Soil reclamation amendments affect long term growth of jack pine following oil sands mining

Abstract

A retrospective study of reclamation soil properties and associated tree growth was conducted on a former tailings pond site containing a 21-year old jack pine stand. The purpose of the study was to explore possible causes of observed variations in mean tree heights in various portions of the stand. An expected link to total depth of the fine textured glaciolacustrine reclamation capping material was not found. Instead, a strong relationship was found between tree height and organic matter (OM) content (by % dry weight), where OM is in the form of predominantly mesic peat mixed with the capping material at the time of placement. Possible OM-related causes of the height growth effect could include (a) contributions to water holding capacity of the soil and (b) contributions to soil nutrition. Contributions to water holding capacity could not be evaluated in this study, but the lack of correlations to total capping depth suggests that moisture may be of lesser importance as a growth limiting factor on this site. Nitrogen supply was identified as the most likely nutritional deficiency. For current soil OM content, substantial increases in tree heights were measured with OM increases to approximately 8 %, followed by marginal increases in tree height with OM greater than 8 %. This study offers a relatively inexpensive methodology through which oil sands operators can test for similar relationships over a broad range of site and stand conditions, and evaluate the benefits of varying their allocation of OM resources to achieve optimum tree growth benefits at the landscape scale.