2015 Volume 71 Issue 3 Pages 174-184
We examined the effects of elevated CO2 (eCO2) on the growth and photosynthetic responses of deciduous trees using a Free Air CO2 Enrichment (FACE). In the FACE, photosynthesis was down-regulated in several trees but not in alder. Except alder, the leaf nitrogen concentration decreased in eCO2. Alder underwent symbiosis with N-fixing micro-organisms (Frankia sp.) in roots, which act as a sink of photosynthates. Leaves of alder had intensively been grazed by leaf beetles in eCO2, due to the enhanced leaf N concentration; grazed leaves died later. The leaf area index was initially increased by eCO2, but this increment minimized over time, as it was found in other FACE systems in global. The light compensation point of the light-photosynthetic curves declined, with an increase in the initial slope of the curve. In eCO2, the stomatal conductance of most species decreased and the photosynthetic water use efficiency (PWUE) increased. We expected the eCO2-induced increase in the PWUE being accompanied by smaller size and density of the vessels. However, in eCO2, the vessel size of petioles and current shoots decreased without evident anatomical changes. We conclude that the whole plant physiology must be studied in order to provide insight into further changes.