中文摘要：

生态系统呼吸在陆地生态系统碳循环中占有重要地位，是碳循环中仅次于生态系统总初级生产力的第二大通量组分。除温度和水分外，生物因子对生态系统呼吸也有着重要的影响。生物因子往往与温度、水分有着相似的季节变化，并且温度还对这些因子有重要的影响，这加深了探讨生物因子对生态系统呼吸影响的难度。复种农田生态系统中生物因子与气象因子季节变化的非同步性为探讨生物因素对生态系统呼吸时间变异的影响提供了有利条件。利用华北平原冬小麦-夏玉米复种农田LAI的季节动态与温度的季节动态存在非同步性这一天然试验条件，本研究通过该农田生态系统连续两年的涡度相关通量观测数据，分析了温度和生物因子对该农田生态系统呼吸季节及年际变化的影响。结果表明，在冬小麦和夏玉米的各个生育阶段，其夜间生态系统呼吸都受到土壤温度的影响，但是这种影响在作物不同的生育阶段有所差异，尤其当土壤温度与叶面积指数（LAI）的季节变化非同步时，LAI会改变土壤温度对生态系统呼吸的控制。基于直线回归方程，LAI能分别解释2003年和2004年冬小麦生态系统参考呼吸（10℃下的生态系统呼吸速率）变异的97％和74％，能分别解释夏玉米生态系统参考呼吸变异的85％和42％。华北平原冬小麦-夏玉米复种农田的生态系统呼吸呈“双峰”季节动态模式，且与生态系统总初级生产力及LAI的季节动态模式相一致，两次峰值分别出现在冬小麦的LAI和夏玉米的LAI达到最大时。冬小麦农田生态系统呼吸的最大值在2003年和2004年分别为6．6gC／（m^2·d）和5．5gC／（m^2·d），夏玉米农田生态系统呼吸的最大值在2003年和2004年分别为7．7gC／（m^2·d）和6．9gC／（m^2·d）。冬小麦农田生态系统在2003年和2004年2个生育期的总呼吸量分别为402g

英文摘要：

The ecosystem respiration （Rc）, following gross primary productivity, is the second largest carbon flux in global carbon cycle. More and more studies indicate that biotic factors （e.g. LAI）, besides temperature and moisture, are expected as key factors in determining the seasonal distribution of R, which reflects the ecophysiological process of plant such as capacity of photosynthesis and photosynthetic substrate supply for R,. Such influence, however, is difficult to be quantified due to the in-phase of seasonal patterns of biotic factors and temperature, as well as the important effect of temperature on biotic factors. The asynchronism in the seasonal distributions of temperature and LAI of winter wheat-summer maize double agroecosystem in the North China Plain enables us to study the influences of biotic factors on Rc. In this study, the influences of temperature and biotic factors on the seasonal and interannual variations of ecosystem respiration （Rc） of a winter wheat-summer maize double agroecosystem were analyzed by using 2 years＇ continuous data from eddy covariance measurements. The results showed that nighttime Rc was influenced by soil temperature across different growing periods of winter wheat and summer maize, but such influences were altered when seasonal trend of LAI was asynchronous with temperature. LAI explained 97% and 74% of the variability in R, at a given soil temperature （Rref） of winter wheat and explained 85% and 42% of the variability of Rref of summer maize in 2003 and 2004, respectively. The seasonal trend of daily R, was highly correlated with LAI and gross ecosystem productivity, and daily R, reached its two peaks when the LAI reached its maximum for winter wheat and summer maize, respectively. The maximum daily Rc of winter wheat was 6.6 gC/（m^2· d） in 2003 and 5.5 gC/（m^2· d） in 2004. The maximum daily R, for summer maize was 7.7 and 6.9 gC/（m^2. d） in 2003 and 2004, respectively. The cumulative R, of winter wheat during the two growth periods in 2