Long-term evaluation of evapotranspiration from a reclaimed boreal forest in the Athabasca Oil Sands Region of Northern Alberta, Canada

Athabasca Oil Sands Region, Alberta, Canada Evapotranspiration (ET) is the greatest loss of water for ecosystems in the subhumid Athabasca Oil Sands Region (AOSR), and its long-term change helps determine the ability of reconstructed boreal forests to return to a functional state following mining disturbances. This article analyzes 16 years (2008–2023) of growing season eddy covariance (EC) data from a constructed aspen-spruce-dominated boreal forest and assesses ET dynamics and energy partitioning over time. The findings demonstrate that (1) Evapotranspiration increased by 15 % from the early (2008–2012) to middle (2013–2017) stages of forest development and declined in the late stage (2018–2023), nearing early period rates. (2) Air temperature was the major factor controlling ET in the study forest. (3) Interannual climate variability resulted in an ET increase during wetter and warmer growing seasons with abundant precipitation and elevated air temperature, and a decline in ET during dry years with reduced precipitation and soil moisture. (4) A multi-year increase in site greenness during winter, a decline in growing season albedo, and decreased ET in later years are attributed to an increase in white spruce species on the site. This study enhances the understanding of hydrometeorological processes in the boreal forest ecosystem and emphasizes the importance of long-term observations for the successful application of reclamation strategies in the region. • South Bison Hill (SBH) is a landform composed of clay-shale overburden deposits. • Growing season evapotranspiration declined due to an increase in conifer presence. • Air temperature was the primary driver of evapotranspiration in the SBH forest. • No extended drought periods limiting water availability for trees were observed. • Projected regional climate changes are unlikely to hinder white spruce development.