Fitossociologia e indicadores ecológicos em áreas de Caatinga com diferentes usos no Sertão da Paraíba, Brasil

Abstract

The Caatinga Biome has a predominantly xerophilic flora, whose characteristics are linked to the conditions in the region. It comprises subsistence activities, such as livestock, which includes cattle farming, meanwhile, in some occasions its intensity can provide direct impacts to the biome. Therefore, this study aimed to evaluate the phytosociology of the adult tree-shrub component, as well as ecological indicators in two areas of the Caatinga with different history of use in the hintexlands of Paraíba. For this purpose, two areas belonging to a rural area of the municipality of Brejo do Cruz-PB were considered, one destined for the creation of cattle raising with a period of approximately 20 years and the other without predominance of activities for 10 years. For the analysis of the adult tree-shrub component, 40 plots of 25 x 10 m (250 m²) were installed in the respective areas, in which individuals were sampled according to family, genus and species and analysis of phytosociological parameters was carried out. The ecological indicators evaluated were: natural regeneration, litter, dispersion syndrome and entomofauna. For the regeneration, 80 subplots of 10 x 10 m (100 m²) were allocated. Subsequently, a phytosociological analysis and introduction into size classes for regeneration were performed. For litter, the material was collected in all plots, present in the areas, totaling 80 samples. Dispersion syndrome was classified into autochory, anemochory and zoochory. The entomofauna was obtained from two traps (Pitfall and aerial trap), which were introduced in ten plots of each area, with two collections referring to the rainy and dry periods. The results showed that the two areas had similar patterns, both in terms of phytosociology and diversity. The most prominent adult species were Poincianella bracteosa, Mimosa tenuiflora and Aspidosperma pyrifolium in both areas. As for the ecological indicators, the natural regeneration also presented similar values with the species Poincianella bracteosa and Croton blanchetianus as the main regenerants. Dispersion syndrome was better represented by autochory, indicating greater propagation performed by the plant itself. In relation to litter, there was a significant difference between the areas, indicating a higher value for the conserved environment. The entomofauna showed no difference between the areas, having as main orders Hymenoptera, Diptera and Lepidoptera. However, despite the periods of use, the areas had similar diversity and statistical values, which indicates that the animal intensity may have a minimal impact, but not as considerable. However, considering the indicators as tools for the development of the environment, in addition to the conditions in the region, so that the strata can fully develop, alternatives are recommended that aim to associate livestock farming, as well as maintain the floristic composition, are recommended.