Simulating decomposition of labile soil organic carbon: Effects of pH

Based on previous studies we suppose common soil carbon turnover modelling approaches to fail to accurately simulate the fate of labile organic carbon in acidic soils possibly because pH effects on decomposition are not accounted for. For mountainous permanent grasslands with higher shares of particulate carbon, turnover times of this fraction were calculated by means of radiocarbon dating and compared with rate constants of the RothC model. The model rate constant for plant litter decomposition was adjusted by pH response functions derived from (i) published data of litter decomposition or soil N dynamics and (ii) a best fit through the radiocarbon-derived turnover rates. After parameterization, the match of radiocarbon-based and model-based values was significantly improved for both rate constants and pool sizes. The results suggest that ignoring soil pH effects in models might produce misleading projections on soil carbon stocks under warming.