Abstract: Based on the continuous measurement of soil respiration in a maize field in Northeast China during maize growth seasons in 2004 and 2005, the temporal variation of soil respiration was studied, with the effects of heat and water factors, soil properties, root biomass, and leaf area index (LAI) analyzed. The diurnal variation of soil respiration showed an asymmetric pattern, with the minimum appeared at 6:00-7:00 and the maximum at 13:00.There was a great fluctuation of soil respiration during the growth season in 2005. The mean soil respiration rate was 3.16 μmol CO₂·m^-2·s^-1, with a maximum of 4.77 μmol CO₂·m^-2·s^-1 on July 28 and a minimum of 1.31 μmol CO₂·m^-2·s^-1 on May 4. Statistic analysis showed that soil temperature was the driving factor to the diurnal variation of soil respiration. Soil temperature and soil moisture were the dominant environmental factors affecting the seasonal variation of soil respiration, and explained 87% of its variability. LAI and root biomass were positively related to soil respiration rate, indicating that biotic factors also affected the seasonal variation of soil respiration. However, soil properties such as soil organic content, total nitrogen content, and C/N ratio had poor correlations with soil respiration. Top-dressing nitrogen fertilizer increased soil respiration significantly.

Key words: Nitrogen mineralization, Land use pattern, Human disturbance