Controls on plot-scale evapotranspiration from a constructed fen in the Athabasca Oil Sands Region, Alberta

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• 作者：S.J. Scarlett ; ^{sjscarlett@uwaterloo.ca} ; R.M. Petrone ^{rpetrone@uwaterloo.ca} ; J.S. Price ^{jsprice@uwaterloo.ca}
• 关键词：Constructed peatland ; Oil sands reclamation ; Western boreal plain ; Evapotranspiration ; Ecohydrology ; Re-vegetation
• 刊名：Ecological Engineering
• 出版年：2017
• 出版时间：March 2017
• 年：2017
• 卷：100
• 期：Complete
• 页码：199-210
• 全文大小：1638 K
• 卷排序：100

文摘

In the Athabasca Oil Sands Region of the Western Boreal Plain mining companies now recognize the importance of reclaiming peatlands, as they cover >50% of the pre-mined regional landscape. To date, reclamation efforts have focused on marsh and open water wetlands. However, these wetland systems are not abundant in the sub-humid climate of the WBP because of their excessive evapotranspiration (ET) losses, compared to peatland wetlands. The experimental Nikanotee Fen was constructed as part of the landscape reclamation, engineered with the intent to support natural fen vegetation and hydrologic processes. The influences of vegetation and treatment types on plot-scale energy fluxes and ET demands were examined over the 2014 growing season, one year post-construction. Actual ET and environmental variables, such as water table, soil moisture, temperature and relative humidity, were monitored in thirty-one study plots comprising control, moss and seedling plots (with and without wood-strand mulch), as well as three ponds. Actual ET was measured with weighing lysimeters and used to correct equilibrium ET, calculated using the Priestley-Taylor combination method. A roaming meteorological station was instrumented to quantify and compare available energy over different cover types. Modeled plot-scale ET was validated against continuously measured eddy covariance ET values. Cumulative ET exceeded precipitation in all plot types with average rates of 4.4, 3.2, 3.9 and 2.8 mm/day from open water, control, seedling and moss plots, respectively. Mulch reduced ET rates in both seedling and moss plots, where moss-mulch plots showed the lowest rates (2.4 mm/day). The presence of mulch lowered the near-surface vapour pressure deficit, thus providing a more favorable microclimate for moss establishment by elevating near-surface relative humidity and reducing air and soil temperature by ∼2 °C. Although vapour pressure deficit did not significantly control ET (p > 0.05), mulch appeared to have a greater influence on ET in moss plots than seedling plots. Water table position displayed a weak yet significant (p < 0.05) control on ET in seedling plots. As these reclamation practices have not yet been well tested in the Alberta oil sands region; this study provides recommendations to reduce evaporative stress and aid in the establishment of functioning constructed peatland ecosystems.