The Efficacy of Ectomycorrhizal Colonization of Pin and Scarlet Oak in Nursery Production

Abstract

Two experiments were conducted to assess the effectiveness of ectomycorrhizae inoculation of pin ( Quercus palustris ) and scarlet oak ( Q. coccinea ) during nursery production. Experiment 1 tested inoculum and substrate protocol. Vegetative and spore inoculum of Pisolithus tinctorius (Pt) were applied to pin and scarlet oak seedlings. All plants were grown in 0.9 liter (1 gal) containers filled with milled pine bark, sterilized milled pine bark, sterilized mineral soil, or sterilized vermiculite-based substrate. After two months, mycorrhizal colonization rates were assessed qualitatively. Vegetative inoculum was unsuccessful at infecting seedlings of both species when grown in all of the substrates. Best results were 90% and 60% of plants colonized with spore inoculum for pin and scarlet oak, respectively, grown in vermiculite-based substrate. Sixty percent of pin oaks were colonized by Pt in milled pine bark, whereas no scarlet oaks were colonized. Overall, the spore inoculum colonized pin oak at a higher rate than scarlet oak, and vermiculite-based substrate proved superior to the other three substrates for inoculating seedlings with commercial Pt spores. In experiment 2, Pt spore inoculum was applied as a bare root dip on scarlet oak liners before transplanting into 51 liter (15 gal) containers in a pot-in-pot growing system. Pt had a colonization rate of zero, but an indigenous mycorrhizal fungus, Scleroderma bovista (Sb), colonized many of the trees. Height and trunk diameter growth during two years of production were similar for trees colonized and not colonized with Sb. Leaf water potentials were more negative and stomatal conductance was reduced for transplanted colonized compared to not colonized trees during a 10-day dry-down, imposed 50 days after transplanting. Under our conditions, mycorrhizal fungi showed no apparent benefit during production and during initial establishment.