PRF: Factors Controlling Periphyton Abundance and ProductionDuring Stream Sucession

生态学的一个中心问题是， 特定营养水平的生产受到资源或 较高的营养水平（捕食、放牧）。 这个项目包括 为初级生产者回答这个问题的研究 （附着生物）的沙漠河流生态系统在其恢复或 洪水过后的洪水。 第一个项目是 提供关于食草动物种群动态的背景资料， 这是迄今为止尚未在该系统中研究的能量学。 项目2将利用两种资源的实地操作 可用性（氮浓度）和食草动物丰度， 确定限制因素如何随演替时间变化。 这将增加越来越多的知识基础， 生态系统对干扰（闪光）作出反应并从中恢复 洪水）。 第三个项目将探讨放牧的影响， 利用放牧密度对初级生产力的影响 操纵 如果发现放牧会刺激初级 生产，解释刺激机制的假设 将通过实验进行测试。 如果放牧不是刺激性的， 将试图解释为什么食草动物释放的营养物质 不会再循环到溪流附生生物中。 最后一个项目涉及 在生态学中有一个有争议的话题， 食草动物实际上可能对被食用的植物有益。 南希B博士。格林的方法与其他人不同之处在于， 将使用实验性实地操作来检验假设。 亚利桑那州立大学将作为主办机构， 为期两年的博士后奖学金。

A central question in ecology has been whether abundance and production at a given trophic level are limited by resources or by higher trophic levels (predation, grazing). This project includes research to answer that question for primary producers (periphyton) of a desert stream ecosystem during its recovery or succession following flash flooding. A first project is to provide background information on grazer population dynamics and energetics which heretofore have not been studied in this system. Project 2 will utilize field manipulations of both resource availability (nitrogen concentration) and grazer abundance to determine how limiting factors change over successional time. This will add to an increasing base of knowledge of how stream ecosystems respond to and recover from disturbance (flash flooding). The third project will explore effects of grazing intensity on primary production using grazer density manipulations. If grazing is found to stimulate primary production, hypotheses explaining the mechanism of stimulation will be tested experimentally. If grazing is not stimulatory, an attempt will be made to explain why nutrients released by grazers are not recycled to stream periphyton. This final project deals with a controversial topic in ecology, the question of whether herbivory may actually prove beneficial to plants that are eaten. Dr. Nancy B. Grimm's approach differs from others in that experimental field manipulations will be used to test hypotheses. Arizona State University will serve as the host institution during the two-year postdoctoral fellowship tenure.