We predicted physiological and anatomical adjustment of deciduous broadleaved trees to increasing atmospheric CO2 [CO2] with use of FACE (Free Air CO2 Enrichment). To investigate physiological adjustment, we grew 3-year-old saplings of alder and two birches for 2 years. We evaluated the responses in two soils: infertile and immature volcanic ash (VA) soil, and fertile brown forest (BF) soil at two [CO2] levels (500 vs. 370ppm). For white birch, photosynthetic down-regulation occurred in both soils. For alder, down-regulation occurred only in BF soil because of the accumulation of starch in foliage, which restricts CO2. In contrast, symbiotic microbes to alder at VA act as a large carbon sink, which may be attributed to no down-regulation. High [CO2] generally decrease transpiration and stomatal conductance (gs). To determine this, sun and shade leaves of diffuse-porous birch and ring-porous oak grown on BF or VA were studied. Regardless of species and soil type, elevated [CO2] consistently decreased water flow (i.e. gs and leaf-specific hydraulic conductivity) and total vessel area of the petiole in sun leaves; however, it had no effect in shade leaves, perhaps because gs of shade leaves was already low. Changes in water flow at elevated [CO2] were associated with changes in petiole hydraulic properties