Impactos ambientais do pastejo sobre a diversidade florística e a estrutura fitossociológica.

Abstract

The Caatinga is a biome located entirely in Brazilian territory and one of the most threatened. Among the various threats, extensive livestock has been identified as a of the most important. The objective of this research was to evaluate the environmental impact of this activity on floristic composition and phytosociological structure. The study was carried out in two experimental conditions in caatinga areas, without grazing (area I) and under grazing (area II), in Municipality of Pombal, Paraíba. The multiple-plot method proposed by Rodal et al. (2013) according to which only live plants of tree-shrub size are included with CNS ≥ 9.5 cm and At ≥ 1.0 m. For both areas, 671 individuals, distributed in 11 families, 19 genera and 19 species. Fabaceae, Euphorbiaceae, Cactaceae and Malvaceae had the highest number of species recorded in the survey. Fabaceae, Apocynaceae, Euphorbiaceae and Malvaceae were the families that exhibited the larger numbers of individuals. Aspidosperma pyrifolium and Piptadenia retusa species, had the highest values ​​for the phytosociological parameters analyzed in area I, while Sida sp. and Cenostigma pyramidale were the most representative of area II. In according to the Jaccard index, the two areas are similar, and in terms of diversity, area I showed a higher value for the Shannon index. The results obtained suggest that the traditional way of managing the herds, practiced in the experimental conditions studied, have negative environmental consequences mainly reflected in the loss of diversity floristics and density of individuals.