Annual variation in soil respiration and its component parts in two structurally contrasting woody savannas in Central Brazil

Background and aims Due to the high spatial and temporal variation in soil CO2 efflux, terrestrial carbon budgets rely on a detailed understanding of the drivers of soil respiration from a diverse range of ecosystems and climate zones. In this study we aim to evaluate the independent influence of vegetation structure and climate on soil CO2 efflux within cerrado ecosystems. Methods We examine the seasonal and diel variation of soil CO2 efflux, including its autotrophic and heterotrophic components, within two adjacent and structurally contrasting woody savannas in central Brazil. Principle results We found no significant difference in the annual soil CO2 efflux between the two stands (p=0.53) despite a clear disparity in both LAI (p<0.01) and leaf litterfall (p<0.01). The mean annual loss of carbon from the soil was 17.32(+/- 1.48) Mg Cha(-1) of which approximately 63% was accounted for by autotrophic respiration. The relative contribution of autotrophic respiration varied seasonally between 55% in the wet season to 79% of the total soil CO2 efflux in the dry season. Furthermore, seasonal fluctuations of all the soil respiration components were strongly correlated with soil moisture (R-2=0.79-0.90, p<0.01). Conclusions Across these two structurally distinct cerrado stands, seasonal variations in rainfall, was the main driver of soil CO2 efflux and its components. Consequently, soil respiration within these ecosystems is likely to be highly sensitive to any changes in seasonal precipitation patterns.