Artificial vegetation restoration is a key strategy to combat desertification in arid regions, yet how different vegetation types regulate the sources and stabilization of soil organic carbon (SOC) remains poorly understood. This study investigated the contrasting contributions of microbial necromass and plant-derived lignin to SOC accumulation across six vegetation restoration types-including shrublands (Artemisia desertorum, Caragana korshinskii, Calligonum mongolicum) and forests (Populus alba var. pyramidalis, Pinus sylvestris var. mongholica, Platycladus orientalis)-and bare sand controls, at two soil depths (20-40 cm and 80-100 cm) in a restored desert ecosystem in northern China. Using amino sugars and lignin phenols as biomarkers, we found that shrubland soils showed distinct microbial necromass patterns, with surface layers enriched in shrub species, while forest soils were consistently enriched in lignin across both depths, reflecting dominant inputs from woody biomass. MNC demonstrated strong positive correlations with SOC pools, particularly in deep soil, whereas lignin exhibited weak or negative correlations, highlighting the superior stabilization efficiency of microbial residues. However, vegetation-specific regressions revealed stronger MNC-SOC relationships in forest soils than in shrub soils, indicating that microbial necromass contributes substantially to SOC in both systems but through potentially different mechanisms. Microbial community analysis revealed that shrublands enriched bacterial taxa (e.g., Actinobacteria, Gammaproteobacteria) positively correlated with MNC, while fungal composition shifted with depth and vegetation type. Random Forest analysis further indicated that surface MNC was primarily driven by labile carbon pools and enzyme activities, whereas deep-layer accumulation was regulated by complex factors. Our findings demonstrate that shrub- and tree-dominated restoration foster contrasting pathways of SOC formation-microbial necromass vs. lignin-both contributing to stable SOC accumulation but with different depth distributions and stabilization efficiencies, highlighting the need to consider these divergent pathways when optimizing vegetation strategies for carbon sequestration in drylands.