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理解，但控制这些力量平衡的因素还远未完全了解。该项目将继续早先对橡树食草动物种群进行的为期三年的实验研究，在该实验中，营养物质和鸟类捕食压力已按析因设计进行了操纵。初步结果与以前的陆地实验研究不同，本项目将试图通过考虑不同大小的树木类别来解释研究之间的差异。它将专门测试自上而下的效应是否发生在大树苗上，但不是小树苗上，自上而下的力量随着养分可获得性的增加而产生的相对强度，以及节肢动物捕食者群落对食草动物的自上而下的力量的产生是否存在时间滞后。这一研究将有助于理解陆地生态系统的营养动态。它还将为众多本科生提供一个获得实质性研究经验的机会。

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.