Formation and maintenance of permanent perched wetlands in the Boreal Plain of Western Canada

• Author / Creator

  James, Lindsay M

• The Boreal Plains Ecozone is characterized by a moisture deficit climate, as regional precipitation is less than potential evapotranspiration. Perched peatlands situated 20 m above regional groundwater have been identified as common features across the landscape in the Utikuma Region Study Area (URSA) in north central Alberta. How does an apparently isolated permanent perched wetland maintain saturated conditions in a sub-humid climate? Research was conducted at Pond Catchment 19 in the URSA on a perched wetland complex in a topographically high landscape position. Alternative hypotheses were evaluated by examining the wetland water budget and geologic setting. Results confirmed the study site to be an autogenic wetland, isolated from allogenic water sources. Wetland precipitation was greater than evapotranspiration. A clay rich confining layer underlies the wetland, maintaining the perched water table; the adjacent upland forest is consistently unsaturated. Autogenic processes maintaining wetland conditions were tested by examining increased precipitation, decreased evapotranspiration and low storage. Snow accumulation and through fall data indicated that decreased wetland interception compared to adjacent forest positively impacted the wetland water budget. Shading and sheltering, prolonged ablation, persistence of frozen soil, deep peatland water table and water isotopic signatures inferred decreased wetland evapotranspiration. Low storage in the margin swamp and decomposed lower peat promoted frequent saturation through rapid water table response, leading to consistent soil anoxia. This research highlights the importance of autogenic processes and soil textural layering in maintaining a permanent isolated wetland in a regional moisture deficit. Radiocarbon dating of basal organics indicated the peatland initiated ~4000 years ago in a climate similar to present. Peat appeared to advance northward over the next 2000 years, via the process of paludification. Since the study perched wetland does not rely on ground or surface water inputs, it may be implied that similar wetlands could be constructed in any landscape position. Incorporating perched wetlands into watershed reconstruction could provide an important fresh water source for headwater streams and surrounding forest vegetation.

• Subjects / Keywords

  • Isolated
  • Negative feedbacks
  • Wetland hydrology
  • Sub-humid
  • Autogenic
  • Peatlands
  • Water generation
  • Wetland reconstruction
  • Perched

• Graduation date

  Spring 2017

• Type of Item

  Thesis

• Degree

  Master of Science

• DOI

  https://doi.org/10.7939/R3930P68H

• License

  This thesis is made available by the University of Alberta Libraries with permission of the copyright owner solely for non-commercial purposes. This thesis, or any portion thereof, may not otherwise be copied or reproduced without the written consent of the copyright owner, except to the extent permitted by Canadian copyright law.