Increasing evidence shows that microbial necromass carbon is the primary constituent of soil stable carbon, yet the dynamics under different land use intensity (LUI) in arable soils are unknown. Here, we evaluated the dynamics of microbial necromass carbon through biomarker amino sugars at topsoil (0–15 cm) and subsoil (15–30 cm) across different LUI. The LUI was calculated by integrating the application amount of nitrogen fertilizer and the planted number of crops in different cropping systems including cotton-wheat, grape-wheat, vegetable-wheat and watermelon-maize-wheat in North China Plain. We found that the fungal necromass C contributed more to SOC compared to bacteria at both soil depths. Total microbial necromass C showed no correlation with LUI. However, the contribution of fungal necromass-C to SOC was significantly negatively correlated with LUI at topsoil, which was mainly driven by C concentration in non-HCl soluble intra-microaggregate silt and clay. The bacterial necromass-C to SOC was significantly positively correlated with LUI at subsoil, which was mainly driven by soil microbial biomass C. This indicates that the microbial-derived organic C for maintaining and stabilizing soil C stock is important and the proper reduction of land use intensity may benefit for enhancing and stabilizing microbially-derived SOC in arable soils.

越来越多的证据表明，微生物坏死体碳是土壤稳定碳的主要成分，但耕地土壤中不同土地利用强度（LUI）的动态变化尚不清楚。在这里，我们通过不同 LUI 的表土（0-15 厘米）和底土（15-30 厘米）的生物标志物氨基糖评估了微生物坏死物质碳的动态。LUI是通过整合华北平原棉花-小麦、葡萄-小麦、蔬菜-小麦和西瓜-玉米-小麦等不同种植系统的氮肥施用量和作物种植数量计算得出的。我们发现，与两种土壤深度的细菌相比，真菌坏死物质 C 对 SOC 的贡献更大。总微生物坏死物质 C 与 LUI 无相关性。然而，真菌坏死物质-C 对 SOC 的贡献与表层土壤 LUI 呈显着负相关，这主要受非 HCl 可溶性微团聚体粉砂和粘土中 C 浓度的驱动。细菌坏死物质 C 与 SOC 与底土 LUI 呈显着正相关，主要由土壤微生物量 C 驱动。这表明微生物源性有机碳对维持和稳定土壤碳库很重要，适当减少土地使用强度可能有利于提高和稳定耕地土壤中微生物衍生的 SOC。