XI WORLD FORESTRY
CONGRESS
Antalya, Turkey, 13 to 22
October 1997
  VOLUME 8E. STUDENT ESSAYS SELECTED FOR THE TRAVEL AWARDTECHNOLOGICAL STUDY IN RESPECT OF TWO SPECIES
Alejandro Barrantes Barrantes1
SUMMARY Socratea exorrhiza and Iriartea deltoidea are two species of arborescent palms specific to tropical humid forests which must be assessed in economic terms for their utilization and protection, since they have great potential for multiple use. In this paper, the density of palms of these two species in the forest and the average height to which the trunk can be exploited for timber production are studied. The sawmill yield, the process of drying and physical/ mechanical properties are determined. The results obtained indicate that there is an average population of 164 palms per hectare, of which 50% are exploitable to a height of 7.5 m, with high-quality drying being observed in a period of 35 days, and adequate physical and mechanical properties which categorize the timber as excessively heavy, with average contractions, high flexion capacity, strong resistance to compression and very great hardness, all of which impart an economic value to the two palms studied. Key words: Palms, density, sawmill, drying, properties INTRODUCTION Resources in tropical forests are being over-exploited without there being any opportunity to study the production potential of the species which compose them, most natural forests being located in developing countries. A decade ago, GONZALEZ, M. (1987), considered that these countries were actively bringing about the destruction of forests in order to improve their own economies. Today, this is still a reality for many of those nations, which, in the effort to find solutions, create ecological and social problems. The owners of natural forests in Latin America are for the most part families with low economic resources, many of them natives. Forestry owners need to know the potential economic value of forest phytogenetic resources in order to achieve efficient exploitation, protecting and managing forests in an appropriate way. As part of the process of assessing forestry resources, research into two species of arborescent palm with a high use potential -Socratea exorrhiza and Iriartea deltoidea - is summarized in this paper. The objectives of the research were as follows: · To compile data which allow the number of palms per hectare for a tropical humid forest in Atlantic Costa Rica to be defined. · To define the commercial height of the trunk of the palms. · To determine sawmill yield in respect of each of the two species. · To evaluate the quality of air drying of the timber. · To determine the physical and mechanical properties of the timber of both species of palm. METHODOLOGY To determine the number of parcels required in calculating the density of the palms, a preliminary sampling was carried out by measuring the diameter of all the individuals on parcels located at random, with an area of 3 000 m 2, and then applying the procedure proposed by the Mexican Forestry and Fauna Subsecretariat (1976). The exploitable trunk height of the palms was obtained by sectioning the trunk of the palm sample up to a height such that the woody or timber-yielding part surrounding the soft centre of the palm trunk will show a thickness not less than two or two and a half centimetres. To guarantee that after the processing of the logs into timber, sections of around one centimetre in thickness were produced. The sawmill yield was obtained by the difference between the total volume of the logs and the volume of timber obtained. To evaluate the drying of the timber, weekly readings were taken of the moisture content until equilibrium with the environment was reached. The physical properties were calculated using a minimum of two test pieces from each palm composing the sample. Each test piece was weighed and measured and its volume determined at different moisture content levels. The mechanical properties of flexion and compression were determined using the methodology proposed by HOHEISEL, H. (1974), while hardness was established using Brinell's timber hardness methodology (NURMINEN, T., 1994). RESULTS Palm density per hectare is high in the case of both species, representing a significant volume of genetic material which could be utilized by means of sustainable management or for the establishment of plantations. This is feasible, given the characteristics of these species as regards the traditional uses and properties of the timber. Table 1. Number of palms per hectare in the case of each species.
Note that the number of individuals is greater in the case of Iriartea. The average usable height of the palms for timber production is 7.5 metres and this, together with the density data, means that the economic value of the palms is considerable. With regard to sawmill production, average yields were noted of some 35% - values similar to those from exploitation on forest plantations. In the following table, sawmill yields are shown. Table 2. Sawmill yields in the case of Socratea and Iriartea.
Sawmill yield is expressed in percentages. In the process of drying the timber, it was found that this reaches equilibrium with the environment in 35 days; it does not suffer warping or contractions and the greatest loss of moisture occurs in the first 14 days, a fact which allows us to describe the drying of the timber as rapid and of high quality. Table 3. Average moisture content values in the case of timber from Socratea and Iriartea.
The basic specific weight and dry specific weight categorize the palms as excessively heavy according to a classification proposed by GONZALEZ (GONZALEZ, 1973) for defining timber quality. The mechanical properties of Socratea and Iriartea are valuable, in accordance with [the findings of] Ecuador's Ministry of Agriculture and Stockfarming (1978), by virtue of a high flexion capacity, strong resistance to compression and extreme hardness. Table 4. Physical and mechanical properties of the two palm trees studied.
a. contraction of unseasoned timber at 0% moisture content b. breakage module. c. compression parallel to the fibre d. lateral hardness These species of palms have been used by the natives of Costa Rica and other countries in Latin America, and this may have influenced their continued existence in the forest. At least in Costa Rica, in the territories inhabited by non-native peoples, the populations of these palms have decreased, perhaps because they are cut down to consume the heart, which is in great demand on account of its taste. The natives use the leaves of the palms to build roofs and containers, which they use for feeding animals, the trunk for building purposes (dwellings, enclosures, etc.) and the fruit as pig feed, while other parts of the palms are used in craft trades and medicine (CASTILLO, U.; BORGE, C., 1995). Since both palm trees possess broad quality, have the capacity for multiple uses and are extensively distributed in tropical countries, conservation and management measures must be taken to prevent their exploitation; this ought not to take place unless the resource is adequately assessed and its continued existence guaranteed for use in the future. REFERENCES CASTILLO, V.; BORGE, C. 1995. Especies de Flora y Fauna usadas por los indígenas Bríbris y Cabécares de Talamanca. San José, Universidad de Costa Rica. pp. 24-34. GONZALEZ, M; GONZALEZ, G. 1973. Propiedades físicas, mecánicas usos y otras características de algunas maderas comercialmente importantes en Costa Rica. pp. 6-20. GONZALEZ MEZA, R. 1987. Algunas causas de la deforestación en Costa Rica y sus posibles soluciones. Costa Rica. Ministerio de Agricultura y Ganadería, Departamento de Investigación Forestal. 11 pp. HOHEISEL, H. 1974. Estipulaciones para los ensayos de propiedades físicas y mecánicas de la madera. Mérida, Centro de documentación y publicaciones del Instituto Forestal Latinoamericano. pp. 1, 22-26. SUBSECRETARIA FORESTAL y de la FAUNA. 1976. Procedimientos básicos para inventarios forestales con fines de aprovechamientos maderables. México. Publicación Nš37. pp. 13, 14. MINISTERIO DE AGRICULTURA Y GANADERIA. 1978. Estudio preliminar tecnológico de 20 especies forestales del Ecuador. Centro Forestal de Coonocoto. pp. 22-25. NURMINEN, T. 1994. Nutzung des Holzes der Pejibaye-Palme. (Bactris gasipaes H.B.K.) Thesis (Diplomholzwirt.) Hamburg, Institut für Holzphysik und Mechanische Tecnologic des Holzes der Bundesforschungsanstalt für Forst - und Holzwirtschaft. Universität Hamburg. pp. 46-49, 113-115. 1 Technological Institute, Costa Rica; Apdo.159-7050, E-mail: beieme@sol.racsa.co.cr Cartago, Rep. de Costa Rica.
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