关键词: 增温, 颗粒有机物, 矿物颗粒结合有机物, 真菌残体, 细菌残体

Abstract: Warming has been consistently observed to reduce soil carbon (C) storage by accelerating the decomposition of soil organic matter. While different soil C fraction may respond differentially to warming, microbial necromass has been considered as an important contributor to the persistent soil C pool. However, the mechanisms by which warming regulates microbial necromass formation and its potential contribution to new soil organic carbon (SOC) fractions remain poorly understood. In this study, we examined the effects of elevated temperature on newly formed amino sugar C (an indicator of fungal and bacterial-derived microbial necromass C) and its allocation in particulate organic matter (POM) and mineral-associated organic matter (MAOM) fractions in alpine soils of Southwest China, based on a 37-day incubation experiment at 15 °C and 25 °C by adding ¹³C labeled glucose and oxalic acid. The results showed that warming significantly reduced the formation of new SOC by lowering the incorporation of new C into both POM and MAOM fractions. Glucose addition was more effective than oxalic acid in promoting new SOC formation, regardless of temperature. Warming also significantly decreased the new microbial necromass in both soil fractions with more bacterial necromass associated with mineral particles, which was primarily attributed to the higher abundance of bacterial community. In addition, glucose addition significantly promoted contribution of the fungal necromass to newly formed SOC. Overall, this study reveals that warming significantly alters the allocation of newly formed SOC and microbial necromass, highlighting the differential microbial responses in soil C sequestration. These findings have important implications for predicting and managing soil C stocks in forest ecosystems under climate change.

Key words: warming, particulate organic matter, mineral-associated organic matter, fungal necromass, bacterial necromass