Hydroclimatic Controls on Peatland CO2 Exchange Following Adjacent Forest Harvesting on the Western Boreal Plain

English Abstract:

The Boreal forest of the Western Boreal Plains (WBP) is experiencing extensive land use changes from industrial expansion and deforestation. Potential alterations to surrounding hydrology and microclimate as a result of upland forest harvesting may threaten the ecosystem function of hydrologically connected-peatlands that are ubiquitous across the region, including the sequestration of greenhouse gases i.e. carbon dioxide (CO₂)_.  Predicting the potential impact of deforestation on adjacent peatland CO₂ source/sink functionality requires comparison of peatland hydrology, microclimate and carbon exchange dynamics following tree removal relative to undisturbed ecosystems under natural climate variability. As such, the objectives of this study were to investigate: (1) Net Ecosystem Exchange (NEE) (i.e. CO₂) of undisturbed peatlands during the snow-free period; (2) the relative impact of upland forest harvesting on adjacent peatland NEE, including the hydrologic and microclimatological controls on this exchange; and (3) estimate the sustainability of WBP peatlands’ functionality as a CO₂ source/sink in context of periodic land use disturbances. Growing season peatland CO₂ exchange was modelled in two neighbouring forest upland-peatland complexes over a four-year period (2005-2008) in the Utikuma Region Study Area of Alberta within the WBP. The forested upland area of one complex was harvested between 2007 and 2008, and the adjacent peatland was evaluated for potential shifts in NEE relative to the peatland in the undisturbed complex. These results, linked to changes in peatland hydrology (e.g. water table, soil moisture) and microclimate (e.g. wind speed, vapour pressure deficit, evaporation), as well as the implications for future forest harvesting in the region will be discussed.