Developing manufactured soils for reclamation of mined land in the boreal forest ecosystem

Abstract

The purpose of this study was to manufacture a cover soil that will be suitable to create ‘cover islands’ of native boreal vegetation for reclamation of large mine rock piles generated through open-pit mining activities in the Boreal Shield region north of Lake Superior. Multiple Technosols were manufactured from blends of mill derived organic residuals and finely crushed mine rock. A ten week growth study assessing the performance of the Technosols as growth media for annual ryegrass demonstrated that blends of at least 50% woody residuals and a mixture of finely crushed mine rock could be used to produce a viable growth media. Reclamation plots were constructed in a field setting using two new Technosols manufactured in ratios of 40 and 80% organics using woody residuals and mixed mine rock, applied to 30 or 60 cm depths over a coarse mine rock pile to simulate ‘vegetation islands’. Soil microclimate data and soil pore-water samples collected over one annual cycle demonstrate that increasing organic matter increased soil moisture and concentration of bioavailable plant nutrients. Increasing depth of plots enabled development of a reservoir of available plant moisture below the rooting zone, but did not increase moisture in surface soils. Low survival rates of tickle grass and green alder can mostly likely be attributed to low moisture availability in the surface soils at the time of planting. Technosols composed of 80% woody residuals and deposited to a 60 cm depth could be appropriate for use in reclamation if surface moisture is increased.