Responses of Ectomycorrhizal Colonization and Morphotype Assemblage of Quercus myrsinaefolia Seedlings to Elevated Air Temperature and Elevated Atmospheric CO₂

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Ectomycorrhizal colonization and morphotype assemblage of Quercus myrsinaefolia seedlings were compared under ambient (399μl liter^-1 of CO₂) atmospheric, elevated air temperature (ca. +4.5°C) (ET), and elevated air temperature (ca. +4.5°C) plus elevated atmospheric CO₂ (753μl liter^-1) (ET-EC) conditions in Experiment 1. In Experiment 2, the ectomycorrhizal status was compared under ambient (395μl liter^-1 of CO₂) and elevated CO₂ (488μl liter^-1) (EC) conditions. The total ectomycorrhizal colonization and the dry weight of the plants significantly decreased under the ET and ET-EC conditions, indicating that the elevated temperature must be above the optimum for ectomycorrhizal colonization. Three ectomycorrhizal morphotypes, Cenococcum geophilum type, Type 12 and Type 40, showed relatively higher colonization under the ambient condition. Colonization of Type 12 significantly decreased, and that of Type 40 was completely prevented by the ET and ET-EC treatments, suggesting that colonization of these two morphotypes is sensitive to the elevated temperature. The ergosterol content in the fine roots significantly increased under the EC condition, suggesting that the ectomycorrhizal fungal mass was increased by CO₂ enrichment.