Abstract: The study of soil respiration under different crops is important to the carbon cycle research in the agro ecosystem. In this study, soil respiration of mung bean (Vigna radiate L.) field and maize (Zea mays L.) field in hilly area of North China were measured during the growing period of July-October 2006 based on the IRGA technique. The diurnal and seasonal variations of soil respiration at two agro ecosystems were analyzed. The results showed that the overall soil respiration rate of mung bean field was 2.11μmol·m-2·s-1, larger than 1.90μmol·m-2·s-1 at maize field significantly.There were significant seasonal variations of soil respiration at two agro ecosystems, and the amplitude changes in maize field was larger than in the mung bean field. The maximum respiration rates of maize and mung bean cropland both occurred at August 9. Statistic analysis showed soil temperature was the dominant environmental factor affecting the seasonal variation of soil respiration. Moreover, both the vant Hoff model and Arrhenius model satisfactorily described the soil respiration as a function of soil temperature at the two systems with R2 more than 0.73. No significant correlation between soil respiration and soil water content was found. The temperature sensitivity of soil respiration (Q10) was 3.31 and 2.16 for the maize and mung bean field, respectively. The Arrhenius model present a better performance than the vant Hoff model, and the soil activation energy in the maize field (79.41kJ·mol-1) was larger than in the mung bean field (55.72kJ·mol-1).

Key words: Soil respiration, Mung bean, Maize, Hilly area