Aims <p>Microbial necromass carbon (MNC) is an important contributor to the soil carbon (C) pool. Rhizosphere with high-quality substrate inputs support higher microbial metabolic activity. However, whether this will affect the contribution of MNC to the soil C pool and the directly related microbial metabolic mechanisms remain unclear.</p> Methods <p>We conducted systematic multi-point sampling in <i>spruce</i> plantations to compare the contributions of MNC to soil organic carbon (SOC) between the rhizosphere and bulk soils, and explore how microbial metabolic traits influence MNC accumulation capacity in the two soil compartments.</p> Results <p>Across four sampling sites, the contribution of MNC to SOC was 36–43% higher in the rhizosphere than in the bulk soil. This was mainly attributed to the difference in microbial growth and investment traits between soil compartments. Specifically, the rhizosphere exhibited higher microbial carbon use efficiency, faster growth and turnover rates, and lower respiratory quotients and biomass-specific enzyme activities than bulk soil. Greater microbial growth and necromass generation in the rhizosphere were observed. The contribution of microbial necromass carbon to soil organic carbon differed between rhizosphere and bulk soils, a variation regulated by trade-offs in microbial metabolic traits.</p> Conclusions <p>Our findings highlight the pivotal function of microbial necromass in SOC accumulation and deepen our understanding of the microbial metabolic mechanisms involved in rhizosphere C accumulation.</p>