VA.
Havstad, K.M., Peters, D.P.C., Skaggs, R., Brown, J., Bestelmeyer, B. T., Fredrickson, E., Herrick, J. E. & Wright, J. 2007. Ecosystem services to and from rangelands of the western United States. Ecological Economics. DOI:10.1016/j.ecolecon.2007.08.005.
Herrick, J.E., Bestelmeyer, B.T., Archer, S., Tugel, A. & Brown, J.R. 2006. An integrated framework for science-based arid land management. Journal of Arid Environments 65: 319-335.
Humphrey, R.R. 1958. The desert grassland: a history of vegetational change and an analysis of causes. Botanical Review 24, pp. 193–252.
Ingalls, J.J. 1948. In praise of blue grass. In: USDA Yearbook of Agriculture. Government Printing Office, Washington, DC. pp. 6–8.
MacMahon, J.A. 1988. Warm deserts. In: Barbour, M.G. & Billings, W.D. (eds). North American terrestrial vegetation. Cambridge University Press, New York, NY, USA. pp. 232–264.
McAuliffe, J.R. 1994. Landscape Evolution, Soil Formation, and Ecological Patterns and Processes in Sonoran Desert Bajadas. In: Ecological Monographs 64, pp. 111–148.
McClaran, M.P. 2003. A century of vegetation change on the Santa Rita Experimental Range. USDA Forest Service Proceedings RMRS-P-30.
McPherson, G.R. 1997. Ecology and Management of North American Savannas. University of Arizona Press, Tucson, AZ.
Milchunas, D.G. 2006. Response of plant communities to grazing in the southwestern United States. Gen. Tech. Rep. RMRS-GTR-169.Fort Collins, CO. U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station. 126 pp.
Miller, R.F, Bates, J.D., Svejcar, T.J., Pierson, F.B. & Eddleman, L.E. 2005. Biology, Ecology and Management of Western Juniper. Oregon Agricultural Experiment Station Technical Bulletin 152, Oregon State University, Corvallis, OR, USA.
National Assessment Synthesis Team, US Global Change Research Program. 2000. Climate Change Impacts on the United States - The potential consequences of climate variability and change: Overview: Great Plains.
National Cooperative Soil Survey Program. 2011. http://soils.usda.gov/partnerships/ncss/. Retrieved 28 March 2011.
Newman, Y.C. 2011. Forages of Florida webpage. Agronomy Department, University of Florida.
Newman, Y.C., Vendramini, J.V. & Blount, A. 2010. Bahiagrass (Paspalum notatum); overview and management. SS AGR-332, Agronomy Department, Cooperative Extension Service, University of Florida.
NRCS.2009. National Range and Pasture Handbook. http://www.glti.nrcs.usda.gov/technical/publications/nrph.html. Retrieved 31 January 2011.
NRCS, 2009. Web Soil Survey. http://websoilsurvey.nrcs.usda.gov/app/HomePage.htm. Retrieved 31 January 2011.
NRCS Soils Website. 2011. http://soils.usda.gov/. Retrieved 31 January 2011.
Peters, D.P.C., Bestelmeyer, B.T., Herrick, J.E., Monger, H.C., Fredrickson, E. & Havstad, K.M. 2006. Disentangling complex landscapes: new insights to forecasting arid and semiarid system dynamics. BioScience 56, pp. 491–501.
Schlesinger, W.H., Reynolds, J.F., Cunningham, G.L., Huenneke, L.F., Jarrell, W.M., Virginia, R. A. & Whitford, W.G. 1990. Biological feedbacks in global desertification. Science 247, pp. 1043–1048.
State LANDSAT Satellite Image. 2002. State Land Use District Map., Hawaii.
Statewide GIS Program, Department of Business and Economic Development, State of Hawaii. state_landsat.jpeg;
State Land Use Commission. 2002. State Land Use District Map. Hawaii Statewide GIS Program, Department of Business and Economic Development, State of Hawaii.
State Land Use Commission. 2002. State Watershed Boundary Map. Hawaii Statewide GIS Program, Department of Business and Economic Development, State of Hawaii.
U.S. Department of Agriculture-Soil Conservation Service. 1981. Land resource regions and major land resource areas of the United States. Agriculture Handbook 296. 156 pp.
Webb, W.P. 1931. The Great Plains. Ginn and Company. Boston, MA. 525 pp.
West, N.E. & Young, J.A. 2000. Intermountain valleys and lower mountain slopes. In: Barbour, M.G. & Billings, W.D. (eds). North American terrestrial vegetation. 2nd ed. United Kingdom, Cambridge University Press, Cambridge. pp. 255–284.
Whitney, L.D., E. Y. Hosaka and J. C. Ripperton. 1939. Grasses of the Hawaiian Ranges. Hawaii Agricultural Experiment Station, Bulletin 82, University of Hawaii, Honolulu, HI.
Wikipedia, 2011. Köppen climate classification. http://en.wikipedia.org/wiki/K%C3%B6ppen_climate_classification. Retrieved 05 February 2011.
Wishart, D.J. (ed). 2004. Encyclopedia of the Great Plains. University of Nebraska Press. Lincoln, NE. 919 pp.
Woods, A.J. & Omernik, J.M. 1996. Ecoregions of Pennsylvania. In Pennsylvania Geographer XXXIV No. 2, pp.3–37.
Woods, A.J., Omernik, J.M., Brockman, C.S., Gerber, T.D., Hosteter, W.D. & Azevedo, S.H. 1998. Ecoregions of Indiana and Ohio. (Map poster). U.S. Geological Survey, Reston, VA.
Woods, A.J., Omernik, J.M., Brown, D.D. & Kiilsgaard, C.W. 1996. Level III and IV Ecoregions of Pennsylvania and the Blue Ridge Mountains, the Ridge and Valley, and the Central Appalachians of Virginia, West Virginia, and Maryland. Corvallis, Oregon, U.S. Environmental Protection Agency, National Health and Environmental Effects Research Laboratory, EPA/600R-96/077. 50 pp.
World Reference Base for Soil Resources, IUSS. 2007. An international reference base for soil classification. http://en.wikipedia.org/wiki/Soil. Retrieved 28 March 2010.
David B. Hannaway
Peter J. Ballerstedt
Joel R. Brown
Evert K. Byington
Andrés F. Cibils
James P. Dobrowolski
Henry A. Fribourg
David B. Hannaway
Yoana C. Newman
Rex D. Pieper
Edward B. Rayburn
George H. Taylor
Steven P. Washburn
ACKNOWLEDGEMENTS: The authors and editors of this Country Pasture Profile for the United States express their thanks to the American Forage and Grassland Council (AFGC) for identifying and arranging for some of their members to contribute to this publication; these include Ed Rayburn and Steve Washburn for Sections 4 and 5.2. Also thanks to the Society for Range Management (SRM) for identifying and arranging for some of their members to contribute to this publication; these include Joel Brown for Section 2 and Joel Brown, Rex Pieper, and Andrés Cibils for Section 5.1. The editors also express their thanks to professional colleagues who contributed their time and expertise for reviewing some sections of this publication; particular mention is appropriate for Don Ball, Auburn University, and John C. Waller, University of Tennessee.
The authors of section 5.2 acknowledge the help of individuals who assisted by providing local knowledge of the climate and pasture-based livestock production systems used throughout this large, diverse, and beautiful region: Don Ball, AL; Michael R. Panciera, AK (currently in KY); Chuck West, AR; Dennis W. Hancock, GA; Richard Hungerford, IL; Victor R. Shelton, IN; Ray Smith, KY; Les Vough, MD; Rich Kersberger, ME; John Zinn, MN; Mark Kennedy, MO; Bob Hendershot, OH; Elcide Valencia, Puerto Rico; John Andre, SC; Gerald W. Evers, TX; Chris Teutch, VA; and Jenn Colby, VT.
Details of those organizations and persons who provided graphics for the profile (especially photographs) are mentioned throughout the text.
This document should be cited as follows:
[The draft profile was completed in July 2011 and lightly edited by S.G. Reynolds and J.M. Suttie in August and September 2011. Additional editorial changes were made in the period December 2011 – February 2012].