Water availability and understory influence on tree growth in reclaimed forest ecosystems, Athabasca oil sands region, Alberta, Canada

• Author / Creator

  House, Jason D.

• Reclaimed forest ecosystems in the Athabasca oil sands region (AOSR) have limiting factors to growth that can result in poor tree performance, as indicated by stunted growth, foliar discolouration and needle dropping, and ultimately threaten reclamation success. Indicators of reclamation success are understory plant community development and productive tree growth. Water availability as well as soil properties such as soil organic carbon content were investigated as limiting factors to growth on previously reclaimed forest ecosystems planted with lodgepole pine (Pinus contorta) and white spruce (Picea glauca). Lodgepole pine and white spruce were planted in peat-mineral mix (PMM) cover soil and had tailings sand (TS) and overburden (OB) substrates, respectively, below the cover soil. Composite samples of PMM, peat, OB and TS were used to calibrate time domain reflectrometers in the laboratory and to develop a soil moisture retention curve so water availability could be measured in the field. Understory plant communities were examined for composition, cover and foliar nutrient concentrations. On the TS plots, total understory layer cover was negatively correlated to mean PMM water availability and on the OB plots, total understory layer cover was positively correlated to PMM soil carbon and nitrogen content. Understory nutrient concentrations in both TS and OB reclaimed forest ecosystems were related to water availability but only on OB sites were understory foliar nutrient concentrations related to tree growth. Tree growth was limited by water availability in 2011, a drier than average year; tree growth was significantly correlated with mean PMM water availability and mean PMM water availability was also correlated with PMM soil organic carbon content on TS plots. Thus, sites with high organic matter content or thick PMM layers had substantially greater water availability and, therefore, more tree growth. On OB plots, mean PMM water availability was not correlated to tree growth, but tree growth was significantly correlated with soil organic carbon content, indicating that other factors are more limiting than water availability on the OB plots. Reclamation practioners should consider re-constructing sites with thick cover soils and high soil organic carbon contents (i.e., more peat) so that the rooting zone of the soil can hold more water for root uptake., reducing the risk of low water availability and likely improving tree and understory growth in reclaimed forest ecosystems.

• Subjects / Keywords

  • Athabasca oil sands region
  • Water availability
  • Tree growth
  • Reclamation

• Graduation date

  Fall 2015

• Type of Item

  Thesis

• Degree

  Master of Science

• DOI

  https://doi.org/10.7939/R3T14TV3R

• 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.