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.
