Hardwood timber resources of the United States
This paper is published in relation to the report on mainly tropical hardwoods reproduced in Unasylva, Volume 23 (2) and (3)7 1969. The authors, D. Hair and B. Spada, are with the Division of Forest Economics and Marketing Research of the U.S. Forest Service.
An analysis of the latest available data indicates that the hardwood timber situation in the United States is improving for most species and in most major producing regions. For example, the 1968 sawtimber inventory was 5 percent above the 1963 inventory and 14 percent greater than in 1953. Net annual growth of sawtimber size trees in 1967 was estimated at 17 500 million board feet ¹ - 31 percent more than removals of 13 400 million board feet.
¹ For conversion tables see FAO yearbook of forest products.
This suggests that the hardwood forests in the United States could support an increased level of cutting, especially in view of the expected intensification in forest management and improved utilization practices. It is probable that during the next ten years most of the additional demand for hardwood lumber and perhaps some of the demand for veneer and plywood could be met from domestic forest resources. But, beyond the next decade or so, the outlook is not so promising, because the projected demands for hardwood lumber, veneer and plywood rise more rapidly than projected supplies. This means that the United States may have to turn toward the hardwood tropical forests of Latin America, Africa and Asia as sources of supply for high quality hardwood products.
Nevertheless, it is considered that the hardwood forest lands in the United States have the capacity, under intensive management, of producing enough hardwood timber to meet projected demands for several decades.
In 1967 there were approximately 269 million acres of commercial hardwood forest types in the United States exclusive of interior Alaska. About 51 percent of these forests were in the north and 45 percent in the south (Figure 1). The remaining 4 percent were in the west, chiefly in western Oregon, western Washington, and the central Rocky Mountain states. The eastern hardwood forest types compose about 70 percent of the commercial forest area in the east and half of all the commercial forest area in the country.
The eastern hardwood forest types contain a large number of commercial hardwood species. In the forest survey statistics of the United States, these species are grouped into six major types (see Table 1).
FIGURE 1. Distribution of hardwood forests
TABLE 1. - MAJOR COMMERCIAL HARDWOOD SPECIES OF THE EASTERN UNITED STATES
|
Eastern hardwood forest type groups |
Area |
|
Million acres |
|
|
Oak-hickory. |
116.0 |
|
Oak-gum-cypress |
37.8 |
|
Maple-birch-beech |
33.3 |
|
Oak-pine. |
27.0 |
|
Aspen-birch. |
23.7 |
|
Elm-ash -cottonwood |
20.4 |
|
Total |
258.2 |
As of 1 January 1968, the total volume of hardwood growing stock 2 ill all forest types was 207 500 million cubic feet, including 487 000 million board feet of sawtimber 3. As illustrated in Figure 2, about 54 percent of this was in the north, 36 percent in the south, and 10 percent in the west. About 70 percent of the hardwood timber was in farm and miscellaneous private ownerships. Another 14 percent was in forest industry ownerships. The remaining 16 percent was about evenly divided between the national forests and other public ownerships, chiefly state and county.
² Growing stock is defined as the net volume in live trees of commercial species 5.0 in dbh and over from a 1-ft stump to a minimum 4.0 in top diameter outside bark of the central stem, or to the point where the central stem breaks into limbs.³ Sawtimber is defined as the net volume of timber in the saw log portions of live trees of commercial species over 11.0 in dbh containing at least one log.
FIGURE 2. Distribution of hardwood timber volume
Logs of large size and high quality can be produced from nearly all hardwood species. However, a few preferred species provide most of the material used in cabinet work, panelling, furniture, and other purposes in which quality and/or surface appearance are important. Generally, the preferred species for these uses include select white and red oaks, 4 yellow birch, hard (sugar) maple, sweetgum, yellow poplar, ash, black walnut, and black cherry. These select species composed about a third of the total volume of hardwood growing stock in the United States in 1968 (Figure 3). The remaining hardwood volume consisted of species such as upland oaks, hickory, beech, cottonwood, and various other species that have more limited potential as a source of high- quality hardwood products.
4 The select white oaks include Quercus alba, Q. michauxii, Q. muehlenbergii, Q. durandii, Q. bicolor, and Q. macrocarpa. Select red oaks include Q. rubra, Q. falcata var. pagodaefolia, and Q. shumardii.
With the spread of fire protection and other forestry programmes in the last few decades, the hardwood timber situation in the United States has been improving. This improvement has been increasingly evident in the last couple of decades. For example, in the 5-year period 196369 the total inventory of hardwood growing stock in the United States increased by 7 percent - rising from 193 800 million cubic feet to 207 500 million cubic feet. In the preceding 10 years - 1953-63 - the inventory rose by 15 percent. Most of the increases have been on the stands in the northern and Pacific Coast areas.
There has been some variation in the percentage increase in inventory of growing stock by diameter class, as indicated in Table 2.
TABLE 2. - INCREASE IN GROWING STOCK BY DIAMETER CLASS
|
Diameter class |
Inventory volume |
Percentage increase |
|
|
1963 |
1968 |
||
|
Inches |
Thousand million cubic feet |
||
|
5.0 - 11 0 |
92.8 |
99.2 |
6.9 |
|
11.0 - 15.0 |
49.4 |
53.3 |
7.9 |
|
15.0 -19.0 |
29.2 |
30.8 |
5.6 |
|
19.0 -29.0 |
19.8 |
21.7 |
9.3 |
|
29+ |
2.5 |
2.5 |
- |
Especially noteworthy is the 9.3 percent increase in the 19.0-29.0-inch diameter classes because much of the material of this size is suitable for the manufacture of high-grade veneer, plywood, and lumber.
The largest part of the increase in timber inventory was in the less desirable species such as the upland oaks, hickory, beech, cottonwood, and soft maple. There were, however, increases in the inventory of some preferred species such as the select white and red oaks (6.6 percent), hard (sugar) maple (10.4 percent), and yellow poplar (19.5 percent) (Figure 4). In contrast, the inventory in yellow birch dropped 16.2 percent and black walnut 10.6 percent. The decline in inventory in these species occurred in all diameter classes - an indication that these intolerant species have had difficulty in competing with other species in the unmanaged second growth stands characteristic of the eastern United States.
FIGURE 3. Distribution of hardwood timber
Most of the important hardwood regions showed some increase in timber inventories in the 1963-68 period. The largest gains were in the southern and middle Atlantic regions, where the inventories rose by 4 347 and 3 730 million cubic feet respectively. There were also substantial increases in inventories in the lake states and central Gulf regions.
The western Gulf and central regions were the only ones showing a decline in growing stock inventories. The drop was especially large in the western Gulf region where the inventory fell from 21 146 to 16 799 million cubic feet. The drop was largest in the bottomland hardwood species and presumably reflects the effects of land clearing.
FIGURE 4. - Change in inventory of hardwood species 1963-68
Sawtimber inventories have followed the general trends outlined above. The inventory of 487 000 million board feet in 1968 was 5 percent above the 1963 inventory and 14 percent greater than that in 1953.
The trends in inventory provide one measure of the improving hardwood timber situation in the United States. Another important measure is the relationship between net annual growth and annual removals. In 1967 the net annual growth of growing stock was some 7 400 million cubic feet - some 67 percent above the removals of 4 400 million cubic feet. In sawtimber size trees, the net annual growth was 17 500 million board feet - 31 percent more than removals.
As illustrated in Figure 5, the net annual growth of growing stock was in excess of removals for all species. However, the excess of growth over removals was small for sweetgum and fragmentary data indicate that removals are substantially greater than growth for black walnut.
Net annual growing stock growth in the north in 1967 was 4000 million cubic feet, or 2.3 times the removals of 1 800 million cubic feet. The largest surplus was in the middle Atlantic region where growth (1 600 million cubic feet) was more than three times removals.
FIGURE 5. Net annual growth and removals of hardwood growing stock
In the south, net annual growing stock growth was 2900 million cubic feet - 14 percent more than removals. Nearly all of the excess of growth over removals in this section was in the south Atlantic and central Gulf regions. Growth and removals were approximately in balance in the eastern Gulf region. There was a deficit in the western Gulf region with removals of about 517 million cubic feet and growth of about 631 million cubic feet.
The sawtimber situation by species and region was similar to that for growing stock with net annual growth substantially above removals for most species. The most important exceptions were yellow birch and sweetgum where removals were 23 percent in excess of growth for both species. Growth was also substantially higher than removals in most regions. The most notable exception was in the western Gulf region where removals were 55 percent greater than growth. Removals were also above growth (14 percent) in the eastern Gulf region.
The data in trends in inventory and growth and removals indicate that the hardwood timber situation in the United States has been improving for most species and in most major hardwood producing regions. The aggregate figures, however, conceal some problems. For example, the hardwood sawtimber volumes are dispersed over not only the 269 million acres in hardwood types but also as scattered trees in the softwood types. Much of the larger size timber suitable for the manufacture of high-quality lumber and veneer occurs as single trees or groups of trees that are not economically harvestable. In addition, part of the hardwood timber in the eastern regions is in small private tracts used primarily for homesites, recreation, or other nontimber purposes not compatible with timber harvesting.
Despite these limitations, it is clear that the hardwood forests, and especially the northern forests, can support an increased level of cutting. Although a substantial part of the available timber is so small or of such poor quality that it is best suited for pulp manufacture, the cut of sawtimber size material could be increased by possibly 2 to 3 thousand million board feet annually.
The improvement in the general hardwood timber situation reflects better management. In recent decades, protection, especially from fire, has been increasingly effective. There has also been gradual growth in management programmes such as planting and timber stand improvement.
Forest Service projections, based on the assumption that recent trends in intensive forest management will continue, show that the supply of hardwood timber will increase over the next couple of decades. The recent upward trends in inventories in the larger diameter classes suggests that there will also be increasing supplies of the larger sized and higher quality trees.
Projected increases in population, economic activity, and income suggest that there will be rapid growth in construction and industrial production - the chief determinants of the demand for hardwood lumber, veneer, and plywood. Forest Service projections, based on the assumptions that (a) recent trends in growth of these economic determinants will continue and (b) there will be no significant change in the prices of these products relative to competing materials, indicate the total demand for hardwood lumber may rise by as much as 3 000 million cubic feet and veneer and plywood by as much as 1400 million cubic feet in the next decade. Most of the additional demand for lumber and perhaps some of the demand for veneer and plywood could be met by use of the timber currently available and the additional growth expected in the years immediately ahead. Technological progress in the utilization of hardwoods could further increase the available domestic supplies.
Beyond the next few years, projected demands rise more rapidly than projected supplies. This narrowing margin between demand and supply could be accentuated by losses in the area available for hardwood timber production. For example, the substantial loss in the area in bottomland hardwood forests in the south in recent years has had a major impact on hardwood timber supplies, especially in the western Gulf region. Future conversions of this kind, the expansion of cities and withdrawals for highways, reservoirs, parks and other uses could substantially reduce the growth and inventory of hardwood timber below the projected levels.
In sum, it appears that there could be enough hardwood timber in the United States to supply most additional demands over the next decade or so. By then the margin between projected supplies and demand will narrow; this means that the United States will have to turn increasingly toward the tropical hardwood forests of Latin America, Asia and Africa as a source of supply for high quality hardwood lumber, plywood and veneer.
This outlook is based on the assumption that recent trends toward intensive forest management will continue. As has been stated, the hardwood forest lands in the United States have the capacity, under intensive management, of producing enough hardwood timber to meet projected demands for several decades, but this would require large investments in stand improvement, reforestation, and other silvicultural practices. Moreover, most of this investment would have to be made on small tracts in farm and miscellaneous private ownerships, which together contain 70 percent of the hardwood timber inventory.
