A MODEL OF WETLAND VEGETATION DYNAMICS IN SIMULATED BEAVER IMPOUNDMENTS

Beavers alter environments to provide food and habitat necessary to su pport themselves, and consequently have a significant effect on vegeta tion structure at both the local and landscape scale. I constructed a simulation model of allogenic wetland vegetation succession as an init ial step in exploring important factors affecting vegetation trends fo r areas disturbed by beaver impoundment. The model is based on general relationships of basic community life history traits, and how each re sponds to hydrologic disturbance. Vegetation succession takes place wi thin the framework of a hypothetical beaver pond, characterized by a s easonally 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 indic ate that beaver impoundment may have long-lasting effects on local veg etation composition. Sensitivity analysis indicates that the model is particularly sensitive to outside seed sources. Based on the results o f the model, parameters requiring additional quantification include lo cal seed sources within riparian river drainages, and both growth and mortality functions for wetland vegetation elevated above the water ta ble. (C) 1998 Elsevier Science B.V. All rights reserved.