Global synthesis of temperature sensitivity of soil organic carbon decomposition: Latitudinal patterns and mechanisms

Abstract

The response of soil organic carbon (SOC) decomposition to global warming is a potentially major source of uncertainty in climate prediction. However, the magnitude and direction of SOC cycle feedbacks under climate warming remain uncertain because of the knowledge gap about the global-scale spatial pattern and temperature sensitivity (Q 10 ) mechanism of SOC decomposition. Here, we collected data of Q 10 and corresponding soil variables from 81 peer-reviewed papers using laboratory incubation to explore how Q 10 varied among different ecosystems at the global scale and whether labile and recalcitrant SOC pools had equal Q 10 values. Q 10 with a global average of 2.41 substantially varied among different ecosystems, ranging from the highest in cropland soils (2.76) and the lowest in wetland soils (1.84). Hump-shaped correlations of Q 10 values with the maximum at SOC = 190 g/kg and the minimum at clay = 37% were observed. However, the main influencing factors of Q 10 differed among various ecosystems. Q 10 values showed a clear decrease with increasing incubation temperature but no significant decrease above 25°C. In general, labile SOC was less sensitive than recalcitrant SOC to warming. Structural equation model analyses showed that total N and SOC accounted for 53% and 46%, respectively, of the variation in Q 10 of labile SOC and recalcitrant SOC. This finding suggested that Q 10 values of labile and recalcitrant SOC pools had different controlling factors. Our findings highlighted the importance of Q 10 ’s variations in ecosystem types and the response of recalcitrant SOC to warming in predicting the soil C cycling and its feedback to climate change. Therefore, ecosystem type and difference in Q 10 of labile and recalcitrant SOC should be considered to precisely predict the soil C dynamics under global warming. A plain language summary is available for this article.