Wildfires Cause Long-Term Shifts In Stream Nutrient Dynamics
Rhea, Allison E 1 ; Covino, Tim P 2 ; Rhoades, Chuck 3
1 Colorado State University
2 Colorado State University
3 USFS, Rocky Mountain Research Station
Wildfires influence stream nutrient processing by fundamentally altering the physical structure and biological composition of upland landscapes, riparian corridors, and stream channels. While numerous post-fire studies have documented substantial short-term increases in stream nutrient concentrations (particularly reactive nitrogen, N), the long-term implications for watershed nutrient cycling remain unclear (Bladon et al. 2008, Hauer & Spencer 1998). For example, recent work indicates that nitrate concentrations can remain elevated for a decade or more following wildfire, yet the controls on these processes are unknown (Rhoades et al., in review). This research utilizes empirical data from water quality monitoring, nutrient diffusing substrates, and stream metabolism to isolate controls on nutrient processing across a burn severity gradient. Nutrient diffusing substrate experiments highlight shifts in trophic structure, with greater autotrophic and total biomass after wildfire. Furthermore, there is a relaxation of N and C -limitation in the burned sites. By isolating the mechanisms that reduce the capacity of fire-affected streams to retain and transform elevated nutrient inputs, we can better predict dynamics in post-fire water quality recovery and help prioritize upland and riparian restoration.
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Hauer, F.R. and Spencer, C.C., 1998, Phosphorous and nitrogen dynamics in streams associated with wildfire: A study of immediate and long-term effects: Int. J. Wildland Fire, c. 8, p. 183-198.
Rhoades, C.C., Chow, A.T., Covino, T., Fegel, T.S., Rhea, A., and Pierson, D., In review, The Legacy of Severe Wildfire on Stream Nitrogen and Carbon in Headwater Catchments: Ecosystems.