Although microbial necromass carbon represents a significant contributor to stable soil organic carbon pools and regulates the response of soil carbon sequestration to climate change, the response of microbial necromass carbon in the soils of invasive species to global climate warming and the factors influencing these responses remain largely unclear. Here, we conducted a 12-year continuous mesocosm climate warming experiment simulating the invasion of Solidago canadensis to quantify the response of soil microbial necromass carbon content to experimental warming and identified the key drivers. Compared with the ambient control, the invasion of S. canadensis in warmed soils increased the accumulation of microbial necromass carbon. Warming increased fungal necromass carbon accumulation by directly increasing fungal abundance (determined via digital PCR), especially in the non-growing season. The contributions of microbial necromass carbon to soil organic carbon were not significantly affected by warming treatments. Soil microorganisms in the warmed soils exhibited higher microbial carbon use efficiency, faster growth and turnover rates, larger abundance, but lower respiratory quotients and biomass-specific enzyme activity than those in the ambient treatment. Additionally, microorganisms tended to exhibit a highyield strategy with decreasing soil pH and increasing soil nitrogen availability, thus positively affecting microbial necromass carbon accumulation. Collectively, although warmed soils support greater microbial growth yield and subsequently greater necromass accumulation, ecosystem carbon-climate feedbacks under climate warming were still neutral. This finding is critical for updating our knowledge on the effects of biological invasion on soil carbon storage under climate warming.
Wang et al. (Thu,) studied this question.