EVOLUCIÓ N DE LAS PRINCIPALES VARIABLES DE Á RBOLES DE Pinus taeda L. SOMETIDOS A DIFERENTES TRATAMIENTOS SILVICULTURALES EN EL NORDESTE DE LA PROVINCIA DE CORRIENTES, ARGENTINA 1 EVOLUTION OF THE MAIN VARIABLES OF Pinus taeda L. TREES UNDER DIFFERENT SILVICULTURAL TREATMENTS IN NORTHEASTERN CORRIENTES PROVINCE, ARGENTINA

A study was developed in order to examine the relationship between thinning, pruning and increment of trees and stands of Pinus taeda L., as well as to determine models that could predict production and quality of logs. Information on diameter at breath height (dbh), total height (h) and volume (dbh 2 * h) were obtained in a trial established in 1996, close to St. Tome city in Corr ientes Province (Argentina). A systematic design was employed; at age three years plots of the original plant ation were thinned to 1666, 833, 416 and 208 stem/ha. In each density, pruning was applied with four intensities, 0, 30, 50 and 70 % of green crown depth removal and with one year interval different pruning-lift were applied, 2,3, and 4 lifts. Five years old data were analyzed. After the analysis it was concluded that tree variables were affected in different grades by thinning, pruning and number of pruning lift applied. Height was the less affected variable, although high intensity pruning (more than 50 %) have a negative effect on height growth. Thinning practice was effective when done in stands of low densities with pruning up to 30 % of green crown removal, growth of these trees was similar to those growing in the control plots.