Multiple States in Grassland Systems: Invasion and Environmental Feedbacks

当非本土植物成为问题入侵物种时，它们似乎会将整个生态系统推向一个门槛，创造出一种难以恢复的替代植被状态。虽然这种模式与关于多个稳定状态的理论预测是一致的，但很少有实证检验。该研究将促进对加州草原恢复和多态动态的理解，该草原是美国受入侵最严重的生态系统之一。通过观察研究和实地实验，它将调查有助于恢复和保护的几个因素：土壤氮供应的变化是否为本地和非本地草创造了避难所，中间水平的氮供应是否可以产生非本地和本地主导的状态，植被和土壤微生物之间的相互作用是否产生正反馈并导致多种状态的形成，以及非本地物种和本地物种之间的区域殖民化差异是否压倒了这些本地相互作用。 该项目还将通过为期一年的体验式科学项目培训年轻科学家。来自当地高中的学生将参与数据收集以及公共示范实验的设计和实施。该项目还将通过征聘和外联工作鼓励妇女，特别是西班牙裔妇女的参与。研究结果将通过定向出版物、讲习班和研讨会广泛传播给应用实践者、科学家和公众。

When non-native plants become problem invasive species, they appear to push the entire ecosystem across a threshold, creating an alternative vegetation state that is difficult to restore. While this pattern is consistent with theoretical predictions concerning multiple stable states, there have been few empirical tests. The research will promote the understanding of restoration and multiple state dynamics in California grasslands, one of the most invaded ecosystems in the United States. Through observational studies and field experiments, it will investigate several factors that will aid in restoration and conservation: whether variation in soil nitrogen availability creates refugia for native and non-native grasses, whether intermediate levels of nitrogen supply can generate both non-native- and native-dominated states, whether interactions between vegetation and soil microbes create positive feedbacks and lead to the formation of multiple states, and whether regional colonization differences between non-native and native species overwhelm these local interactions. The project will also train young scientists through year-long experiential science programs. Students from local high schools will be involved with data collection as well as with the design and implementation of a public demonstration experiment. The project will also encourage the participation of women, particularly Hispanic women, by recruitment and outreach efforts. The results will be disseminated broadly to applied practitioners, scientists, and the general public through directed publications, workshops, and seminars.