| Abstract: | Net photosynthetic rates (NPRs) of four species seedlings, Pinus koraiensis, Pinus sylvestriformis,Fraxinus mandshurica and Phellodendron amurense, were measured at different CO2 concentrations and time respectively in Changbai Mountain during the growing season in 1999. The seedlings were cultivated in open-top chambers (OTCs), located outdoors and exposed to natural sunlight. The experimental objects were divided into four groups by tree species. CO2 concentrations in chambers were kept at 500 μL·L-1 and 700 μL·L -1 and contrast chamber and contrast field were set. The results showed that the effects of elevated CO2 on NPR of the trees strongly depended on tree species and time NPRs of Pinus koreainsis and Pinus sylvestriformis seedlings increased with the rising of CO2 concentration, while that of Phellodendron amurense and Fraxinus mandshurica increased at some time and decreased at another time. |
