Effects of warming and increased precipitation on soil carbon mineralization in an Inner Mongolian grassland after 6 years of treatments

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 13C and 15N 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 (C0) from cumulative CO2-C evolved as indicators for labile organic C. The experimental warming significantly decreased soil C mineralization and C0 at the 10–20-cm depth (P < 0.05). Increased precipitation, however, significantly increased soil pH, NO3−-N content, soil C mineralization, and C0 at the 0–10-cm depth and moisture and NO3−-N content at the 10–20-cm depth (all P < 0.05), while significantly decreased exchangeable NH4+-N content and 13C natural abundances at the two depths (both P < 0.05). There were significant warming and increased precipitation interactions on soil C mineralization and C0, indicating that multifactor interactions should be taken into account in future climatic scenarios. Significantly negative correlations were found between soil C mineralization, C0, and 13C 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.