Dinâmica da vegetação arbórea de uma floresta estacional decidual, Triângulo Mineiro, Brasil

Abstract

Among the different forest types in the world, the tropical dry forests (TDF) has a highly threatening situation. In Brazil, commonly called seasonally dry deciduous forests (SDF), these forests are characterized by pronounced climate seasonality and more intense dynamic than other forest. This study investigates aspects of tree community dynamics, functional groups and functional response groups at SDF within time interval of 6 years. The study was realized in a SDF fragment, located in the Parque Estadual do Pau Furado (PEPF), Uberlândia, Minas Gerais, Brazil. The fragment has a total area of one hectare divided into 50 plots of 10 x 20 meters, distributed in a soil gradient (basalt and micaxisto) and topographic (strongly inclined and very strongly inclined). Data on the phytosociological structure of the tree community were collected in two stages, 2004 (T0) and 2010 (T1). In T1, all individuals, recruits and dead individuals were located and recorded. The inclusion criterion adopted was diameter greater or equal than 4.77 cm, measured at 1.30 m above the ground level. Significant differences were found for the increase in the number of individuals, basal area and species number (p < 0.05), although not showed a change in diversity (p > 0.05). The tree community showed mortality and recruitment rate of 1.5% and 2.25% yr-1, respectively, exhibiting a less intense dynamic and results inferior to demonstrated by the current literature for these forests. In the soil and topographic gradient, significant differences were recorded only for mortality rate (p = 0.037), higher in the very strongly inclined areas, to the net change rate in number of individuals (p = 0.032), higher in the strongly inclined areas and marginally significant for the loss rate (p = 0.060), higher in the basalt. The functional response groups better explain the changes showed by the species, with significant results for all dynamic variables (p < 0.002). In general, pioneer and light demanding species and groups demonstrate a high intense dynamics, showing high mortality and recruitment rates. The results for a less intense dynamics and lack of large variations in precipitation suggest two conclusions (1) the forest must be one of the few fragments that still have a primary forest condition in the Triângulo Mineiro region and / or (2) in the period, the external factors that influence the dynamic processes show positive conditions for a dynamic less intense. Considering the fragment SDF and the current characteristics of a primary forest, prove how the creation of protected areas as PEPF are fundamental to the maintenance and conservation of forest ecosystems. Furthermore, this work is the first study of SDF within conservation unit in the region, offering the opportunity to conduct dynamics further studies and make better inferences about the ecology of these communities, mainly on the effect of current climate change.