Riparian Vegetation Response to High-intensity Fire and Flood Disturbance in Two Montane Canyons in the Jemez Mountains, New Mexico
 
Patrick B. Shafroth1*, Samuel Alfieri2, Craig D. Allen3, Kay Beeley4, Barbara Leighnor5, Jonathan M. Friedman6, Eduardo Gonzalez7, Jamie M. Gottlieb8, Laura G. Perry9, Michael L. Scott10, Jens T. Stevens11, Anne C. Tillery12 
 
1U.S. Geological Survey Fort Collins Science Center, Fort Collins, CO, USA; shafrothp@usgs.gov
2Contractor with U.S. Geological Survey Fort Collins Science Center, Fort Collins, CO, USA; salfieri@contractor.usgs.gov
3University of New Mexico, Albuquerque, NM, USA; craigdallen@unm.edu
4National Park Service Bandelier National Monument, Los Alamos, NM, USA; Kay_Beeley@nps.gov
5Contractor with National Park Service Bandelier National Monument, Los Alamos, NM, USA
6U.S. Geological Survey Fort Collins Science Center, Fort Collins, CO, USA; friedmanj@usgs.gov
7Colorado State University Department of Biology, Fort Collins, CO, USA; eduglez@colostate.edu
8Northern Arizona University School of Forestry, Flagstaff, AZ, USA
9Colorado State University Department of Biology, Fort Collins, CO, USA; Laura.Perry@colostate.edu
10Colorado State University Department of Geosciences, Fort Collins, CO, USA
11U.S. Geological Survey Fort Collins Science Center, Fort Collins, CO, USA
12U.S. Geological Survey New Mexico Water Science Center, Albuquerque, NM, USA; atillery@usgs.gov
 
 
Globally and regionally, extreme disturbance events have become increasingly common with hotter drought in recent decades. Combinations of high-severity fire, debris flows, large-magnitude floods, and high sediment fluxes drive a range of disturbance intensities within riparian and aquatic environments. While fires and floods occur naturally in riparian systems, the high cumulative severity of some combinations of events creates uncertainty regarding ecosystem responses, trajectories, and appropriate resource management response. We examined the effects of fire and flood disturbance on riparian vegetation in two montane canyons in the Jemez Mountains, New Mexico. The 2011 Las Conchas fire burned at high severity in many parts of the two study watersheds, and multiple debris flows and large floods followed from 2011-2013. We conducted a suite of studies between 2018 and 2020 to retrospectively assess spatial variation in the intensity and effects of fire and flood disturbance, and responses of riparian vegetation. Canyon segments that experienced high-severity fire were characterized by a loss of formerly dense forest canopy cover, channel expansion, and gradual recolonization by riparian pioneer plants (e.g., cottonwoods and willows), and resprouting of other taxa (e.g., box elder, Gambel’s oak, choke cherry). Where burn severity was low to moderate, mature tree canopy remained, but the understory in lower canyon segments was highly disturbed due to high sediment flux, woody debris transport, and flood flow accumulation. Riparian vegetation response also varied along the ~4000 foot elevation gradient within our study canyons. Based on our results, we propose a general framework to provide information to inform potential restoration actions in the context of canyon ecosystems impacted by compounded, severe disturbances.