Sucessão ecológica na caatinga sobre áreas de mineração.

Abstract

Ecological succession in the caatinga over mining areas. This research aims to analyze the floristic composition based on the ecological succession of the herbaceous stratum of the Caatinga, under degraded areas from the mineral exploration, developed in the municipality of Soledade state of Paraíba. For the accomplishment of the floristic survey, four exploration areas were selected mineral (20, 15 and 10 years and one with current holding). These areas have herbaceous cover in different successional stages and also was delimited another, denominated control area, that presented a forest of arbustivaarbóreafitofisionomia. In those areas were made collections of all individuals of the herbaceous stratum, during the rainy season in the months of June and July 2017. In addition, all individuals were counted by species, with frequency and dominance verified. In this study, the statistical method used for cluster analysis was a measure of dissimilarity to the Euclidean Distance by the simple link method, which verified the nearest neighbor We also used Ward's hierarchical grouping method, where species frequency and dominance were calculated, and the minimum variance (species x number of individuals) was calculated. To analyze floristic diversity, the Shannon-Wienere index of species richness was the Jarcknife 1st Order Index, which estimates total richness using the number of species. The floristic composition in the study area was represented by 3,186 individuals, distributed among the 19 families and 37 species. It was verified that Euphorbiaceae and Rubiaceae form the families that presented greater abundance, whereas the ones with greater richness of species were the Convulvulaceae and the Fabaceae. It is verified that the species registered in the five areas, presented differences as far as diversity, that the area with current mining use in the rainy season from May to July had the greatest diversity of species, even though it was in a secondary succession stage, in relation to the other areas under study. It was possible to verify that the species Cnidoscolus urens presented greater dominance due to being present in all areas. However, it was observed that the areas of Ten years and of current exploration presented greater floristic richness, diverging from those abandoned to 20, 15 years of exploration. Through Ward's Hierarchical Grouping, Distance Euclidiane and Factor Analysis methods, it was possible to verify that the 20 and 15 year old areas with the control presented a higher regeneration, with the lower diversity of successional species. From the results it was possible to know the process of succession of some herbaceous species of the Caatinga, since it contributes to the preservation of these and the recovery of degraded areas in the semi - arid Paraíba.