ELEVATED ATMOSPHERIC CO2 CONCENTRATION CHANGES ECTOMYCORRHIZAL MORPHOTYPE ASSEMBLAGES IN BETULA-PAPYRIFERA

Ectomycorrhizae are extremely diverse, with different species of fungi having very different physiologies and morphologies that, in turn, co nfer a range of different benefits to the host plant. To test the hypo thesis that elevated CO2 leads to changes in the assemblage of ectomyc orrhizae associated with trees, we examined the number and frequency o f ectomycorrhizal morphotypes colonizing roots of Betula papyrifera Ma rsh. saplings grown at an ambient or elevated (700 ppm) atmospheric CO 2 concentration for 24 weeks. Elevated CO2 resulted in significant cha nges in the composition of the ectomycorrhizal assemblage toward morph otypes with a higher incidence of emanating hyphae and rhizomorphs. We conclude that B. papyrifera saplings will be able to support a more c ostly mycorrhization in future elevated-CO2 atmospheres.