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<p>Grassland degradation threatens global soil carbon (C) stocks, yet the mechanisms by which wind-dispersed tumbleweeds regulate soil C stabilization remain insufficiently resolved, particularly regarding how litter-driven priming effects (<i>PE</i>) and the partitioning of litter-derived C into particulate organic carbon (<i>POC</i>) and mineral-associated organic carbon (<i>MAOC</i>) respond to grazing intensity. We conducted a <sup>13</sup>C/<sup>15</sup>N-labeled litter incubation experiment using soils collected from a long-term grazing intensity gradient (non-grazing, light, moderate, and heavy grazing). Litter derived from two tumbleweed species (<i>Cleistogenes squarrosa</i> and <i>Saposhnikovia divaricata</i>) and the dominant grass <i>Leymus chinensis</i> was added individually and in mixtures to soils from each grazing treatment for incubation. <i>S. divaricata</i> and its mixtures rapidly releases C and nutrients, stimulating microbial activity and thereby suppressing microbial mineralization of native <i>SOC</i>. Compared to <i>L. chinensis</i>, its mean <i>PE</i> is reduced by 25.1%, effectively mitigating the loss of native <i>SOC</i>. In contrast, <i>C. squarrosa</i> litter and its mixtures promote litter fragmentation during later decomposition stages through its curled, multi-node stem structure and specific key microorganisms (<i>Curvularia</i> and <i>Sarocladium</i>), enhancing the incorporation of litter fragments into <i>POC</i> and their subsequent transformation into <i>MAOC</i>. The contribution of <i>C. squarrosa</i> litter-derived carbon to newly formed SOC was 1.45-fold higher than that derived from <i>L. chinensis</i> litter. Overall, the two species may contribute complementarily to increase grassland <i>SOC</i> storage by mitigating loss of old C and promoting formation of new C, respectively. Notably, the <i>SOC</i> sequestration effects of tumbleweeds were significantly higher under light and moderate grazing than under non-grazing and heavy grazing, indicating that moderate grazing enhances the C sequestration capacity of tumbleweeds. These findings extend the conventional view of tumbleweeds as mobile species and highlight their functional role in regulating landscape-scale C cycling in degraded grasslands. By integrating the conservation and strategic management of tumbleweeds into sustainable grazing practices, the soil C sequestration capacity of degraded grasslands can be increased.</p>

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Tumbleweeds mitigate loss of native soil carbon and promote new soil carbon formation in degraded grasslands

  • 期刊论文

  • 发表日期：

    2026年7月25日

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  • Guisen Yang,
  • Jirui Gong,
  • Shangpeng Zhang,
  • Ruijing Wang,
  • Tong Wang,
  • Yaohong Yu,
  • Qin Xie,
  • Qilu Zhuang,
  • Zongpeng Zhang,
  • Jinshuo Lian,
  • Zhiying Ning

摘要

Grassland degradation threatens global soil carbon (C) stocks, yet the mechanisms by which wind-dispersed tumbleweeds regulate soil C stabilization remain insufficiently resolved, particularly regarding how litter-driven priming effects (PE) and the partitioning of litter-derived C into particulate organic carbon (POC) and mineral-associated organic carbon (MAOC) respond to grazing intensity. We conducted a 13C/15N-labeled litter incubation experiment using soils collected from a long-term grazing intensity gradient (non-grazing, light, moderate, and heavy grazing). Litter derived from two tumbleweed species (Cleistogenes squarrosa and Saposhnikovia divaricata) and the dominant grass Leymus chinensis was added individually and in mixtures to soils from each grazing treatment for incubation. S. divaricata and its mixtures rapidly releases C and nutrients, stimulating microbial activity and thereby suppressing microbial mineralization of native SOC. Compared to L. chinensis, its mean PE is reduced by 25.1%, effectively mitigating the loss of native SOC. In contrast, C. squarrosa litter and its mixtures promote litter fragmentation during later decomposition stages through its curled, multi-node stem structure and specific key microorganisms (Curvularia and Sarocladium), enhancing the incorporation of litter fragments into POC and their subsequent transformation into MAOC. The contribution of C. squarrosa litter-derived carbon to newly formed SOC was 1.45-fold higher than that derived from L. chinensis litter. Overall, the two species may contribute complementarily to increase grassland SOC storage by mitigating loss of old C and promoting formation of new C, respectively. Notably, the SOC sequestration effects of tumbleweeds were significantly higher under light and moderate grazing than under non-grazing and heavy grazing, indicating that moderate grazing enhances the C sequestration capacity of tumbleweeds. These findings extend the conventional view of tumbleweeds as mobile species and highlight their functional role in regulating landscape-scale C cycling in degraded grasslands. By integrating the conservation and strategic management of tumbleweeds into sustainable grazing practices, the soil C sequestration capacity of degraded grasslands can be increased.