Data from: Impacts of grazing by different large herbivores in grassland depend on plant species diversity

1. It is well documented that large herbivores have pronounced effects on plant communities in grassland ecosystems, and the extent and course of their effects can largely depend on both plant and herbivore characteristics. Previous studies highlighted the importance of plant productivity in predicting the impact of herbivores on grasslands. Yet, there has been little consideration of how different herbivores affect plant communities that, in turn, differ in plant diversity. 2. In a 2-year grazing experiment, we tested the effects of large herbivores (cattle or sheep, or both together) on plant communities under high and low plant diversity levels in eastern Eurasian steppe. 3. We found that, for high plant diversity grassland, mixed grazing by cattle and sheep significantly increases plant diversity, but we found no effect of grazing by cattle or sheep alone. Grazing by cattle or sheep alone or mixed grazing by cattle and sheep did not significantly affect plant biomass in the high diversity grassland. However, for low plant diversity grassland, grazing by cattle alone and mixed grazing by cattle and sheep significantly increased plant diversity, but significantly decreased plant biomass. There was no significant impact on both plant diversity and biomass from sheep grazing. 4. Synthesis and applications. We conclude that the effects of grazing in grassland strongly depend on herbivore assemblages and pre-grazing plant diversity. Herbivore grazing might contribute more to the maintenance of grassland structure and ecosystem functioning under high plant diversity compared with low plant diversity. Furthermore, our data suggest that multiple-species mixed grazing regimes in grassland systems with high plant diversity could represent the optimal protocol for grazing management. This study emphasizes the importance of maintaining both plant and herbivore diversity to optimize ecosystem functioning.1. 已有充分研究证实，大型草食动物（large herbivores）对草原生态系统（grassland ecosystems）中的植物群落（plant communities）具有显著调控作用，其作用的范围与进程在很大程度上取决于植物与草食动物的自身特征。既往研究强调了植物生产力在预测草食动物对草原影响中的重要性，但鲜有探讨不同草食动物对植物群落的影响——而植物群落本身的植物多样性（plant diversity）也存在差异。2. 本研究在欧亚大陆东部草原（eastern Eurasian steppe）开展了为期2年的放牧实验，探究了大型草食动物（牛、羊或二者混合放牧）对高、低植物多样性梯度下植物群落的影响。3. 研究结果显示：在高植物多样性草原中，牛与羊混合放牧可显著提升植物多样性，但单一牛放牧或单一羊放牧均未对植物多样性产生显著影响；无论是单一牛放牧、单一羊放牧还是混合放牧，均未显著改变高多样性草原的植物生物量（plant biomass）。而在低植物多样性草原中，单一牛放牧与混合放牧均显著提升了植物多样性，却显著降低了植物生物量；单一羊放牧则未对植物多样性与生物量产生显著影响。4. 综合与应用：本研究得出结论，草原放牧的调控效果在很大程度上取决于草食动物类群组成与放牧前的植物多样性水平。相较于低植物多样性草原，在高植物多样性草原中，草食动物放牧更有助于维持草原结构与生态系统功能。此外，本研究数据表明，在高植物多样性的草原系统中采用多物种混合放牧模式，可作为最优的放牧管理方案。本研究强调，维持植物与草食动物的多样性，是优化生态系统功能的关键所在。