The sensitivity of watershed models to the spatial distribution of forests of different physiologic types (2016)

Undergraduates: Andrea Stewart, Larry Band

Faculty Advisor: Larry Band
Department: Environmental Science

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Forests with species compositions that comprise different physiologic characteristics use different amounts of water and respond differently to drought. In general, isohydric plants with diffuse-porous xylem anatomy are more susceptible to drought, while anisohydric plants with ring-porous xylem are less susceptible to drought and use less water. The spatial distribution of these forests in the landscape may impact annual and seasonal watershed yield and water balance. However, few studies have used species-level ecophysiological information to improve catchment models or predict future watershed behavior. In this study, we used a spatially-distributed hydro-ecological model, the Regional Hydro-Ecological Simulation System (RHESSys), to simulate two small catchments in Durham and Chapel Hill, NC. We estimated leaf area index for common forest types and manipulated the spatial distribution and ecophysiological parameters of forests with different physiological characteristics to quantify model improvements, future watershed yield, and future water balance. Initial results suggest that modeled watershed yield is impacted by the spatial distribution of forests of different physiologic types and the inclusion of species-level ecophysiological parameters, particularly with respect to the major types of xylem anatomy. Results will aid modelling efforts of future regional water supply and help us understand the hydrologic impacts of changing forest landscapes at the species level.