A plant ecophysiological approach to assess the performance and potential success of mine revegetation

摘要

The Canadian oil sands industry is actively engaged in the revegetation and reclamation of sites associated with bitumen mining. One current reclamation research effort sponsored by Syncrude Canada Ltd., referred to as the Sandhill Fen Research Watershed (SFRW) project, is taking place on a former open pit mine in northern Alberta. One aspect of this project involves the establishment of a wetland on the former mine pit, which has since been back filled with soft tailings. A component of the active research taking place at the SFRW is the evaluation of using plant ecophysiological parameters as markers of success. The parameters being used include rates of photosynthesis, transpiration, stomatal conductance, and additional derived parameters (e.g., water use efficiency). These ecophysiological measures provide quantitative information on the physiological status of the plants and a potential assessment tool for plant performance during the early stages of reclamation. Additionally, this approach could provide insight into the trajectory of the plants in the reclaimed vegetation community, and the long term potential success/stability of the reclamation. Comparable data from the same plant species growing on disturbed and undisturbed benchmark sites is being collected. These sites can provide a frame of reference for predicting reclamation trajectories, as well as expectations for plant physiological performance as a function of time. Ecophysiological data collected one year after the initiation of the project demonstrated that plants in the wetland were showing similar performance to plants on the benchmark sites, suggesting that the reclamation was on a comparable ecological trajectory to those reference sites. For example, an array of ecophysiological parameters was monitored for water sedge (Carex aquatilis), a key species planted in the pilot wetland. Photosynthesis rates for water sedge in the Sandhill Fen pilot ranged from 2.2 - 20.5 jumoles CO_2 m~(-2) min~(-1) as compared to values ranging from 1.4 -14.2 jumoles C0_2 m~(-2) min~(-1) for plants on the benchmark sites. Water use efficiency values ranged from 0.9 to 6.1 for water sedge in the pilot site as compared to 0.6 to 4.8 on the benchmark sites. Across the SFRW, there is a gradient of soil moisture from dry to inundated. Plant performance relative to this moisture was monitored closely to offer guidance on how water levels influence plant establishment. The results thus far illustrate the value of this ecophysiological approach in providing markers of success for wetland reclamation efforts. The results also suggest that this same approach might be applicable to other mine closure scenarios, providing a means to relate the ecological trajectory of reclamation to relevant benchmark sites.