Abstract
Considering the emergence of ecosystems dominated by invasive species, there is growing interest in estimating the effect of biological invasions in ecosystem processes and provision of services. African grasses are the most invasive plants in the Cerrado (Brazilian savanna), but their impact on C and N stocks is poorly known. We compared patterns of C and N stocks in the aboveground biomass, root biomass and soil in open Cerrado (campo sujo) sites, both uninvaded and invaded by the African grass Urochloa decumbens. In both sites we estimated the aboveground biomass of U. decumbens and native grasses, as well as the root biomass up to 50 cm. We obtained C and N contents in the soil, as well as C and N stocks, up to 1 m depth, and variation in soil δ13C and δ15N. Although invasion did not affect the aboveground biomass, it did affect belowground biomass, leading to higher C stock in fine roots and soil N content close to soil surface, as well as higher C content along the soil profile. C and N soil stocks, soil δ13C and δ15N values did not significantly differ between invaded and uninvaded site. Even a relatively low level of invasion by U. decumbens changed the root distribution pattern and increased C and N contents in the upper soil, which may promote ecosystem changes by altering nutrient dynamics. Although still preliminary, our study shows that dominance by U. decumbens can have severe effects in the Cerrado belowground environment.