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

D‘Antonio是美国大陆最大的生物群之一，这片半干旱的牧场在过去150年里被人类活动戏剧性地改变了。最广泛和最明显的植被变化是木本植物的扩张，而草本植物、莎草和杂草的数量却减少了。这项研究将探索以下一般性问题：1)有没有任何生态过程可以解释目前山艾草和草本植物的格局？2)这些群落目前的变化趋势是什么？3)草本植物物种恢复的障碍是什么？这将通过实验和观察相结合的研究来检验山艾树和草本植物之间的相互作用。这些实验将涉及大型牛的封育、较小的地鼠封育、植被的移除(修剪)和水的处理。此外，还将在一系列处于建立初期的草甸恢复地块上进行试验。这些实验和详细的观测研究将使PI能够阐明在不断扩大的鼠尾草群落中限制草本植物物种的因素。人们希望，拟议的研究不仅将为该系统目前的恢复计划贡献一个坚实的生态框架，而且还将有助于解决更广泛的问题，即使用一般生态学理论来解决特定地点的恢复问题。

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.