Impacts and management implications of multiple extreme disturbance events to formerly diverse, canyon riparian ecosystems within Bandelier National Monument, New Mexico.

Allen, Craig; Shafroth, Patrick

Statement of Need: Impacts and management implications of multiple extreme disturbance events to formerly diverse, canyon riparian ecosystems within Bandelier National Monument (BAND). Problem Statement: The proposal is focused on two streams and their watersheds (Capulin and Frijoles creeks) in the eastern Jemez Mountains, New Mexico, where a series of severe fires, post-fire floods and debris flows, and hotter droughts have impacted an area of over 300,000 acres since 1996 (Allen 2016), including most of BAND (Fig. 1 and 2). In particular the Dome (1996), Cerro Grande (2000), and Las Conchas (2011) fires were all far outside the historical range of variability for fire severity (Swetnam et al. 2016), with effects likely unprecedented for at least a thousand years (Allen 2016). The nearly complete burning of living and dead plant biomass from much of these watersheds (including riparian gallery forests) contributed to dramatically increased post-fire runoff, stormflow discharges, and sediment transport (Fig. 3-7). Flood peaks in Capulin (USGS gaging station 083133655) and Frijoles (USGS gaging station 08313350) increased up to 160 times the pre-fire peak flows following the Dome and La Mesa (1977) fires, respectively (Veenhuis 2002). Flood magnitudes in 2011-2013 following the Las Conchas fire were >450 times larger than typical pre-fire peak flows in Frijoles, and likely in Capulin also based on heights of high-flood debris lines. Extensive vegetation removal, and sediment erosion and deposition, dramatically cut, filled, widened, & straightened channels in many canyon reaches, and numerous log jams and woody debris piles were left behind. While fires and floods occur naturally in these systems, the cumulative severity of these events is historically unprecedented and related to human activities (e.g., grazing, fire suppression & associated fuel buildups, hotter droughts), creating uncertainty regarding natural ecosystem responses (Johnstone et al. 2016) and appropriate NPS resource management response (Hobbs 2016).