Coarse woody debris as a land reclamation amendment at an oil sands mining operation in boreal Alberta, Canada.
Coarse woody debris (CWD) is an important component of natural forests and is now being used in reclaiming oil sands land to control erosion, enhance diversity, and function as longer term storage of organic matter. However, the impact of woody debris on reclaimed ecosystems may vary depending on the amount applied and the soil it is applied to. We studied the impact on the plant community (including tree regeneration and understory plants) and soil properties of four levels of CWD cover (None, Low, Moderate, High) on two reclamation soils (forest floor-mineral mix and peat-mineral mix) and natural post-fire soils. Significant differences were observed among soil types in terms of the plant community and soil properties but fewer differences were attributable to CWD. However, overall native plant species' diversity and abundance decreased with High CWD while cover of non-native species on the reclaimed soils greatly decreased with Low CWD. Natural seedling regeneration density of trembling aspen was unaffected by CWD on both reclamation soil types. The soil nutrient supply rates and soil moisture were significantly different among soil types but there were no differences among debris treatments while soil temperature decreased with CWD. Overall, a Low (up to 30% ground cover) woody debris application appears to be optimal for maintaining native plant species diversity and abundance while controlling undesirable plant species.