Abstract: To reveal CO2 environmental characteristic in super-span plastic covered tunnel greenhouse,the temporal and spatial variation of CO2 concentration in the greenhouse with cucumber was tested and the relationship between CO2 concentration and leaf area index(LAI),photosynthesis rates and soil respiration rates was analyzed.The results showed that CO2 concentration reached maximum level during 7:00-8:00 and decreased to minimum during 12:00-14:00 in one day.The variation of CO2 concentration was wider in sunny day comparing with that in cloudy day.Photosynthesis consumption CO2 rates was higher than soil respiration release CO2 rates during 8:00-15:00 at fruit stage,and CO2 concentration was kept at 293～330μL·L-1 level by ventilation.The vertical distribution of CO2 concentration was the ground>the middle>the canopy.The horizontal distribution was the eastthe middle>the west during 14:00-16:00.The seasonal change of CO2 concentrations were affected by LAI,canopy photosynthesis rates and soil respiration rates.The linear regression equation between average decreasing rates of CO2 concentration and LAI was y=78.468x+48.694 in sunny day and y=54.358x+18.322 in cloudy day.

Key words: Super-span plastic covered tunnel greenhouse, Super-span plastic covered tunnel greenhouse, CO2 concentration, Leaf area index, Soil respiration rates