Fire in the Arctic: The effect of wildfire across diverse aquatic ecosystems of the Northwest Territories

S.E. Tank, D. Olefeldt, W.L. Quinton, C. Spence, N. Dion, C. Ackley, K. Burd, R. Hutchins, and S. Mengistu

The southern Northwest Territories (NWT) experienced an unprecedented fire season in the summer of 2014. Burned areas were spread across more than 3.4 million hectares of land. The areas covered a landscape with a range of permafrost coverage, vegetation types, and previous fire history.

We studied the way that wildfire affects the chemistry of water flowing from land to streams and how stream ecosystems function. Three factors were looked at:

1) soil pore water in burned and unburned plots of land in watersheds near Fort Simpson (on the Taiga Plains);

2) the chemical composition of water flowing out of streams, using repeated measurements in paired burned and unburned watersheds in the Taiga Plains (Fort Simpson area) and Taiga Shield (Yellowknife area); and

3) a broad survey of 50 streams whose watersheds had, or had not, been affected by wildfire.

Soil pore waters were clearly affected by wildfire. However, the difference between the paired burned and unburned watersheds was small and somewhat short-lived. Across the 50 streams that were surveyed, wildfire was just one of many landscape variables that affected water chemistry. These results show that the effects of wildfire on stream water chemistry in this region may be relatively short-lived. Over longer time scales, the effects of wildfire may be similar to other landscape factors.

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