Cross-Site: Collaborative Research: Effects of Different-Sized Herbivores on Grassland Plant Diversity

本研究探讨了不同大小的食草哺乳动物对北美6个不同草原植物多样性的影响。这些站点代表了两组站点，它们的内在站点生产力不同。一种假设是，生产力的差异将导致食草动物对植物多样性的影响非常不同。在低生产力地区，大多数植物物种的质量足够高，可以被所有食草动物吃掉，但它们的防御机制是，较大的食草动物吃劣等植物，而较小的食草动物以优势植物的种子为食。在高生产力地点，竞争优势物种可能只被能够适应其低氮含量的大型食草动物消耗。这些权衡表明，较大的食草动物对高生产力地点的植物生物量的影响更大，而较小的食草动物对低生产力地点的生物量的影响更大。此外，较大的食草动物可能会增加高生产力地点的多样性，并在低生产力地点减少多样性，而较小的，更具选择性的觅食食草动物可能会产生相反的效果。该提案的目标是开始监测一个长期（未来10 - 20年）计划的前3年，因为植物物种组成和多样性的变化可能需要很长时间才能对处理产生充分的反应。LTER和承诺支持这一项目的其他场址的协作网络应大大促进这种监测。研究结果有助于了解草食动物在控制草原植物多样性中的作用，并有助于草地生态系统的恢复、保护和管理。

This study addresses the effects of different-sized mammalian herbivores on plant diversity at six different North American grassland sites. These sites represent two sets of sites that differ in their inherent site productivity. One hypothesis is that differences in productivity will lead to very different effects of herbivores on plant diversity. At low productivity sites, most plant species are of sufficiently high quality to be consumed by all herbivores, but are defended such that larger herbivores eat inferior plants, while smaller herbivores feed on seeds of dominant plants. At high productivity sites, competitively dominant species may be consumed only by larger herbivores that can accommodate their low N content. These trade-offs suggest that larger herbivores will have greater effects on plant biomass at high productivity sites, while smaller herbivores will have greater effects on biomass at low productivity sites. In addition, larger herbivores may increase diversity at high productivity sites and reduce it at low productivity sites, while smaller, more selectively foraging herbivores may have the opposite effects. The goal for this proposal is to begin monitoring for the first 3 years of a long-term (next 10 - 20 years) program as it is likely that changes in plant species composition and diversity will require that long to respond fully to treatments. The collaborative network of LTER and other sites committed to support this project should greatly facilitate such monitoring. The results should provide a general understanding of the role of herbivores in controlling grassland plant diversity, and should aid efforts to restore, preserve, and manage grassland ecosystems.