Impacts of an intense wildfire smoke episode on surface radiation, energy and carbon fluxes in southwestern British Columbia, Canada

A short, but severe, wildfire smoke episode in July 2015, with an aerosol optical depth (AOD) approaching nine, had a significant impact on air quality, radiation and energy budgets across four land use types, and elicited a clear ecosystem response with respect to carbon fluxes at a bog and a forested site. Greatest impacts on radiation and energy budgets were observed at the forested site where the role of canopy architecture, and the complex physiological responses to an increase in diffuse radiation were most important. With widespread standing water, and little physiological control on evapotranspiration, the impacts on the partitioning of turbulent fluxes were modest at the bog compared to the physiologically dominated fluxes at the forested site. Despite the short duration and singular nature of the event, there was evidence of a diffuse radiation fertilization effect when AOD was less than two. With lighter smoke, both the wetland and forested site appeared to show enhanced photosynthetic activity (a greater sink for carbon-dioxide). However, with dense smoke the forested site became a strong source. Given the extensive forest cover in the Pacific Northwest and the growing importance of forest fires in the region, these results suggest that wildfire aerosol during the growing season potentially plays an important role in the regional ecosystem response to smoke and ultimately the carbon budget of the region.