A model of wetland vegetation dynamics in simulated beaver impoundments

Beavers alter environments to provide food and habitat necessary to support themselves, and consequently have a significant effect on vegetation structure at both the local and landscape scale. I constructed a simulation model of allogenic wetland vegetation succession as an initial step in exploring important factors affecting vegetation trends for areas disturbed by beaver impoundment. The model is based on general relationships of basic community life history traits, and how each responds to hydrologic disturbance. Vegetation succession takes place within the framework of a hypothetical beaver pond, characterized by a seasonally fluctuating hydrologic regime and periodic flood disturbance. A submodel of sediment accumulation is also included. Model results are consistent with past studies of beaver wetland change, which indicate that beaver impoundment may have long-lasting effects on local vegetation composition. Sensitivity analysis indicates that the model is particularly sensitive to outside seed sources. Based on the results of the model, parameters requiring additional quantification include local seed sources within riparian river drainages, and both growth and mortality functions for wetland vegetation elevated above the water table.