施肥与不施肥措施下小麦田的CO2、CH4、N2O排放日变化特征

二氧化碳（CO2）、甲烷（CH4）、氧化亚氮（N2O）是对全球气候变化影响最大的温室气体。由于土壤与大气之间的水热交换需要一定的传导平衡时间，因此土壤温室气体与温湿度之间的关系存在不同的表现形式。目前，有关温室气体研究多集中于季节性排放特征，而关于CO2、CH4、N2O的日变化研究却少见报道。以北京小麦（Triticum aestivuml）农田土壤为研究对象，对施肥和不施肥条件下CO2、CH4、N2O交换通量和气温、土壤温度进行连续观测，来探讨3种温室气体的日变化特征。采用人工静态暗箱法对小麦田土壤进行连续48 h原位观测，每2 h测定1次，每次盖箱时间为30 min。气体样品中的CO2、CH4、N2O用气相色谱仪（Agilent 6890A，FID/ECD）测定。结果表明：施肥与不施肥条件下小麦生育后期麦田土壤CO2、CH4、N2O交换通量具有明显的日变化特征。土壤表现为CH4的吸收汇、CO2和N2O的排放源。CH4的吸收通量、CO2和N2O的排放通量均表现为施肥区＞对照区。CO2、CH4的交换通量的70%以上出现在白天，而施肥区和对照区的N2O白天排放通量分别达到全天的81.8%、91.1%。另外，相关性分析表明，CO2、N2O交换通量的日变化与气温和5 cm地温呈极显著（P＜0.01）或显著（P＜0.05）的正相关关系，且N2O交换通量日变化与10 cm地温呈现极显著的正相关关系，说明温度是影响CO2、N2O交换通量日变化的重要因素；而气温、5 cm地温、10 cm地温对CH4交换通量日变化不存在显著性影响。

Diurnal variations of CO2, CH4 and N2O fluxes from wheat land under the treatments of fertilization and no-fertilization

CO2, CH4 and N2O are the most important greenhouse gases on global climate change. Since water-heat exchange between the soil and the atmosphere requires a certain time, there are different relationships between greenhouse gases and soil parameters,such as the temperature and humidity. Currently, researchers have concentrated in the studies of seasonal variations of greenhouse gas emissions, while diurnal variations were rarely reported. This study was conducted to investigate diurnal variations of CO2, CH4 and N2O fluxes in the late growth stage of wheat （Triticum aestivuml） under conventional fertilization and no-fertilization treatments from wheat land in Beijing. In this study, artificial static chamber method was used for investigating CO2, CH4 and N2O fluxes in situ continuously for 48 hours. The samples were collected every two hours and each time lasted 30 minutes. CO2, CH4 and N2O were determined by gas chromatography （Agilent 6890A, FID, ECD）, atmospheric temperature and soil temperature were also measured. The results showed that CO2, CH4 and N2O fluxes had obvious diurnal variation tracks. Wheat land soil might be a sink of CH4 but a source of N2O and CO2. The daily mean fluxes of CO2, CH4 and N2O after fertilization were higher than those without fertilization. More than seventy percents of the fluxes of CO2, CH4 occurred in daytime. The N2O emission fluxes under both fertilization and no-fertilization treatments during the daytime reached 81.8% and 91.1%respectively.There were highly significant （P〈0.01） or significant （P〈0.05） positive correlations between CO2 fluxes and atmospheric temperature, soil temperature of 5 cm depth. Also there were highly significant （P〈0.01 ） positive correlations between N2O fluxes and soil temperature of 10 cm depth, thus the temperature might be a crucial factor in diurnal variations of CO2 and N2O fluxes.However, atmospheric temperature, soil temperature of 5 cm and 10 cm depth didnt impact CH4 fluxes significantly.