Diametric distribution of three species of Lecythidaceae after reduced impact logging in Eastern Amazon

ABSTRACT

Eschweilera coriacea, Eschweilera ovata and Lecythis idatimon are potentially commercial tropical species, therefore, widely harvested in Eastern Amazon. This research aims to evaluate the performance of three probabilistic density functions in the adjustment of the diametric distribution of three Lecythidaceae species, after one and ten years of the forest harvest, in a managed area, in the municipality of Moju, Pará state. Nine gaps proceeding from the reduced impact logging carried out in 1997 were studied. Around each gap, four 10 x 50 m strips were installed, starting from the edge of the gap into the forest, in the northern, southern, eastern and western directions, in a sampling of 1,8 ha. All individuals with DBH ≥ 5 cm were measured in two measurements (1998 and 2007). Probabilistic density functions Weibull 3P, Gamma and Weber were tested. For selecting the best model, we analyze the Kolmogorov - Smirnov D value (α = 0.05), standard error of the estimate (Syx%), the adjusted determination coefficient (adjusted R²) and the graphical analysis of the frequency curves estimated on the histogram of the observed ones. In both years, the Weibull 3P function presented the best fit and accuracy statistics to describe the diametric distribution of Eschweilera coriacea and Lecythis idatimon, and the Weber model for Eschweilera ovata. Gamma function was discarded for all species. The results indicate the non-feasibility of using the same function to describe different species, needing to consider the intrinsic characteristics to each species.

Keywords:
Forest exploration; Tree diameter; Probabilistic density function