Drought-induced changes in rare microbial community promoted contribution of microbial necromass C to SOC in a subtropical forest

摘要

Microbial necromass is considered as one of the primary drivers in soil organic carbon (SOC) formation and persistence. However, how microbial traits (e.g., diversity, composition) influence microbial necromass C and its contribution to SOC remains unclear, especially under persistent drought. Here, we took advantage of a 7-year Throughfall Exclusion Experiment (TEE) to examine effects of drought on microbial necromass C and its contribution to SOC at different soil depths in a subtropical forest. Microbial DNA sequencing and amino sugars biomarker analysis were integrated to probe regulation of microbial traits on microbial necromass C and its contribution to SOC storage under drought. Our results showed that persistent drought increased the contribution of microbial necromass C to SOC with increasing soil depth, ranging from 32.0% in 0-10 cm to 39.7% in 45-60 cm for fungal necromass and from 15.3% in 0-10 cm to 22.6% in 45-60 cm for bacterial one under drought. Interestingly, bacterial necromass C was more important for SOC accumulation than fungal necromass C in subsoil while vice versa in topsoil. Moreover, drought significantly altered the rare microbial diversity and community composition. Drought-induced shifts in rare microbial taxa largely explained the contributions of fungal and bacterial necromass C to SOC in both sub- and top-soils. Thus, microbial traits, especially rare microbial diversity and community composition, regulated the contribution of microbial necromass C to SOC at different soil depths. These findings highlight the crucial role of the rare microbial community on bacterial- and fungal-derived C in subsoil and topsoil, especially under persistent drought, which should be incorporated into land surface models to improve SOC prediction under future climate change.

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