Wetlands and wildfires: Trophic resilience in Canada’s boreal forest?

Wetlands and wildfires: Trophic resilience in Canada’s boreal forest? Freshwater wetlands are a key feature of the boreal landscape, where the predominant natural disturbance is wildfire. The size and frequency of wildfires, however, are increasing, especially in North America’s boreal areas. To make informed predictions about the effects of such landscape-level changes on freshwater ecosystems and the wildlife that depend on them, understanding bottom-up effects of wildfire, particularly in nutrient-limited boreal wetlands, is a key research need. To address questions related to impacts of fire on wetland trophic structure, we measured total nitrogen, total phosphorous, and chlorophyll-a concentrations, true water colour, macroinvertebrate community characteristics, and indicated breeding scaup (Aythya spp.) pairs in burned and unburned wetlands one to two years following wildfire in a boreal wetland complex in northwestern Canada. Under the trophic enrichment hypothesis, we expected that wetlands in areas recently burned by wildfires would have higher nutrient and productivity levels, darker coloured water, unique macroinvertebrate communities, and a greater abundance of breeding duck pairs than wetlands in unburned areas. Consistent with our predictions, total phosphorous and chlorophyll-a levels were approximately two-fold higher in burned than in unburned wetlands, although this effect was seasonally variable. Conversely, total nitrogen levels and true water colour were similar in burned and unburned wetlands, as were macroinvertebrate taxa and numbers of indicated breeding scaup pairs. Our results suggest that wetland ecosystems in the northwestern boreal forest have some resiliency to and may even benefit from moderate to severe fires under current climate conditions. However, concurrent with ongoing climate change in the north, fire impacts on these freshwater ecosystems are likely to intensify, and continued research will be necessary to understand whether this resilience will persist in the coming decades. 2025-01-17 Environment and Climate Change Canada enviroinfo@ec.gc.ca Nature and EnvironmentAnimal healthAnimal researchWater qualityBoreal ecosystemsForest fires Wetlands and wildfiresHTML https://data-donnees.az.ec.gc.ca/data/species/scientificknowledge/wetlands-and-wildfires-Trophic-resilience-in-canada-s-boreal-forest%20?lang=en Wetlands and wildfiresHTML https://data-donnees.az.ec.gc.ca/data/species/scientificknowledge/wetlands-and-wildfires-Trophic-resilience-in-canada-s-boreal-forest%20?lang=fr Digital Object Identifier (DOI)XML https://doi.org/10.18164/53fe2022-7939-4ce1-86ab-b276a8b4f837

Freshwater wetlands are a key feature of the boreal landscape, where the predominant natural disturbance is wildfire. The size and frequency of wildfires, however, are increasing, especially in North America’s boreal areas. To make informed predictions about the effects of such landscape-level changes on freshwater ecosystems and the wildlife that depend on them, understanding bottom-up effects of wildfire, particularly in nutrient-limited boreal wetlands, is a key research need. To address questions related to impacts of fire on wetland trophic structure, we measured total nitrogen, total phosphorous, and chlorophyll-a concentrations, true water colour, macroinvertebrate community characteristics, and indicated breeding scaup (Aythya spp.) pairs in burned and unburned wetlands one to two years following wildfire in a boreal wetland complex in northwestern Canada. Under the trophic enrichment hypothesis, we expected that wetlands in areas recently burned by wildfires would have higher nutrient and productivity levels, darker coloured water, unique macroinvertebrate communities, and a greater abundance of breeding duck pairs than wetlands in unburned areas. Consistent with our predictions, total phosphorous and chlorophyll-a levels were approximately two-fold higher in burned than in unburned wetlands, although this effect was seasonally variable. Conversely, total nitrogen levels and true water colour were similar in burned and unburned wetlands, as were macroinvertebrate taxa and numbers of indicated breeding scaup pairs. Our results suggest that wetland ecosystems in the northwestern boreal forest have some resiliency to and may even benefit from moderate to severe fires under current climate conditions. However, concurrent with ongoing climate change in the north, fire impacts on these freshwater ecosystems are likely to intensify, and continued research will be necessary to understand whether this resilience will persist in the coming decades.

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