Final report: A natural experiment investigating effects of a wildfire on stream insect communities in Banderlier National Monument, New Mexico

MacRury, Nicole; Clements, Will

While the effects of wildfire on stream hydrology and water chemistry are well documented, impacts of wildfire on stream insects are poorly understood. In this research, WE had the unique opportunity to assess the impacts of wildfire and post-fire flashfloods on with a natural experiment, where WE compared benthic invertebrate communities before and after the fire in a burned and a reference stream. Invertebrate communities in both streams were sampled seasonally in two years before, and six years after, the 1996 Dome fire in Bandelier National Monument, New Mexico. WE found that although post-fire floods in the burned stream reduced benthic insect densities to near zero, quick recovery to pre-fire and reference stream densities occurred due to the colonization of Simulium black flies, Baetis mayflies, and chironomid midges. Taxa richness took longer to recover since more disturbance-sensitive taxa, such as stoneflies and Elmid beetles, were slower to recover during severe post-fire flooding. While invertebrate community composition was similar between the two streams prior to the fire, composition differed dramatically immediately after the fire and did not return to pre-fire or reference composition, even after flooding ceased. Strong negative impacts observed in this study suggest that aquatic insect communities in Bandelier National Monument may be highly susceptible to flashfloods and erosion typically associated with severe canopy fires. Community composition proved to be the most sensitive response in documenting post-fire recovery.