Top-Down and Bottom-Up Effects on Herbivores: Nutrient Availabilty and the Trophic Interactions of Insects on Oak

自上而下和自下而上的力量以各种方式相互作用以控制生态系统的基本特征，这一点得到了广泛的认可，但控制这些力量平衡的因素远未完全理解。 本计画将延续先前三年的实验研究，以因子设计来控制橡树食草动物族群的营养与鸟类捕食压力。最初的结果与以前的陆地实验研究不同，本项目将通过考虑不同大小的树木类别来解释这些研究之间的差异。 它将专门测试是否发生自上而下的影响，但不是小树苗，自上而下的力量与营养物质供应的相对强度，以及在从节肢动物捕食者社区的食草动物产生自上而下的力量的时滞的存在。 本研究将有助于陆地生态系统营养动态的理解。 它还将为众多本科生提供一个获得大量研究经验的机会。

Hunter9906366That top-down and bottom-up forces interact in various ways to the control basic features of ecosystems is widely appreciated but the factors that control the balance of these forces is far from completely understood. This project will continue an earlier three-year experimental study of oak herbivore populations in which nutrients and bird-predation pressure had been manipulated in a factorial design. Initial results had differed from previous terrestrial experimental studies and the present project will seek to explain those differences among studies by considering different size classes of trees. It will specifically test whether top-down effects occur on large but not small saplings, the relative strength of top-down forces with increasing nutrient availability, and the existence of a time lag in the generation of top-down forces on herbivores from the arthropod predator community. This study will contribute to the understanding of the trophic dynamics of terrestrial ecosystems. It will also provide an opportunity for numerous undergraduate students to gain a substantial research experience.