Effect of a semi-permanent road on N, P, and CO2 dynamics in a poor fen on the Western Boreal Plain, Canada

Peatlands of the Western Boreal Plains (WBP) are under stress from oil and gas development and associated infrastructure such as road construction and removal. An improved understanding of nutrient cycling and atmospheric carbon dioxide (CO2) exchange interactions in peatlands can assist in recommending Best Management Practices to industry to minimize the ecohydrological disturbance footprint of road features. Peat nutrient (nitrogen, N, and phosphorus, P) supply, net mineralization, groundwater concentrations, and peatland-atmosphere CO2 exchange rates were quantified within a poor fen bisected by a semi-permanent road located in the Athabasca Oil Sands region of Alberta, Canada over one growing season. Results demonstrate that the road impeded groundwater movement across the site; however, water table and moisture differences were minimal, likely due to the unusually wet season. No clear impacts of the road on nutrient dynamics were observed, but subtle differences in productivity and respiration resulted in significantly lower net CO2 sequestration (NEE) on the down-flow side of the road. Differences in vegetation composition between sides of the road were apparent and likely indicate longer-term moisture differences at the site. Elevated rates of productivity and respiration coincided with a seasonal change in the relative supplies of N and P (increased N:P ratios), suggesting that the relative availability of N versus P may be important to CO2 fluxes in WBP peatlands. Collectively, these findings demonstrate the need to capture interactions between hydrology, ecology and nutrient biogeochemistry when evaluating peatland carbon cycling response to road disturbances across this region.