Benthic macroinvertebrate assemblages in five central Idaho (USA) streams over a 10-year period following disturbance by wildfire

Abstract

e t a l .S t r e a m m a c r o i n v e r t e b r a t e s o v e r 1 0 y e a r s f o l l o wi n g w i l d f i r e W F 0 1 0 1 8 G . W a y n e M i n s h a l l , C h r i s t o p h e r T . R o b i n s o n , D e r o n E . L a w r e n c e , D o u g l a s A . A n d r e w s a n d J a m e s T . B r o c kAbstract. The effects of wildfire on benthic macroinvertebrate assemblages of streams in mixed-conifer forest were examined for 10 successive years following the Mortar Creek Fire of 1979. Changes in burned-catchment streams were evaluated relative to a paired set of reference-catchment streams. Taxa richness and total abundance tended to be lower in burn than in reference streams but to converge near the end of the study; increases in the final years in both burn and reference streams were associated with reduced flows due to drought. Total biomass and that of the scraper, filterer, and miner functional groups usually were greater in the burn streams. Lack of a strong relationship of macroinvertebrate metrics with weather conditions showed that factors specific to each stream also were influencing the biotic community. Mean among-year Jaccard similarity was lower for burn than for reference streams. Specific taxa responded differently to the effects of fire. Densities of disturbance-adapted forms (e.g. Chironomidae, Baetis) increased after the fire but not during the drought period of more stable flows at the end of the study; many other taxa showed the opposite response. Adverse effects of wildfire on the biotic community were largely the result of physical changes in habitat due to increased runoff. Timing and magnitude of effects differed widely among streams as a result of differences in stream size, burn severity, and specific storm or snowmelt events. Though major effects of the fire on the macroinvertebrates dissipated within 7 years, adjustment in the habitat and biotic conditions still were taking place at the end of 10 year and normal recovery patterns may have been obscured by the drought.

Short-term changes in-stream macroinvertebrate communities following a severe fire in the Lake Tahoe basin, California

“…The continued divergence of the BMI community from pre-fire conditions and deteriorating in-stream biotic conditions indicate that the resilience of BMI communities to environmental stress in Angora Creek may have declined further in the second year, although that decline may have begun to reverse during our last sampling period (August 2009). Longer-term studies have observed that in small streams with well-managed and intact watersheds, divergence from pre-fire conditions may persist from 1 to 10 years, and high within-year variability may continue for an unknown ([15 years) length of time (Roby & Azuma, 1995;Mihuc et al, 1996;Minshall et al, 2001b, c). We report significant community changes for at least 2 years following the Angora fire, but further sampling is needed to determine if recovery indeed began in August 2009.…”

“…In general, larger effects tend to be observed in small, first-order streams, similar to Angora Creek (Minshall et al, 2001b, c;Hall & Lombardozzi, 2008). This study provides information on the short-term effects of a severe fire on high-elevation aquatic benthic macroinvertebrates in the context of low precipitation years.…”

“…Previous studies have investigated the response of benthic macroinvertebrate communities to wildfire disturbances of differing intensities and extent of watershed area burned, but overall results have been inconclusive (e.g., Minshall et al, 1995;Roby & Azuma, 1995;Minshall et al, 2001b;Vieira et al, 2004).…”

Microsatellite variation reveals weak genetic structure and retention of genetic variability in threatened Chinook salmon (Oncorhynchus tshawytscha) within a Snake River watershed

“…Among other factors, gene flow may have provided an important buffer against expected losses of genetic variability in the face of both historical and recent population reductions. The natural landscape of the Middle Fork Salmon River is dynamic, with massive landslides (Meyer and Leidecker 1999), wildfires (Minshall et al 2001), and climatic extremes influencing habitats and, undoubtedly, populations of Chinook salmon. In more recent decades, changes to migration corridor habitats outside the MFSR, combined with the influences of harvest and hatchery propagation, have likely contributed to population declines across the Columbia River basin (McClure et al 2003b).…”

The trophic basis of reference and post-fire stream food webs 10 years after wildfire in Yellowstone National Park

“…The 1988 fi res were a major disturbance event, consuming over 45 % of the 2 million ha Yellowstone park landscape (Schullery, 1989). Modifi cation of trophic pathways is one of the many ecosystem responses to wildfi re disturbance along with altered channel morphology, nutrient dynamics, sediment suspension, leaf litter input, and changes in the composition of aquatic biota (Minshall et al, 1989;1997;2001a;2001b;Mihuc et al, 1996;Robinson and Min-542 T. B. Mihuc and G. W. Minshall Stream foods webs after wildfi re disturbance shall, 1996). In the fi rst decade after wildfi re Yellowstone streams exhibited elevated nitrate levels, increased channel alteration, increased periphyton biomass (after the fi rst two years), higher summer water temperature and, of course, an increase in the amount of available burned organic material as carbon (Minshall et al, 1997;2004).…”