On- and off-year management-induced changes in microbial communities cause microbial necromass carbon variation in subtropical Moso bamboo forests

Moso bamboo, with its high carbon sequestration capacity, plays a unique role in addressing climate change. An on- and off-year management system has traditionally been used in Moso bamboo forest management to maintain productivity and soil fertility. Microbial necromass carbon (MNC) is a major contributor to soil organic carbon (SOC) in terrestrial ecosystems; however, research into changes in MNC and their driving mechanisms in Moso bamboo forests under this management system remains sparse. This study investigated soil MNC and microbial communities in Moso bamboo stands under on- and off-year management. Results showed that total MNC, bacterial necromass carbon (BNC), fungal necromass carbon (FNC), and the contribution of BNC to SOC were significantly higher in off-year managed soils than on-year managed soils. On average, total MNC and FNC comprised 41.69 % and 34.80 % of SOC in Moso bamboo forests, respectively. Additionally, off-year managed soils exhibited higher SOC and available nitrogen but lower pH, available phosphorus, and microbial community alpha diversity compared to on-year managed soils. Microbial groups associated with litter decomposition were significantly enriched in off-year managed soils, while those promoting plant growth were enriched in on-year managed soils. Partial least squares path modeling demonstrated that bacterial communities and SOC directly influenced BNC and FNC accumulation, respectively, with soil pH indirectly affecting MNC through these pathways. These findings indicated that on- and off-year management-induced changes in microbial communities cause MNC variation. This study revealed that on- and off-year management can effectively secure soil nutrient supply in intensively managed bamboo forests and that changes in MNC play a crucial role in maintaining SOC.