【摘要】 在连续6 a耕作模式的基础上,利用静态箱-气相色谱法对常规耕作与免耕条件下小麦生育后期麦田CO2、CH4、N2O通量日变化进行了连续48 h观测,并确定1 d中最佳的观测时间。结果表明,常规耕作与免耕条件下小麦生育后期麦田CO2、CH4、N2O通量具有显著的日变化特征,常规耕作处理和免耕处理土壤表现为CH4的吸收汇、CO2、N2O的排放源。CH4日均吸收通量:常规耕作无秸秆还田处理(AC)>常规耕作秸秆还田处理(PC)>免耕(PZ);CO2日均排放通量:常规耕作秸秆还田处理(PC)>常规耕作无秸秆还田处理(AC)>免耕(PZ);N2O日均排放通量:常规耕作秸秆还田处理(PC)>常规耕作无秸秆还田处理(AC)>免耕(PZ)。相关性分析表明,常规耕作及免耕条件下CO2、CH4、N2O通量日变化与地表温度和5 cm地温呈极显著(P<0.01)或显著(P<0.05)的正相关关系,温度是决定温室气体日变化的主要决定因素。通过矫正系数和回归分析表明,在小麦生育后期(4—6月),CO2的最佳观测时间段在8:00—10:00,CH4为8:00—10:00,N2O为8:00—12:00。更多还原

【Abstract】 A study on diurnal variations of CO2,CH4 and N2O fluxes in the late growth stage of wheat under conventional tillage and no-tillage were conducted at the sixth year of a long term located experiment.The Gas Chromatography(GC),ascertained the optimal observation durations for CO2,N2O and CH4 fluxes were investigated for 48 hours using the Static-Chamber method.The results showed that the CO2,CH4 and N2O fluxes had significant diurnal variations under both conventional tillage and no-tillage treatments,which it might be a sink of CH4 but a source of N2O and CO2.The diurnal flux of CO2 emission peaked in PC 752.58 mg·m-2·h-1 at 12 p.m.,and the lowest value was AC 186.42 mg·m-2·h-1 at 2 a.m.;while the N2O peak fluxes of AC,PC and PZ presented were performed at 2 p.m.,4 p.m.,4 p.m.,respectively,and the peak fluxes values of AC,PC and PZ was 45.85 μg·m-2·h-1,41.89 μg·m-2·h-1,34.38 μg·m-2·h-1,respectively,however,N2O flux of AC decreased rapidly after 6 p.m.and presented the lowest value at 0 a.m.with 16.69 μg.m-2.h-1,but PC and PZ was at 4 a.m.,the similar trend was noted in CH4,but there were two flux peaks in a day,which observed at 2 p.m.and 0 a.m.,and the lowest flux observed at 6 a.m..The daily mean emission fluxes of CO2 was PC > AC > PZ,CH4 was AC > PC > PZ,but N2O was PC > AC > PZ.There were highly significant(P<0.01) or significant(P<0.05) positive correlations between gas fluxes and land surface temperature or soil temperature of 5cm depth under conventional tillage and no-tillage systems,and the temperature might be a crucial factor in diurnal variation.The percentage of CO2,N2O and CH4 fluxes in daily showed that CO2,N2O and CH4 fluxes in daytime was 74%,66% and 61%,respectively,further,the ratio between daytime and night presented that CO2 was 3 to 1,N2O was 3 to 2 and CH4 was 2 to 1,there are significant fluxes difference between each gases.In order to make sure the optimal observation duration for this periods and areas,we calculated the correction coefficient and regression analysis between the observation duration and the daily total fluxes of three gases,which showed that the correction coefficient of CO2 flux on the verge of 1 from 8 a.m.to 10 a.m.,and the related coefficient was 0.8175(P<0.01),it′s showed that this time period significantly represented daily mean flux of CO2 or it was the optimal observation duration for CO2 collection in this period and area.The optimal observation duration for N2O was 10 a.m.to 12 a.m.and the related coefficient was 0.7642(P<0.05),but two values for CH4 were 8 a.m.to 10 a.m.and 0.8396(P<0.01),respectively,which correspondingly presented the representative emission flux of a day and was the optimal observation duration of the late growth stage of wheat for greenhouse gases in this area.更多还原