Meeting Abstract

P2.1  Friday, Jan. 4  Brins Fire: One Year Post Wildfire Aquatic Community Response in Oak Creek, AZ BERN, M/D*; SHANNON, J/P; Doane College; Northern Arizona University mitch.bern@doane.edu

Wildfires can influence the heterogeneity and bio-diversity of aquatic ecosystems through ash deposition and increased sedimentation from run-off during post-fire storms for extended periods of time. In June of 2006 the Brins Mesa fire burned 4,317 acres in and around Oak Creek Canyon and deposited large amounts of ash, soil, and debris in Oak Creek by monsoon rains the autumn following the fire. To gauge the impact of the debris flow on the stream ecosystem, over a period of one year we measured macroinvertebrate density, biomass, and composition as well as the hydraulic properties of the stream. Our results revealed that macroinvertebrate density estimates varied significantly by site and season, with Site 1 having about 40% more during the collection period. Site 1 macroinvertebrate density varied the least, by about 38% between collections, while Site 2 and Site 3 varied by 93 and 96%, respectively. Trichoptera and Ephemoptera were abundant at Site 1 and were rare at sites 2 and 3. In contrast Chironomid (Diptera) densities at Site 2 and 3 were 75% higher compared to Site 1 indicating a compositional response to the fire impacted site. We have determined that the run-off from the Brins Fire can be detected all the way to the confluence of Oak Creek and the Verde River. Little attached filamentous algal growth was observed at any of seven collection sites in July 07 while inorganic estimates comprised more than 94% of the material collected on the cobbles downstream of the debris flows. Sustained monitoring is required to fully understand the Brins Fire and Oak Creek ecosystem interaction. We also suggest that priority be given to the riparian-upland interface (RUI) in order to protect the few riparian and stream communities left in the Southwestern United States.