The dominance of K-strategy microbes enhances the potential of soil carbon decomposition under long-term warming

Soil microorganisms play a central role in regulating ecosystem carbon (C) cycle. Changes in soil microbial communities caused by climate warming could have pervasive impact on terrestrial ecosystem C cycle. However, how soil microbial community, a key player in C cycle in subtropical forests, responds to long-term warming is poorly characterized. We conducted a long-term (6-year) soil warming experiment in a subtropical forest to examine the response of microbial community structure, C-associated metabolic function, and respiration to two levels of soil warming (+2 °C and +5 °C). Both bacterial and fungal alpha-diversity declined under warming treatments. The increased microbial ratio of K- to r-strategists suggests that warming promoted the dominance of K-strategy microbes. C-degradation genes abundance and associated enzyme activities increased by soil warming. Moreover, warming decreased soil organic C content and increased soil microbial respiration under both warming levels. Our results indicate that future global warming can accelerate soil C decomposition in subtropical forests through altering the structure of microbial communities and promoting the C-associated metabolic function.