BENTHIC COMMUNITY STRUCTURE IN 2 ADJACENT STREAMS IN YELLOWSTONE-NATIONAL-PARK 5 YEARS AFTER THE 1988 WILDFIRES

Physical characteristics, benthic macroinvertebrates, and periphyton a ssemblages in two adjacent headwater streams in Yellowstone National P ark were evaluated five years after the 1988 wildfires. The catchment of one stream was burned by wildfire (burned stream) while the other c atchment was unburned (unburned stream). Physical measures revealed ch annel alteration in the burned stream relative to the unburned stream. Periphyton biomass was lower in the burned than the unburned stream ( 29.2 vs. 50.5 g/m(3) AFDM, respectively), further demonstrating the un stable physical conditions of that system. Kendall's coefficient of co ncordance (an index of similarity) between diatom assemblages was 0.22 , indicating distinct assemblage composition between streams. Navicula permitis Hust. was the most abundant diatom in the burned stream whil e Hannaea arcus (Ehr.) Patr. was dominant in the unburned stream. Macr oinvertebrate taxa richness, density, and biomass were all greater in the unburned stream, although Chironomidae was the most abundant taxon in both streams. Results suggest the removal of terrestrial/riparian vegetation by wildfire can directly influence stream benthic assemblag es by altering the inherent disturbance regime of the physical habitat templet.