Selected Willow Clones for Use in Reclaimed Ecosystems Impacted by Elevated Salt Levels

In Alberta oil sands reclamation, the waste product of Oil Sands Process-affected Water (OSPW) can contain naphthenic acids and salts that can adversely affect plant growth. Willow species commonly occur in areas most at risk from exposure to OSPW, are often a major component of lowland and riparian ecosystems, and are often deployed early in reclamation of these areas due to their value for slope and shoreline stabilization. A recent greenhouse study conducted by Natural Resources Canada (NRCan) identified several clones of various native willow species that appear to have particularly high tolerance to OSPW; the current study follows this up with field deployment of 15 native willow clones identified as having highest tolerance levels. The objectives are to: (1) determine if these clones are also tolerant to in-situ conditions along the shoreline of Basemine Lake by monitoring survival, growth rate and foliar chemistry; (2) monitor the soil moisture and soil chemistry in the rooting zone of the willows as lake levels fluctuate; and (3) assess potential of willows to stabilize shorelines of end-pit lakes by evaluating root growth of these willow clones.

This study confirmed there are salt tolerant willows in the native population in Alberta, and found tolerance is both species and clone dependent. Overall, the greenhouse screening method for selecting clones for this trial predicted field performance 66% of the time – methodology refinement is needed to improve this number. This research suggests that Salix exigua, Salix lucida and Salix lutea clones would be the best choices for this reclamation challenge. Salix exigua has the added advantage of producing suckers from the root system, which could expand the reclaimed area without the need for planting additional seedlings. Salix petiolaris and Salix scouleriana are the least suitable for planting on salt impacted sites. Salix bebbiana clones grew well in the field but did not root well in the greenhouse trial. This study also found that the use of mulch to provide a short term pulse of available nutrients for newly planted trees may be a helpful option for establishing willow or other tree species on a site with high competition.