STUDY AND MODELING OF THE DIAMETER GROWTH IN Pinus taeda L. STANDS UNDER PRUNING AND THINNING IN ARGENTINA

The aim of this research was to study and to model the effect of pre-commercial thinning and pruning on diameter growth, on a 15th year old stand of Pinus taeda L. in northeastern Argentina. The study was established in a deep red clay soil, with a systematic design of blocks for thinning intensity and sub-blocks for pruning intensity. The thinning treatments, performed at 3 year old were: 1666 (without thinning); 833; 416 and 208 trees ha(-1). The pruning were done annually, starting at 3 year old, and applied by 2, 3 or 4 consecutive years removing 30, 50 and 70 % of the living crown, respectively. The general model obtained by linear regression allowed to estimate, with good precision (mean absolute deviation as a percentage equal to 5.71), the quadratic mean diameter (QMD) in function of age. The variable remnant trees, remnant crown, and number of prunings were considered to estimate the general function coefficients. At 15 year old, the QMD varied from 25.6 to 41.5 cm to 1666 and 208 trees ha(-,1) respectively, without pruning. The QMD growth was negatively affected by pruning and positively affected by thinning.