Characterizing dominant controls governing evapotranspiration within a natural saline fen in the Athabasca Oil Sands of Alberta, Canada

Abstract

Natural Boreal saline fens provide analogues for reclaimed wetland systems constructed with sodium‐rich tailings materials. These natural analogues can improve our understanding of vegetative controls on dominant ecohydrological processes (i.e. evapotranspiration (ET)) in constructed landscapes. Therefore, the objective of this study is to characterize ET within a natural boreal saline fen over a growing season to determine the primary hydro‐climatic controls using community‐scale ET measurements targeting dominant vegetation communities within different microforms along with environmental controls. ET rates were highest during periods of peak vegetation growth and temperatures between June and August, with rates decreasing slightly in July. Vegetation species' physiology was the dominant variable governing ET. The more salt tolerant species maintained higher ET rates despite the lower leaf area index and water table levels found within these species. The lower ET rates measured in July can be attributed to high water tables from above average precipitation causing soil inundation and salt stress, increasing stomatal closure. However, community plots containing Triglochin maritima maintained transpiration rates under the coupled stress conditions. Therefore, this is a potentially important species for use in boreal reclamation planting schemes. Last, the findings emphasize that the dominant vegetation selected for reclamation projects must coincide with the materials used (peat and subsurface materials), as results within this study demonstrate that some native boreal fen species (Calamagrostis inexpansa, Hordeum jubatum, and Juncus balticus) were unable to maintain transpiration rates during flood and saline conditions that can occur within the mining area of this region. Copyright © 2015 John Wiley & Sons, Ltd.

Growing season CO2 exchange and evapotranspiration dynamics among thawing and intact permafrost landforms in the Western Hudson Bay lowlands

“…This suggests that under low‐energy conditions (i.e., early morning and late afternoon), VPD is controlling the ET rates while radiative controls may be strongest at mid‐day. Similar relationships between instantaneous ET and VPD were found over two growing seasons in two different boreal peatlands, 48,50 with a slightly weaker relationship about a mean VPD of 1.5 kPa for one of their study years.…”

Growing season evapotranspiration in boreal fens in the Athabasca Oil Sands Region: Variability and environmental controls

“…During the study period, variability of growing season ET rates at Pauciflora, Poplar, Saline and JACOS Fens were comparable to values F I G U R E 6 Mean daily ET (mm d −1 ) (a), total ET (mm) (b), coefficient of variation (%) for ET (c), precipitation -potential evapotranspiration (P/PET) ratio (d), precipitationtotal evapotranspiration (P/ETJ) ratio (e), actual evapotranspiration -potential evapotranspiration (ETJ/PET) ratio (f) in July at Pauciflora and Poplar Fens (2013-2018), Saline Fen (2015-2018) and JACOS Fen (2011-2014). *In 2016, more than 50% of data were missed at Saline Fen reported by other studies from WBP (e.g., Brown et al, 2010;Phillips et al, 2016). Overall, variability of growing season ET rates at four fen sites were characteristic of the WBP with the highest rates in June-July when the warmest T air and the highest R net and VPD were observed (Amiro et al, 2006;Baldocchi et al, 2000;Brown et al, 2010;Cienciala et al, 1998;Grelle et al, 1997;Lafleur et al, 1997;Phillips et al, 2016;Rouse, 2000 Kim & Verma, 1995;Lafleur et al, 1997).…”

Response of herbaceous wetland plant species to changing precipitation regimes

“…The interaction between precipitation frequency, VMC, and timing of plant growth led to the observed differences in performance of eudicots between watering treatments. Plants respond to water stress through stomatal closure to reduce transpirative water loss (Phillips, Petrone, Wells, & Price, ; Yin et al, ), which also reduces carbon assimilation and plant growth (Jacobs, Mergelsberg, Lopera, & Myers, ; Kooyers, ). Most of the eudicot growth occurred in the latter‐half of the season, when soil moisture stress was high in the infrequent treatments, which likely resulted in stomatal closure, reduced photosynthesis, and thus lower biomass accumulation (Figure a–c).…”