Annual Cycle of Heat and CO_2 Fluxes Over an Artificial Rice Wetland in the Liaohe Delta of China

摘要

Seasonal variations in sensible heat flux (H_s), latent heat flux (LE), and carbon dioxide flux (F_c) during 2005 over an artificial rice wetland in the Liaohe Delta, Northeast China, were investigated using the eddy covariance (EC) technique. The results show that H_s is relatively larger (>200 W m~(-2)) in spring, whereas LE is relatively larger in summer and autumn (>500 W m~(-2)). F_c depends strongly on the status of the crops and mostly reaches about -2.0 mg CO_2 m~(-2) s~(-1) at daytime from June to September but varies around zero in the other months. CO_2 concentration is in the range of 300-500 ppm and varies similarly with F_c from June to September. The largest negative F_c values usually occur at mid-day, with values of -0.6 mg CO_2 m~(-2) s~(-1) during the early growth stage (5-8 June), -1.8 mg CO_2 m~(-2) s~(-1) during the middle growth stage (17-20 July), and approximately -0.2 to 0.3 mg CO_2 m~(-2) s~(-1) during the late growth stage (19-22 September). The cumulative CO_2 flux during 2005 was estimated to be -1570 g CO_2 m~(-2) year~(-1), which suggests that the rice wetland in Panjin acts as a large CO_2 sink.