[Effects of Canopy Temperature on Carbon Dioxide Exchange of Winter Wheat in Taiyuan Basin].

We measured daily changes of carbon dioxide exchange in a winter wheat site in Taiyuan basin using chamber method for two years and analyzed relationships between environmental factors affecting carbon exchange of the wheat, including air temperature (), soil temperature (), canopy radiation temperature () and carbon exchange of the wheat on daily and seasonal scales. The results showed that variations of both and on daily and seasonal scales were consistent with a correlation coefficient of above 0.90. On daily scale, the correlation coefficients of NEE, gross primary productivity (GPP) and ecosystem respiration () against on most of the measurement days were smaller than those against or , but the correlation coefficients for NEE, GPP and against and showed no difference. On seasonal scale, the relationships between GPP, NEE, and all the temperatures (, and ) showed a significant parabola-shape. Optimal temperature of for photosynthesis was slightly lower than that of , but the difference between the optimal and was only about 1℃. Relationship between and for the two-year measurement data was better than that with , but correlation coefficients of with and had nearly no difference ranging from 0.95 to 0.96. Our results could give some implications for ecosystem carbon exchange estimation with remote sensing method based on canopy temperature.