DISSERTATION RESEARCH: Mechanisms of compensatory dynamics in natural systems

理解控制生态稳定性的机制，例如为什么初级生产力等属性在一些群落中是稳定的，而在另一些群落中是可变的，一直是生态学的中心焦点。环境条件和物种动态之间的相互作用通常被认为是群落水平长期稳定的关键决定因素。在可变环境中，当种群水平的非同步波动缓冲群落水平的波动时，环境-物种相互作用可能产生补偿动态。例如，降水对草地生产力有很强的控制作用，在以高降水变异性为特征的草原上，植物物种往往会随着时间的推移而权衡，因为一些物种更能忍受干旱年，而另一些物种在潮湿年更有竞争力。该项目将表明，在降水变化的环境中，补偿动力学的稳定作用是否取决于1)物种对降水的响应和2)物种对生产力的影响。研究人员将通过操纵降水变化和物种相互作用，在物种权衡频繁的加利福尼亚草原上进行实验来验证这一点。结果将产生对补偿动态如何影响社区稳定性的第一个机械的、基于实地的测试。这项研究对社会很重要，因为许多人依赖稳定的自然资源来源，但全球变化可能会增加降雨和温度的可变性。例如，加州的牧场主依靠草原提供饲料，但这种生态系统服务的可靠性受到气候变化的威胁。结果将通过“中央海岸牧场联盟”和“加州自然主义者和牧场”等管理者阅读的出版物传播给这些土地管理者，该项目的数据集将向公众开放。该项目还将培养一名博士生和本科生，其中五人已经完成了与研究相关的荣誉论文项目。

Understanding the mechanisms governing ecological stability, such as why a property such as primary productivity is stable in some communities while variable in others, has long been a central focus of ecology. Interactions between environmental conditions and species dynamics are generally thought to be key determinants of stability at the community level over time. In variable environments, environment-species interactions may generate compensatory dynamics, which occur when asynchronous fluctuations at the population level buffer against fluctuation at the community level. For example, precipitation is a strong control of grassland productivity, and in grasslands characterized by high precipitation variability plant species tend to tradeoff over time because some species better tolerate drought years, whereas other species are more competitive in wet years. This project will show whether the stabilizing effect of compensatory dynamics in environments with variable precipitation depends on 1) the responses of species to precipitation and 2) the effects of species on productivity. Researchers will test this with experiments in California grasslands, where species tradeoffs are frequent, by manipulating precipitation variability and species interactions. Results will yield one of the first mechanistic, field-based tests of how compensatory dynamics shape community stability.This research is important to society because many people rely on stable sources of natural resources, but global change is likely to increase variability in rainfall and temperature. For example, ranchers in California depend upon grasslands for forage, but the reliability of this ecosystem service is threatened by climate change. Results will be disseminated to such land managers via the Central Coast Rangeland Coalition and through publications read by managers such as the California Naturalist and Rangelands, and the sets of data from the project will be made available to the public. The project will also train a Ph.D. student and undergraduates, five of whom have developed honors thesis projects related to the research.