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


Other title
soil pH
boreal forest
oil sands reclamation
Type of item
Degree grantor
University of Alberta
Author or creator
Supervisor and department
Zwiazek, Janusz (Renewable Resources)
Examining committee member and department
Bork, Edward (Agricultural, Food and Nutritional Science)
Hacke, Uwe (Renewable Resources)
Chang, Scott (Renewable Resources)
Repo, Tapani (Finnish Forest Research Institute, Finland)
Department of Renewable Resources
Forest Biology and Management
Date accepted
Graduation date
Doctor of Philosophy
Degree level
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.
Permission is hereby granted to the University of Alberta Libraries to reproduce single copies of this thesis and to lend or sell such copies for private, scholarly or scientific research purposes only. Where the thesis is converted to, or otherwise made available in digital form, the University of Alberta will advise potential users of the thesis of these terms. The author reserves all other publication and other rights in association with the copyright in the thesis and, except as herein before provided, neither the thesis nor any substantial portion thereof may be printed or otherwise reproduced in any material form whatsoever without the author's prior written permission.
Citation for previous publication
Zhang W, Calvo-Polanco M, Chen ZC, Zwiazek JJ (2013) Growth and physiological responses of trembling aspen (Populus tremuloides), white spruce (Picea glauca) and tamarack (Larix laricina) seedlings to root zone pH. Plant Soil 373: 775-786.Zhang W, Xu F, Zwiazek JJ (2015) Responses of jack pine (Pinus banksiana) seedlings to root zone pH and calcium. Environmental and Experimental Botany 111: 32-41.

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