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

Abstract

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 (Ta), soil temperature (Ts), canopy radiation temperature (Tc) and carbon exchange of the wheat on daily and seasonal scales. The results showed that variations of both Tc and Ta 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 (Reco) against Ts on most of the measurement days were smaller than those against Ta or Tc, but the correlation coefficients for NEE, GPP and Reco against Ta and Tc showed no difference. On seasonal scale, the relationships between GPP, NEE, Reco and all the temperatures (Ta, Tc and Ts) showed a significant parabola-shape. Optimal temperature of Tc for photosynthesis was slightly lower than that of Ta, but the difference between the optimal Ta and Tc was only about 1℃. Relationship between Reco and Ta for the two-year measurement data was better than that with Ts, but correlation coefficients of Reco with Tc and Ta 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.