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

Abstract

Large and severe wildfires can dramatically alter terrestrial and aquatic ecosystems. We documented changes in benthic macroinvertebrate communities and physical habitat at two sites along Angora Creek, CA, USA for 2 years following a severe fire. Although post-fire years had low precipitation, canopy cover and bank stability declined dramatically following the wildfire (canopy cover: 88% pre-fire, 22% post-fire; stable bank: 93% pre-fire, 11% post-fire). Substrate also changed substantially, with fine sediment 89 more abundant post-fire and cobble 79 less abundant post-fire. We found no consistent changes in taxonomic richness or diversity following the fire, but post-fire densities and percentage of sensitive taxa were significantly reduced. We observed large reductions in relative abundances of shredder and scraper taxa, while collector-gatherer abundances increased. Community composition shifted away from pre-fire configurations, and continued to diverge in the second year following the fire. Scores from a regionally derived index of biotic integrity (IBI) were variable but overall much lower in post-fire samples and did not show recovery after 2 years. Overall, our study demonstrated substantial post-fire effects to aquatic ecosystems even in the absence of large flooding or scouring events, and showed that these effects can be transmitted downstream into unburned reaches.

Impacts of extreme events on southeastern Australian freshwater crayfish

“…As such, it will be important to protect permanent sources of surface water from disturbance (both natural and anthropogenic) in the future to minimise the impacts of drought on freshwater crayfish Robson 2011, 2013 Verkaik et al 2014). Minshall (2003) suggested that intense fires will have larger effects on stream fauna, which has been corroborated by findings following an intense fire in California (Oliver et al 2012) and another in central Victoria, Australia (Verkaik et al 2014). In contrast, some authors suggest that wetland invertebrates cope well with a variety of stresses (Beganyi and Batzer 2011) and may show little response to fire compared to stream communities (Minshall 2003).…”

“…The sediment layer had the effect of reducing habitat heterogeneity by burying boulders, cobbles and woody debris, simplifying habitats and reducing water depth (especially in the case of stream pools which filled with ash and sediment), thereby also reducing habitat area (Figure 2). An increase in fine sediment is a common finding in studies examining fire effects on aquatic ecosystems (Oliver et al 2012;Verkaik et al 2014). Such sediment may also be washed downstream where it may also affect unburnt reaches (Lane et al 2006;Peat et al 2005;Oliver et al 2012).…”

“…An increase in fine sediment is a common finding in studies examining fire effects on aquatic ecosystems (Oliver et al 2012;Verkaik et al 2014). Such sediment may also be washed downstream where it may also affect unburnt reaches (Lane et al 2006;Peat et al 2005;Oliver et al 2012). …”

Effects of burn status and conditioning on colonization of wood by stream macroinvertebrates

“…However, our prediction of higher prevalence of scrapers on water-than on soil-conditioned wood was not supported. We based our prediction on the expectation that periphyton growth would be greater on water-than on soil-conditioned wood (Oliver et al 2012), but the conditioning period might have been too short for us to detect a response Webster 1988, Hall et al 2001).…”

“…Several investigators have examined the effects of wildfire on stream macroinvertebrates (Minshall et al 1997, Minshall 2003, Vieira et al 2004, Robinson et al 2005, Malison and Baxter 2010, Oliver et al 2012), but none addressed the role of fire-derived wood in stream function. Knowledge regarding interactions between macroinvertebrates and allochthonous inputs is based mainly on leaflitter studies (Wallace et al 1997, Gessner et al 1999, Graça 2001, Gulis et al 2006, Casas et al 2011), but leaf and wood decomposition differ greatly (e.g., Hax and Golladay 1993).…”