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

这项研究讨论了不同大小的哺乳动物食草动物对北美六个不同草原地点植物多样性的影响。这些站点代表了两组在其固有站点生产力上不同的站点。一种假设是，生产力的差异将导致草食动物对植物多样性的非常不同的影响。在生产率低的地方，大多数植物物种的质量足以供所有食草动物食用，但经过保护，较大的食草动物吃劣质植物，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N含量的较大的食草动物消耗。这些权衡表明，较大的食草动物将对高生产率地点的植物生物量产生更大的影响，而较小的食草动物将对低生产率地点的生物量产生更大的影响。此外，体型较大的食草动物可能会增加高生产率地点的多样性，而在低生产率地点则会减少多样性，而较小的、更有选择性地觅食草食动物可能会产生相反的效果。这项提议的目标是开始监测长期计划的头3年(未来10-20年)，因为植物物种组成和多样性的变化很可能需要这么长的时间才能完全对治疗做出反应。LTER和致力于支持这一项目的其他地点的协作网络应极大地促进这种监测。研究结果将使人们对草食动物在控制草原植物多样性中的作用有一个总体的了解，并有助于恢复、保护和管理草原生态系统的努力。

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.