Understanding the peak growing season ecosystem water‐use efficiency at four boreal fens in the Athabasca oil sands region

Abstract

Ecosystem water-use efficiency (WUE), a ratio between gross ecosystem production (GEP) and water loss through evapotranspiration (ET) can be helpful for the assessment of coupled peatland carbon and water cycles under anthropogenic changes in the Athabasca oil sands region (AOSR) where extensive oil sands development has been occurring since the 1960's. As such, this study assessed multiyear peak growing season variability of WUE at four fens (poor treed, poor open, treed moderate-rich, open saline) near Fort McMurray using the eddy covariance technique combined with a set of environmental variables. Freshwater fens were characterized by WUE values within the range reported from other boreal wetlands while a saline fen had significantly lower values of WUE. Negative correlation (R s < À0.55, p < 0.05)between WUE and net radiation was observed. Moisture conditions were responsible for interannual differences in WUE, whereby increasing WUE under wetter conditions was observed. However, such a pattern was offset by decreased air temperature (T air ) resulting in moisture oversupply. This study also revealed a negative effect of wildfire on WUE due to a prominent decline in GEP and a moderate decrease in ET. WUE can be useful for monitoring the functioning of natural and constructed fens, but a better understanding of WUE variability under a wide range of climatic conditions with respect to differences in vegetation is required.

The global distribution of paired eddy covariance towers

“…Our understanding of the carbon and water cycle consequences of land cover change and land management have been shaped by the paired tower approach to quantify impacts of forest management (Desai et al, 2005; Goulden et al, 2006; Starr et al, 2016), ecological restoration (Hemes et al, 2019), ecological disturbances (Amiro, 2001; Kowalski et al, 2004; Rebane et al, 2019), agricultural management (Baker and Griffis, 2005; Chi et al, 2016; French et al, 2020; Moore et al, 2020; Runkle et al, 2018), and more. Our understanding of how ecosystem carbon and water cycles interact to determine the ecosystem water use efficiency has therefore also been shaped by paired tower studies (Anapalli et al, 2019; Stoy et al, 2008; Volik et al, 2021) and observations over multiple years have been used to quantify interactions between the carbon and water cycles across multiple scales in time (Novick et al, 2015).…”

Increasing precipitation during first half of growing season enhances ecosystem water use efficiency in a semiarid grassland

“…Ecosystem WUE is generally estimated as the ratio of gross ecosystem productivity (GEP), net ecosystem CO 2 exchange (NEE), or gross primary productivity (GPP) to evapotranspiration (ET) ( Hu et al., 2008 ; Guerrieri et al., 2016 ; Medlyn et al., 2017 ). GEP/ET is the most commonly used metric of ecosystem WUE ( Beer et al., 2009 ; Niu et al., 2011 ; Bai et al., 2020 ; Volik et al., 2021 ). Ecosystem WUE is driven by the trade-off between GEP and ET, and thus biotic and climatic factors that affect C assimilation or water loss or both could cause changes in WUE ( Leonardi et al., 2012 ).…”