The photosynthetic response of four seral deciduous broad-leaved tree seedlings grown under elevated CO2 concentrations

To test the relationship between successional traits and photosynthetic response to elevated CO2, we evaluated the photosynthetic and biochemical traits in the leaves of four deciduous broad-leaved tree species with different successional traits grown under ambient (370 mu mol mol(-1)) and elevated (720 mu mol mol(-1)) CO2 concentrations (CO2). All four seedlings showed photosynthetic downward regulation, which is characterized by successional type-specific differences. In the mid-successional tree species, Magnolia hyporeuca Siebold et Zucc., both stomatal factors; stomatal conductance (gs) and stomatal limitation (Is) and non-stomatal factors; maximum carboxylation rate of RuBP ( V-cmax), leaf nitrogen content (N-area), leaf mass per area (LMA) are affected, but in the mid-successional tree species, Quercus mongolica Fischer ex Ledeb. var. crispula (Blume) Ohashi, and the two late successional tree species, Prunus ssiori F. Schmidt and Carpinus cordata Blume, non-stomatal factors are affected by the photosynthetic rates. The decrement of N-area and increment of LMA imply the accumulation of photosynthates in the leaves and the dilution of nitrogen. The accumulated photosynthates and the dilution of nitrogen affected the photosynthetic response of the studied species to elevated CO2. The results suggested that tree species with different successional traits show different stomatal and non-stomatal responses to elevated CO2.