MEASUREMENTS OF CO₂ FLUXES OVER TWO DIFFERENT UNDERLYING SURFACES IN AN AGRICULTURAL ECOSYSTEMOVER LOWER BASINS OF THE YANGTZE

In order to better understand the regional climate change, it is necessary to quantify the CO₂ flux over agricultural ecosystem. CO₂ fluxes are collected directly by using eddy covariance over a rice paddy in the summer of 2001 and over an inhomogeneous crop surface in the summer of 2002 respectively. On average, daytime absorption and nighttime release of CO₂ flux by the rice paddy are 55.16 g· m^-2·d^-1and 14.19 g·m^-2·d^-1, and by the inhomogeneous crop surface are 22.67 g·m^-2·d^-1and 12.40 g·m^-2·d^-1. Rice paddy and the inhomogeneous crop surface are sinks of atmospheric CO₂. China is a great agricultural country, increasing the area of rice paddy will help CO₂ deposition, and will slow down increase of atmospheric CO₂ and greenhouse effect. In addition, the relationship between daytime absorption of CO₂ flux and Photosynthetically-active radiation is investigated for the rice paddy, and resulting a negative correlation. Hopefully the results obtained in present work will provide an important basis for numerical modeling of CO₂ flux between atmosphere and land。