Global soil profiles indicate depth-dependent soil carbon losses under a warmer climate

Soil organic carbon (SOC) changes under future climate warming are difficult to quantify in situ. Here we apply an innovative approach combining space-for-time substitution with meta-analysis to SOC measurements in 113,013 soil profiles across the globe to estimate the effect of future climate warming on steady-state SOC stocks. We find that SOC stock will reduce by 6.0 +/- 1.6% (mean +/- 95% confidence interval), 4.8 +/- 2.3% and 1.3 +/- 4.0% at 0-0.3, 0.3-1 and 1-2 m soil depths, respectively, under 1 degrees C air warming, with additional 4.2%, 2.2% and 1.4% losses per every additional 1 degrees C warming, respectively. The largest proportional SOC losses occur in boreal forests. Existing SOC level is the predominant determinant of the spatial variability of SOC changes with higher percentage losses in SOC-rich soils. Our work demonstrates that warming induces more proportional SOC losses in topsoil than in subsoil, particularly from high-latitudinal SOC-rich systems. The response of soil organic carbon to climate warming may be soil depth-dependent, but remains unquantified in situ. Here the authors show that warming induces more proportional soil carbon losses in topsoil than in subsoil, particularly from high-latitudinal carbon-rich soils.

Automated summary

This study combines space-for-time substitution with meta-analysis to estimate the effect of future climate warming on steady-state soil organic carbon (SOC) stocks. The results show that SOC stock will reduce under warming, with larger proportional losses in topsoil and in boreal forests. The existing SOC level is the main determinant of spatial variability in SOC changes.