Spatial Variability in Disturbed Boreal Ecosystems: Aboveground and Belowground Controls

  • Author / Creator
    Das Gupta, Sanatan
  • The recent open pit mining for oil sands in the Athabasca Oil Sands Region (AOSR), northern Alberta has created an unprecedented industrial scale disturbance whose ecological consequences is not well understood, and requires intensive investigation. This study focused on the temporal dynamics of spatial variability in aboveground (canopy cover, understory vegetation cover and forest floor) and belowground (soil nutrient availability, microbial biomass, respiration and enzyme activities) processes in wildfire disturbed upland boreal forests to create a benchmark condition for measuring reclamation success.
    The wildfire chronosequence used for the spatial study contained three trembling aspen (Populus tremuloides Michx.) stands; a one-year old post fire stand (PF), a 9 year old stand at canopy closure (CC) and a 72 year old mature (MA) stand. The PF stand had the highest total inorganic N, P and K availability compared to the CC and MA stands. Most of the above and belowground properties, including macronutrients, in the PF stand either had a large scale spatial pattern or did not show any spatial structure, whereas the CC and MA stands had a spatial range equal to or less than 10 m. The PF stand also showed the weakest spatial coupling between aboveground and belowground properties. The aboveground and belowground properties in the CC stand appear to be more similar to the MA stand. This indicates that natural recovery probably happen much faster rate than what is reported in the literature. The current research also quantified the spatial variability of soil respiration (Rs) in the same fire chronosequence over two growing seasons. No spatial structure was detected in Rs of the PF stand during the peak growing season (June-July), whereas Rs was auto-correlated at a scale of < 6 m in the CC and MA stands, which confirms the disturbance legacies in spatial patterns found in the nutrient study.
    Finally, the research investigated whether spatial patterns in biogeochemical properties were developed in a 14-year old aspen stand reclaimed after oil sands extraction. A fine scale (< 10 m) spatial pattern was found in the majority of above and belowground properties. However, soil chemical properties showed large scale spatial auto-correlation indicating persistence of disturbance effect. A strong soil microbial influence on the availability of macronutrients was found when compared to stand characteristics. The weak spatial coupling between nutrient availability and aboveground properties even after a decade of reclamation suggests that the ecosystem recovery rate in the reclaimed area is slower than in wildfire disturbed areas, and might require further time to develop. This research highlights the importance of spatial heterogeneity as a tool for measuring ecosystem recovery after disturbance and data on natural benchmark function to quantify reclamation success in oil sands mine disturbed areas.

  • Subjects / Keywords
  • Graduation date
    Fall 2015
  • Type of Item
  • Degree
    Doctor of Philosophy
  • DOI
  • 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.