Quantifying the Positive Effect of Ungulate Herbivory on Living Root‐Derived Soil Organic Carbon Formation: Evidence From an Eight‐Year Simulated Grazing Field Experiment With 13 C Pulse Labeling

作者：Ruihuan Zhang, Yuqi Wei, Chujun Dong, Bin Wei, Matthias C. Rillig, Warwick Badgery, Gaowen Yang, Nan Liu, Yingjun Zhang · 发表于：Global Change Biology · 年份：2025 · DOI：10.1111/gcb.70336 · 被引用次数：10 · 研究领域：Soil Carbon and Nitrogen Dynamics、Ecology and Vegetation Dynamics Studies、Peatlands and Wetlands Ecology

ABSTRACT Ungulate grazing encompasses multiple components, including defoliation, trampling, and excreta return, all of which affect soil organic carbon (SOC) dynamics by influencing the balance between rhizodeposition and the subsequent C input and release. However, it remains unclear how ungulate grazing regulates SOC through living roots, especially as evidence from the field is lacking. A 13 CO 2 pulse labeling experiment was conducted on an 8‐year simulated grazing field experiment, involving separate or combined treatments of defoliation, excreta return, and trampling from grazing animals. We investigated the fate of newly assimilated C in different soil C pools and quantified CO 2 release under grazing treatments. Defoliation enhanced C assimilation in soil microorganisms and promoted fungal necromass formation, thereby increasing the microbial carbon pump (MCP) “capacity” (i.e., the net microbial necromass accumulation), contributing more C to SOC (+32%) and mineral‐associated organic C (+34%) while reducing soil respiration (−19%). Excreta return stimulated C incorporation into bacterial necromass, enhanced MCP “efficacy” (i.e., the contribution of microbial necromass to SOC) and “capacity”, and reduced heterotrophic respiration (−19%). Significant interactions existed between defoliation and excreta return on 13 C recovery of SOC and CO 2 : excreta return reduced the positive effect of defoliation on 13 C recovery of SOC, while defoliation mitigated the inhibitory e...