Changes in growth, photosynthetic parameters, carbon and nitrogen uptake of Pinus densiflora S. et Z. under elevated temperature and CO2 level

The effects of two (25 and 30oC) temperature setting and CO2 (400 and 800 ppm) levels on growth, photosynthetic parameters, and carbon and nitrogen uptake of one-year-old Pinus densiflora S. et Z. were investigated in order to obtain information on the acclimation of forest tree species to elevated temperature and CO2 concentration. Relative growth rate (RGR) of height at the same CO2 level was higher in plants grown at higher temperature (30oC), and RGR of root collar diameter at the same temperature was increased by elevated CO2 (800 μmol CO2 mol-1 air). In addition, dry matter yield was enhanced under higher temperature and CO2 level, and the increase of shoot/root ratio was observed under higher temperature but not at higher CO2 level. Photosynthetic rates measured at 400 and 800 μmol CO2 mol-1 air were not affected by elevated temperature and CO2. However, stomatal conductance and transpiration rate increased with elevated temperature and CO2, whereas carboxylation efficiency and photorespiration rate were reduced by elevated temperature. Total carbon and nitrogen uptake increased with elevated temperature regardless of CO2 level. Shoot/root ratio of carbon uptake increased by elevated CO2 regardless of temperature level. In conclusion, the elevated temperature and CO2 level increased dry matter and carbon uptake without the changes of photosynthetic rate, but the increase of carbon uptake in the needles led to a source/sink imbalance.