Particulate organic carbon (POC) and mineral-associated organic carbon (MAOC) are critical to soil organic carbon (SOC) accumulation and stabilization, yet their responses to intercropping duration and underlying microbial drivers remain poorly understood. Using a long-term apple orchard experiment on the Loess Plateau, this study evaluated white clover intercropping of 8 years (8-yr) and 16 years (16-yr) on POC and MAOC contents across the 0-60 cm soil profile, and examined accumulation mechanisms through microbial life-history strategies, enzyme activities, and microbial carbon pump efficiency. The results demonstrate that MAOC (66-90 %) accounted for a larger proportion of SOC than POC (10-34 %). In the 0-20 cm soil layer, MAOC primarily drove SOC increases induced by intercropping. In deeper soil layers, 8-yr increased POC in the 20-40 and 40-60 cm but did not alter MAOC, whereas 16 yr increased MAOC by 62 % and 34 %, respectively. Intercropping increased microbial necromass carbon (MNC), but the extent varied with intercropping duration and soil depth. Specifically, 8-yr increased both bacterial and fungal necromass (BNC and FNC) in the 0-40 cm soil layer. In contrast, 16-yr enhanced MNC across the entire 0-60 cm profile and notably promoted the accumulation of BNC in 40-60 cm soil layers. Random forest and path modeling indicated stronger links of microbial necromass and resource-acquisitive traits to MAOC than POC. These findings reveal duration-dependent shifts in SOC fraction dynamics regulated by microbial life-history strategies and MCP efficiency. Our work provides a mechanistic basis for optimizing intercropping duration to enhance SOC sequestration in intercropping systems.