Abstract: By using LI-8100 and LI-6400-09, the soil CO₂ flux of a winter wheat field in North China Plain was determined from April to June 2008, with its change patterns and affecting factors analyzed. The soil respiration had a single peak diurnal variation, with the maximum at 12:30-14:30 and the minimum at 5:00-6:30, and the respiration rate was higher in sunny days than in cloudy or overcast days. There was a significant negative correlation between the CO₂ concentrations at all canopy heights and the soil respiration rate at daytime, but a significant positive correlation at night. The soil respiration rate presented a seasonal variation similar to the soil temperature at 5 cm depth, and had a significant exponential relationship with the soil temperature. Significant correlation was also found between the soil respiration rate and soil humidity when the soil moisture content was within the range of field capacity. Soil humidity less than 30% would limit the soil respiration, inducing a decrease of soil CO₂ flux. A multiple exponential regression model of soil temperature and moisture could better explain the variation of soil respiration, especially when the soil temperature was below 15 ℃.

Key words: Landscape pattern, Landscape changes, Driving force, Shenzhen