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

这项建议阐述了河狸对水文的改变对北方森林景观水生部分的植被模式、演替过渡和营养物质分布的影响。这项研究围绕着三个相关的预测进行：(1)景观的物理结构决定池塘的建立和位置、湿地形状和季节动态，但生物反馈(海狸食物、有机物-氧化还原潜力)决定了池塘的废弃和景观的长期动态。(2)过渡概率的变化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。在不同的过程中，不同的滞后时间会产生多个持续路径和多个均衡。(3)由此产生的营养途径是对河狸种群动态、系统的滞后时间、受影响地区的地形和历史的响应。这一结果体现在营养特征、水文学和初始植被的独特组合的植被演替模式上。这些假说将通过量化明尼苏达州北部294平方公里的卡贝托加马半岛上的海狸-景观相互作用来检验取自1927年至1991年(65年)的14张航拍照片。将对食物供应、水文学、氧化还原潜力和养分可获得性进行实地研究。试验性的小区营养操作将被用来测量植物群落对不断变化的水文条件的反应。这些结果将与关于海狸种群动态的信息相结合，以使用嵌套的、非静态的马尔科夫模型来检查景观斑块的动态。这项研究的结果将对理解时空转换的动力学产生直接的生态系统影响。在不同的尺度上，基石食草动物在影响景观斑块和边界动态、多演替路径、景观营养经济、以及生态系统内的滞后反应。

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.