Food Web Responses to Environmental Productivity and Predation

食肉动物对种群既有积极的影响，也有消极的影响。积极的影响可能是直接的，也可能涉及食物链中的其他物种。影响产量的营养物质如何与食肉动物对较低营养水平的影响相互作用还没有被调查。建议进行实验，在75个室外中附体中，四个食物网将暴露在最多5个营养水平和5个捕食水平的蝾螈中。这四个食物网在林蛙幼虫和水蚤的发生上将有所不同。将监测浮游动物、浮游植物、滨海甲壳类和附生植物的群落发展和生产。据预测，这些生物对捕食和营养水平的反应将强烈依赖于食物网的结构。这将是检验这种预测的第一次实验。这些调查应为了解生物丰度的自然变化和预测群落对富营养化和捕食强度变化的反应提供重要的见解。

Carnivores can have positive as well as negative effects on populations. Positive effects may be direct or they may involve other species in the food web. How nutrients that affect production might interact with a carnivore's impact on lower trophic levels has not been investigated. Experiments are proposed in which four food webs will be exposed to up to 5 levels of nutrients and 5 levels of predation by newts in an array of 75 outdoor mesocosms. The four food webs will differ in the occurrence of Rana larvae and Daphnia. Community development and production of zooplankton, phytoplankton, littoral crustaceans and periphyton will be monitored. It is predicted that the responses of these organisms to predation and nutrient levels will depend strongly on the structure of food webs. This will be the first experiment to test such predictions. These investigations should provide critical insights for understanding natural variation in the abundance of organisms and in predicting the responses of communities to eutrophication and changes in predation intensity.