Bedrock and climate jointly control microbial necromass along a subtropical elevational gradient

Abstract

Microbial necromass is closely related to the formation and turnover of soil organic carbon (SOC) in terrestrial ecosystems. Previous studies have elucidated the important influence of climate on microbial necromass carbon (MNC) contents, but the effect and interaction of bedrock with climate on MNC accumulation remains unclear. In a subtropical forest of southwestern China, we examined MNC in the soil surface layer (0–15 cm) on an elevational gradient (800–2100 m) that had alternating bedrock types (clasolite and limestone). Fungal necromass carbon (MNCF) content and total microbial necromass carbon (MNCT) content on limestone were significantly higher than on clasolite. Bacterial necromass carbon (MNCB) content was not significantly different between two bedrock types. MNC (including MNCF, MNCB and MNCT) generally significantly increased with increasing soil mean annual temperature on both bedrock types. The structural equation modelling showed MNC was indirectly controlled by climate and bedrock via soil physicochemical properties, i.e., SOC content and soil texture, but not via the plant community. Overall, variation of the MNC contents along the subtropical elevational gradient was jointly controlled by climate and bedrock variation, emphasizing the importance of bedrock as a driver of the spatial pattern of soil MNC. Increasing our understanding the spatial variation of MNC may require the consideration of the spatial variation in bedrock.