Vegetation structure and species diversity coupled to soil water heterogeneity in a Cerrado core area
Ferreira, University of Brasilia, firstname.lastname@example.org
Bustamante, University of Brasilia, email@example.com
Simpson-Junior, University of Brasilia, firstname.lastname@example.org
Davidson, The Woods Hole Research Center, email@example.com
Cerrado landscapes are experiencing fast changes that threaten its rich plant diversity. However, very little is known about the factors maintaining such diversity. Also, the main factors related to its large structural heterogeneity are debated. Here we investigate how plant available water (PAW) heterogeneity is related with spatial variation in vegetation structure and species diversity in a Cerrado area. PAW (down to 10m depth) was assessed by a geophysical tool, soil electrical resistivity profiling. Interpolated data of soil resistivity were converted into volumetric water content, and then into PAW. We have estimated PAW along three 275-m transects placed at Águas Emendadas Ecological Station (Distrito Federal). Resistivity profiling has revealed strong PAW spatial variability among and within transects. Vegetation was surveyed within 22 100m2-plots centered on the resistivity transect. All woody plants were identified to species level and were measured in height, basal circumference, crown depth and volume. Leaf area index was estimated every 10m using hemispherical photographs. Strong co-organization was found between structural attributes and PAW. Despite their similar species richness, the three transects showed differences in species diversity. Species richness, as well as plant density, was positively correlated with PAW 0-400 cm depth. Simpson’s diversity, however, was negatively related to PAW beneath 700cm. Dominance of one species, as more soil water became available at depth, contributed to this decline in species diversity. These links suggest that shifts in soil water resources, from changes in hydrological cycles, for example, may provoke important changes in structural patterns and woody species diversity of the Cerrado.