[Photosynthetic characteristics of three tree species seedlings in Changbai Mountain under different CO2...

The photosynthetic characteristics of three-year-old seedlings of coniferous Pinus koraiensis and Pinus sylvestriformis and broadleaf Fraxinus mandshurica in open-top chambers in Changbai Mountain were studied. Seedlings were planted at four different conditions respectively:elevated CO2 concentration(700 and 500 mumol.mol-1) and ambient CO2 concentration (control chamber and in open field). After treating of two growing seasons in the first two years, seedlings were continuously grown under different CO2 concentration for another eight weeks. The results indicated that the photosynthetic capacity of three species was enhanced under high CO2 concentration in the first two growing seasons. The maximum net photosynthetic rates and light response parameters of different tree species were different at the same CO2 concentration. No photosynthetic acclimation was observed in the third growing season except Pinus sylvestriformis seedlings grown under 500 mumol.mol-1 CO2. The increase or decrease of net photosynthetic rates and light response parameters were related to the time of CO2 treatment. Elevated CO2 concentration could alter the ability of utilizing strong light and low light of seedlings.