Diversidade β (Beta) em Florestas Tropicais Sazonalmente Secas: relações florísticas entre gradientes fisionômicos e entre microambientes

Abstract

Seasonally Dry Tropical Forest (SDTF) is a biome presenting a disjointed distribution and occurs in places of high environmental heterogeneity. Such feature yields species dissimilarities among their areas or high beta diversity. Issues concerning floristic classifications of this different formation are not clear yet. Thus, we aim to figure how species turnover is among different SDTF microenvironments located at northern Minas Gerais and southwestern Bahia. Edaphic and florist surveys were carried out in six areas (Bonito de Minas, Peruaçu, Montalvânia, Iuiú, Guanambi and Caetité). In order to establish intrinsic relationships among each area and microenvironments found, both ordination (DCA, CCA and TWINSPAN) and classification techniques were performed. Santos (2009) floristic classification was employed to figure how the several deciduous formations are distributed among the surveyed areas. A total of 258 species were found distributed in 17 microenvironments. The CCA performed showed significant relation between soil and vegetation and Al3+, coarse sand and V (base saturation) were the soil variables more strongly correlated to species distribuition. Floristic connections among the microenvironments formed five groups: Caatinga of Crystalline (CH), Dry Forest (FED), Cerrado Dry Forest Enclaves (FED-C), Atlantic Dry forest Enclaves (FED-MA) and Agreste (CR). Arboreal Caatinga was the dominant floristic unit in all surveyed sites. Our results reinforce the role of analyzing several FTSS microenvironments in order to understand how species turnover in SDTF as well as creating conservation strategies.