HR: 14:00h
AN: B43B-03    [Abstracts]
TI: Effects of fire and subsequent channel-reorganizing events on invertebrate drift and rainbow trout diet in small headwater streams 10 years post-disturbance
AU: * Rosenberger, A E
EM: arosenberger@fs.fed.us
AF: Ecohydraulics Research Group, University of Idaho & RMRS Boise Aquatic Sciences Lab, US Forest Service, 322 E. Front St., Bosie, ID 83702 United States
AU: Dunham, J B
EM: jbdunham@fs.fed.us
AF: US Forest Service Rocky Mountain Research Station Boise Aquatic Sciences Lab, 322 E. Front St., Boise, ID 83702 United States
AU: Wipfli, M S
EM: mark.wipfli@uaf.edu
AF: Alaska Cooperative Fish and Wildlife Research Unit - USGS, Institute of Arctic Biology 209 Irving I Bldg., Box 757020 University of Alaska Fairbanks , Fairbanks, AK 99775-7020 United States
AU: Buffington, J M
EM: jbuffington@fs.fed.us
AF: US Forest Service Rocky Mountain Research Station Boise Aquatic Sciences Lab, 322 E. Front St., Boise, ID 83702 United States
AB: Studies examining the effects of fire on the biota of streams are often confined to immediate post-disturbance impacts; however it is also important to consider longer-term effects of fire and fire-related channel disturbances, including both negative and positive influences on stream communities. Fire and subsequent debris flows and hyperconcentrated flows destroy streamside vegetation and alter the channel morphology such that streams are wider and shallower with larger, less mobile substrate. Increased light, high temperatures, and altered stream morphology have the potential to greatly impact invertebrate communities, invertebrate drift, and drift-feeding fish diet. The goal of our study was to determine the effects of wildfire and wildfire-related disturbance on the amount and composition of stream invertebrate drift and how that translates to the diet of resident fishes 10 years post-disturbance. In the summer and fall of 2003, we set drift nets and examined the diet of fishes in 9 streams: 3 unburned; 3 burned (1992-4); and 3 burned with a subsequent channel disturbance (1992-4). Key questions include: does the taxonomic composition (richness, functional feeding groups), origin (terrestrial or aquatic), or total production (biomass) of invertebrate drift and fish diet vary with burn history? Does the composition and biomass of invertebrate drift indicate main sources of energy (allochthonous vs. autochthonous) for headwater streams affected by fire? Differences among streams in channel morphology, streamside vegetation, light input, and temperature did not correspond to consistent or marked differences in invertebrate drift productivity and only slight differences in functional feeding group composition. However, preliminary data suggest that taxon richness, though similar among burned and unburned streams, is lowest in burned and disturbed streams. Although there is a terrestrial component to fish diet in all three treatment groups, in the summer, there is a greater terrestrial contribution in burned streams; while fish in unburned streams have a greater terrestrial component in their diet in the fall. Our results indicate that the effects of fire and disturbance on invertebrate communities are difficult to detect 10-years post event. Resilience in the invertebrate community and a flexible diet may be contributing to the resilience of resident trout found throughout our study streams. However, geomorphic changes and habitat alterations caused by massive channel-reorganizing events after wildfire may prevent full invertebrate community recovery for some time after the disturbance.
DE: 0400 Biogeosciences
SC: Biogeosciences [B]
MN: 2005 Joint Assembly