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Trees for energy in Central America
Rich forests, poor soils
A manual on Prosopis tamarugo
Preserving wood in the tropics
How to make charcoal

Trees for energy in Central America

Silvicultura de especies promisorias para producción de leña en América Central. Resultado de cinco años de investigación. Publicación co-patrocinada por los Proyectos leña y fuentes alternas de energía. San José de Costa Rica. Technical Series, Technical Report No. 86, 230 pp.

This is a valuable monograph, which assembles data and information pertinent to wood-fuel for 24 native and exotic tree species of current use, or considered to have potential for cultivation in Central America.

Species included are: Acacia mangium, Alnus acuminata, Azadirachta indica, Caesalpinia velutina, Calliandra calothyrus, Cassia siamea, Casuarina cunninghamiana, C. equisetifolia, Eucalyptus camaldulensis, E. citriodora, E. deglupta, E. globulus, E. grandis, E. saligna, E tereticornis, Gliricidia septum, Gmelina arborea, Grevillea robusta, Guazuma ulmifolia, Leucaena diversifolía, Leucaena leucocephala, Melia azedarach, Mimosa scabrella and Tectona grandis.

Among the 13 exotics, the casuarinas, the eucalypts, Melia (chinaberry) and teak, are the most popular, showing their progressive penetration in a new forest tropical environment.

The field tests and observations were carried out in 1980-85 on a large number of localities of each of the six countries of the region and compared with many other species: thus, the information about the chosen 24 species implies that they are a very promising group for most of the needs and habitats, and uses of the rural people. The number of samples and study plots amount to about 670 units. In most cases the units have been measured three times in that period. The field observations were carried on by technical staff (of about 600 people) of the Proyecto Lena (the Fuelwood Project) under the coordination of the technicians of CATIE in El Salvador, Guatemala, Costa Rica, Honduras, Nicaragua and Panama.

A TEAK PLANTATION IN HONDURAS popular exotic in Central America

The study begins by analysing the importance of fuelwood in Central America and the two projects (on fuel wood and on alternative sources of energy) at the base of the present report-publication: a brief ecological description of the life zones of the region facilitates the placement and selection of the species. Information on each species includes a description of its taxonomy, environmental requirements, silvicultural features, growing limiting factors.

The study identifies the species behaviour under the various site situations like the volcanic highlands, isthmic highlands and neighbouring lowlands, volcanic highlands and lowlands of the Antillean coastline.

The classification of the natural vegetation uses life zones, following Holdridge's classification: the predominant (34 percent) zones were of the very humid forest type, followed by the premountain humid zones (27 percent), the tropical moist forest (15.5 percent), the very moist tropical (7.3 percent), and other types (16.2 percent).

The study covers the whole area of Central America with an area of 489000 km², and a population density of 47 per km², where agriculture is the fundamental economic activity. The forests occupy 40 percent of the territory, exposed to heavy rates of deforestation, estimated at an annual rate of 2-4 percent.

Through direct consultation with the technicians of each country, a preliminary list of species potentially interesting for the production of fuelwood was outlined on the basis of yields, growth and adaptation to the new or natural habitat. The list was progressively perfected and reduced to 34 species, 24 of which were selected and are at the base of the information for the present document, leaving the other ten earmarked for the future expansion of the studies. Almost half of them are native, of direct utilization or under cultivation in small stands, rows or hedges; the other ones are the exotics: some of local old tradition, and others of recent introduction.

The results on yields, which refer to very young plants and plantations (1600 to 2500 plants/ha), are limited; the information mainly concentrates on the adaptability to different environments and soils, and to the early growth in height and diameter. Other interesting observations, basic for the future development of specific utilization projects, refer to their behaviour under cultivation (seeds, planting material, nurseries, costs). Most of this information has been logged in computers and is therefore available for subsequent programming phases.

For example, for this type of crop any experience on coppice regeneration is very valuable for reforestation planning and expected output. So far, 19 out of the 24 species could be coppiced.

A. Flinta

Rich forests, poor soils

Nutrient cycling in tropical forest ecosystems: principles and their application in management and conservation. Carl F. Jordan. Institute of Ecology, University of Georgia. Athens, Georgia 30602 USA. John Wiley & Sons Ltd. 1985. 190 pp.

In the early 1980s, the University of Georgia's Institute of Ecology held a number of seminars on tropical forest ecology. The present book is an outgrowth of those seminars. Its principal purpose is to provide a scientific basis for the current debate over tropical deforestation.

The mystifying paradox of the humid tropical forest is the following: how can the most luxuriant and the richest ecological system on earth maintain itself upon apparently nutrient-poor soils? Elsewhere, rich forests mean rich soils and abundant crops. Why do they not do so in the tropics?

Briefly stated, Dr Jordan's answer is that tropical forests have developed effective ways of dealing with environmental stress. In their case, the principal stress does not come about through lack of moisture as in deserts or through low temperatures as in high latitudes. The stress comes about principally through the marginal functioning of the nutrient loss through leaching. Their most significant differences with forests in other regions of the world are the mechanisms they have developed to combat the stress of nutrient loss. Those mechanisms can only exist and function successfully within a complex ecosystem. In so far as disturbances interfere with that system, the stress of nutrient loss increases.

Hence the book's primary aim is to deal with nutrient cycling, a theme which it develops in five chapters.

Chapter I lays out the reasons why nutrients may be expected to be more critical in the tropics than at higher latitudes. The year-long high temperatures and high moisture availability largely eliminate the stresses of drought and cold. But those same circumstances have a high potential for nutrient loss. Actual loss is low because of the ecosystem's effective adaptations.

Chapter II explains in detail how the naturally occurring processes conserve nutrients. Most significantly they relate to the roots and below ground community. The forms of leaves and bark provide other means of combating nutrient loss. On the other hand, high nutrient concentration in leaf and wood tissues is not a nutrient-conserving mechanism characteristic of tropical species.

The environmental conditions of tropical regions are highly variable along three principal gradients. The first gradient which Chapter III discusses is that correlated with the state of weathering of the soil in evergreen forested ecosystems. The ecosystems on the most highly weathered soils display the highest development of nutrient-conserving mechanisms. The second gradient relates to elevation and the third to moisture availability. Apparently, ecosystems respond to stress of whatever kind in similar ways.

Although the number of nutrient elements found to be essential to life keeps increasing as research methods improve, Chapter IV discusses the nutrient cycles of eight in detail, divided into the volatile and non-volatile. Each follows a distinct pathway while interacting with each other in ways that maintain the functioning ecosystem, but only when no disturbances occur. Nevertheless, disturbances are part of the ecosystem. Therefore, an extremely important aspect to study and understand is the response of the various nutrient element cycles to disturbances of different kinds, intensities and durations.

Fittingly, therefore, Chapter V discusses the changes in nutrient cycles due to disturbance. While natural disturbances can be as light as the fall of a tree or as total as the effects of a volcanic eruption, the disturbances of most consequence to mankind are those of swidden agriculture. Moreover, unless another and better system of food crop production evolves for the tropics, swiddens will be with us for a long time to come. The responses of nutrient cycles thereto are thus matters of great moment to untold millions of people. The author's rather unstartling conclusions are that the most acceptable disturbances are the least in size, intensity, duration and frequency. How to reconcile them with man's needs for food, shelter and fuel are, however, beyond the scope of this book.

The author has presented clearly and logically a difficult, complex subject. There are an impressive 24 pages of references.

H. Kernan

A manual on Prosopis tamarugo

Prosopis tamarugo: today's state of knowledge. FAO, 1985. Prosopis tamarugo: estado actual del conocimiento. Round table. Arica, Chile. June 1984. 483 pp.

The Pampa del Tamarugal is a fascinating desert in the longitudinal valley of northern Chile, between the Sierra de la Costa and the Andes: a salty desert with underground moisture, accumulated partly centuries ago and partly through annual renewal; tropical by latitude and temperate by altitude. A predominant feature in this environment is the umbrella-shaped tamarugo (Prosopis tamarugo), tolerant to drought and highly resistant to salinity. Spanish settlers in the 1500s mentioned this tree and the uses made of it by the Indians for food, feed, fuel, posts and timber. Anthropological studies confirm its utilization by men as long as 6000 years ago. Although not much used for human food today, it still nourishes cattle, sheep, goats, bees and wildlife, with its leaves, pollen and fruits.

A century ago, devastated by mining activity and human use, the tamarugo was already threatened by overcutting. But not until the 1930s was anything done about it: manmade plantations were started, building up to about 14000 ha today.

Several local institutes have been doing research on the species and spreading interest into testing this species along with other Prosopis (P. chilensis, P. juliflora, P. alba, etc.) and related species in arid zones of the world.

It thus was not difficult for the FAO Regional Office for Latin America, jointly with Chilean institutes, to awaken interest in various countries to prepare pertinent papers and to propose a round table to discuss potential uses for the tamarugo.

The meeting took place at Arica, Chile, from 11 to 15 June 1984. It was attended by 91 technical delegates, 28 from outside Chile. Forty-two technical papers were submitted, including three for Africa and the Near East, one for Bolivia, two for Brazil and one for Haiti.

The University of Tarapacá, the Corporación Nacional Forestal Chilena (CORFO), FAO's Regional Office and the Agriculture Department of FAO, Rome, have contributed to publish the proceedings.

The round table handled the discussion in several panels.

Panel 1. The Chilean Case introduced six documents dealing with the present status of knowledge about the species and the natural region, the ecological and hydrological characteristics of the Pampa del Tamarugal, and the nutritional values of fruits and leaves of tamarugo.

Panel 2. Ecology introduced 12 documents dealing with these species and ecologically related ones, including experiences in Brazil, Chile, Haiti, India, the Libyan Arab Jamahiriya, the Near East and Africa. These documents dealt primarily with animal feed values (fruits and branches) from these species and crucial problems for the areas where they grow or where they can be cultivated.

Panel 3. Botany dealt with ten documents, nine of them on the tamarugo in Chile and one on P. chilensis. The discussion covered anatomy, fruit, seed and leaf morphology, water relationships and some phenological aspects.

Panel 4. Technological aspects included four papers covering physical and mechanical properties of the wood, natural durability and permeability, chemical composition of the wood and bark, and a method to extract gum from seed.

Panel 5. Animal production. This was discussed in four documents covering subjects such as land-stocking capacity and the utilization of the Pampa del Tamarugal with its nutritional values in forage and trees, including vitamin supplement requirements.

Panel 6. Various other aspects. These included problems with rodents and insects, as well as studies on the application of nitrogen to the Prosopis tamarugo, P. alba and P. chilensis.

PROSOPIS TAMARUGO report for arid zone foresters

Three regional "commissions" were convened during the meeting, for America, for Africa, the Near and Far East and for Chile. Each of the three commissions held sessions on its specific regional problems and made recommendations reflecting the magnitude of the problem of desertification, and the important role that these species could play in their natural environment. The delegate from Brazil made the proposal, unanimously approved, to hold a second international session on the tamarugo and other Prosopis in the northeast of Brazil, to be followed subsequently by a third session in Argentina. It was agreed that industries should be invited to attend the future sessions to exhibit their products and that each one of the interested countries should foster the organization of a national Prosopis association. The University of Chile offered its facilities to establish a centre of documentation of Prosopis. It was furthermore pointed out that, in addition to the need for permanent general coordination, interested countries should start establishing germ-plasm banks.

The final plenary session approved unanimously the recommendations of the three commissions as well as the creation of an International Prosopis Association.

As a final note, attention should be drawn to the bibliography on the genus Prosopis, based on the Data Centre for Desert Zones, CORFO, and the library of Ciencias Agrarias, Veterinarias y Forestales, Universidad de Chile. The subjects have been organized following the categories established by the AGRIS system. The preliminary systematic classification already indicates areas of major or minor knowledge, and where research may be most needed.

A. Flinta

Preserving wood in the tropics

Manuel de préservation des bois en climat tropical (2nd ed.). G. Deon. 116 pp. Numerous illustrations and tables. Price: FF 75 in France (excluding tax); abroad: FF 95.

This manual on wood preservation in tropical climates is a revised edition of the work published by the same author in 1978.

It is intended for all those who want to use wood, a material about which a great deal of ignorance still exists, and who want to do so in the best possible way, from both a technical and an economic point of view.

The author has tried to make the book simple, easy to read and, to a certain extent, attractive, by excluding difficult technical terms and too much scientific theory; the typical expressions very often used in connection with wood preservation are introduced as simply as possible as the book proceeds.

Each chapter generally consists of a theoretical part, i.e. analysis of the problem studied, a practical part explaining the methods used to solve it, a short conclusion and a summary.

The manual consists of three main parts:

· preservation of logs (wood-destroying agents and preservation rules);

· temporary protection of fresh sawn-wood and peeled veneer (attacks by insects and fungi, appropriate treatment);

· preservation of wood before use (causes of deterioration, natural durability of wood, preservative processes and products).

Copies may be obtained from Centre technique forestier tropical, Division des publications, 45 bis, Av. de la Belle-Gabrielle , 94736 Nogent-sur-Marne, CEDEX, France.

How to make charcoal

Guide technique de la carbonisation. D. Briane, J. Doat and A. Riedacker. EDISUD, Aix-en-Provence, 1985. 179 pp.

Three organizations collaborated in preparing this work: the Agence française pour la maîtrise de l'énergie (French Energy Control Agency), which is concerned with the rational use of energy, the development of new and renewable sources of energy, and economics in raw materials; the Association bois de feu (Fuelwood Association), whose aim is to help solve fuelwood problems in the developing countries; and the Centre technique forestier tropical (Tropical Forestry Technical Centre), whose Chemical Energy Division studies both the chemical properties and the energy characteristics of tropical wood.

The preface to the manual outlines the history of charcoal, without which the human race would probably never have emerged from the Stone Age, and which has enabled people to extract metal from stone and thus make the objects and tools that have shaped their environment. The technique, perfected over the years, was employed up to the nineteenth century, when coke gradually replaced charcoal, although even today charcoal is still used in producing certain metals that require great purity.

The aim of this book is to spell out the factors affecting charcoal yield and describe the many technical improvements and methods that can raise it. It also tries to identify the elements for assessing the advisability of setting up charcoal-making plants both in Europe and in the developing countries.

The first part of the book is devoted to analysing wood and its physical characteristics, charcoal and torrefied wood, the promising intermediate product. It also examines the uses of charcoal, which date back to remote times: in the developing countries this multipurpose fuel has been used for centuries for cooking food and heating houses and for artisanal work. An analysis is also made of the main factors affecting charcoal-making: reaction temperature, temperature gradient, length of operation and raw material used (species, moisture content, dimensions).

The second and by far the most important part deals with different types of kilns for the three kinds of carbonization: (partial combustion, contact with hot gases, and external heating) and the type of plan (artisanal or industrial).

There are two important annexes, describing the artisanal procedures currently in use or the subject of research, and various industrial and semi-industrial plants.

This compact volume provides in a relatively small space a mass of information for charcoal users everywhere, and shows how people in developing countries can obtain the maximum yield from their fuel and thereby ease the already intolerable pressure on their forests.

F. Banoun

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