Fatores ecológicos da diversidade beta em florestas tropicais

Abstract

We investigated fragments of Tropical Forests with the aim of assessing how habitat characteristics (soil, climate, and fragmentation) influence beta diversity over time across an environmental gradient. We tested the hypothesis that the effect of fragmentation varies depending on changes in climate and soil. The method used had two distinct parts: (1) we tested the effect of climate-fragment interaction and soil, and (2) the individual effect of soil, climate, and fragmentation variables on beta diversity in the southeastern region of Brazil. We expected higher beta diversity in larger areas with a more regular shape. We utilized data from tree communities and soil collected in 36 inventoried areas with sampling units of 20 x 20 m (400 m2) distributed non-contiguously in the state of Minas Gerais, Brazil. Within each sampling unit, all arboreal individuals with Diameter at Breast Height (DBH) greater than or equal to 5 cm were measured and identified. The sites covered three types of forests: deciduous, semi-deciduous, and rainforests, located in the Phytogeographical Domains of the Atlantic Forest, Cerrado, and Caatinga. The greatest distance between the sampled forests is 900 km (latitude) and 177 km (longitude), with altitudes ranging from 450 to 1500 m above sea level. The variables that showed a positive relationship with beta diversity in tree communities were: shape index, average annual temperature, and annual precipitation. On the other hand, soil variables associated with fertility (K, OM) and texture (% silt) exhibited a negative relationship with beta diversity. Our first hypothesis was not supported by the results, as there was no interaction between the variables. The second hypothesis was supported, revealing the importance of the effects of habitat characteristics (shape, climate, and soil) on beta diversity in Seasonal Tropical Forests. Thus, the integration of these data helps identify areas with characteristics that confer resilience to climate changes.