Diversidade, estrutura e dispersão de espécies arbóreas e arbustivas em área de caatinga no município de Malta, PB.

Abstract

Floristic diversity in the caatinga is regarded as being large in spite of having great hydric deficiencies, result of the interaction of local factors and the weather, altitude, relief, superficial deposits as these factors determine the variations of its types. Despite the existence of several phytosociology works, there is a lack of proper knowledge of the caatinga as a whole. The aim of this work was to perform an analysis of the floristic composition, compare the phytosociology structure and determine dispersal syndrome of woody species in two areas of caatinga at Cuncas ranch, in the municipality of Malta (PB). In both areas (Area A: average altitude of 200m – 300m and Area B: average altitude of 300m – 500m) a floristic and phytosociology inventory was carried out in which the sample areas of each environment were constituted of 25 (Area A) and 10 (Area B) permanent plots, with areas of 400 m2 (20m x 20m), systematically distributed in the delimited area, with spacing between plots of 150m x 150m. The Shannon index of diversity (H') and Pielou’s evenness index (E) were calculated for each area. For all the shrub-woody species, measurements of the circumference at 0.30m above the ground and circumference at breast height (CAP) and total height were properly taken. The living and dead standing individuals were counted and measured. It was found 21 species, 10 families and 20 genera in the study area. In area A, 1.613 living individuals were sampled, distributed into 11 families, 11 genera and 11 species and in area B, 1.526 individuals belonging to 17 families, 17 genera and 17 species. The families with the largest number of species in both areas were Fabaceae and Euphorbiaceae and the most abundant taxa was Croton blanchetianus Baill. The index of diversity and evenness in Area A were 1,09 and 0,44 and in Area B 1,85 and 0,76 respectively. The species with the highest density were: Mimosa tenuiflora, Poincianella pyramidalis and Croton blanchetianus in Area A and Croton blanchetianus, Poincianella pyramidalis and Bauhinia Cheilantha in Area B. The specie with the greatest IV in 2006 is C. blanchetianus with 38,3% (Area A) and 24,24% (Area B). In vertical structure, class II (1,69 ≤ H < 4,29) height, presented the greatest distribution of sample stems in density in the study area. In both areas, the three first diametric classes (2,5; 7,5 e 12,5 – Area A; 1,9; 6,9 e 11,9 – Area B) presented the largest number of sample stems in the forest. Out of 21 sampled species, 18 were woody and 3 were shrub species and the observed ways of dispersion were autochoric (12), anemochoric (5) and zoochoric (4), with predominance of the autochoric (57,14%), with dried fruits (91,67%) and dehiscent (81,81%) and the anemochoric with dried fruits (100%) and dehiscent (60%)