The increase of atmospheric carbon dioxide (CO 2 ) and tropospheric ozone (O 3 ) concentrations has affected forest ecosystems both above and below ground. A high dose of O 3 alters stomatal function and accelerates foliar senescence, which lead to changes in assimilation and water use efficiency. Consequently, biomass production and plant growth are suppressed by elevated levels of O 3 . In contrast, elevated CO 2 ameliorates these responses of plants to high O 3 via stomatal closure. The

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... ul effect of O 3 on above ground is indirectly linked with below-ground. Importantly, the fine root dynamics and the relationship with symbiotic fungi are significantly influenced. However, the effects of such a changing environment on forest rhizosphere are still poorly understood. The aim of this study is to analyze the combination effect of CO 2 and O 3 on tree roots and ectomycorrhizae. In particular, we summarize and discuss 1) the response of ectomycorrhizal symbionts (colonization rate, community composition, richness, and diversity) under these environmental stresses; and 2) the root dynamics under elevated CO 2 and O 3 concentrations, along with current methodologies used for root sampling.