Pinus tabulaeformis, a dominant industrial plantation species in northern China, is vital for soil carbon sequestration and ecosystem management. However, the mechanisms by which microbial necromass carbon (MNC) influences the formation and stabilization of soil organic carbon (SOC) under various forest management practices remain unclear. Here, we compared four management regimes on the Loess Plateau: Pinus tabulaeformis monoculture plantations (PM), P. tabulaeformis-Forsythia suspensa (a deciduous shrub) intercropping plantations (PF), mixed plantations of P. tabulaeformis and Quercus wutaishanica (PQ), and naturally regenerating P. tabulaeformis secondary forests (PSF). We quantified MNC content and its contribution to particulate organic carbon (POC) and mineral-associated organic carbon (MAOC). High-throughput sequencing was employed to assess microbial community, diversity, networks, and life strategies. Microbial life strategies (r-vs. K-selection) were inferred based on established taxonomy-trait relationships. Results showed that PQ increased POC and SOC, while PF and PSF enhanced MAOC and SOC accumulation. In addition, POC and MAOC were positively correlated with fungal necromass carbon (FNC) and bacterial necromass carbon (BNC), respectively. Distinct SOC formation pathways emerged among management types, driven by MNC composition and microbial life strategies. The PQ treatment favored r-strategist fungi and enriched fungal key modules associated with FNC, representing key clusters in the microbial network. In contrast, PSF combined r-strategist bacteria with K-strategist fungi and showed higher abundance of BNC-related bacterial modules. Partial least squares path modeling revealed that microbial life strategies directly regulated BNC to promote MAOC, while key microbial modules facilitated POC formation via FNC. Overall, these findings demonstrated that converting coniferous monocultures to intercropped, mixed (particularly with broad-leaf tree species like Q. wutaishanica), or naturally regenerating forests can enhance SOC storage through distinct MNC mediated mechanisms. This study provides critical mechanistic insights for forest management strategies aimed at improving soil carbon sequestration in industrial coniferous forests across semi-arid to semi-humid regions.