Heavy grazing leads to increased dominance of plant and soil nematode communities

Herbivore grazing plays a crucial role in grassland ecosystems, yet its comprehensive impact on plant and soil nematode diversity in desert steppe remains unclear. We assessed the impact of different grazing intensities (CK: no grazing, LG: light grazing, MG: moderate grazing, HG: heavy grazing, EG: extremely heavy grazing) on plant and soil nematode diversity in desert steppe. In the HG treatment, the diversity of plants and nematodes was the lowest and significantly lower than that in the CK treatment. Compared with CK, the Sobs, Shannon-Wiener, Inverse Simpson Index, and Heip index of the plant community under HG decreased significantly by 23.78%, 37.97%, 47.43%, and 41.51%, respectively (P < 0.05). Simultaneously, the diversity indices of soil nematodes under HG also decreased significantly, being 22.2%, 40.3%, 50.9%, and 47.1% lower than those of CK, respectively. Linear and non-linear correlation analyses demonstrated a significant positive correlation between plant diversity and nematode diversity, indicating a synergistic relationship between plant communities and soil nematode communities. Pearson correlation analysis revealed that Cleistogenes songorica (Roshev.) Ohwi and Stipa breviflora Griseb. were significantly positively correlated with the herbivorous nematode genus Paratylenchus (P < 0.05), while Convolvulus ammannii Desr. was significantly positively correlated with the genus Acrobeloides (P < 0.05). These results indicate that certain specific plant species exert significant regulatory effects on specific soil nematode species. Overall, heavy grazing is detrimental to the sustainable development of grasslands. Therefore, in light of previous research in this field, maintaining grazing intensity below the level of heavy grazing (LG or MG) is the most appropriate grassland management strategy.

草食动物放牧在草原生态系统中发挥着至关重要的作用，但其对荒漠草原植物与土壤线虫多样性的综合影响仍不明晰。本研究评估了不同放牧强度（CK：禁牧，LG：轻度放牧，MG：中度放牧，HG：重度放牧，EG：极重度放牧）对荒漠草原植物与土壤线虫多样性的影响。在重度放牧（HG）处理下，植物与线虫的多样性均为最低，且显著低于禁牧（CK）处理。与CK相比，HG处理下植物群落的Sobs指数（Sobs）、香农-威纳指数（Shannon-Wiener）、逆辛普森指数（Inverse Simpson Index）以及海普指数（Heip）分别显著下降23.78%、37.97%、47.43%与41.51%（P < 0.05）。与此同时，HG处理下土壤线虫的多样性指数也显著降低，较CK分别低22.2%、40.3%、50.9%与47.1%。线性与非线性相关分析表明，植物多样性与线虫多样性之间存在显著正相关关系，显示植物群落与土壤线虫群落之间存在协同关系。皮尔逊相关分析（Pearson）显示，本氏隐子草（Cleistogenes songorica (Roshev.) Ohwi）与短花针茅（Stipa breviflora Griseb.）均与植食性线虫类群短体线虫属（Paratylenchus）呈显著正相关（P < 0.05），而银灰旋花（Convolvulus ammannii Desr.）则与真滑刃线虫属（Acrobeloides）呈显著正相关（P < 0.05）。上述结果表明，特定植物物种对特定土壤线虫类群具有显著的调控作用。总体而言，重度放牧不利于草原的可持续发展。因此，结合该领域既往研究，将放牧强度维持在重度放牧以下（即轻度或中度放牧）是最为适宜的草原管理策略。