Microbial necromass as a critical driver of soil organic carbon accumulation in Qinghai-Tibet Plateau under climate warming: A meta-analysis

Microbial necromass plays a significant role in soil carbon storage under climate warming, as it is considered a crucial component of the stable carbon pool in soils. However, how the warming, including various warming patterns, affects microbial necromass and its contribution to the organic carbon pool in alpine regions remains largely unexplored. A meta-analysis was conducted utilizing data from ten publications to assess the effects of warming on microbial necromass on the Qinghai-Tibet Plateau. The findings indicated that the soil organic carbon (SOC) content did not exhibit significant changes after warming; however, microbial necromass carbon (MNC) and its ratio to SOC experienced significantly increases of 17.7 % and 52.0 %, respectively. The effect size of warming on fungal necromass carbon (FNC; +19.5 %) was larger than that of bacterial necromass carbon (BNC; +9.2 %). Furthermore, the warming patterns influenced the accumulation of microbial necromass and its ratio to SOC. The accumulation of microbial necromass and its ratio to SOC were increased (19.8 % and 63.9 %) under the low-magnitude warming and slowed down (14.0 % and 20.3 %) under the high-magnitude warming. The MNC and FNC were increased under both long-term warming (1.61 g/kg and 0.86 g/kg) and short-term warming (0.96 g/kg and 0.50 g/kg), but there was no significant change in BNC under long-term warming patterns. The effect sizes of warming on BNC, FNC and MNC were larger in the subsoil (16.3 %, 25.1 % and 24.2 %) than that in the topsoil (7.8 %, 19.1 % and 17.5 %). These results highlight the importance of warming patterns as predictors of microbial necromass. Nonetheless, these conclusions may be restricted by the insufficient sample size, and future researches should expand the sample size to reveal the threshold and mechanism underlying the effect of warming patterns on microbial necromass.