Comunidades herbáceas em áreas preservadas e antropizadas da caatinga e seus usos

Abstract

This study aimed to compare and evaluate the changes in the composition, richness, density and diversity of herbaceous species in a mature forest (about 50 years), a young forest (17 years) and an area of recently abandoned crop field (two years). Hypotheses related to the recognition, potential use, effective use of these herbaceous community within Riachão de Malhada de Pedra and socioeconomic factors serve as predictors of recognition of useful herbs in semiarid environments were also tested. Then two populations (Sida rhombifolia and Bidens bipinatta) who were among the most used within the community for a study on population dynamics have been selected. Initially the floristic sampling was performed for the knowledge of herbaceous flora (300 plots of 1m2, 100 plots in each study area). Later, with the residents of the community of Riachão de Malhada de Pedra, semi-structured interviews and the method interview-checklist in order to test the hypotheses were made. The population dynamics were evaluated monthly for four consecutive years in 200 plots of 1 m2 set within mature and young forests. Regarding the composition and structure of the herbaceous community, regardless of the area, the species with the highest densities were Delilia biflora, Conyza bonariensis, Pilea hyalina, Gomphrena vaga, Acalypha multicaulis and Panicum trichoides. D. biflora, G. vaga and P. hyalina were among the most representative species in mature forests and young. The set of most significant in herbaceous species was formed by the field C. bonariensis, A. multicaulis, Centratherum punctatum, Borreria verticillata and Commelina obliqua. Considering each area, mature, young forest and field, were represented by 62, 63 and 104 species, respectively. There were significant differences in average wealth between all three areas. The density was higher in the field and similar between young and mature forests. The diversity index was significantly different between areas. 24 species were common to all three areas, 16 were unique to mature forest, 14 unique to young forest and 57 of the field area. For recognition and use of herbs within the community, 157 species have been identified, of which only 70 were recognized, 59 were considered potentially useful, and 34 species are effectively utilized. There was a relationship between recognition and use, since the most recognized herbaceous showed the greatest number of uses. Considering the variation in use at the time, there was a higher reporting use during the rainy season compared species use throughout the year. As socioeconomic, age and occupation variables, in this community, it seems is not related to the recognition of herbaceous. The study of population dynamics showed that the age of the forest and temporal rainfall variations can significantly influence the dynamics of Sida rhombifolia and Bidens bipinatta, however, the low explanatory power of the variables (age of the forest, rainfall totals and their interactions), showed that these are not the main responsible for the dynamics, showing there are other variables active in regulating the dynamics of herbaceous plants, which need to be further elucidated.