Exploring spatial variation in aquatic ecosystem responses to wildfire in the Pacific Northwest
Citation:
Roon, D., J. Bellmore, J. Benjamin, F. Robinne, J. Ebersole, R. Flitcroft, J. Compton, K. Bladon, AND J. Dunham. Exploring spatial variation in aquatic ecosystem responses to wildfire in the Pacific Northwest. Oregon Chapter American Fisheries Society, Bend, OR, February 26 - March 01, 2024.
Impact/Purpose:
· People are increasingly concerned about the effects of wildfire on water resources. Water values at risk include water quality and supply for human needs as well as ecological values such as habitat for fish and wildlife. But risks are not equal everywhere; some places are more vulnerable than others, and some values may more sensitive to wildfire impacts than others. In this presentation we describe a food web modeling approach to characterize and anticipate wildfire effects on stream food webs, macroinvertebrate assemblages, and fish populations.
Description:
Aquatic ecosystem responses to wildfire can vary widely depending on the characteristics of fire and the spatial context of where a fire takes place. Assessment of wildfire risk to aquatic ecosystems requires an understanding of sources of such variability (see Ebersole et al. this session). Here we applied a food web simulation model to explore the influence of different spatial contexts on aquatic ecosystem responses to wildfire in the Pacific Northwest. In the model we varied riparian forest and instream physical channel dimensions to represent different spatial contexts that may contribute spatial heterogeneity to aquatic ecosystem responses to fire including different positions along a river continuum (headwater vs. floodplain), and the unique thermal and flow regimes associated with different ecoregions within the Pacific Northwest (westside vs. eastside forests). Model simulations compared unburned conditions to burned conditions across multiple fire severities (low, moderate, and high), and were run for 40 years to capture initial post-fire effects as well as longer-term responses to fire. Collectively these model simulations illustrate that fire effects on aquatic ecosystems are likely to vary widely according to sources of spatial heterogeneity associated with both exposure (fire characteristics) and inherent vulnerability (e.g., geomorphology, hydrologic and thermal regime). These results highlight the importance of taking spatial context into account when considering the potential implications of wildfire for fish. Such insights can inform broader regional spatial assessments of wildfire effects on fish and aquatic ecosystems.