Complexity and Stability of an Old-field Ecosystem: The Role of Asymmetrical Interaction Strengths and Food Web Toplology

生物多样性提供了支持人类健康和经济福祉的重要环境服务。一个重要但尚未得到解答的问题是：物种如何结合在一起，以提供最稳定的这些服务？这个问题将通过对昆虫捕食者、食草动物和草原植物进行实验来回答。这项研究将检验新的理论，即最稳定的服务供应来自复杂系统，在这个系统中，许多相互作用弱的物种抵消了一些相互作用强的物种的影响。这个为期四年的实地项目将通过组装实验食物网来验证这一理论，这些食物网包含了相互作用强和弱的捕食者和食草动物物种的不同混合物。这项研究将测量不同的物种混合如何维持重要的生命支持服务，如植物生产饲料和氮循环。人类活动正在从根本上改变生态系统，随之而来的是生物多样性的丧失。本研究将通过量化物种丧失对生态功能的风险来检验生态系统的恢复能力。它将展示看似良性的、相互作用弱的物种如何与许多其他相互作用弱的物种结合在一起，最终成为维系生态系统的重要线索。研究结果将有助于指导保护战略，确保重要环境服务的长期可持续性。该项目还将训练下一代本科生和研究生掌握自然生态系统功能的实验分析方法，使他们能够对环境政策作出富有成效的直接贡献。

Biodiversity provides important environmental services that support human health and economic well-being. One important and as yet unanswered question is: How do species fit together to provide the most stable supply of those services? This question will be answered by experimentation with species of insect predators and herbivores, and grassland plants. The study will test new theory that the most stable supply of services comes from complex systems in which many weakly interacting species counterbalance the effects of a few strongly interacting species. The four-year field project will test this theory by assembling experimental food webs containing different mixtures of strongly and weakly interacting predator and herbivore species. The study will measure how well the different species mixtures sustain important life-support services such as plant production for forage and the nitrogen cycle. Human activities are fundamentally changing ecological systems with attendant loss of biodiversity. This study will test the resilience of ecological systems by quantifying the risks to ecological function of species loss. It will show how seemingly benign, weakly interacting species can, in combination with many other weakly interacting species, end up being the important threads that hold ecosystems together. The results will help guide conservation strategies that ensure long-term sustainability of vital environmental services. The project will also train the next generation of undergraduate and graduate students in methods for experimental analysis of natural ecosystem function in ways that enable them to make productive, direct contributions to environmental policy.