REU: Animal Influences on the Aquatic Landscape: Vegetative Patterns, Successional Transitions, and Nutrient Dynamics

本研究旨在探讨河狸对北方森林水生部分植被格局、演替过渡和营养物质分布的影响。研究围绕三个相关预测展开：(1)景观的物理结构决定了池塘的建立和位置，湿地的形状和季节动态，但生物反馈(海狸-食物；有机质-氧化还原电位)决定池塘弃置和景观的长期动态。(2)过渡概率的变率是由不同时间尺度上的水文状况和食物供应的变化决定的。不同过程的滞后时间不同，产生了多种演替路径和多种均衡。(3)所产生的营养途径是对海狸种群动态、系统滞后时间、地形和受影响地区历史的响应。其结果体现在营养特征、水文和初始植被的独特组合的植被演替模式上。这些假设将通过量化明尼苏达州北部294平方公里的卡贝托伽马半岛上海狸与景观的相互作用来验证，这些照片来自1927年至1991年14个日期的航空照片岁)。将对食物供应、水文、氧化还原电位和养分有效性进行实地研究。试验样地的养分调节将用于测量植物群落对变化的水文条件的反应。这些结果将与海狸种群动态信息相结合，使用嵌套的非平稳马尔可夫模型来检查景观斑块动态。这项研究的结果将对理解不同尺度的时空变化动态具有直接的生态系统意义，关键食草动物在影响景观斑块和边界动态、多演替路径、景观养分经济和生态系统滞后响应中的作用。

This proposal addresses the effect of hydrologic modifications by beaver on vegetative patterns, successional transitions, and the distribution of nutrients on the aquatic portion of the boreal forest landscape. The research is oriented around three related predictions (1) The physical structure of the landscape determines pond establishment and location, wetland shape and seasonal dynamics, but biological feedbacks (beaver- food, organic matter-redox potential) determine pond abandonment and long-term dynamics of the landscape. (2) Variability in transition probabilities is determined by variations in the hydrologic regime and the food supply over different temporal scales. Different lag times in various processes produce multisuccessional pathways and multiple equilibria. (3) Resultant nutrient pathways are a response to beaver population dynamics, lag-time in the system, topography, and history of the affected areas. The result is manifested by vegetative succession patterns from unique combinations of nutrient characteristics, hydrology, and initial vegetation. The hypotheses will be tested by quantifying beaver- landscape interactions on the 294 km2 Kabetogama Peninsula in northern Minnesota from aerial photographs taken on 14 dates from 1927 to 1991 (65 yrs). Field studies will be conducted of the food supply, hydrology, redox potential, and nutrient availability. Experimental nutrient manipulations of plots will be used to guage plant community response to changing hydrologic conditions. These results will be coupled with information on beaver population dynamics to examine landscape patch dynamics using nested, non-stationary Markovian models. The results of this research will have direct ecosystem implications for understanding the dynamics of spatial and temporal transitions over various scales, the role of a keystone herbivore in influencing landscape patch and boundary dynamics, multisuccessional pathways, landscape nutrient economies, and lag-time responses within ecosystems.