Use of shrub willows (Salix spp.) to develop soil communities during coal mine restoration

Authors: Sylvain, Zachary; MOSSELER, ALEX - Canadian Forest Service

Submitted to: Canadian Journal of Forest Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/27/2017
Publication Date: N/A
Citation: N/A

Interpretive Summary: Reforesting degraded landscapes such as surface mines is important in order to restore plant cover and productivity and minimize effects of erosion. This is made more difficult by the end goal of long-lived, later-successional trees in restored forests that start as highly-disturbed landscapes better suited for early-successional plant communities. Re-initiating soil processes such as decomposition and nutrient cycling may assist recovery. Willow species are promising for restoration because they can develop and spread on even marginal habitats, however it isn’t clear whether they can support populations of soil organisms such as nematodes, which are a diverse group of microscopic worm-like animals with a variety of feeding behaviors. These soil fauna contribute to soil processes important for plant growth and development. We sampled nematodes from under willow cover and bare ground along different landforms (lowland, hillslope and sloping stream channel) at a former coal mine site in New Brunswick, Canada in order to determine how cover and landform influence the restoration of nematode communities and their functions. We found that willows can increase the numbers of nematodes with different feeding behaviors, which helps restore soil ecological functioning. We also found that sites on slopes had fewer nematodes of all feeding types than flat sites did, suggesting that restoration of soil processes may proceed more slowly on slopes, likely because of greater surface water flow (which can wash soil and nematodes downslope) and quicker drainage of soil on hillslopes (which limits how active nematodes can be through time). Willows therefore play beneficial roles in reforesting degraded landscapes and restoring soil functions in these areas.

Technical Abstract: Afforestation or reforestation in highly degraded environments (e.g. surface mines) is often complicated by the total removal of vegetation and severe soil degradation that occurs during mining operations, necessitating revegetation to be undertaken in tandem with the re-establishment of soil developmental processes. Shrub willows are effective as colonizer species initiating revegetation dynamics, however it is unclear if they also serve as nurse-plants facilitating the establishment of soil communities, such as those of nematodes. We established a study in a former coal mine site in New Brunswick, Canada to assess whether the presence of willows on otherwise bare, poorly developed soil contributed to nematode community development and to what degree landform design (e.g. slope) may influence these dynamics. Our results demonstrate that willows can facilitate nematode communities at this site, but that slope strongly influence these effects, likely as a consequence of hydrology and overland water flow. These results confirm the beneficial role willows can play in reforestation of highly degraded environments both for revegetation and for the re-initiation of soil ecosystem processes.