CRB: Context-Dependent Constraints on Sagebrush-Herb Dynamics in Sierra Nevada Meadow

9815813D’antonio美国大陆最大的生物群落之一，半干旱的牧场，在过去150年里由于人类活动而发生了巨大的变化。最广泛和最显著的植被变化是以草、莎草和草本植物为代价的木本植物的扩张。本研究将在山艾草扩张发生的内华达山脉山地草甸中探讨以下一般性问题：1)是否有任何生态过程可以解释山艾草和草本植物的当前模式？2)这些群落目前的变化趋势是什么？ 3)草本物种恢复的障碍是什么？这将结合实验和观察研究来检查山艾树和草本物种之间的相互作用。实验将包括大型牛的封闭，小型地鼠的封闭，植被的移除（修剪）和水的操作。此外，还将在一系列处于初步建立阶段的草甸恢复样地进行试验。这些实验以及详细的观察研究将使PI能够阐明在扩大的山艾树群落中限制草本物种的因素。希望本研究不仅能为该系统当前的修复计划提供一个坚实的生态框架，而且还将有助于解决将一般生态学理论应用于特定地点修复问题的更广泛的问题。

9815813D'Antonio One of the largest biomes in the continental United States, the semi-arid rangeland, has been dramatically altered by human activities over the past 150 years. The most widespread and conspicuous vegetation change has been the expansion of woody plant at the expense of grasses, sedges and forbs. This research will explore the following general questions in the montane meadows of the Sierrra Nevada where the expansion of sagebrush has occured: 1) Are any ecological processes that can explain the current patterns of sagebrush and herbs? 2) What are the current trends of change in these communities and 3) What are the barriers to the recovery of the herbaceous species? This will be done with a combination of experimental and observational studies to examine the interactions between sagebrush and herbaceous species. The experiments will involve large cattle exclosures, smaller gopher exclosures, removal of vegetation (clipping) and water manipulations. In addition, experiments will also be conducted in a series of meadow restoration plots that are in their initial stages of establishment. These experiments along with the detailed observational studies will enable the PI to elucidate the factors that constrain herbaceous species within the expanding sagebrush community. It is hoped that not only will the proposed research contribute a solid ecological framework to current restoration plans for this system, but it also will help address the more widespread problem of using general ecological theory to site-specific restoration issues.