Input of plant residue carbon (C) stimulates microbial growth and activity, and thus may alter native soil organic matter (SOM) mineralization. The partition of plant residue C between microbial growth and respiration, and priming effect on soil organic C (SOC) are affected by initial SOM levels and plant residue types. However, how the interaction between SOM level and plant residue on microbial C use efficiency (CUE) and soil priming effect remains not very clear. Here, we quantified the ratio of plant residue C converted to microbial biomass production (as MBC) over that uptake by microorganism (MBC + respiration) and the priming effect on native SOC in two soils (with low and high initial SOM levels, abbreviated as LSOM and HSOM, respectively) added with ¹³C-labeled maize residues (root, stem and leaf) through a 180-day incubation. Microbial CUE of maize residue was the highest in the HSOM soil with leaf residue addition, and was the lowest in LSOM soil with stem and leaf residues addition. About 37% ~ 47% of maize residue C was remained in the soil after 180 days. At the end of incubation, the positive cumulative priming effects on native SOC mineralization induced by stem and leaf residues were 23% and 30% stronger (P < 0.05) in the HSOM soil than those of the LSOM soil, respectively. In contrast the root residue addition induced the negative priming effect on native SOC in the two SOM levels of soils. Overall, microbial CUE of maize residue was higher in soil with high initial SOM level, which is likely to promote SOM formation via microbial biomass, although there are many other factors that influence SOM formation. The interactive effect between initial SOM level and plant residue quality should be considered when understanding long-term SOM storage.

植物残留碳 (C) 的输入会刺激微生物的生长和活动，因此可能会改变原生土壤有机质 (SOM) 的矿化。植物残留碳在微生物生长和呼吸之间的分配以及对土壤有机碳 (SOC) 的启动效应受初始 SOM 水平和植物残留类型的影响。然而，SOM 水平和植物残留对微生物碳利用效率 (CUE) 和土壤启动效应之间的相互作用仍不是很清楚。在这里，我们量化了植物残留 C 转化为微生物生物量产量（作为 MBC）与微生物吸收量（MBC + 呼吸作用）的比率以及两种土壤中天然 SOC 的启动效应（初始 SOM 水平低和高，缩写为LSOM 和 HSOM 分别）添加了¹³通过 180 天的孵育，C 标记的玉米残留物（根、茎和叶）。玉米渣的微生物CUE在添加叶渣的HSOM土壤中最高，在添加茎叶渣的LSOM土壤中最低。180天后，约37%~47%的玉米渣C残留在土壤中。在孵化结束时，茎叶残留物对原生 SOC 矿化的正累积启动效应分别强 23% 和 30% ( P < 0.05) 在 HSOM 土壤中比在 LSOM 土壤中，分别。相比之下，根残留物的添加对两种土壤 SOM 水平的天然 SOC 产生了负启动效应。总体而言，在初始 SOM 水平较高的土壤中，玉米残留物的微生物 CUE 较高，这可能通过微生物量促进 SOM 的形成，尽管还有许多其他因素会影响 SOM 的形成。在了解长期 SOM 储存时，应考虑初始 SOM 水平和植物残留质量之间的交互作用。