The Effects of Trees on Peatland Evapotranspiration Across Scales

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The Western Boreal Plain (WBP) of Canada, provides important ecosystem services such as water and carbon storage and also represents a substantial component of Canada’s economic engine through its resource-based industries (mineral mining, forestry, oil and gas), the most significant of which is the oil sands development region. In the generally dry climate of the WBP, water availability is limited, making the peatlands that dominate this region vulnerable to climate variability as well as stresses from intense industrial pressures that affect peatland ecological and hydrological functioning. Understanding the internal and external ecohydrological and climatological processes that permit peatland ecosystems to efficiently use available moisture is important for managing these systems in light of climate and landuse change. The literature suggests that carbon, energy and water exchange can be strongly influenced by external local boundary layer conditions in addition to internal biophysical controls. However, little work has been done on peatlands in general and much of the research thus far has focused on bog ecosystems rather than fens in this climatically tenuous region. Internally, feedbacks exist between changes in surface cover, particularly tree density, soil conditions and evapotranspiration losses. Externally, the landscape mosaic of wetlands and forestlands suggests that not only do peatlands provide water to forested uplands, but that the forested uplands shelter peatlands, limiting evaporative losses. Understanding the mechanism of how peatlands protect themselves against moisture stress will refine our predictive capacity of how these systems will respond to climate change, as well as permit us to design more robust and resilient reclaimed systems.