Estrutura a vegetação em duas áreas de fragmento de caatinga alterado na Fazenda NUPEÁRIDO, Patos - PB.

Abstract

The Brazilian semi-arid área is about 900 thousand km2, 70% of northeastern region, with predominance of xerofitic and heterogeneous vegetation, with small trees and scrubs of caducous and small leaves named caatinga. The predatory exploitation in caatinga areas has caused drastic consequences to natural resources, with loss on floristic and faunistic diversities. This study aims to detect floristic and structural differences between two contiguous fragments of caatinga vegetation, under anthropic interventions, at Nupearidos’ farm, municipality of Patos, Paraíba. Twenty five plots were established in each area (A and B), 20 x 20 m, with systematic distribution, and sampled those individuals with circumference at the soil level ≥ 10 cm and ≥ 1 m high. In area A were sampled 2.226 individuals of 21 species, 21 genera and 11 botany families, while in area B were sampled 1.930 individuals of 17 species, 16 genera and 09 families. The Shannon-Wienner index and Pielou equability values were 1,92 nats/ind. and 0,63 (area A) and 1,76 nats/ind. and 0,62 (area B), respectively. The similarity, measured by Sørensen’s similarity índex was 79%. Fabaceae and Euphorbiaceae were the richest families in both areas. Species with largest values in IVI in area A were Poincianella pyramidalis, Mimosa tenuiflora, Aspidosperma pyrifolium, Croton blanchetianus and Combretum leprosum. This same species were the most important in area B, with modifications in IVI values, except for P. pyramidalis, A. pyrifolium and C. leprosum. About 89,04% e 90,52% individuals in A e B areas, respectively, had diameter lower than 16 cm. The diameter distribution showed a tendency of reversed-J shape in both areas. The individuals high were lower than 5 m in 98,74% in area A and 96,32% in area B. The total density and stem basal area in area A were 2.226 individuals and 18,79 m2 /ha and these values were superior to those found an area B, with 1.930 ind. and 15,13 m2 /ha. Abouto 80% of the questionnaire applied showed area B with highest level of disturbance than area A. The floristic and structural parameters measured in both areas pointed out differences between them, probably because of different levels of anthropic interventions, and confirmed the hypothesis tested.