Temporal fluctuations in the diametric distribution patterns of the trees and shrub community and 15 populations in a forest fragment

Abstract

Aiming to characterize possible fluctuations in the patterns of diametric distribution, the community and the populations of the 15 most abundant tree species in a fragment of semideciduous forest were analyzed in a five year interval (2000-2005). The diametric distribution of the community showed a high concentration in the smaller classes and accentuated reduction in the biggest classes (reverse-J-shape), for both surveys. The populations presented different patterns, randomly distributed in two groups. Group1, formed by species of smaller diameters and abundant in the sub-canopy, such as Galipea jasminiflora, Allophylus edulis, Sebastiania commersoniana, Dendropanax cuneatus and Mollinedia widgrenii, and also by pioneer species of high trees, Acacia polyphylla and Piptadenia gonoacantha followed the reverse-J-shape curve diametric distributions. All species of Group2 (Platycyamus regnellii, Cupania vernalis, Machaerium stipitatum, Machaerium villosum, Copaifera langsdorffii, Persea major and Cassia ferruginea) except Calycorectes acutatus, present bigger diameters, and their individual adults predominate in the forest canopy, increasing the basal area and presenting a density of smaller individuals in the lower diametric classes. In the evaluated interval, only D. cuneatus altered their distribution pattern (Group1-Group2), while the others increased. In Group1 the main dispersion syndrome is anemochory or autochory, while in Group2 the zoochory syndrome predominates. As the fragment presents a small area, elongated form and semi-urban location associated to a regime of intense disturbances, which may have caused a decrease of the fauna disperseres, compromising the recruitment rate.