Accumulation of microbial necromass carbon and its contribution to soil organic carbon in artificial grasslands of various vegetation types

Microbial necromass carbon (C) is a crucial soil organic carbon (SOC) component. In the context of alpine grassland degradation on the Qinghai-Tibet Plateau, the establishment of artificial grasslands is an effective restoration method; however, the accumulation of microbial necromass C and its contribution to SOC in these ecosystems, especially for the different plant species composition, remain unclear. We collected surface soil (0-10 cm) from artificial grasslands of four different types in 2022, including annual unicast Triticale and annual grass-legume mixed artificial grasslands sown last time in 2022, and perennial Elymus nutans and perennial Poa pratensis artificial grasslands sown in 2019. By measuring soil moisture and pH value, contents of amino sugars, and microbial biomass (MB) characteristics, we aimed to investigate the variations in microbial necromass C and its contribution to SOC and identify the factors influencing these processes. The content of microbial necromass C followed the order: perennial Elymus nutans > perennial Poa pratensis > annual grass-legume mixed > annual unicast Triticale. This was mainly because belowground biomass indirectly affected microbial necromass C by altering soil properties. The ratio of MB C/N and soil moisture were identified as the primary factors influencing the contribution of microbial necromass C to SOC. The contribution of microbial necromass C to SOC was more favorable under perennial grasslands with a low MBC/MBN ratio and high SWC than under annual grasslands. Thus, from the perspective of microbial necromass accumulation, perennial grasslands were the most suitable vegetation type for sustainable soil restoration.