First-year effects of an unusual tundra fire on an Arctic stream

During late summer and early fall 2007 a tundra fire caused by a lightning strike burned approximately 1,000 km² on the North Slope of Alaska. We wondered how large-scale fires – which may increase in frequency on the tundra as a consequence of arctic climate change – might influence stream ecosystems.  We sampled streams in the burned area during the first snowmelt and growing season after the fire (2008). We compared long-term water chemistry data from the Kuparuk River (an intensively studied 4^th order tundra stream about 50 km southeast of the burned area) to a similar river (the “South River”) within the severely burned area. There was a short-term pulse of inorganic nutrients, with the exception of nitrate, during the spring snowmelt (26 May - 3 June 2008) in the South River (mean±SE: 2.5±0.4 µM NH₄⁺; 0±0 µM NO₃^-;1.3±0.5 µM SRP), but not in the Kuparuk (0.3±0.05 µM NH₄⁺; 1.2±0.3 µM NO₃^-;0.05±0.01 µM SRP). Nutrient levels in the South River diminished throughout the summer to concentrations similar to those in the Kuparuk River. Given the high severity of the burn in this area we expected a greater short-term response.  However, longer-term responses to a potential increase in thermokarst may be the more important impact.