Canadian Forest Service Publications

Assessing the long-term ecosystem productivity benefits and potential impacts of forests re-established on a mine tailings site. 2018. Metsaranta, J.M.; Beauchemin, S.; Langley, S.; Tisch, B.; Dale, P. Forests 9(11):707.

Year: 2018

Issued by: Northern Forestry Centre

Catalog ID: 39481

Language: English

Availability: PDF (download)

Available from the Journal's Web site.
DOI: 10.3390/f9110707

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Restoring sites disturbed by industrial activity to a forested condition can ensure the continued provision of economic and ecosystem services from these areas. Impounded mine tailings are particularly challenging sites, and positive benefits of establishing trees must be balanced against risks associated with metal contamination, ongoing tailings stability, and the possibility of acid mine drainage. We used a hybrid biometric modelling approach based on dendrochronological reconstruction to retrospectively (1980–2015) quantify productivity and carbon dynamics of pine plantations growing on impounded mine tailings at the Vale waste management facility near Sudbury, Canada. Historical reclamation practices had remediated conditions sufficiently to allow conifer plantation establishment in the late 1970s. The revegetated sites were highly productive, when compared to reference conditions based on site index, wood volume growth, and ecosystem production, congruent with other studies showing that forests on revegetated post mining sites can be highly productive. However, metal concentrations in the forest floor were high, and further research is warranted to evaluate ecosystem impacts. Due to the requirement for energy-intensive inputs, we estimated that it took 12 years or more to recover the emissions associated with the revegetation process through C accumulated in biomass and soil at the revegetated sites.

Plain Language Summary

It can be really hard to get plants and trees to grow on former mine sites, especially if the soil is contaminated by the mining waste material, which is called tailings. In an area of mine tailings near Sudbury, Ontario, trees have been successfully growing for the last 30–40 years after a lot of work was done to improve the growing conditions. From trees growing on the tailings, we extracted core samples and then measured the width of the annual rings. We put that information into a computer model called the Carbon Budget Model of the Canadian Forest Sector (CBM-CFS3) to calculate how fast the trees were growing and how much carbon was being stored in the forest. The trees were growing relatively quickly and the site was accumulating carbon in both the trees and the soil faster than expected. It took about 10 years to make up the amount of carbon that was put into the air by all the activities that were needed to get the trees growing. The amount of toxic metal in the soil under the trees was pretty high, and so getting the trees to grow fixed only some of the environmental problems at the site.