中文摘要：

基于东北地区玉米生态系统土壤呼吸连续2个生长季的观测，阐明了土壤呼吸日、季节变化特征，综合分析了水热因子、土壤性质、生物量及叶面积指数（LAI）对土壤呼吸的影响。结果表明：玉米地土壤呼吸日变化为不对称的单峰型曲线，最小值和最大值分别出现在6：00-7：00和13：00左右。2005年玉米生长季土壤呼吸速率均值为3．16μmol CO2·m^-2·s^-1，最大值为4．77μmol CO2·m^-2·s^-1，出现在7月28日；最小值为1．31μmol CO2·m^-2·s^-1，出现在5月4日。统计分析表明：土壤温度是玉米生态系统土壤呼吸日变化的驱动因素；土壤温度和土壤水分是影响土壤呼吸季节变化的关键因素，二者可以解释玉米生长季土壤呼吸时间变异的87％；LAI和根系生物量与土壤呼吸速率呈正相关，说明生物因子对土壤呼吸季节变化也有影响；土壤有机质、全氮和碳氮比等土壤理化特性与土壤呼吸速率的关系较弱；玉米生长季追施氮肥明显促进土壤呼吸速率。

英文摘要：

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^-1·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 respira- tion 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.