Soluble Calcium and Sulphate Excesses Related to Stress in Pinus contorta on Peat Amendments of Reclaimed Landscapes in the Boreal Oil Sands Region

The objective of this study was to evaluate impacts of three peat soil amendments containing variable amounts of soluble calcium and sulphate-S on soil quality and Pinus contorta (lodgepole pine) growth in a terrestrial boreal ecosystem. A 13-year old stand of lodgepole pine displayed various symptoms and degrees of nutrient deficiency on a reclaimed tailings sand dyke at an oil sands mining operation in northeastern Alberta, Canada and were representative of three unique peat-mineral soil amendments applied to a tailings pond slope in 1992. The poorest growth occurred on soil from a deep mesic peat deposit underlain by marl, the intermediate growth on a peat-mineral mix of shallow, fibric origin, and the best growth on soil of moist upland forest floor origin, with a cover of moss and litterfall. Transects were established in each of the three zones of variable pine performance to survey the vegetation and soil characteristics. Soil samples were analysed for salinity and soluble cations, reaction, and available nutrients in early fall, 2005. Soil moisture profiles to 160 cm were collected at each survey location during the 2006 growing season. Results indicated a negative relationship among pine performance with increasing soluble calcium and available sulphate-S. These relationships were stronger than indicators typically linked to poor peat amendment quality. Calcium and sulphate were the main contributors to electrical conductivity, and were also associated with elevated CaCO₃ eq.