Substrate availability reconciles the contrasting temperature response of SOC mineralization in different soil profiles

PurposeThe purpose of this study was to investigate how changes in substrate availability (stimulating root exudate input) affect the temperature response (Q(10)) of soil organic carbon (SOC) mineralization across different soil profiles to increase our ability to predict the response of soil organic matter dynamics to climate change.Materials and methodsWe sampled the topsoil and subsoil of two typical mineral soil profiles and one buried soil profile. Soils were incubated at 10-25 & DEG;C at 0.75 & DEG;C intervals, SOC mineralization rates were continuously measured with and without glucose addition, and Q(10) was calculated.Results and discussionOur results showed that Q(10) decreased with increasing depth in typical mineral soils, but decreased before increasing with depth in buried soil. As expected, substrate addition significantly increased Q(10) across soil depths; however, the magnitude of this increase (& UDelta;Q(10)) differed with soil depth and type. Unexpectedly, in typical mineral soils, & UDelta;Q(10) was higher in topsoil than in subsoils, and vice versa for buried soil. & UDelta;Q(10) was negatively correlated with initial soil substrate availability (CAI) and positively correlated with soil inorganic N.ConclusionsOverall, our results suggested that increased substrate availability under climate change scenarios (i.e., increased root exudates with elevated CO2 concentrations) could further strengthen the temperature response of SOC mineralization, especially in soils with high inorganic N content or regions with high N deposition rates.