D.U.U. Okali
D.U.U. OK ALI is with the Department of Forest Resources Management of me University of Ibadan in Nigeria. This article is taken from his paper Forest resources given at the symposium on the state of Biology in Africa held in Accra, Ghana, April 1981. The symposium was sponsored by the International Council of Scientific Unions (ICSU) and Unesco.
All the forest values of Africa are threatened with extinction as the ecosystems which provide them recede through degradation or conversion to less stable forms. In setting priorities for forestry research in Africa, therefore, pride of place must go to conservation research, and here the immediate task is the elaboration of methods to increase the productivity and efficiency of ecosystem utilization. (1)
Much has been written in recent years on forest resources conservation and the research needed to achieve this. Roche (2) cites many of the publications. To them must be added the very relevant treatments of the broader subject of research that are needed to fill in gaps in scientific information on tropical ecosystems (see Unesco reports). (3, 4, 5)
If, as suggested by Harley.(6) priority must go to increasing the production and efficiency of ecosystem utilization, the first task of conservation research must be to learn how to do this. It requires setting aside adequate portions of the ecosystems of interest, particularly those that are threatened with extinction, in order to study them and understand how they function. Identification of such ecosystems, determination of adequate size and appropriate shapes and patterns of such areas, and an understanding of appropriate management techniques form the first practical steps. These must be based on some knowledge of the requirements of the ecosystem components, so quick surveys and preliminary investigations must be undertaken to provide the necessary guidelines. The study of species/area curves (7, 8) is relevant to the size of the area chosen to be set aside for effective conservation of communities.
Because of the great diversity of plant and animal life in Africa, the complexity of biological structures and organizations and the variety of adaptive processes, practically all aspects of biological research contribute to the advancement of basic scientific knowledge.
The next task is the examination of the structural dynamics and the evaluation of factors which may lead to changes in the preserved ecosystem. All aspects of ecosystems study are involved here. They are not enumerated singly since there is hardly an aspect of ecosystems study in Africa for which a reasonably complete knowledge can be claimed.
Monitoring of changing dynamics will be aided by surrounding the preserved plots with comparable areas under various management treatments. Strict natural reserves set within the Biosphere Programme of Unesco in conjunction with the International Union for the Conservation of Nature and Natural Resources (IUCN) fit this model of ecosystems preservation for scientific study.
Improved utilization of forest resources depends next on the possession of quantitative knowledge of the distribution and availability of these resources and of the ecosystems which bear them. Research is needed to improve methods of inventory and evaluation. Quantitative analysis of plant form (9) from which allometric relationships can be established, (10) as an aid to rapid evaluation of resource amounts in forest crops, is relevant in this field. Particular importance is attached to taxonomic appraisal of organisms in forest resources because of the necessity for precise definition of the source of desirable attributes for the purposes of selection, breeding and improvements. Taxonomic research is one of the least developed fields in many African institutions concerned with training or research in forest resources. Knowledge of the available resource includes exploring comprehensive uses for already-known species and for new species that can be used for various purposes. Expansion of existing lists of economic species and full use of the so-called secondary species are one way of improving utilization of the forest wood resources.
Full utilization is also promoted by controlling big-deterioration of harvested products. Particularly for wood, this can be achieved through intensified research on the biology of the causal agents of big-deterioration, as a basis for effective control measures. (11) The discovery of the source of natural timber resistance to wood-decaying fungi is also a challenging area of conservation research.
Managing ecosystems so that they yield their benefits in perpetuity means conserving them. Therefore, research is required to develop optimal management regimes for natural ecosystems that yield forest resources. Sustained use demands utilization practices that ensure adequate regeneration. Detailed studies of the major components of ecosystems will be needed to define limits within which the environment can be altered to ensure continued regeneration. Information on productivity and carrying capacities for species of interest will be needed to plan sustained utilization. There are large gaps in the study of plant response to tropical environments. Field, or at least whole-plant, physiological studies need to be intensified in order to understand factors controlling growth periodicities in tropical environments. The trigger mechanisms for the change from vegetative to reproductive growth, for the alternation of periods of active growth and dormancy and for leaf shedding and renewal, which are not apparently synchronized with obvious changes in the environment, must be discovered.
SELECTING A MOTHER TREE IN GHANA conservation = productivity
The inability to interpret growth rings and, therefore, to date many tropical trees remains a serious constraint to forest management. It limits the ability to use age in the assessment of growth rates and, hence, productivity on which rational utilization depends.
The increased production of wood and food from the same piece of land in a stable agro-forestry system will relieve natural ecosystems of the pressure of exploitation and make it much easier to conserve them than is now the case.
When desired levels of utilization or production cannot be attained in natural systems, attention is turned to artificial production, as in plantation establishment or domestication. Similarly, conservation ex situ may require the establishment of plants in plantations, botanical gardens or arboreta or the rearing of animals in captivity in zoological gardens. A knowledge of the total biology of the species involved, including their relations with other organisms, e.g., as symbionts in mycorrhiza, as pests, or as pollinating and seed dispersal agents, is a prerequisite to successful establishment or rearing. Some of the most intractable biological problems under study in forest resources research are in this area. There is still inadequate knowledge of the reproductive behaviour, seedling establishment requirements and pest relationships of such important forest trees as Chlorophora spp. and the mahoganies, some of the most valuable and, therefore, most heavily exploited African timber species. Yet, there are no satisfactory techniques for their multiplication or regeneration by artificial establishment, mainly because of unsolved insect pest problems. Knowledge of drought adaptation mechanisms is also essential for selecting or developing species adapted to use in shelterbelts.
Problems of multiplication and propagation by vegetative means - grafting, budding and rooting of cuttings - need to be solved, as do problems of artificial pollination required for breeding research. The whole area of breeding for improved stock of African forest products, barely touched until now, needs urgent attention in the interests of conservation. In this regard, it should be noted that the breeding strategy for improving individual tree performance is different from that required for improving stand productivity. Evidently, the physiological components affecting growth of individual trees are not the same as those affecting the productivity of the total stand (12) and both need to be investigated.
In a sense, the most radical approach to solving the problem of optimizing productivity of ecosystems that have been converted from the natural state is agro-forestry. The efforts of many international organizations, principally the International Council for Research in Agro-Forestry (ICRAF) based in Nairobi, the United Nations University (UNU) at Turrialba and the International Development Research Centre (IDRC) of Canada, are concentrated in this area. The biological research needs for optimization of production systems are outlined in several publications of these organizations or their agencies. (13, 14) The mixed-cropping system envisaged in agro-forestry requires the selection of tree and agricultural crop species that can be grown together, simultaneously or sequentially, with or without overlapping phases, on the same piece of land. An understanding of the problems of interference and competition in such mixtures is basic to the selection of ideal mixes. Such problems may include allelopathic influences from residues of any of the component species. The basis of the soil-rejuvenating abilities needs to be more quantitatively understood than at present. This area of research is emphasized in the agro-forestry project now being implemented in the Department of Forest Resources Management, University of Ibadan, with financial support from IDRC. If the possibilities of agro-forestry now being researched are eventually realized and widely adopted in practice, the system will represent a fundamental change in land-use practice for conservation, especially in humid tropical forest ecosystems. The increased wood and food production from the same piece of land in a stable agro-forestry system will relieve natural ecosystems of exploitation pressure, thus making their conservation more possible than would otherwise be the case.
BUILDING A FISH TRAP IN NIGERIA life = a balanced ecosystem
Contributions of fundamental significance can result, and have resulted, from research endeavours primarily directed at solving some of the practical problems outlined above. The need to assess the resource potentials of the tropical rain-forest ecosystem, for instance, requires that its structure and floristics be studied. Many new species have thus been discovered among the rich flora and fauna of tropical forest ecosystems. The complexity of structural organization and the variability revealed from such studies have contributed to a revision of ideas on the organization of plant communities based on the experience of less complex temperate ecosystems. For instance, the notion that plant communities are organized in "discrete associations," to be studied by the methods of the Zurich-Montpellier School of Phytosociology and classified, has been modified to accommodate the continuum concepts of North American vegetation ecologists. (15) In fact, the combination of both classification techniques used for the study of continua and classificatory techniques has been found to be useful at different levels of vegetation analysis. (16) The point is that intensifying research into the complex tropical forest ecosystems that exist in Africa can contribute to the improvement of vegetation analysis and inventory techniques. In the same way, recent studies of plant architectural forms developed from examination of tropical trees are contributing to the under standing of strategies by which plants exchange energy and matter with their environment. (17) These studies also need to be intensified. In addition, recent ideas that represent plant succession as a Markovian replacement process, to be understood and predicted by the use of replacement probabilities. (18) need to be verified by tests on tropical forest vegetation.
Generalizations the range of plant and animal behaviour remain premature until full account has bee taken of tropical organisms. This was the case with the mechanism of photosynthesis which was believed to be generally by the C3 pathway (19) until the C4 pathway (20) was discovered in tropical plants. Similar fundamental discoveries can still be made by intensifying biological research on African forest resources. One of the Ibadan University Department of Forest Resources Management's special areas of interest is the study of water use by forests. It has been argued that it is necessary to assess at least some of the environmental impacts of the large-scale changes taking place in the forested landscape in developing countries. This is being done in part by making measurements that will allow the development of models that can be used for predicting water use by various tree species. One of the measurements made is the stomatal conductance of leaves. In two separate studies (21) (and Grace, Okali and Fasehun, unpublished), the stomatal conductances recorded for the two most widely planted forest trees in Nigeria - Gmelina arborea and teak (Tectona grandis) - were found to be very high indeed, at least three times the values published for trees by Korner et al. (22) in a recent review based on data from species of different ecological groups. High values of stomatal conductance have also been obtained by other workers (Osonubi and Davies, unpublished) for Gmelina. It is not yet known whether such high values are characteristic of the family Verbenaceae, to which the two species studied belong, or whether they are a general feature of tropical trees. Stomatal conductance and the conductance of the boundary layer of air surrounding leaves - aerodynamic conductance - together contribute to the control of water loss by transpiration. Aerodynamic conductance is low for large-sized leaves (e.g., Gmelina and teak). Wind tunnel measurements on models of leaves of the two species,(23) however, show this to be counterbalanced by the very high stomatal conductances, so that overall conductance and, hence, the effect of this on the rate of water loss is similar to that of temperate species with smaller sized leaves. Attempts have been made by some authors (24, 25) to specify optimum leaf size in terms of efficiency of water use in relation to assimilation rate. Since, as- in the illustration given above, the effects of large-sized leaves on water loss and assimilation can be greatly modified by high stomatal conductances, such attempts are clearly premature for tropical forests where the range of values of stomatal conductances has not been fully explored.
Managing ecosystems so that they yield their benefits in perpetuity means conserving them.
The point made here is that basic scientific knowledge can be enhanced by biological research aimed primarily at solving the practical problems of African forest resources. Practically every aspect of biological research can contribute something because of the great diversity of plant and animal life, the complexity of structure and organization and the variety of adaptive processes induced by these attributes. Much research remains to be done on tropical ecosystems before generalizations can be made on plant and animal response and behaviour patterns.
The nature of forest resources as geographically bound entities demands that each resource be studied where it exists. So, it is imperative that study centres be established in strategic locations in the various ecological zones and sub-regions of Africa. However, in order that the effort may not be dissipated by too tenuous a network of researchers, centres of importance where particular kinds of research may be concentrated must be recognized. The location of such centres will be determined not only by the resource problems prevailing in them, but also by the availability of the necessary expertise and a developed tradition of research in the particular fields. For instance, an important research centre on methods of rehabilitating degraded forest ecosystems, particularly through the development of agro-forestry, should be located in the West African sub-region; for research on natural forest management systems, in the Central African sub-region; for resource survey, evaluation and monitoring, in East Africa, using institutions like the Kenya Rangeland Monitoring Unit as the nucleus; for wildlife management, again in East Africa based on the Wildlife School at Mweka; while a centre for shelterbelt research should be located in the Sahelian zone. Concentration in strategic centres should also promote multi-disciplinary approaches to forest resource management studies because of the larger numbers and variety of scientists so assembled. The centres should serve also for training in research techniques so that trained scientists can be dispersed to build up local research capabilities where the resources actually exist.
All the forest values of Africa are threatened with extinction; the ecosystems that provide them are receding because of degradation or conversion to less stable forms.
A major constraint to the implementation of the network idea for research in forest resources is likely to be the lack of adequate manpower. Increased mobility of scientists between centres might alleviate this problem temporarily, but, for the long term, massive training in the biological and other sciences is required. Another constraint is likely to be the securing of national commitments, first, to the idea of stepping up biosciences research in the various countries by increasing funding, and, second, to the idea of international cooperation so that centres of importance located outside national boundaries are recognized and supported. A flow of information between centres through publications and meetings will need to be developed.
Finally, the means of conveying research findings to decision makers, resource developers and users must be incorporated into the idea of the research centre network. Biological research scientists must develop their investigations and interpretations so that they can be readily disseminated, if necessary, through extension specialists. It has to be recognized by both the scientists and those responsible for funding research that the bottleneck to the application of science to resource utilization often materializes at this point. After all, what is the use of scientific research if it is not put to use for the benefit of mankind?
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3. UNESCO. 1978 Tropical forest ecosystems: a state of knowledge report. Unesco Natural Resource Research XIV, Paris.
4. UNESCO. 1979a Trends in research and in the application of science and technology for arid zone development. Unesco MAB Technical notes 10, Paris.
5. UNESCO. 1979b Science and technology in humid tropical ecosystems. Unesco contribution to ACAST Colloquium on Science, Technology and Society, Vienna.
6. HARLEY, J. 1978 Op. cit.
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