Functioning of reclaimed oil sands ecosystems and the implications for reclamation certification

Water use indicators of evapotranspiration, water use efficiency, and gross ecosystem productivity were derived using eddy covariance (EC) measurements of surface-atmosphere exchanges of water, carbon, and energy. They were examined with the goal of identifying potential indicators for assessment and certification of reclaimed landscapes in the Athabasca Oil Sands Region (AOSR). The research outcomes suggest that these indicators provide meaningful assessments of reclaimed AOSR upland and wetland landscapes, thus improving our understanding of ecosystem function, reclamation practices, and certification guidelines. An initial study using a 12-year EC data record for a single reclaimed upland forest dominated by aspen suggested that following approximately 10 years of post-construction variability, the water use characteristics of the site were within the range of variability of natural upland forests in the region. The second study of this thesis expanded the scope of the research to include seven additional EC data records with four AOSR reclaimed sites and four western boreal reference sites. By ~ 20 years of age, the post-disturbance sites' water use indicators were within the range of natural variability. The initial post-disturbance water use variability was related to disturbance type, vegetation cover, moisture, and temperature. The final study examined annual growing season EC-derived water use indicators for 21 upland reference and reclaimed sites, which provided > 100 site years for assessing the potential of these data sets to contribute to assessment and certification in additional ways beyond what can be provided by other ecosystem assessment techniques such as biometrics (including soil and vegetation surveys) and remote sensing. The integrated assessments of ecosystem functioning derived from EC measurements of water and carbon fluxes may be used to situate reclaimed landscapes in relation to the range of variability and along development trajectories for upland boreal sites

Developing a Functional Approach to Assessment of Land Capability: Utilizing Ecosystem Water and Carbon Nutrient Fluxes as Integrated Measures of Reclamation Performance

This report synthesizes over 15 years of research (and 64 site-years of data) on water use, carbon assimilation, and associated ecosystem development on reclaimed oil-sands-mine sites and on non-mine reference sites. A key feature of this research is the use of eddy-covariance methods to make integrative measurements of ecosystem performance. This approach uses instruments mounted on towers above the vegetation canopy to take continuous measurements of the atmospheric products of ecosystem function, specifically water and carbon dioxide exchange. (As cited in Summary.

Ecological and environmental transition across the forested-to-open bog ecotone in a west Siberian peatland

Climate change may cause increasing tree cover in boreal peatlands, and the impacts of this encroachment will be noted first at forested-to-open bog ecotones. We investigate key metrics of ecosystem function in five such ecotones at a peatland complex in Western Siberia. Stratigraphic analysis of three cores from one of these transects shows that the ecotone has been dynamic over time with evidence for recent expansion of forested peatland. We observed that the two alternative states for northern boreal peatlands (forested/open) clearly support distinct plant and microbial communities. These in turn drive and respond to a number of feedback mechanisms. This has led to steep ecological gradients across the ecotones. Tree cover was associated with lower water tables and pH, along with higher bulk density, aquatic carbon concentrations, and electrical conductivity. We propose that the conditions found in the forested peatland of Western Siberia make the carbon sink more vulnerable to warmer and drier conditions

A comparison of the net ecosystem exchange of carbon dioxide and evapotranspiration for treed and open porti

Net ecosystem exchange of carbon dioxide (NEE) and evapotranspiration (ET) were measured at open and treed portions of a temperate ombrotrophic bog using the eddy covariance technique to examine the potential influence of plant community characteristics on peatland carbon and water vapour exchange. The sites were located 2.7km from each other within the same peatland complex and thus experienced similar weather. Both sites were characterized by a Sphagnum ground cover and a shrub layer with similar total biomass. However, at the treed bog, 35% of this understory vascular plant layer was made up of Picea mariana (<0.5m tall) compared to less than 0.2% in the open bog. The treed bog was also characterized by an overstory dominated by a patchy distribution of stunted P. mariana. Over a single year, net CO 2 uptake and ET was lower at the treed bog (NEE: -72gCm -2year -1 and ET: 449mmyear -1) than at the open bog (NEE: -104gCm -2year -1 and ET: 493mmyear -1). Chamber measurements revealed that P. mariana was associated with low rates of net primary productivity (NPP) compared to the relatively more productive ericaceous and deciduous shrubs. Although the presence of a P. mariana overstory increases both the total aboveground biomass and leaf area index in this peatland, P. mariana appears to be important in reducing both ecosystem-scale carbon sequestration and water vapour loss