Grazing affects soil carbon (C) storage in grassland ecosystems through livestock trampling, defoliation, and excretion of urine and dung. However, independent effects of those grazing behaviors on soil organic C (SOC) remains unclear, particularly in alpine grassland ecosystems. To address this knowledge gap, a one-year field experiment was conducted on the eastern edge of the Qinghai-Tibetan Plateau to study the effect of grazing behaviors, including light vs. heavy trampling, light vs. heavy defoliation, and excretion of urine and dung, of yak (Bos grunniens) on SOC stock. Our results showed that trampling, particularly light trampling, significantly increased SOC stock in the 0–10 cm soil layer. The increase of soil bulk density and SOC concentration were the main reasons for the increase of surface SOC stock under trampling. Heavy defoliation significantly increased SOC stock in the 20–30 cm depth in comparison to light defoliation (4.4 vs. 2.9 kg C m^-2), but neither affected SOC stock in the 0–30 cm soil profile. In contrast, excretion significantly lowered SOC stock by 9.3 kg C m^-2 (0–30 cm), linked to the decreased soil bulk density and SOC concentration, and the decreased microbial biomass C, which might have lowered the microbial contribution to SOC storage. Our study of independent grazing effects showed that short-term livestock excretion caused the loss of SOC stock while intensive trampling or defoliation did not. Our findings have implications for managing livestock grazing behavior to maintain SOC stock in alpine grassland ecosystems.

放牧通过牲畜践踏、落叶以及尿液和粪便的排泄影响草地生态系统中的土壤碳 (C) 储存。然而，这些放牧行为对土壤有机碳 (SOC) 的独立影响仍不清楚，尤其是在高寒草地生态系统中。为了解决这一知识缺口，在青藏高原东部边缘进行了为期一年的野外试验，以研究放牧行为的影响，包括轻度与重度践踏、轻度与重度落叶、尿液和粪便的排泄。牛粪（Bos grunniens) 在 SOC 股票上。我们的结果表明，践踏，尤其是轻度践踏，显着增加了 0–10 cm 土层中的 SOC 储量。土壤容重和SOC浓度的增加是踩踏下地表SOC储量增加的主要原因。^{与轻度落叶（4.4 对 2.9 kg C m -2}）相比，重度落叶显着增加了 20-30 cm 深度的 SOC 储量，但均未影响 0-30 cm 土壤剖面中的 SOC 储量。相比之下，排泄显着降低了 SOC 储量 9.3 kg C m ^-2(0-30 cm)，与土壤容重和 SOC 浓度降低以及微生物生物量 C 降低有关，这可能降低了微生物对 SOC 储存的贡献。我们对独立放牧效应的研究表明，短期牲畜排泄会导致 SOC 库的损失，而密集践踏或落叶则不会。我们的研究结果对管理牲畜放牧行为以维持高山草地生态系统中的 SOC 存量具有重要意义。