Data from: Grazer effects on soil carbon storage vary by herbivore assemblage in a semi-arid grassland

1. Accounting for 10-30% of global soil organic carbon, grassland soils potentially present a large reservoir for storing atmospheric CO2. Livestock grazing management can substantially affect grassland soil carbon (C) storage, but few controlled experiments have explored how herbivore assemblages (different herbivore species and combinations) affect soil C storage. 2. We examined effects of moderate grazing by different herbivore assemblages (no grazing; sheep grazing; cattle grazing; mixed grazing by sheep and cattle) on soil organic carbon storage in two types of grassland communities (high forbs/high diversity and low forbs/low diversity), within a semi-arid grassland with a five-year grazing history. 3. We found that herbivore assemblage generated varying effects on soil C storage and the effects were subject to grassland community types. In the low diversity community, none of three herbivore assemblages studied had obvious effects on soil C storage. In the high diversity community, however, sheep grazing significantly decreased soil C storage due to high selectivity for high quality forbs, and cattle grazing had no effects on soil C storage, while mixed grazing by sheep and cattle significantly increased soil C storage. Overall, soil C storage was highest in mixed-grazed grassland sites with high diversity. 4. Synthesis and applications. Our study suggests that explicitly incorporating grazer species and the combination of grazing livestock into grassland grazing management may help mitigate greenhouse gas emissions. Caution should be exercised when using grazer species with high food selectivity when grazing management is also aimed at climate mitigation, especially in grasslands with abundant high quality forbs and high plant diversity, as sheep grazing may reduce soil carbon (C) storage. Moreover, mixed grazing, including multiple herbivore species, may contribute to a reduction in foraging selectivity for a plant community by means of complementary foraging. It could therefore be considered as an optimal grazing management strategy to maintain and improve soil C storage.1. 草原土壤约占全球土壤有机碳（soil organic carbon）的10%-30%，是储存大气二氧化碳的重要碳库。家畜放牧管理可显著影响草原土壤碳（C）储量，但目前鲜有受控实验探究草食动物组合（herbivore assemblages，不同草食动物物种及其组合）对土壤碳储量的影响。 2. 本研究在具有5年放牧历史的半干旱草原中，针对两种草原群落类型（高杂类草（forbs）/高多样性群落、低杂类草（forbs）/低多样性群落），探究了不同草食动物组合（禁牧、绵羊放牧、肉牛放牧、绵羊与肉牛混合放牧）的适度放牧对土壤有机碳储量的影响。 3. 研究结果表明，草食动物组合对土壤碳储量的影响存在差异，且该效应受草原群落类型调控。在低多样性群落中，本研究涉及的3种草食动物组合均未对土壤碳储量产生显著影响。而在高多样性群落中，绵羊放牧因对优质杂类草具有高选择性，显著降低了土壤碳储量；肉牛放牧对土壤碳储量无显著影响；绵羊与肉牛混合放牧则显著提升了土壤碳储量。总体而言，高多样性且实施混合放牧的草原样地土壤碳储量最高。 4. 结论与应用启示。本研究表明，在草原放牧管理中明确纳入放牧动物物种及其组合模式，有助于减缓温室气体排放。若放牧管理同时以气候减缓为目标，在优质杂类草丰富、植物多样性高的草原中使用高采食选择性的放牧动物时需谨慎，因为绵羊放牧可能降低土壤碳储量。此外，包含多种草食动物的混合放牧可通过互补采食行为降低对植物群落的采食选择性，因此可被视为维持并提升土壤碳储量的最优放牧管理策略。