The Sustainability of Grazing Ecosystems

提案#9726569 （Frank and Groffman）标题：放牧生态系统的可持续性机构：SYRACUSE UNIVERSITY本研究探讨了大型食草动物是否通过对土壤碳(C)和氮(N)过程的影响，实际上有助于它们所占据的草原的可持续性。普遍认为食草动物降低地下生产力的观点并没有得到黄石国家公园的结果的支持，在黄石国家公园，食草动物似乎增加了地下产量，特别是稳定土壤C的输入。有待验证的假设是，食草动物促进稳定土壤C的输入是加速黄石营养循环的基础，可能是维持黄石和其他放牧生态系统能量和营养动态的关键。这项工作解决了黄石公园的三个问题：(1)食草动物如何影响土壤C的输入？(2)食草动物如何影响土壤碳氮联系？(3)放牧草地植物生长和配置特征对土壤维持过程有何影响？这些问题的答案很重要，因为大量的大型食草动物和草原共存了几千年，但我们目前对这些动物对草原过程的影响的看法表明，放牧生态系统具有内在的不稳定性。由于50%或更多的地球陆地表面被大型食草动物放牧，增加我们对食草动物如何影响生态系统C积累和N循环的认识将大大提高我们对陆地对全球C和N循环的影响的理解。

ABSTRACT Proposal #9726569 (Frank and Groffman) Title: THE SUSTAINABILITY OF GRAZING ECOSYSTEMS Institution: SYRACUSE UNIVERSITY This research examines the question of whether large herbivores actually contribute to the sustainability of grasslands that they occupy, through their effects on soil carbon (C) and nitrogen (N) processes. The prevalent view that herbivores decrease belowground productivity is not supported by results from Yellowstone National Park, where grazers appear to increase belowground production, particularly the input of labile soil C. The hypothesis to be tested is that the promotion of labile C input by grazers is fundamental to acceleration of nutrient cycling in Yellowstone and may be critical in sustaining the energy and nutrient dynamics of Yellowstone and other grazed ecosystems. This work addresses three questions in Yellowstone: (1) How do grazers affect soil C input? (2) How do grazers influence soil C-N linkages? (3) What effects do the plant growth and allocation traits that are selected for in grazed grassland have on sustaining soil processes? Answers to these questions are important because abundant large herbivores and grasslands have coexisted for millennia, yet our current view of the effects of these animals on grassland processes suggest inherent instabilities of grazing ecosystems. Because 50% or more of the Earth's land surface is grazed by large herbivores, increasing our knowledge of how herbivores influence ecosystem C accumulation and N cycling should significantly improve our understanding of terrestrial effects on global C and N cycles.