Nutrient distribution in sandy soils along a forest productivity gradient in the Athabasca Oil Sands Region, Alberta, Canada

• Author / Creator

  Barnes, William A

• Brunisolic soils developed on coarse textured (sandy loam to sand) deposits comprise a significant portion of the land currently being disturbed by surface mining in the Athabasca Oil Sands Region of Alberta, Canada. The goals of this study were to determine (i) how the physical properties of these sandy soils influence the accumulation of different forms of nutrients in the soil profile, (ii) the processes at work that govern the amounts and availability of soil nutrients, (iii) how nutrient cycling processes differ between aspen and jack pine dominated stands, which are the two most common canopy species associated with these soils in the AOSR, and (iv) how differences in their associated productivity levels relate to soil physical properties and nutrient levels. To accomplish this, I measured total nutrient stocks contained in the forest floor, available soil nutrients as measured using Plant Root Simulator (PRS) probes, which are ion exchange membranes buried in the soil for a 35 to 38 day field incubation, and select B horizon nutrients. I used correlation analysis and non-metric multidimensional scaling to quantify relationships between these nutrients and soil texture and vegetation productivity. When all sites were considered together, differences in forest floor total and available nutrients were found to largely be influenced by the texture of the upper soil profile, most likely through its influence on canopy type and vegetation productivity levels and therefore the quantity and quality of litter nutrient inputs to the forest floor. However, soil textural controls on nutrient forms are likely different between jack pine and aspen stands. In soils under jack pine, relatively small increases in silt and clay content (≤ 8 %) were associated with a greater site index, greater total nutrient stocks in the forest floor, as well as a higher forest floor quality (lower C:N and C:Ca ratios), potentially linked to more optimal moisture conditions in finer textured jack pine stands. Interestingly, most PRS nutrients showed little relationship with soil texture under jack pine, while available NH4, P and K actually increased with coarser textures, potentially due to low tree nutrient uptake associated with coarser sites. Forest floor nutrient stocks under aspen related most strongly to B horizon texture, with finer B horizon texture (silt + clay) being associated with larger forest floor nutrient stocks (C, N, P, S, Ca, Mg, K), although availability of Ca and Mg was lower with finer B horizon textures (clay; silt + clay). However, only soils with fine lower soil profile textures were associated with higher forest floor quality (lower C:N and C:Ca ratios). These results indicate that B horizon texture may control the quantity of forest floor nutrients while lower profile texture may control the quality of litter nutrient inputs under aspen. Therefore, while upper profile silt + clay may correlate best with differences in nutrient amounts and availability in sandy soils of the AOSR overall, and correlate strongly with soil nutrients under jack pine, more complex interactions between the relative textures of the B horizon and lower soil profile regulate soil nutrient stocks and forms under aspen.

• Subjects / Keywords

  • Coarse
  • Sandy
  • Productivity
  • Brunisol
  • Nutrients
  • Sand
  • Forests
  • Soil
  • Boreal
  • Texture

• Graduation date

  Fall 2016

• Type of Item

  Thesis

• Degree

  Master of Science

• DOI

  https://doi.org/10.7939/R3KK94P5F

• 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.