Diametric Increment Patterns of Open-Grown and Under Competition Pinus taeda L. Trees in Southern Brazil.

The main goal of this study was to evaluate the patterns of diametric increment of open-grown and under competition trees of Pinus taeda L. as an expression of breast height diameter. The dendrometric variables and the diameter increment of these trees were measured. The increments were obtained by measuring tree rings on cores extracted at breast height using a Pressler borer. An allometric model was fitted to describe the percentage periodic annual increment in diameter (PAId%) as a function of the initial diameter (d_i) for two tree groups. The analysis of covariance (ANCOVA) allowed comparing the effect of intercept (α₀) and slope (α₁) of the fitted equations between groups. The overall average of PAId5 was 0.83 cm year^-1 for open-grown trees and 0.57 cm year^-1 for under competition trees. The ANCOVA showed differences in intercept (α₀) - (Pr > F = 0.0066) and not in slope (α₁) - (Pr > F = 0.8883) for the adjusted regression equations. This finding enabled the development of a singular equation to express the increment, using dummy variables, described as: PAId% = exp [...], with R² = .69 and Syx = 2.4%. The results of this study contribute to highlight the influences of the growth space in the increment of the species, as well as its maximum potential, elements that are very important for the monitoring and decision-making process in silvicultural activities of individual P. taeda trees. [ABSTRACT FROM AUTHOR]