Carbon flux dynamics and its environmental controlling factors in a desert steppe

Net ecosystem carbon dioxide exchange (NEE) above a desert steppe in Inner Mongolia was measured with eddy covariance technique in growing season of 2008. Environmental factors were also observed during the same period. Our results show that the minimum of growing season daily cumulative NEE appeared on August 26 (−1.6 g Cm−2), while the maximum appeared on June 11 (0.9 g Cm−2). Monthly cumulative NEE distributed in the growing season unevenly. The minimum of monthly cumulative NEE appeared in June (0.74 g Cm−2); the maximum appeared in September (−14.94 g Cm−2). The sum of the growing season NEE was −45.5 g Cm−2. The most important environmental factor affecting the half-hour average NEE was photosynthetically active radiation. The most important environmental factor affecting the daily cumulative NEE was 20–30 cm soil water content.