Seasonal variation of CO2 flux and its environmental factors in evergreen coniferous plantation

The effects of environmental factors on carbon flux were analyzed, the spatial and temporal variation of carbon flux was studied at the two heights of 23 m and 39 m with the eddy covariance technique, and the carbon budget was evaluated for evergreen coniferous plantation in the red earth hilly area during the year 2003. The results showed that photosynthetically active radiation (PAR) and soil temperature are essential factors strongly affecting the net ecosystem exchange (NEE); in the daytime, the response of NEE to PAR shows a rectangular hyperbola trend, and in the nighttime, the significant correlation was observed between soil temperature and soil respiration which was filtered using friction velocity. This ecosystem appeared as a carbon sink along the whole year of 2003, and the carbon flux showed the obvious seasonal fluctuation and diurnal variability. The seasonal peak of NEE occurred in May and June with the daily sum about 0.61-0.67 mg ·CO2 ·m-2·s-1. For the severe drought in the mid-summe