Although the quantitative assessment of plant- and microbial-derived carbon (C) chemical composition in soil profiles has been initially explored, the vertical distribution pattern of these two C sources and their relative contribution in SOC formation based on the insights related to the rhizosphere are still lacking. We quantified the divergent accumulation of microbial-derived C (i.e., microbial residues), plant-derived C (i.e., lipids and lignin phenols) and SOC in the rhizosphere at various depths (0–10 cm, 10–20 cm and 20–30 cm) in the upper mineral soil and analyzed its control factors in an alpine coniferous forest (Picea asperata. Mast). We further revealed the relative contribution of plant- or microbial-derived C to rhizosphere SOC in the soil profile. The contents of microbial- and plant-derived C and SOC in the rhizosphere decreased with soil depth and were mainly regulated by root biomass and microbial biomass. Moreover, the contribution of microbial-derived C dominated by fungal residues to rhizosphere SOC at each soil depth (more than 62%) was much higher than that of plant-derived C (less than 6%), implying that the soil microbial C pump was intensely stimulated in the rhizosphere. These results indicated that microbial-derived C was the main contributor of rhizosphere SOC at various depths in the upper mineral soil. Our findings provide direct experimental evidence for assessing the relative contribution of microbial- or plant-derived C to SOC in the soil profile from the perspective of the rhizosphere.

尽管已经初步探索了土壤剖面中植物和微生物来源的碳 (C) 化学成分的定量评估，但这两种 C 源的垂直分布模式及其在基于根际相关见解的 SOC 形成中的相对贡献是仍然缺乏。我们量化了不同深度（0–10 cm、10–20 cm 和 20– 30 cm) 并分析其在高山针叶林 ( Picea asperata.桅杆）。我们进一步揭示了植物或微生物来源的 C 对土壤剖面中根际 SOC 的相对贡献。根际微生物和植物来源的C和SOC含量随着土壤深度的增加而降低，主要受根系生物量和微生物生物量的调控。此外，在每个土壤深度，以真菌残留为主的微生物源碳对根际 SOC 的贡献（大于 62%）远高于植物源碳（小于 6%），这意味着土壤微生物碳泵在根际受到强烈刺激。这些结果表明，微生物来源的 C 是上部矿质土壤中不同深度根际 SOC 的主要贡献者。