Phytosociological analysis of the tree-shrub component of the Caatinga, Alagoas, Brazil

The Brazilian semiarid region presents very heterogeneous natural conditions of climate, soil, topography and vegetation, forming a mosaic of unique ecosystems. This research aims to carry out a phytosociological analysis of the tree-shrub stratum of two Caatinga areas in the Sertão (backlands) of Alagoas. The experiment was carried out in the municipalities of Olho D 'Água do Casado (area I) and Delmiro Gouveia (area II), state of Alagoas, a quantitative evaluation of the vegetation was carried out by contiguous plots within an area of 1.0 ha. The phytosociological parameters analyzed were Density, Relative Frequency and Dominance, Importance Value, Shannon-Weaver Diversity Index and Aggregation. The families with the greatest number of species are Mimosaceae and Bignoniaceae in area I and Mimosaceae and Anacardiaceae in area II, with a higher relative density for the species Tabebuia sp. and Schinopsis brasiliensis, respectively; the species Myrcia sp., Tabebuia sp. and Pilosocereus pachycladus in area I presented a higher value of importance, standing out Schinopsis brasiliensis, Pilosocereus gounellei and Pityrocarpa moniliformis in area II. The Shannon-Weaver (H') diversity index is considered high in area I and II when compared to other areas of Caatinga; similarly, floristic richness was considered similar in both areas