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Background and aims <p>Grazing removal is a globally implemented strategy for rehabilitating degraded grasslands. However, its effect on soil organic carbon (SOC) fractions remains inadequately understood.</p> Methods <p>Herein, the SOC pool was divided into coarse particulate OC (cPOC), free fine POC (fPOC), intra-microaggregate fine POC (iPOC), and mineral-associated OC (MAOC) by a physical fractionation scheme to quantify the changes in SOC after 4 and 12&#xa0;years of grazing removal in Tibetan alpine meadows.</p> Results <p>The results demonstrated that OC associated with macroaggregates (MA) was more sensitive to grazing removal than that within microaggregates (MI). Grazing removal enhanced the contents of fPOC-MA (27–42%) and MAOC-MA (154–172%), driving the accumulation of OC within MA. The content of unprotected OC (cPOC and fPOC) in bulk soil significantly increased by 77–92% following grazing removal, primarily attributed to the accrual of unprotected OC within MA. While grazing removal promoted the accumulation of protected OC (iPOC and MAOC) within MA, it simultaneously reduced the content of protected OC within both MI and silt and clay particles. Consequently, the content of protected OC in bulk soil showed minimal variation after grazing removal. Partial least squares path modeling further revealed that unprotected OC in bulk soil was jointly influenced by plant biomass and microbial necromass C (MNC), whereas protected OC was mainly governed by MNC.</p> Conclusions <p>We concluded that the accumulation of unprotected OC in MA and the reallocation of protected OC in soil matrix were crucial to SOC dynamics during grazing removal in Tibetan alpine meadows.</p>

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Enhanced unprotected organic carbon in macroaggregates facilitates soil organic carbon accumulation following grazing removal in Tibetan alpine meadows

  • 期刊论文

  • 发表日期：

    2025年8月4日

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  • Xiang Liu,
  • Zhiwen Ma,
  • Wenping Qin,
  • Xiaoyan Li,
  • Hongxiao Shi,
  • Bagen Hasi,
  • Honglin Li,
  • Zhifang An,
  • Lihui Tian

摘要

Background and aims

Grazing removal is a globally implemented strategy for rehabilitating degraded grasslands. However, its effect on soil organic carbon (SOC) fractions remains inadequately understood.

Methods

Herein, the SOC pool was divided into coarse particulate OC (cPOC), free fine POC (fPOC), intra-microaggregate fine POC (iPOC), and mineral-associated OC (MAOC) by a physical fractionation scheme to quantify the changes in SOC after 4 and 12 years of grazing removal in Tibetan alpine meadows.

Results

The results demonstrated that OC associated with macroaggregates (MA) was more sensitive to grazing removal than that within microaggregates (MI). Grazing removal enhanced the contents of fPOC-MA (27–42%) and MAOC-MA (154–172%), driving the accumulation of OC within MA. The content of unprotected OC (cPOC and fPOC) in bulk soil significantly increased by 77–92% following grazing removal, primarily attributed to the accrual of unprotected OC within MA. While grazing removal promoted the accumulation of protected OC (iPOC and MAOC) within MA, it simultaneously reduced the content of protected OC within both MI and silt and clay particles. Consequently, the content of protected OC in bulk soil showed minimal variation after grazing removal. Partial least squares path modeling further revealed that unprotected OC in bulk soil was jointly influenced by plant biomass and microbial necromass C (MNC), whereas protected OC was mainly governed by MNC.

Conclusions

We concluded that the accumulation of unprotected OC in MA and the reallocation of protected OC in soil matrix were crucial to SOC dynamics during grazing removal in Tibetan alpine meadows.