Large herbivore grazing plays a key role in regulating ecosystem functioning and nutrient cycling in terrestrial ecosystems. However, the effects and mechanisms of large herbivore grazing intensity on soil nutrient fractions remain largely unclear in alpine grasslands. Here, we determine 20 indicator variables associated with soil nutrient fractions (e.g., particulate organic carbon, POC; mineral-associated organic carbon, MAOC) to investigate how grazing intensity on labile fractions through a well-controlled grazing experiment in an alpine meadow on the eastern Tibetan Plateau. Our results show that microbial biomass carbon, dissolved organic carbon, light fraction organic carbon, microbial biomass nitrogen and phosphorus, total potassium, and available potassium significantly decrease with increased grazing intensity, whereas other fractions (e.g., POC, MAOC, dissolved organic nitrogen, ammonium nitrogen, nitrate nitrogen, available nitrogen, etc.) have marginal or non-significant responses to grazing intensity. Further analysis reveals that above-and below-ground biomass, soil moisture, and soil pH jointly determine the grazing effects on soil nutrient fractions, without the impact of species richness. Moreover, correlation analyses indicate that grazing intensity decouples carbon and nitrogen from phosphorus and potassium in alpine meadows. Collectively, our results emphasize the importance of grazing intensity effects on nutrient cycling in alpine grasslands and incorporate the impacts of grazing intensity into terrestrial ecosystem models may help accurately predict carbon sequestration potential in grazinglands.

中文翻译：

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放牧强度对高寒草甸土壤养分组分影响的不同


大型食草动物放牧在调节陆地生态系统的生态系统功能和营养循环方面发挥着关键作用。然而，在高寒草原，大型食草动物放牧强度对土壤养分组分的影响和机制在很大程度上仍不清楚。在这里，我们确定了与土壤养分组分相关的 20 个指示变量（例如，颗粒有机碳，POC;矿物伴生有机碳，MAOC），以通过在青藏高原东部高山草甸中通过控制良好的放牧实验来研究不稳定组分的放牧强度。我们的结果表明，微生物生物量碳、溶解有机碳、轻馏分有机碳、微生物生物量氮和磷、总钾和速效钾随着放牧强度的增加而显著降低，而其他组分（例如，POC、MAOC、溶解有机氮、铵态氮、硝酸盐氮、速效氮等）对放牧强度的反应微乎其微或无统计学意义。进一步分析表明，地上和地下生物量、土壤水分和土壤 pH 值共同决定了放牧对土壤养分组分的影响，而不受物种丰富度的影响。此外，相关性分析表明，放牧强度使高山草甸的碳和氮与磷和钾脱钩。总的来说，我们的结果强调了放牧强度对高寒草原养分循环影响的重要性，并将放牧强度的影响纳入陆地生态系统模型可能有助于准确预测放牧区的碳封存潜力。