Dissertation Research: Incorporating Ecological Stoichiometry into a Multi-trophic, Multi-resource Community Framework

为什么环境变化会影响不同地区的物种组成？物种在生态系统的能量和营养循环中扮演什么角色？这些重要但困难的问题仍然挑战着生态学家对自然的机械理解。然而，最近的实验和理论证据表明，一种研究物种相互作用的新方法可能有助于生态学家解决和整合这两个问题。这种方法被称为“生态化学计量学”，将关键营养物质(如磷和氮)的质量平衡施加的限制纳入到植物-食草动物相互作用的描述中。我们的研究计划侧重于改进这些描述，并评估化学计量学在复杂的自然和半自然实验条件下的重要性。目前，我们了解到，在池塘中，浮游动物食草动物的物种组成对其藻类食物中磷和碳的相对比例的变化很敏感。此外，这种食物的基本质量至少在一定程度上是由池塘生态系统相对和绝对的光和营养供应推动的。在我们未来的工作中，我们计划更强烈地量化不同光照下植物-食草动物相互作用的时间动力学：营养环境状况和不同水平的捕食压力对食草动物的影响。这种对动力学的关注将使我们能够更定量地评估“生态化学计量学”在自然界中可能发挥的作用，并将其整合到现有的数学理论中。最终，我们的目标是了解生态系统的关键资源供应如何影响植物和食草动物物种的组成以及通过食物网的能量流动。“生态化学计量学”可能为实现这一目标提供一个有价值的框架。

DIG DEB-0105014 - Leibold, M. and Hall, S.Why do environmental changes affect composition of species among different localities? What role do species play in the cycling of energy and nutrients in ecosystems? These important yet difficult questions still challenge ecologists' mechanistic understanding of nature. However, recent experimental and theoretical evidence suggests that a new approach to studying species interactions may help ecologists tackle and integrate these two questions. This approach, called "ecological stoichiometry", incorporates constraints imposed by mass balance of key nutrients (such as phosphorus and nitrogen) into descriptions of plant-herbivore interactions. Our research program focuses upon improving these descriptions and evaluating the importance of stoichiometry in complex natural and semi-natural, experimental conditions. Currently, we are learning that, in ponds, species composition of zooplankton grazers is sensitive to changes in the relative proportion of phosphorus and carbon contained in their algal food. Furthermore, the elemental quality of this food is driven, at least in part, by the relative and absolute supply of light and nutrients to pond ecosystems. In our future work, we plan to more intensely quantify temporal dynamics of plant-grazer interactions in differing light:nutrient environmental regimes and with differing levels of predation pressure upon grazers. This focus upon dynamics will enable us to more quantitatively evaluate the role that "ecological stoichiometry" may play in nature and to integrate it into extant mathematical theory. Ultimately, our goal is to understand how supply of key resources to ecosystems influences composition of plant and herbivore species and flow of energy through food webs. "Ecological stoichiometry" may provide a valuable framework to achieve this goal.