Morphologie de la base du fut et contraintes de croissance chez Eperua falcata Aublet

Eperua falcata Aublet, best known under its vernacular name Wapa, represents more than 20%, in volume, of the potential wood production of the French guianian forest (its spatial repartition is aggregative). Its xylem has an excellent natural durability with good mechanical properties in relation to density (0,85). However, its use as a resource is very limited because the output of raw material is very uncertain. This is particulary affected by an important split risk when felling and deformation during sawing and drying, because of tension-wo<: A presence and a high fissility (DETIENNE and THIEL, 1988), (VALENTIN et al., 1987). The objective of this study was to measure the quality of standing-timber. We tried to establish a reliable relationship between external macro-characteristics (in this case the morphology of the bole base) and wood quality. For the latter, the selected criterion was the intensity of longitudinal growth tensions on the surface of upright stems, by measuring the residual longitudinal deformations of maturation, (R.L.D.M.)(BAILLERES , 1991). The number of samples selected was limited to 10 Wapas and measurements were carried out in the Yiyi forest, track of Saint-Elie, French Guiana. All these trees had buttresses, generally 5 in number. Their organization was as follows: facing the slope, the tree presented a hollow, surrounded by two buttresses, making an angle* between 45' and 90' with the slope direction. The others buttresses were more variably distributed around the circumference. The R.L.D.M. measurements (698 in total) are made in accordance to the method termed "Single-hole method". It consists of measuring the increase variation, due to the drilling of a central hole, between 2 pins initially 45mm apart and aligned along the grain. (Résumé d'auteur)