箱体结构及计算方法对夏玉米农田N2O排放测定结果的影响

为探讨不同箱体结构及计算方法对夏玉米农田N_2O排放测量结果的影响,于2012—2013年在中国农业大学曲周实验站采用静态箱-气相色谱法研究了4个处理在夏玉米季N_2O排放结果,即大箱+直线算法、小箱+直线算法、大箱+曲线并直线算法及小箱+曲线并直线算法。小箱顶部中央留孔使玉米茎能够通过采样箱顶部而不影响玉米生长,大箱在玉米生长到50 cm以后压弯玉米植株。研究表明:在定量夏玉米农田土壤N_2O排放时,与不破坏玉米根系正常生长的小箱测定结果相比,因使用大箱并压弯玉米造成玉米生长不良,不会显著影响N_2O累积排放量的测定结果。在N_2O日排放通量较强时,曲线并直线算法与直线算法得到的结果没有显著差异;而在N_2O日排放通量较弱时,曲线并直线算法测定结果高于直线算法。由于N_2O排放较弱时的通量对夏玉米季农田N_2O累积排放量贡献很小,因此,曲线并直线和直线算法在计算夏玉米季农田N_2O累积排放量时并无显著差异。

Effects of chamber size and calculation method on N2O emissions during the summer maize growing season

Chamber sizes and calculation methods may significantly affect the measurement results for N₂O emissions in terrestrial ecosystems when the static chamber method is used. This study compared the N₂O emissions of summer maize growing season on the North China Plain under four treatments regarding different chamber sizes and calculation methods, i.e., big chamber+linear model, small chamber+linear model, big chamber+quadratic/linear model, and small chamber+quadratic/linear model. N₂O fluxes were measured by the static chamber-gas chromatograph method. When the big chamber(hampering the growth of maize) was compared with the small chamber(no destructive effect on maize growth), the results showed that the use of the big chamber had no significant effect on the total cumulative N₂O emissions across the whole maize growth season. The daily N₂O flux calculated by the quadratic/linear model was not significantly difference with that by the linear model when the daily N₂O flux was high. However, the daily N₂O flux calculated by the quadratic/linear model was higher than the flux calculated by the linear model when the daily N₂O flux was relatively low. As the N₂O emissions within the low N₂O flux events only made a small contribution to total cumulative N₂O emissions of whole summer maize season, no significant differences were observed in total cumulative N₂O emissions between the quadratic/linear model and the linear model.