Effects of Root Zone pH, Calcium and Phosphorus Supply on Selected Boreal Forest Plant Species

• Author / Creator

  Zhang,Wenqing

• Soil pH is among the major environmental factors affecting plant growth. In the reclaimed areas following open-pit oil sands mining in northeastern Alberta, Canada, the pH of reclaimed soil is commonly higher than 8.0. The optimum range of soil pH for growth and the tolerance of pH extremes widely varies among plant species, but is generally low for boreal forest plants. High soil pH affects many processes in plants in a complex manner. A common problem associated with high soil pH is reduced availability of certain essential elements including phosphorus, iron, manganese and zinc. High soil pH can also reduce root water flux. Calcium is known to aggravate the detrimental effects of high pH on plants by inhibiting root growth. High calcium levels are of concern in calcareous soils and in some of the oil sands reclamation areas due to the use of gypsum during the tailings consolidation process. The goal of oil sands reclamation is to restore disturbed forest ecosystems to their original state including forest productivity and biodiversity. In this project, I examined the effects of root zone pH, calcium and phosphorus supply on several boreal forest plant species including trembling aspen, white spruce, black spruce, jack pine, tamarack, paper birch, green alder, red osier dogwood, blueberry and bearberry. The studies were conducted through a series of controlled-environment experiments with hydroponically-grown plants. I found that the effects of high root zone pH varied between the different plant species and in sensitive plants high root zone pH and high calcium levels reduced growth, net photosynthesis, transpiration rates, root water flux, leaf chlorophyll concentrations, root cortex cell lengths, and tissue elements concentrations in seedlings. The effects of high pH, including those on leaf chlorophyll concentration, were partly alleviated by exposing a part of the root system to low pH while the remaining part was exposed to high pH. However, I did not find substantial beneficial effects of increasing phosphorus supply to the plants subjected to high root zone pH conditions. The reasons for greater tolerance to high pH in some of the studied plant species likely included enhanced ability to maintain optimum apoplastic pH, high root hydraulic conductivity, and high ferric chelate reductase activity under high pH conditions. Among the examined species, dogwood, white spruce and black spruce showed greater resistance to high root zone pH and are likely to outperform the other plants following planting in oil sands reclamation sites with elevated pH levels.

• Subjects / Keywords

  • Hydroponic
  • Soil pH
  • Phosphorus
  • Oil sands reclamation
  • Calcium
  • Boreal forests

• Graduation date

  Spring 2015

• Type of Item

  Thesis

• Degree

  Doctor of Philosophy

• DOI

  https://doi.org/10.7939/R3B27Q04X

• 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.