Stream macroinvertebrate community responses to fire: are they the same in different fire-prone biogeographic regions?

Droughts, fires, and floods are natural disturbances influencing aquatic ecosystems. If drought is accompanied by fires, and if fires are closely followed by floods, teasing apart their distinctive and potentially interactive responses can be difficult. We compared the responses of macroinvertebrate communities to fire via comparisons of streams in burned and unburned catchments in 3 fire-prone biomes that differ biogeographically and climatically (northwestern Mediterranean, southeastern Australia, and northwestern intermountain USA). The responses of macroinvertebrate communities in streams in burned catchments were similar in all biogeographic regions, but the magnitude of these responses varied. Fire combined with high seasonal stream flows, flooding, or drought was associated with reduced measures of taxonomic richness and increased abundance, especially of r-strategist taxa. Differences between sites in burned and unburned catchments were consistently stronger in southeastern Australia than in northwestern intermountain USA and northwestern Mediterranean regions. Our observations suggest that the timing and magnitude of postfire flows (snowmelt, seasonal high flows) may substantially alter the recolonization process and override fire effects, and that drought may play a strong role in limiting the resilience and resistance of macroinvertebrate communities in streams in catchments that have experienced wildfire.