Water Resources Research Act Program

Details for Project ID 2018ID218B

Post-fire phosphorus availability and mobility in forest soils and the effects on water quality

Institute: Idaho
Year Established: 2018 Start Date: 2018-03-01 End Date: 2019-02-28
Total Federal Funds: $14,923 Total Non-Federal Funds: $29,847

Principal Investigators: Erin Brooks, Daniel Strawn

Project Summary: Roughly 41% of Idaho’s territory is covered by forests, which are the source for most of the water the state uses for irrigation, hydropower, and recreation. Although much of this water is pristine, the recent increase in wildfires severity and extent, and the legacy of historic mining and timber, are affecting the quality of water coming from these forested environments. High severity wildfires can reduce litter cover, which in turn cause high erosion, and transport of sediment and nutrients to streams and lakes. However, there is also some evidence that even in relatively undisturbed forested ecosystems, which have not experienced wildfire for long periods of time due to historic fire suppression policies, nutrient loading can be significant enough to cause toxic algal blooms in receiving water bodies (e.g. Fernan Lake near Coeur d’Alene, ID). Recent publications in the Lake Tahoe region and preliminary soil sampling in the Coeur d’Alene region indicate that there are large pools of organic and inorganic phosphorus (P) in the thick forest litter layers, which are bioavailable to algae in lake environments. As a result of these complex interactions with wildfire, there is a pressing need to better understand phosphorus management in forested landscapes. It is possible that an ideal practice for phosphorus management in forested ecosystems is managing carbon sources and forest fuel loads through prescribed burns. A prescribed burn reduces forest fuels and the risk of a catastrophic wildfire while at the same time generates biochar which immobilizes the inorganic phosphorus. We are seeking funding through the USGS 104b to supplement data from two preliminaries studies and confirm a number of hypotheses related to post-fire P availability in forest soils and litter, and the effects on water quality. Specifically we will: Objective 1: Characterize the effect of wildfire on the form and amount of phosphorus in forest soils and litter. Objective 2: Characterize the P concentration in the ash and charcoal residue from sites that burned at both low and high intensities Results from this study are significant for a number of state and federal agencies (Idaho DEQ, Forest Service, Tribes, BLM, etc.) that are responsible with managing forest ecosystems while protecting the downstream water resources