Ecological thresholds in Brazilian savanna: Environmental conditions modulating the composition of woody species in different substrates

Abstract

Neotropical savannas are complex ecosystems whose species compositions are determined by different environmental factors, acting at regional (altitude, geomorphology, and climate) and local scales (substrate deep, soil properties, relief, and fire). We investigated the ecological thresholds, at the large (regional) and small scale (local), at the community levels of woody plants in two adjacent savanna environments. These savannas occur on distinct substrates with deep soils and flat relief (DS) and shallow soils with rocky outcrops and steep relief (RS). We compiled abundance data of the woody species and regional and local variables in 32 sites, with 1 ha each (16 DS and 16 RS). All sites are in protected areas with no recent sign of fire. We applied the Threshold Indicator Taxa Analysis (TITAN) to detect changes in species distribution in response to environmental predictors. The communities of the two environments differed in their responses to the local (soil properties) and regional (altitude), but climate had little influence on the vegetation of these environments. The woody communities of DS and RS present differences in response to predictors. We conclude that the distribution of species in both environments is determined by multiple and distinct factors, which depend on the scale analyzed.