*Squirrels and fires: how do biotic agents influence post-fire erosion?

Danica Roth

droth@mines.edu

Prolonged drought conditions and intensifying winter storms in the Western US have dramatically increased wildfire occurrence and associated hazards in recent decades—a trend that climate forecasts indicate will continue in coming years. As megafires and megadroughts spread up the west coast, the historic reference frames in which we have come to understand post-fire processes are shifting rapidly, and our ability to model and predict the effects of fire on erosional processes and hazards are quickly falling behind. This is largely a reflection of fundamental gaps in our understanding of the processes and variables that control sediment transport and landscape evolution. For example, sediment transport laws are currently unable to account for dry ravel—the rolling, sliding and bouncing downhill motion of sediment, often mobilized by burrowing animals or tree fall, or by the incineration of vegetation and other surface roughness elements during fires—which is a primary postfire erosional process in many steep landscapes and known to play a role in postfire hazards like landslides and debris flows. We are also currently unable to bridge the gap between small-scale sediment transport processes such as those that occur in dynamic post-fire settings, and the long-term, large-scale evolution of landscapes and topographic features like slope or relief, which must both influence and eventually be influenced by sediment transport. Without connecting these scales, we cannot accurately predict the long-term effects of a changing fire regime on whole landscapes. This project will use a range of approaches to examine erosion rates and topographic characteristics associated with sediment transport caused by biotic agents (i.e., “bioturbation”), including CA ground squirrels, Botta’s pocket gopher and invasive wild boar. This work will contribute to better understanding of the role of bioturbation-driven dry ravel and regional variables like lithology, vegetation, hillslope aspect, and seasonal rainfall in controlling both long-term landscape evolution and shorter-term erosion and hazards after wildfire.

Grand Challenge: Engineer the tools of scientific discovery

CSM Surface Processes & Geomorphology Lab Group Website: https://surfaceprocesses.mines.edu/ Recent Landscapes Live online seminar by Dr. Simon Mudd ("If you don’t like the stream power law, wait until you get a load of what we do on hillslopes”): https://www.youtube.com/watch?v=OPqV609tJwk McLauchlan, Kendra K., Philip E. Higuera, Jessica Miesel, Brendan M. Rogers, Jennifer Schweitzer, Jacquelyn K. Shuman, Alan J. Tepley et al. "Fire as a fundamental ecological process: Research advances and frontiers." Journal of Ecology 108, no. 5 (2020): 2047-2069. https://besjournals.onlinelibrary.wiley.com/doi/10.1111/1365-2745.13403 Gabet, Emmanuel J., O. J. Reichman, and Eric W. Seabloom. "The effects of bioturbation on soil processes and sediment transport." Annual Review of Earth and Planetary Sciences 31, no. 1 (2003): 249-273. https://www.annualreviews.org/doi/pdf/10.1146/annurev.earth.31.100901.141314 Perreault, Lauren M., Elowyn M. Yager, and Rolf Aalto. "Effects of gradient, distance, curvature and aspect on steep burned and unburned hillslope soil erosion and deposition." Earth Surface Processes and Landforms 42, no. 7 (2017): 1033-1048. https://onlinelibrary.wiley.com/doi/epdf/10.1002/esp.4067 Roth, Danica L., Tyler H. Doane, Joshua J. Roering, David J. Furbish, and Aaron Zettler-Mann. "Particle motion on burned and vegetated hillslopes." Proceedings of the National Academy of Sciences 117, no. 41 (2020): 25335-25343. https://www.pnas.org/content/pnas/117/41/25335.full.pdf

Danica Roth (droth@mines.edu)