Global patterns of soil heterotrophic respiration – A meta-analysis of available dataset

Abstract

Soil heterotrophic respiration (RH) represents the carbon losses from the decomposition of litter detritus and soil organic matter by microorganisms. Despite conflicting findings on the dominant climatic, soil and vegetation controls on RH from local studies, little is known on the global patterns of RH and the potential drivers behind these patterns. Based on the updated Global Soil Respiration Database, we conducted a meta-analysis to evaluate the direct and indirect effects of climatic, soil and vegetation controls on RH across the globe using structure equation model (SEM). Our results showed that the global weighted mean RH was 457 ± 139 g C m−2 a−1 (mean ± standard deviation), but RH differed significantly among ecosystem types and positively correlated with gross primary production, highlighting the importance of the vegetation control on RH. Climate was the most important environmental control on RH indicated by SEM. Soil organic carbon (SOC) content had a negative influence on RH at the global scale, challenging the current understanding that SOC leads to a positive effect on RH at site or ecosystem scale, further indicating that SOC quantity may dominate RH at local scales, while SOC quality and availability may dominate RH at regional or global scales. Great differences were found not only between observed and dymanic global vegetation model (DGVM)-based RH, but also among different DGVMs, highlighting a better parameterizing of DGVMs, particularly the model output not validated by field observations, to better understand RH and belowground carbon dynamics.