Grazing and precipitation are pivotal factors influencing the productivity and biodiversity of grassland ecosystems, largely through their effects on the growth and reproduction of dominant species. Approximately 50 % of terrestrial ecosystems are concurrently affected by grazing and precipitation addition (PA), yet the interactive effects of these factors remain underexplored. To elucidate the combined impacts of grazing and PA on the growth of dominant species and their influence on community structure and function, we initiated a four-year combined grazing and PA experiment based on a long term of grazing experiment in a typical steppe. The synergistic interaction between PA and grazing enhanced canopy diameter (CD), tiller density (TD), and seedling density (SD) in dominant species, while decreasing reproductive branch density (RB). Conversely, an antagonistic interaction increased plant height (PH) and TD but reduced SD. These responses suggest that dominant species adapt to combined grazing and PA pressures by shifting growth strategies towards lateral growth and asexual reproduction. The growth characteristics of dominant species exhibited four response patterns to grazing and PA interactions: full saturation, sufficient saturation, equal saturation, and deficit saturation, each with three corresponding thresholds: adaptation, optimum, and saturation points. Grazing decreased the precipitation response thresholds for PH, CD, RB, and population density, while increasing the optimal points for TD and SD. These changes in the growth of the dominant species resulted in a 33 % reduction in the aboveground biomass (AGB) of the community and triggered a 18 % increase in the coupling index between AGB and species richness within the community. Our findings highlight the role of dominant species in facilitating community adaptation to increased precipitation and rotational grazing, offering critical insights for developing sustainable grazing strategies under climate change.

中文翻译：

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放牧和降水增加的相互作用缓解了典型草原中优势物种的过度生长，促进了群落生产力和生物多样性


放牧和降水是影响草原生态系统生产力和生物多样性的关键因素，主要通过它们对优势物种生长和繁殖的影响。大约 50% 的陆地生态系统同时受到放牧和降水增加 （PA） 的影响，但这些因素的交互影响仍未得到充分探索。为了阐明放牧和 PA 对优势物种生长的综合影响及其对群落结构和功能的影响，我们启动了一项为期四年的放牧和 PA 联合试验，该试验基于典型草原的长期放牧试验。PA 和放牧之间的协同作用提高了优势物种的冠层直径 （CD）、分蘖密度 （TD） 和幼苗密度 （SD），同时降低了生殖分支密度 （RB）。相反，拮抗相互作用增加了植物高度 （PH） 和 TD，但降低了 SD。这些反应表明，优势物种通过将生长策略转向横向生长和无性繁殖来适应放牧和 PA 的联合压力。优势物种的生长特性对放牧和 PA 相互作用表现出四种响应模式：完全饱和、充足饱和、相等饱和和赤字饱和，每个阈值都有三个相应的阈值：适应、最佳和饱和点。放牧降低了 PH 、 CD 、 RB 和种群密度的降水响应阈值，同时增加了 TD 和 SD 的最佳点。优势物种生长的这些变化导致群落的地上生物量 （AGB） 减少了 33%，并引发了 AGB 与群落内物种丰富度之间的耦合指数增加了 18%。 我们的研究结果强调了优势物种在促进群落适应增加的降水和轮牧方面的作用，为在气候变化下制定可持续放牧策略提供了重要见解。