USING BIG BLUESTEM (ANDROPOGON GERARDII) FOR RESTORATION OF METAL CONTAMINATED STAMP SANDS IN UPPER PENINSULA, MICHIGAN

As a consequence of the mining industry in the Keweenaw Peninsula in Michigan generated vast quantities of heavy metal contaminated stamp sands in the Upper Peninsula of Michigan were generated during the early part of the 20^th Century. The stamp sands are highly polluted, containing 600-2,000 ppm copper, in addition to 100 ppm aluminum, and various other heavy metals. Due to the inhospital condition of the stamp sand dumping sites, restoration has been a major challenge; with local weeds often dominating. Using metal tolerant native plant species for restoration may be an environmentally-friendly and economical approach. In the current study we transplanted big bluestem (Andropogon gerardii) seedlings, to the field. Big bluestem is a native, drought tolerant species that is fast growing and suitable for restoration projects. Big bluestem plants were treated with plant growth promoting bacteria (PGPB) isolated from copper contaminated sediments from Torch Lake, MI (Pseudomonas sp. TLC 6654), which have been shown to enhance plant growth and copper uptake in maize in a previous studies. Big bluestem seedlings were grown in a greenhouse for 3 months in containers that were coated with copper (Copper), a substance known to stimulate root growth, or uncoated (Uncoated). At the time of transplanting (June 2011), the seedlings (Copper versus Uncoated) were inoculated with the following treatments: PGPB alone, PGPB with native mycorrhizal fungi, mycorrhizal fungi alone and control group with no treatment. The seedlings were given no additional watering or fertilizing. Data collected in July 2014 show that all big bluestem survival was 100% regardless of treatment. However, a higher fresh and dry weight was associated with seedlings treated with the PGPB bacteria alone as well as the plants treated with PGPB and mycorrhiza in comparison with control.