Simulated Effects of Stream Restoration on the Distribution of Wet-Meadow Vegetation

Meadow restoration efforts typically involve the modification of stream channels to re-establish hydrologic conditions necessary for the maintenance of native vegetation. To predict change in the distribution of common meadow plant species in response to meadow restoration, a hydrologic model was loosely coupled to a suite of individual plant species distribution models. The approach was tested on a well-documented meadow/stream restoration project on Bear Creek, a tributary to the Fall River in northeastern California, U.S.A. We developed a surface-water and groundwater hydrologic model for the meadow. Vegetation presence and absence data from 170 plots were combined with simulated water-table depth time series to develop habitat-suitability models for 11 herbaceous plant species. In each model, the habitat suitability is predicted as a function of growing-season, water-table depth, and range. The hydrologic model was used to simulate water-table depth time series for the pre- and post-restoration conditions. These results were used to predict the spatial distribution of habitat suitability for the 11 herbaceous plant species. Model results indicate that restoration changed water levels throughout the study area, extending well beyond the near-stream region. Model results also indicate an increase in the spatial distribution of suitable habitat for mesic vegetation and a concomitant decrease in the spatial distribution of suitable habitat for xeric vegetation. The methods utilized in this study could be used to improve setting of objective and performance measures in restoration projects in similar environments, in addition to providing a quantitative, science-based approach to guide riparian restoration and active revegetation efforts.