MODELING THE EFFECTS OF POST-WILDFIRE REHABILITATION TREATMENTS ON NUTRIENT CYCLING IN EXPERIMENTAL WATERSHEDS IN COLORADO

The number of seasonal wildfires and the total burned area has been increasing in Colorado, mostly driven by climate change and human activities. Besides disturbing vegetation, wildfires have both immediate and long-term effects on hydrologic and biogeochemical cycles of forested mountainous areas. Severe fires reduce water infiltration into the soil, causing nutrients and sediments to wash away and compromise the quality of downstream water resources (in addition to creating slope stability and flood hazards). After wildfires, agencies rapidly act to minimize nutrient loss and topsoil erosion using different slope-stabilization methods. Surprisingly, the long-term biogeochemical effects of post-fire rehabilitation techniques such as mulching (among the most commonly used) are not well understood. We have applied the Agricultural Ecosystems Services (AgES) distributed ecohydrology model to simulate long-term post-fire nitrogen, carbon, and hydrological responses at sites affected by the Cameron Peak fire in Colorado. We investigate the influence of post-fire rehabilitation techniques in severely burned areas on nutrient cycling dynamics (e.g. dissolved and total organic carbon and nitrogen fluxes) by collecting samples and using field measurements from sensor networks in mulched and un-mulched hillslopes to calibrate models, which can be scaled to simulate full watersheds. We have partnered with the US Forest Service (USFS), Colorado State University (CSU), and USDA Agricultural Research Service (ARS) to access previously instrumented and treated sites, as well as sites with ongoing instrument installation and mulch application. This research helps advance hydrologic and water quality modeling and informs agencies of the impacts of best practices in critical zone rehabilitation treatments post wildfire.