Ectomycorrhizal colonization and growth of the hybrid larch F1 under elevated CO2 and O3.

We studied the colonization of ectomycorrhizal fungi and species abundance of a hybrid larch (F1) under elevated CO2 and O3. Two-year-old seedlings were planted in an Open-Top-Chamber system with treatments: Control (O3 < 6 nmol/mol), O3 (60 nmol/mol), CO2 (600 µmol/mol), and CO2 + O3. After two growing seasons, ectomycorrhiza (ECM) colonization and root biomass increased under elevated CO2. Additionally, O3 impaired ECM colonization and species richness, and reduced stem biomass. However, there was no clear inhibition of photosynthetic capacity by O3. Concentrations of Al, Fe, Mo, and P in needles were reduced by O3, while K and Mg in the roots increased. This might explain the distinct change in ECM colonization rate and diversity. No effects of combined fumigation were observed in any parameters except the P concentration in needles. The tolerance of F1 to O3 might potentially be related to a shift in ECM community structure.