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 CO ₂ 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 CO ₂ efflux within cerrado ecosystems. Methods: We examine the seasonal and diel variation of soil CO ₂ 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 CO ₂ 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 C ha ^-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 CO ₂ 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 CO ₂ efflux and its components. Consequently, soil respiration within these ecosystems is likely to be highly sensitive to any changes in seasonal precipitation patterns.