Impact Of Large-Scale Actinorhizal Alder Plantations on Soil Quality

In pursuit of improved reclamation and revegetation approaches, this research explored the use of actinorhizal alder plantations in reforestation and their effects on soil quality in the Oil Sands Region. The objectives were to (1) determine the effects of large-scale plantations of two species of actinorhizal alders (Alnus crispa and A. rugosa) on oil sands site materials; (2) determine the effects of alder plantations on soil quality; and (3) determine the impact of Frankia inoculation on alder survival and growth in oil sands site materials.

After four years of field monitoring, clear differences were observed between Frankia inoculated alders and non-inoculated alders. Though all plants on site were generally healthy and producing lots of seed (some were over 3 m), the seedling volume index (SVI) was 3-5 times greater for the inoculated plants. No clear differences could be seen between the two species. An examination of roots of inoculated plants revealed a high density of nodules in comparison to non-inoculated plants. Parameters indicative of soil quality changes were also examined; microbial numbers and activity were improved in planted soils in comparison to non-planted soils. These results support the use of inoculated alders as a viable approach for site reclamation. Greenhouse inoculation had a positive effect on plant growth on stressed lands. Future work could expand on this concept on a larger scale, possibly including mixed alder and conifer plantations on affected sites. Continued longer-term monitoring of the existing plantations would also provide valuable data on change over time and the amount of time required to see clear evidence of soil quality change and succession on impacted sites.