SOME ASPECTS ON CONSERVATION OF GENETIC RESOURCES OF INDIGENOUS FOREST TREE SPECIES OF CURRENT COMMERCIAL VALUE IN VENEZUELA ¹

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¹ From paper presented at the “Seminário Avanzado de Genética Agrícola para América Latina” (“Advanced Seminar on Agricultural Genetics in Latin America”), held in Maracay, Venezuela, 19–29 October 1969.
This article is a condenced version of one published in Revista Forestal Venezolana 1970, Vol. VIII, nbrs. 19/20

1. INTRODUCTION

On a par with other countries which are developing their silviculture and forest economy, Venezuela is taking its first steps in this field. This results in large-scale exploitation designed to meet the requirements of wood products of the growing population and to meet the needs of an expanding agriculture which constantly demands more land. As an example the inroads in the Sur del Lago region can be mentioned. In this region “the forest covered most of the region” (total area 642 375 ha) only 17 years ago. With the construction of the Pan-American Highway this forest area was reduced to some 80 000 ha, of which only 15 000 ha are now covered by forests of any commercial interest (Corrales et al., 1967). Regrettably this is but one of dozens of similar examples. State concern over this current, ever-present situation is well justified.

For this reason the Government has proposed “to make energetic and concrete decisions regarding forest policy and to adapt programmes which will ensure the uninterrupted, long-term development of forest resources and the re-establishment of forest areas that have been exploited, depleted or destroyed, to preserve the existing forests and to manage them in a more rational way, as this is the only way in which Venezuela can avoid future difficulties in the supply of forest products which could eventually turn Venezuela into a wood importing country” (MAC¹ 1968, p.53).

However, since past experience suggests that it is not possible to conserve all forest areas, we feel obliged to propose a programme for the conservation of forest genetic resources of species native to Venezuela.

¹ Ministério de Agricultura y Cría (Ministry of Agriculture and Livestock)

II. VENEZUELA'S MOST VALUABLE FOREST SPECIES AND THEIR NATURAL DISTRIBUTION

The volume cut of a given species is always a good criterion for its commercial value. A breakdown into producing units also gives an idea of the natural distribution which, incidentally, is roughly presented in “The Forest Atlas of Venezuela” (MAC 1961). We have made our evaluations for this paper on the basis of figures of timber cut in the years 1963/65, for lack of more recent data. However, it is reasonable to assume that the relative ranking of the exploited species has not changed even though the total volume of timber cut rose from 319 000m³ in 1963 to 476 000m³ in 1967 (MAC, 1968, p.266).

The information presented is taken from official MAC data published in Forestry Bulletins 3 and 4 (1963), 5 and 6 (1964) and 8 and 9 (1966). According to the figures presented by MAC we have calculated the average amounts of timber cut by States and by species. The figures are given in Table 1. The horizontal column reflects the importance of each species; light hardwood species, Anacardium excelsum and Bombacopsis quinata, head the list. They are followed by high-quality hardwoods; Tabebuia rosa, Swietenia macrophylla and Cedrela spp., after which come Pithecellobium saman (hardwooded) Hura crepitans (softwooded) Cordia alliodora (high-quality hardwood) and Erisoma uncinatum. The remaining species accounted for less than 2.5 percent of the cut during the three years considered.

The vertical columns in Table 1 show the most important wood producing areas and refer to States and MAC administrative districts. The district of Llanos Occidentales shows the biggest production of timber, followed by the Oriental, Occidental, Centro Occidental and Central districts, in that order. The States of Barinas and Portuguesa supplied approximately 66 percent of the total average cut for three years.

III. OBJECTIVES OF CONSERVATION OF GENETIC RESOURCES

The object of safeguarding forest genetic resources is to preserve the diversity of species, both commercial and potentially commercial, for the benefit of future generations. The use of genetic resources through tree breeding implies not only the protection of a few specimens, but that as much as possible of the genetic diversity of a species should be conserved. Unfortunately many native forest tree species of commercial value have already lost a great deal of this diversity. For example, in the state of Zulia, Bulnesia arborea, Aspidosperma spp., Tabebuia spp. and Bombacopsis quinata are species that will be practically lost to future generations unless effective measures to preserve them are urgently undertaken.

IV. POSSIBILITIES OF CONSERVATION

The Institute of Silviculture at the Faculty of Forest Sciences in Merida can practise genetic conservation only at a limited scale in its small experimental natural forests; however, having both responsiblity and knowledge of the situation, the Institute can draw the attention of the Bureau of Renewable Natural Resources of MAC to the urgent need to set up areas for genetic conservation of forest tree species on Government land. These areas could, for example, comprise:

1. National Parks*

2. Forest Reserves*

3. Botanical Reserves

4. Clone Banks

5. Seed Banks

a. National Parks. Present legislation (the Forestry and Water Law, Chapter 1, Articles 10 to 12) allows for satisfactory measures to conserve forest genetic resources. Article 10 states: “All areas which, because of their flora and fauna of national importance so warrant, shall be declared National Parks”. It is our opinion that genetic conservation of commercial forest tree species is included in this Article. The current allocation of forested areas for agricultural use makes this matter even more urgent. However, the greatest part of existing national parks do not coincide with the most important distribution areas of the forest species of greatest commercial value.

b. Forest Reserves. Their main function under the Law is “to ensure the continuous supply of raw material for the national industry” (Art. 54). This does not guarantee the conservation of native forest tree species since the requirement for a sustained supply of wood could also be met by cutting the natural forests and establishing new plantations of exotic species, such as Tectona grandis, Pinus caribaea, Gmelina arborea, Eucalyptus spp., etc. It is indispensable that in each type of forest and in every forest reserve sectors be set aside which can be managed rationally using silvicultural techniques that will ensure spontaneous or directed natural regeneration of the species in question (Finol, 1963, 1968; Petit, 1963). Another possibility is to set aside sectors of typical forests to be kept exclusively as botanical reserves and left untouched or, at the most, managed very conservatively so as to guarantee the perpetuity of the desired species of commercial or potentially commercial value.

c. Botanical Reserves. It is indispensable that MAC study the possibilities of establishing small botanical reserves to guarantee conservation of the variety of native forest tree species of present and future commercial value in those forested areas of the country that are not protected by decree as national parks or forest reserves and especially in areas where there is a heavy pressure for land for farming and cattle raising.

There is no firm rule for determining the optimal dimensions of areas devoted to gene conservation. However, existing knowledge on the composition and structure of some virgin Venezuelan forests indicate that 100 ha set aside for each forest type and for each of the country's life zones (as described by MAC) would meet the requirements.

d. Clone Banks. In addition to the above three means of conservation, it is possible to make use of the possibilities offered by vegetative propagation, feasible for numerous broad-leaved tropical forest species. A clone bank would contain a certain number of clones of every commercial species from each forest type and every life zone. Clones should be representative of their origin and their number should depend on the extension of the area of origin and its homogeneity. Each clone propagated by cuttings and/or grafts should be represented by 2 to 4 ramets.

e. Seed Banks. The most common way of preserving forest tree species for future genetic improvement is to store seed from individuals, varieties and populations of current or potential commercial value in conditions that will guarantee the viability of the germ plasm for several years.

In general seeds of species in the family of Pinaceae show high longevity when stored at low temperatures and with proper moisture contents. On the other hand, we still do not know the optimal storage conditions for most of the Angiosperms: the germinative capacity of these species may decline within a few months. For this reason there is an urgent need for research in this field.

* Legislative Provision is made for National Parks and Forest Reserves in the Forestry Law.

V. EVALUATION OF THE METHODS DESCRIBED

A prerequisite for the first three methods of in situ conservation of genetic resources - national parks, forest reserves and botanical reserves - is that appropriate areas are selected which will include the broadest possible genetic range of the species in question. The last-mentioned two methods - clone banks and seed banks - on the other hand, do not require selection of representative areas or individual selection. The material, collected at random, will include a representative range of the genetic spectrum of each of the species.

Setting aside and managing large Forest Reserves is the method closest to an optimum conservation method. However, because certain species are endangered with extinction due to the pressure from agriculture (especially in the Region of Llanos Occidentales) it is recommended that all the methods mentioned are applied to secure the conservation of forest genetic resources in Venezuela.

Because forest stands are constantly in a process of development, spontaneous natural regeneration is not sufficient (Finol, 1963; Petit, 1963) to ensure against the disappearance of commercial species in national parks and botanical reserves; - spontaneous natural regeneration would only be effective in conservation areas established in climax forests.

For this reason we insist that national forest policy in conservation aspects should be based on rationally managed forest reserves. Their protection must be efficient since they also form the base population for clone and seed banks. These last-mentioned two methods of genetic conservation of forest tree species are the ones most influenced by man and they thus have some disadvantages: firstly, the quantity and/or quality of the material introduced cannot be fully representative, and secondly, variation may not be sufficiently broad for future genetic improvement programmes. In other words, the selection is made on the basis of criteria which may differ from those that will be required in the future.

This grave danger must be foreseen well in advance. Geneticists direct their efforts towards increasing the volume of commercial yield and improving the properties of the wood in various environmental conditions. This makes it indispensable to preserve the widest possible range of variation of a species from the very beginning. If this principle is respected from the very beginning, the advantages of both these types of genetic conservation are outstanding, since both clone banks and seed banks require very little space and are very easy to manage and control.

VI. SUMMARY

Future work in genetic improvement of commercial forest tree species must be based on a wide range of variation within each species. National parks, forest reserves and botanical reserves can ensure conservation of genetic resources of native species provided certain requirements are met. The most economic and safe means of genetic conservation is the establishment of clone banks and seed banks for each of the important species from each forest type and each life zone of the country.

VII. RECOMMENDATIONS

Over one half of the world's forests are found in the tropics and subtropics, where forested areas are likely to be reduced because of the following reasons:

1. planned de-forestation of extensive areas to meet agricultural needs;

2. irrational exploitation of forests;

3. shifting cultivation;

4. forest fires.

The indication of the above is that in the future it will be necessary to produce wood and wood products from a smaller area than before. To meet the needs of a constantly growing population, relatively greater quantities of higher quality wood will have to be produced. In addition, some species are in danger of extinction or the natural variation in them is in danger of being reduced considerably. The species will thus be lost for future genetic improvement work. These considerations have led to the following recommendations:

1. Forest stands should be set aside on a national and/or international basis for conservation of forest genetic resources. The following possibilities may be considered:

   1. Certain areas where forest tree species of current or future commercial value are found should be declared national parks;

   2. Adequate representative areas in each life zone and forest type should be set aside as “seed stands” for forest species of commercial value (in Venezuela as forest reserves);

   3. Botanical reserves should be established where pressure from agriculture is greatest and where natural forests have practically disappeared (e.g. the tall xerophytic forests of the State of Zulia, rich in species with hard wood);

   4. Clone banks should be established for commercially valuable forest tree species, representing each life zone and every forest type;

   5. National and/or international seed banks should be created, that could be used jointly by countries interested in the conservation of the same forest tree species.

2. Research should be carried out concerning the viability of seeds of tropical forest tree species - especially the Angiosperms - under varying storage conditions.

3. Seed certification should be introduced, stating the origin of seeds for experimental and commercial purposes.

4. The recommendations given in the above points should in the case of Venezuela be applied as a minimum for all the species listed in table 1.

VIII. BIBLIOGRAPHY

Corrales, J.A., Soler R., Morales, E., and Gonzalez, M. Catastro rural de la zona sur del Lago de Maracaibo. Bol. For. No. 10, 51–67, MAC Caracas, 1967.

Finol, U.H.: Ensayos preliminares para lograr el establecimiento de la regeneración natural de unas especies comerciales en el bosque “El Caimital”. El Instituto de Silvicultura y sus Actividades de Investigación. Cuarta Semana de Conservación de los Recursos Naturales Renovables, Universidad de Los Andes, 118–124, Mérida 1963.

Finol, U.H.: Ensayos preliminares para lograr el establecimiento de la regeneración natural de unas especies comerciales en el bosque “El Caimital”. Primer Seminario sobre el Manejo de los Bosques Tropicales. Soc. Ven. Ing. For. Caracas 1968 a.

Finol, U.H.: Posibilidades del manejo silvicultural para las Reservas Forestales de la Región Occidental. Primer Seminario sobre el Manejo de los Bosques Tropicales. Soc. Ven. Ing. For. Caracas 1968 b.

Ley Forestal de Suelos y Aguas. Caracas, Marzo de 1966.

Ministério de Agricultura y Cría: Atlas Forestal de Venezuela, Caracas 1961.

Ministério de Agricultura y Cría: Memoria y Cuenta 67, Caracas 1968.

Ministério de Agricultura y Cría: Mapa ecológico de la República de Venezuela.

Petit, P.M.: Resultados preliminares de unos estudios sobre la regeneracíón natural espontánea en el bosque ‘El Caimital’. El Instituto de Silvicultura y sus actividades de Investigación. Cuarta Semana de Conservación de los Recursos Naturales Renovables, Universidad de Los Andes, 105 117, Mérida, 1963.

Wadsworth, F.: Sitios para investigación silvicultural en Venezuela. Dep. de Manejo de los Bosques, Centro de Estudios de Postgrado, Facultad de Ciencias Forestales. Mérida, Venezuela, 1969.

Table 1. MEAN ANNUAL EXPLOITATION OF COMMERCIAL FOREST TREE SPECIES (in m³) IN 1963/ 1965 IN THE DIFFERENT REGIONS OF VENEZUELA