Surface Soil Handling on Mines in the Boreal Forest – from Textbook to Operations

Conservation of forest surface soil is critical for the development of self-sustaining forested ecosystems on post-mined land. Salvaging surface soil from upland boreal forests received little attention in the past and was often not required. Current research has shown forest surface soil provides an economical, diverse and abundant source of native propagules and an important source of nutrients and soil fauna. Salvage depth affects soil quality and potential for in situ propagules to emerge. Salvaging too deep will dilute the propagule and organic matter content of the forest floor with underlying mineral soil; however, salvaging too shallow may not provide sufficient root to soil contact for successful emergence of vegetative propagules. Optimal salvage depth will be impacted by various factors such as soil texture, source location and reclamation objectives. Salvaged surface soil should be directly placed, as stockpiling surface soil for even short periods of time reduces viability of most boreal plant species and causes substantial changes to soil chemical properties. The time between harvesting deciduous forests and soil salvage affects success of establishing deciduous trees; salvaging surface soil when trees have a sufficient amount of carbohydrate reserve in the root system can result in higher establishment rates. During salvage if too much mulch is incorporated with upland surface soil, viability of native propagules can be reduced. Optimal placement depth and distribution of surface soil is also dependent on many factors including salvage depth, substrate quality and reclamation objectives. Placement of coarse woody debris and/or straw on the surface soil creates microsites that aid in reestablishment of native plants. Data from field research at operational and plot scales are presented to support best practices. Various adaptive management practices developed from theory, research and operations to help reduce negative impacts on soil quality and viability of native propagules are discussed.