Impacts of roads on tree and shrub productivity
Over 217,000 km of roads have been constructed across Canada’s boreal region. In wetlands, roads can act as a barrier to water movement, particularly when the road is constructed perpendicular to the direction of water flow. This damming effect can in turn influence vegetation composition on either side of the road. Despite this, few studies have examined the magnitude and direction of the vegetation shifts in peatland trees and shrubs as a result of road construction. To fill this gap Saraswati et al. (2020) examined the annual growth and aboveground productivity of woody species at a bog site and a fen site in boreal Alberta.
Saraswati et al. determined that the road constructed parallel to the direction of water movement (fen site) resulted in few changes in vegetation, whereas the road constructed perpendicular to water flow (bog site) resulted in substantial changes in the woody vegetation present. Upstream of the road, the bog was inundated, had rapid tree mortality, and substantially lower annual growth. Downstream, drier conditions resulted in increased growth of woody vegetation in the first years following construction. This study highlights the importance of considering road orientation during the planning phases as roads constructed perpendicular to hydrologic flow may shift long-term carbon sinks into sources. Learn more here.