Floristic and Phytoosociological Survey in a Caatinga Fragment under Extensive Grazing in Patos-PB Municipality

Introduction: The caatinga is a typical Brazilian semi-arid vegetation, where dominant shrub species and some dispersed arboreal individuals are found, in addition to the marked presence of cacti

Aims: The aim of the present study was to evaluate the arboreal-shrub component, analyzing the floristic composition and phytosociology in caatinga area under extensive grazing in the Paraíba hinterland

Methodology: The study area extends over 60 ha, and presents vegetation of the caatinga type with the presence of extensive cattle grazing. The vegetation data were obtained using the simple random sampling method, with plots with a standard size of 20 x 20 m, and randomly arranged 15 sample units. In each sample unit were measured all living or dead individuals, with Chest Height Circumference (CAP) ≥ 6 cm as well as total height of each individual. Phytosociological parameters were analyzed and floristic diversity was determined using the Shannon-Weaver index (H '), Simpson dominance (S), Pielou equability (J').

Results and Discussion: There were 1285 individuals belonging to 9 families, 16 species, 15 genera. The Fabaceae family obtained the largest number of individuals and species, with the Poincianella pyramidalis species being the most important, with 650 individuals. The first class of diameter, concentrated the largest number of individuals with 627 individuals (48.8%), followed by the second class with 464 individuals (36%) confirming a tendency to reverse in the diameters classes. Regarding height distribution, it was observed that 1154 individuals (89%) are grouped in the first three classes. In relation to floristic diversity, the shannon-wienner index was 3,094 nats / ind, while the furrow index was 0.995, simpson 0.999.

Conclusion: The species Poincianella pyramidalis presented the highest parameters of horizontal structure, whereas indexes indicated that the study area presents a low diversity, proving that the extensive grazing has been changing the floristic composition of the area.