Soil pH accounts for differences in species distribution and leaf nutrient concentrations of Brazilian woodland savannah and seasonally dry forest species

Abstract

Understanding the environmental factors shaping savannah and tropical forest boundaries is important to predict tropical vegetation responses to climate change and other human-mediated disturbances. To better understand the soil characteristics affecting the distribution of Cerradão (Brazilian woodland savannah) and seasonally dry forest (SDF), two vegetation types occurring next to each other in a similar seasonal climate in south-eastern Brazil, we compared several leaf chemical and morphological traits associated with soil pH and resource availability of Cerradão and SDF woody species. Leaf functional traits were measured for 25 Cerradão and 27 SDF species. We performed between-site comparisons with either all species pooled using phylogenetically independent contrasts or species shared between Cerradão and SDF, as well as congeneric pairs. We found higher specific leaf area and leaf nitrogen, potassium, calcium and sulfur concentrations for SDF species. We did not find higher concentrations for leaf phosphorus and manganese (Mn) for SDF species, despite a higher concentration of these nutrients in SDF soil. Cerradão plants had higher leaf iron (Fe), Mn and aluminium (Al) concentrations. For most of the traits assessed, variance was higher among species and genera than between sites. Nutrients with greater availability in the SDF soil did not invariably exhibit higher concentrations in the leaves of SDF species, indicating that these were not limiting for plant productivity. Higher concentrations in the leaves of Cerradão species for Al, Fe and Mn are probably a consequence of lower soil pH, which increases the availability of these elements. In spite of the differences in belowground resources and the divergence for some traits between Cerradão and SDF, our results show high diversity in leaf functional traits within communities and a similarity of leaf functional traits in closely related species in the contrasting habitats. Besides, we surmise that soil pH is an important factor affecting Cerradão and SDF species distribution, excluding SDF species from more acidic soils, because of the toxic effects of Al, and possibly also Mn and Fe.