Sowing crop affects soil microbial necromass carbon via altering soil fungal community structure in a macadamia-based agroforestry system

Agroforestry management practices governed soil organic carbon (SOC) and microbial community structure in terrestrial ecosystems, yet the effect of these practices on microbial necromass carbon (C) remain poorly understood in a subtropical region. Here, we compared the differences in fungal, bacterial, and microbial necromass C (indicated by amino sugars) and their contributions to SOC among different forest types including macadamia monoculture plantation (MMP) and macadamia-based agroforestry systems intercropping with dasheen (MDAS), konjac (MKAS), and maize (MMAS) in the Lincang city, southwest Yunnan province, China, and assessed the impact of aboveground biomass, soil fertility, and soil microbial community structure on microbial necromass C and its contribution to SOC. Compared with monoculture plantation, macadamia-based agroforestry decreased SOC, and changed significantly soil microbial alpha diversity, beta diversity, and microbial necromass C and its contribution to SOC (P < 0.01). Microbial necromass C and its contribution to SOC were no significant difference between MMP and MMAS. MDAS and MKAS had lower microbial necromass C than MMP (35.11 % and 63.62 %, respectively). SOC increased with increasing soil fungal and microbial necromass C among the agroforestry systems. Soil fertility was the most important factor affecting fungal (41.45 %), bacterial (33.84 %), and microbial necromass C (40.63 %). Importantly, soil fertility and fungal beta diversity directly negatively affected soil fungal and microbial necromass C and their contributions to SOC. Furthermore, woody aboveground biomass affected microbial necromass C directly or indirectly via soil fungal beta diversity. Overall, our findings suggest that soil fungal beta diversity drove microbial necromass C accumulation and its contribution to SOC in a macadamiabased agroforestry systems, which reveal that sowing crop may be key considerations in mitigating climate change.