Climate Sensitivities of Carbon Turnover Times in Soil and Vegetation: Understanding Their Effects on Forest Carbon Sequestration

Abstract The high uncertainty associated with the response of terrestrial carbon (C) cycle to climate is dominated by ecosystem C turnover time ( τ eco ). Although the relationship between τ eco and climate has been extensively studied, significant knowledge gaps remain regarding the differential climate sensitivities of turnover time in major biomass ( τ veg ) and soil ( τ soil ) pools, and their effects on vegetation and soil C sequestration under climate change are poorly understood. Here, we collected multiple time series observations on soil and vegetation C from permanent plots in 10 Chinese forests and used model‐data fusion to retrieve key C cycle process parameters that regulate τ soil and τ veg . Our analysis showed that τ veg and τ soil both decreased with increasing temperature and precipitation, and τ soil was more than twice as sensitive (1.27 years/°C, 1.70 years/100 mm) than τ veg (0.53 years/°C, 0.40 years/100 mm). The higher climate sensitivity of τ soil caused a more rapid decrease in τ soil than in τ veg with increasing temperature and precipitation, thereby significantly reducing the difference between τ soil and τ veg ( τ diff ) under warm and humid conditions. τ diff , an indicator of the balance between the soil C input and exit rate, was strongly responsible for the variation (more than 50%) in soil C sequestration. Therefore, a smaller τ diff under warm and humid conditions suggests a relatively lower contribution from soil C sequestration. This information has strong implications for understanding forest C‐climate feedback, predicting forest C sink distributions in soil and vegetation under climate change, and implementing C mitigation policies in forest plantations or soil conservation.