Diametric structure and spatial distribution of Dipteryx odorata (Aubl.) Willd. In western Pará State, Brazil

Abstract

The objective of this study was to evaluate the diametric structure and spatial distribution of Dipteryx odorata (Aubl.) Willd. (cumaru), in western Pará State, Brazil. The study was carried out in nine Work Units of 100 ha each, inserted in the Annual Production Area nº8. The studied areas belong to the Tapajós National Forest Mixed Cooperative, municipality of Belterra. We collected the data through a 100% inventory, with mapping of all individuals with a diameter at 1.30 m above the ground (DAP) equal to or greater than 20 cm. The diametric structure was obtained through multivariate analysis. From this structure, we tested five probabilistic density functions (Weibull-3P, Gamma, Normal, Lognormal, and Exponential). The adjustment was assessed using the Kolmogorov-Smirnov test, at 95% probability and histograms. The spatial distribution was obtained using Ripley's K function. The species had a diametric distribution tending to be normal for individuals with DAP ≥ 20 cm. This suggests problems of regeneration, probably caused by the boom in the collection of cumaru seed in the 1940s; low number of adults with high regenerative capacity and extremely low recruitment percentage. The spatial distribution of cumaru is predominantly random - probably due to the species' life cycle: as the individuals grow, the distribution becomes more random. The cumaru boom is another hypothesis that supports randomness. Seed collection may have affected the emergence of new individuals that would be responsible for the expected aggregation for the species.