Carbon Dioxide Exchange in an Irrigated Agricultural Field within an Oasis, Northwest China

Continuous eddy covariance measurements of CO2, water vapor, and heat fluxes were obtained from a maize field within an oasis in northwest China from 1 May 2008 to 30 April 2009. The experimental setup used was shown to provide reliable flux estimates on the basis of cross-checks made using various quality tests of the flux data. Results show that the highest half-hourly CO2 fluxes (Fc) were −55.7 and 6.9 μmol m−2 s−1 during the growing and nongrowing seasons, respectively. The daily net ecosystem exchange of carbon (NEE) ranged from −14.7 to 2.2 g C m−2 day−1 during the growing season; however, the daily NEE fell to between 0.2 and 2.1 g C m−2 day−1 during the nongrowing season. The annual NEE calculated by integrating flux measurements and filling in missing and spurious data was about −487.9 g C m−2. The total NEE during the growing season (−692.9 g C m−2) and the annual NEE were in the middle of the range, when compared with results obtained for maize fields in different studies and regions, w...