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Understanding the responses of soil C mineralization to climate change is critical for evaluating soil C cycling in future climatic scenarios. Here, we took advantage of a multifactor experiment to investigate the individual and combined effects of experimental warming and increased precipitation on soil C mineralization and C-13 and N-15 natural abundances at two soil depths (0-10 and 10-20 cm) in a semiarid Inner Mongolian grassland since April 2005. For each soil sample, we calculated potentially mineralizable organic C (C (0)) from cumulative CO2-C evolved as indicators for labile organic C. The experimental warming significantly decreased soil C mineralization and C (0) at the 10-20-cm depth (P < 0.05). Increased precipitation, however, significantly increased soil pH, NO (3) (-) -N content, soil C mineralization, and C (0) at the 0-10-cm depth and moisture and NO (3) (-) -N content at the 10-20-cm depth (all P < 0.05), while significantly decreased exchangeable NH (4) (+) -N content and C-13 natural abundances at the two depths (both P < 0.05). There were significant warming and increased precipitation interactions on soil C mineralization and C (0), indicating that multifactor interactions should be taken into account in future climatic scenarios. Significantly negative correlations were found between soil C mineralization, C (0), and C-13 natural abundances across the treatments (both P < 0.05), implying more plant-derived C input into the soils under increased precipitation. Overall, our results showed that experimental warming and increased precipitation exerted different influences on soil C mineralization, which may have significant implications for C cycling in response to climate change in semiarid and arid regions.