Gw. Minshall et al., POSTFIRE RESPONSES OF LOTIC ECOSYSTEMS IN YELLOWSTONE-NATIONAL-PARK, USA, Canadian journal of fisheries and aquatic sciences, 54(11), 1997, pp. 2509-2525
Wildfire is a major large-scale disturbance affecting terrestrial land
scapes and lotic ecosystems in many regions of the world. We examined
environmental and biological responses of 20 streams in Yellowstone Na
tional Park, U.S.A., over 5 years following extensive wildfires in 198
8. Streams of burned catchments displayed increases in dissolved nitra
te-nitrogen following the fires. Summer water temperatures often excee
ded 20 degrees C in small (first-and second-order) streams of burned c
atchments compared with <15 degrees C in their unburned counterparts.
Habitat heterogeneity decreased in streams of burned watersheds as dem
onstrated by changes in substrate embeddedness and near-bed velocities
. Substantial alteration of channels and major restructuring and movem
ent of large woody debris occurred in fire-impacted but not reference
streams. Transported and benthic organic matter, mostly charcoal, incr
eased in burned sites. No major changes were found in macroinvertebrat
e density, biomass, or richness, although significant changes occurred
in relative abundances of miners, gatherers, and scrapers of burned s
ites. Chironomidae abundance was greater initially (postfire years 1-3
), followed by later increases (postfire years 3-5) by the mayfly Baet
is bicaudatus in burned sites compared with reference streams. Our fin
dings demonstrate an integral relationship over time between a stream
and its catchment, following large-scale disturbances such as wildfire
.