Fire regimes and watershed-scale hydrological processes are inextricably linked, with wildfire affecting the ecosystem services that watersheds provide, and watershed dynamics impacting fire regimes. These coupled interactions, and ensuing ecosystem services, will be sensitive to climate change, requiring improved understanding of their integrated dynamics. Ecohydrological models couple physical and biological processes to project watershed dynamics under various climate and management scenarios. Usually wildfire is included as an exogenous forcing in ecohydrological projections, neglecting the bidirectional relationship between fire regimes and watershed ecohydrology. Integrating most models of fire spread and effects with an ecohydrological model is complicated by the detailed characterization of fuel loading and structure required for predicting the spread of individual wildfires, but such explicit fuel characterization is usually extraneous to the core algorithms for ecohydrological modeling. WMFire, a fire spread model of intermediate complexity, eschews these complications, having been designed specifically for coupling with the Regional Hydroecological Simulation System (RHESSys), an ecohydrology model. Subsequently RHESSys has been updated to compute fire effects based on fire spread predicted by WMFire.
Results/Conclusions
This integrated simulation system evaluates coupled fire-regime and watershed processes at multi-decadal temporal scales, under climate and management scenarios, to understand the potential impact of climate change on fire regimes and watershed ecosystem services. We present preliminary simulations of several watersheds in the Western US under a simple factorial combination of increased temperature and decreased precipitation. We evaluate which watershed ecosystem services and fire regime characteristics are most sensitive to these dimensions of climate change. We further evaluate how the coupling of wildfire with ecohydrology impacts our ability to evaluate these sensitivities.