A temporal snapshot of ecosystem functionality during the initial stages of reclamation of an upland-fen complex

Abstract

Study region: Athabasca River Watershed, Athabasca Oil Sands Region (AOSR), Alberta, Canada. Study focus: AOSR pre-disturbance landscape consists of a mosaic of upland-peatland complexes, dominated by fens, which have become the focus of recent mandatory reclamation efforts. Quantifiable metrics for evaluating reclamation project trajectories and long-term sustainability are required. Here, the initial performance of a constructed upland-peatland complex (Nikanotee Fen Watershed) is evaluated through a functional-based, ecosystem-scale approach focused on carbon dynamics and water use efficiency (WUE). Initial seven years (2013–2019) post-construction were monitored using eddy covariance and multispectral imagery to capture ecosystem evolution. New hydrological insights for the region: Results indicate the fen quickly evolved from a bare-ground, carbon source (2013) to a sedge-dominated (Carex aquatilis), carbon sink (2015). Slower growth rate of trees (Pinus banksiana, Populus balsamifera) and dry edaphic upland conditions initially resulted in net carbon losses. However, as upland vegetation became established, plant CO2 uptake increased. After 2015, fen WUE remained relatively stable despite fluctuations in seasonal rainfall. Stable WUE reflects a well-connected groundwater network between the two landscape units that supports hydrological self-regulation sufficient to maintain adequate plant function. Because of this groundwater supply, fen plants were no longer dependent solely on precipitation – increasing resilience to intervals of periodic water stress. Overall, carbon and water dynamics during early-development suggests the system is evolving towards a self-sustaining, carbon-accumulating, functional ecosystem.

Keywords

• Ecosystem function
• Net ecosystem exchange
• Reclamation
• Water-use efficiency
• Eddy covariance
• Boreal