Influence of site index on the growth of Pinus patula Schltdl. et Cham. plantations

Abstract

The objective of this study was to evaluate the influence of the site quality on the growth and increase of a Pinus patula plantation in Ixtlán de Juárez, Oaxaca. In a plantation established in 1995, there were thirty 400 m2 sites systematically distributed for carrying out a forest inventory of the trees. Dendrometric variables were measured and growth cores were extracted from two dominant trees at each site in order to obtain the mean annual increment (MAI), the current annual increment (CAI) and the ring width in the early and late wood. With data on the height and age of trees from the plantation and natural forest, functions were adjusted to estimate the site index (SI) by using the curve method with a baseline age of 40 years. Analysis of variance was performed using site qualities as a classification variable, and the increase in early and late wood was estimated by means of regression models. The quality of the site influences the dasometric and growth variables in P. patula (p = 0.0001). In addition, the total ring width for a low and an excellent SI was found to be 5 and 8.85 mm, respectively. Increases in early and late wood are positively correlated with the site quality (p = 0.0001). Therefore, the specific gravity of the wood is lower in higher quality sites. The optimal growth for the early and late wood varies in relation to the site quality. The increase and growth of Pinus patula is determined by the site quality.