How do forest fires impact subarctic lakes?

Fires are a natural phenomenon in the boreal forest, but their frequency is expected to increase over the coming century. Fires may affect water quality and invertebrates in lakes, but there have been few studies in the northern boreal forest to describe these impacts. We collected data on water quality, macrophytes, and invertebrates from 20 lakes in the Sahtú Settlement Area of the Northwest Territories. Nine lakes were affected by fires in their catchments 4-5 years prior to data collection, while eleven were not. Our results showed that few water quality variables were related to burn history. However, macrophyte biomass increased in lakes affected by burns, and was a significant predictor of invertebrate community composition. Burn history was an important predictor of the richness and abundance of invertebrates, but natural variability in lake properties was more important for explaining differences among lakes. Our results indicate that the effects of fires on lakes are still detectable after 4-5 years, suggesting that an increased frequency of fires in the north could have important impacts on boreal lakes.

Associated students: Thomas Pretty, Matthew Chanyi

Funding: Northern Water Futures (Global Water Futures)

Associated publications: Pretty et al. (2021)