Abstract: The ecophysiological effects of doubled CO₂ concentration on Legmus chinensis which is a good herbagae in grasslands were studied.The results showed that doubled CO₂ concentration could promote the physiological process of Leymus chinensis,such as:increassing net-photosynthesis rate and water use ratio and reducing water loss of leaf. It specifically showed that the stomatal resistance increased 4% to 13%, the transpiration rate reduced 6% to 13%, the Net-photosynthesis rate increased 49% to 87%,and the water use efficiency increased 65% to 101%. This kind of increase trend could continuously appear in every phenological period. This indicated that the Net-photosynthesis rate of the Leymus chinens is did not produce downward“acclimation”under high concentration of CO₂ within a vegetative season. Doubled CO₂ concentration made the physiological process active and accelerated its phenological couse as well. The changes of physiological and biological characteristics mentioned above were mutually affected and promoted. Doubled CO₂ concentration increased the biomass of the Leymus chinensis. Dry matter weight above ground increased 10.4% to 23.2%, the root increased 48.4%. Root/shoot ratio is obviously increased. In general, the physiological effect of doubled CO₂ concentration on the Leymus chinensis was positive and could increase bioproductivity.

Key words: ecosystem services, ecosystem services supply, ecosystem services consumption, human well-being.