Effects of native ectomycorrhizal fungi on aspen seedlings in greenhouse studies : inoculation methods, fertilizer regimes, and plant uptake of selected elements in smelter-impacted soils

Abstract

In southwestern Montana, areas near Butte and Anaconda support little or no vegetation mainly because of impacts from copper mining. Aspen (Populus tremuloides) stands occur naturally in these areas and rely heavily on native mycorrhizal fungi to moderate below ground conditions. Aspen associates with over 60 species of mycorrhizal fungi, but only a subset occurs on acidic, low nutrient soils. For these reasons, and the fact that aspen is an important colonizing tree on disturbed landscapes, a study was undertaken to examine aspen and its native ectomycorrhizal fungi in pot studies for future use in reclamation projects. The first goal was to develop a method for mycorrhization of aspen in the greenhouse by examining inoculation methods, fertilization regimes, and selection of fungi. Nine native ectomycorrhizal fungi from smelter impacted sites near Butte- Anaconda aspen stands were tested using seed from Silverbow county, MT.

Results demonstrated that mycorrhization of aspen in the greenhouse is possible, and that banding is the most effective method, although also labor intensive. Some fertilization was necessary, and high levels of liquid soluble fertilizer dramatically reduce mycorrhization, while the time release fertilizer Osmocote allowed mycorrhization. In general, mycorrhization in peat:vermiculite reduced aspen growth at 3 months, which might reflect an initial carbon drain. Secondly, effects of ectomycorrhizal fungi on aspen growth and metal uptake in pots from Smelter Hill and Mt. Haggin were examined. In contrast to our earlier findings, mycorrhization in field soils increased seedling growth, although controls were slightly compromised. Inoculation technique was important and only banded seedlings formed mycorrhizae. Copper uptake was depressed about 50% in both roots and shoots of banded aspen compared to seeding a soil inoculum. Iron, zinc, nickel and phosphorus uptake appeared affected by fungi, but was dependent on species and particular metal, and, in some cases, appeared enhanced. Laccaria, Paxillus, Pisolithus and Scleroderma are of interest for their impact on aspen growth and metal uptake characteristics. Results indicate that inoculation of aspen seedlings with native mycorrhizal fungi has potential for use on smelter-impacted field soils. Once established, aspen's clonal nature could be an advantage in re-vegetating large tracts of land.