Native Mycorrhizal Fungi with Aspen on Smelter- Impacted Sites in the Northern Rocky Mountains: Occurrence and Potential Use in Reclamation

Aspen (Populus tremuloides) is an early successional tree that has naturally colonized large tracts of land near functioning and defunct smelter sites in the northern Rocky Mountains. This is evidenced by extensive aspen stands on the East Ridge of Butte (MT), behind the smelter stack at Anaconda (MT), near the (removed) smelter in Kellogg (ID), and downwind of the Trail, B. C. smelter (Canada). Aspen is able to colonize these areas due to mutualistic relationships with mycorrhizal fungi which increase phosphorus uptake, and ameliorate soil conditions such as low pH, high heavy metals, low fertility, and drought. Mycorrhizal fungi have been used to establish various trees on coal spoils and mine sites in eastern U.S., Ohio, and Utah, but use of aspen has not been examined. Typically a commercial fungal inoculum is added to trees, but inherent problems are: spread of exotic fungi, and use of expensive generic fungi which are not site/host specific. One solution is use of native fungi adapted to a particular tree species, soil type, and climatic region. This research is initiating investigation of the use of native mycorrhizal fungi to enhance aspen establishment on smelter-impacted sites. Thirty species of native fungi are reported on these sites, half of which grew under laboratory conditions. A few grew well enough to warrant further interest as inoculum, including: Laccaria proxima, Tricholoma flavovirens, Tricholoma populinum, Scleroderma cepa, and Paxillus vernalis. Inoculum is presently being developed for use in greenhouse and field studies with aspen. Potential for heavy metal immobilization and uptake are discussed.