CIMP 180_ The impact of wildfire on diverse aquatic ecosystems of the NWT

During the summer of 2014, the southern Northwest Territories (NWT) experienced an unprecedented fire season, with a burn fingerprint that spread across two ecoregions (the Taiga Plains and Taiga Shield), and a landscape that is underlain by mosaic of permafrost coverage, vegetation type, and previous fire history. Our study was conducted across the Dehcho, Wek’èezhii, and Akaitcho Geographic Regions, which encompass the most significantly burned areas from the 2014 fire season. Within these regions, we examined water quality across a series of 50 catchments that varied based on within-catchment fire extent, ecoregion (Taiga Plains vs. Taiga Shield), and within-catchment characteristics such as wetland extent. This sampling scheme – which covers as significant a range of landscape variability as possible – is allowing us to tease apart the effects of wildfire from other landscape variables that cumulatively impact aquatic ecosystem health. We find that the effects of wildfire on stream water chemistry are relatively weak when measured at stream outlets, but that these effects can teased apart from other, key landscape attributes with the use of multivariate analyses and a large sample size. However, we do find transient changes in water quality immediately post-fire, and changes in pore water chemistry and hydrologic parameters within catchments affected by wildfire. Future work should examine long term fire-induced changes within catchments, and focus on determining the effect of wildfire during years that are relatively wet.