Effects of forest fire on headwater stream macroinvertebrate communities in eastern Washington, U.S.A.

Abstract

1. Recent increases in fire frequency in North America have focused interest on potential effects on adjacent ecosystems, including streams. Headwaters could be particularly affected because of their high connectivity to riparian and downstream aquatic ecosystems through aquatic invertebrate drift and emergence. 2. Headwater streams from replicated burned and control catchments were sampled in 2 years following an intense forest fire in northeastern Washington (U.S.A.). We compared differences in benthic, drift and emergent macroinvertebrate density, biomass and community composition between five burned and five unburned catchments (14-135 ha). 3. There were significantly higher macroinvertebrate densities in burned than control sites for all sample types. Macroinvertebrate biomass was greater at burned sites only from emergence samples; in benthic and drift samples there was no significant difference between burn and control sites. 4. For all sample types, diversity was lower in the burned catchments, and the macroinvertebrate community was dominated by chironomid midges. 5. Compared to the effects of fire in less disturbed ecosystems, this study illustrated that forest fire in a managed forest may have greater effects on headwater macroinvertebrate communities, influencing prey flow to adjacent terrestrial and downstream aquatic habitats for at least the first 2 years post-fire.

Effects of wildfire of varying severity on benthic stream insect assemblages and emergence

“…Shifts to more r-strategist taxa in the years immediately following wildfire have been described previously (Mihuc et al 1996, Minshall et al 1997). Mellon et al (2008) also found increased macroinvertebrate densities dominated by Chironomidae 2 y after severe forest fire in northeastern Washington. We found that compositional shifts to rstrategist taxa can persist for at least 5 y after highseverity fire, but these shifts did not appear to occur after low-severity fire.…”

“…Although several studies have investigated the effects of wildfire on stream insect assemblages (e.g., Mihuc et al 1996, Minshall et al 1997, Minshall 2003, Vieira et al 2004, Robinson et al 2005, few have evaluated its effects on aquatic insect productivity or patterns of emergence (but see Mellon et al 2008). If fire results in increased productivity among primary consumers, this increase could propagate up the food chain to invertebrate or vertebrate predators within the stream and to terrestrial predators that feed on emerging adult insects (Baxter et al 2005).…”

Prescribed fires as ecological surrogates for wildfires: A stream and riparian perspective

“…Wildfires result in a cascade of environmental changes in riparian and stream ecosystems in temperate forests of the western U.S. (Bisson et al, 2003;Everett et al, 2003;Gresswell, 1999;Minshall, 2003;Mellon et al, 2008;Pettit and Naiman, 2007;Power and Dietrich, 2002). Changing habitat conditions can influence community composition, instream energy production, and food web interactions that redirect energy flow towards higher instream trophic levels including predatory macroinvertebrates and salmonids (Minshall, 2003;Heck, 2007;Rieman and Clayton, 1997;Wootton et al, 1996).…”

The impact of wildfire on stream fishes in an Atlantic-Mediterranean climate: evidence from an 18-year chronosequence

“…While the potential importance of compounded fire-habitat impacts has recently been addressed for lotic macroinvertebrates (Mellon et al, 2008), information on stream fishes remains scarce (Verkaik et al, 2013). As fish are permanently restricted to the stream channel, their potential for ecological resistance and resilience to disturbance differs to that of invertebrates.…”