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在华北平原冬小麦/夏玉米轮作田进行了连续3年的涡度相关观测,对农田生态系统光能利用效率(LUE)及其影响因子进行分析。结果表明:农田生态系统的LUE季节变化明显。冬小麦田和夏玉米田的最大日平均LUE分别出现在4月中下旬和8月初。2003~2005年的季节平均LUE冬小麦田分别为0.8、1.2、1.0 gC.M J-1;夏玉米田分别为2.0、1.9、2.0 gC.M J-1。冬小麦田的LUE随叶面积指数(LAI)增加呈对数增长。在玉米田,营养生长阶段的LUE随LAI增加先增后降;生殖生长阶段的LUE随LAI减少线性降低。相同LAI下,玉米生殖生长阶段的LUE明显低于营养生长阶段。LAI大于4时,冬小麦田和夏玉米田的LUE均随光合有效辐射(PAR)的增加线性下降。夏玉米田LUE随饱和差(VPD)增加而降低,而冬小麦田LUE与VPD之间的关系不明显。
Three years of continuous eddy covariance analysis of winter wheat / summer maize rotation in the North China Plain was conducted to analyze the LUE and its influencing factors of farmland ecosystem. The results showed that the seasonal variation of LUE in farmland ecosystem was obvious. The maximum daily average LUE of winter wheat field and summer corn field appeared in late April and early August respectively. The seasonal average LUE winter wheat fields from 2003 to 2005 were 0.8, 1.2 and 1.0 gC.M J-1, respectively, and the summer maize fields were 2.0, 1.9 and 2.0 g C.M J-1, respectively. The LUE of winter wheat increased logarithmically with the increase of leaf area index (LAI). In maize field, the LUE of vegetative growth stage increased first and then decreased with the increase of LAI; LUE of reproductive growth stage decreased linearly with the decrease of LAI. Under the same LAI, LUE in maize reproductive growth stage was significantly lower than vegetative growth stage. The LUE of winter wheat and summer corn fields decreased linearly with the increase of photosynthetically available radiation (PAR) when LAI was greater than 4. LUE in summer maize fields decreased with increasing VPD, but the relationship between LUE and VPD in winter wheat was not obvious.