Decadal Impacts of Wildfire on Stream Food Webs

Wildfire frequency and severity in the western U.S. has increased in recent decades and is predicted to increase with climate change.  Wildfire can alter stream characteristics resulting in warmer water temperatures, higher sediment and nutrient loading, as well as shifts in aquatic benthic community composition.  Even though short-term impacts have been demonstrated, few studies have looked into decadal impacts on stream food webs.  We investigated the decadal influences of wildfire on the composition of invertebrate drift and Westslope Cutthroat Trout diets by comparing drift and stomach contents in burned and unburned streams to evaluate whether wildfire was impacting the percent of terrestrial contribution to stream food webs and/or food web flows.  We deployed drift nets and collected fish diets in July, August, and September. All samples were returned to the lab for identification to the highest resolution necessary to determine habitat of origin (Order or family).  Fish diets reflected our drift samples.  There were no significant differences between burn treatment and portion of terrestrial insects in the drift or diets of trout.  But, invertebrate community composition did differ between burned and unburned streams indicating long-term decadal impacts of wildfire on stream food webs.