PHYSIOGNOMY AND VEGETATION STRUCTURE IN DIFFERENT ENVIRONMENTS OF "CAATINGA" IN "SERRA TALHADA" PERNAMBUCO STATE, BRAZIL

This study aimed to investigate the influence of spatial heterogeneity of abiotic factors on the spatial patterns of vegetation structure of the woody component and of its regeneration; it was carried out in an area of "caatinga" located in the Parque Estadual Mata of Pimenteira, municipality of "Serra Talhada", interior of Pernambuco State, Brazil. The sample was divided into two environments, one near the watercourse with denser vegetation (I) and another at 100 meters away from the watercourse with more open vegetation (II). In each environment, four permanent plots of 20x50 m were installed and divided into ten plots of 10x10 m; alive individuals with stem ground level diameter (GD) of >= 3 cm and total height of >= 1 m were measured. In one corner of each plot, a sub-plot of 2x2 m was allocated to measure the individuals' height and diameter of the sampled species in woody component with GD from 0.5 to 2.9 cm (regeneration). Community's general phytosociological descriptors of the different environments were calculated and the individuals' distribution in histograms was evaluated for the woody component as for regeneration. After testing for normality using Kolmogorov-Smirnov test, values of phytosociological descriptors per plot were compared between the environments. Analysis of variance (ANOVA) of a criterion was used for data with normal distribution. Data without normal distribution were analyzed by non-parametric Mann-Whitney test. Environments showed significant differences in the number of individuals (4047.5 versus 3332.5 ind. ha(-1)) and basal area (23.6 versus 17.6 m(2). ha(-1)) with significantly higher values in environment I; this pattern was opposite to the regenerating pattern in which the number of individuals and basal area were higher in the environment II (9187.5 vs. 10937.5 ind. ha(-1) and 1.9 vs. 2.5 m(2). ha(-1), respectively). In total, fifty species, including woody and regenerating component, were sampled; significant differences in diversity were found between environments in the different strata, although the similarity was more than 80%. Most chemical and textural soil variables did not differ statistically, except for levels of Al3+, which showed higher levels in the environment I. Among other edaphic variables, only the stony variables differed between environments I and II (3.87 versus 1.47%). The vegetation physiognomic distinction between the environments is result from populations' presence of individuals with greater heights and diameters in the environment I. The spatial heterogeneity of environmental variables found in the studied environments explained part of changes in floristic and structural characteristics of the vegetation.