Canadian Forest Service Publications
Root competition, not soil compaction, restricts access to soil resources for aspen on a reclaimed mine soil. 2017. Bockstette, S.W.; Pinno, B.D.; Dyck, M.F.; Landhäussen, S.M. Botany 95(7):685-695.
Issued by: Northern Forestry Centre
Catalog ID: 38727
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Restricted rooting space in response to soil compaction and belowground competition with herbaceous plants are two main limiting factors for successful reforestation after surface mining. Fine-textured, nutrient-rich soils with adequate soil moisture are particularly susceptible to both of these concerns and while there are recognized ways to manage competition, attempts to alleviate soil compaction through mechanical means have produced varying results. While roots of some herbaceous plants may penetrate compacted soil layers, possibly offering an alternative means to overcome physical restrictions, these potential benefits need to be weighed against negative effects from competition with planted trees. We examined the individual and combined impact of soil decompaction (deep tillage) and management of competing vegetation (herbicide) on soil properties, resource availability, and above- and below-ground growth of aspen (Populus tremuloides Michx.) seedlings on a reconstructed mine soil affected by severe subsoil compaction. Our findings suggest that although deep tillage reduced bulk density, this did not increase resource availability and had limited effect on seedling growth. In contrast, competition with smooth brome grass (Bromus inermis Leyss.) drastically reduced aspen belowground growth because the grass rapidly occupied available rooting space, while simultaneously lowering the availability of water and nutrients, in particular nitrogen.
Plain Language Summary
There is interest in restoring land used for coal mining in Alberta to the original aspen-forest ecosystem when the mines are closed. However, reforestation after surface mining can be difficult because the soil has been compacted to deep levels, hindering roots from reaching nutrients, and because tree seedlings must compete with grass and other vegetation that have moved in. Fine-textured, nutrient-rich soils are particularly susceptible to both of these issues. While competition can be managed by removing other plants, tilling the soil deeply to alleviate soil compaction can be very difficult and costly. This study examined the effects of deep tillage, vegetation management, or both on the growth of aspen seedlings on a reconstructed mine soil. Tilling to alleviate soil compaction had no effect on tree seedling growth, but competition from grasses drastically reduced tree growth by using water and nutrients the seedlings needed. Therefore, we recommend that reclamation should focus on reducing plant competition to establish new forests successfully.