【摘要】 利用地下气体原位采集系统-气相色谱法,周年监测休耕裸地与轮作菜地（茼蒿-空心菜-大青菜）7、15、30和50 cm土层N₂O浓度变化,旨在探究菜地土壤剖面N₂O扩散通量变化和净周转率.结果显示:菜地土壤剖面N₂O浓度呈现较大的时空变异性,轮作菜地7、15、30和50 cm土层N₂O平均浓度分别达到休耕裸地对应土层的1.9、8.7、9.2与26.7倍,0-30 cm土层土壤N₂O浓度随土层深度增加而增加,30-50 cm土层逐渐降低,表明氮肥施用显著促进了上层土体内N₂O的产生.休耕裸地与轮作菜地4个土层N₂O扩散通量（以N计）变幅分别为-354-420μg m^-2h^-1与482-1 510μg m^-2h^-1,其中休耕裸地30-50 cm土层N₂O扩散通量为负值,表明该土层N₂O以吸收为主.轮作菜地7-15 cm土层N₂O扩散通量最高为1 510μg m^-2h^-1,分别比0-7 cm、15-30 cm与30-50 cm高68.1%、2.5%与36.6%,表明7-30 cm为N₂O的主要产生位点.休耕裸地与轮作菜地0-15 cm土层间N₂O净周转率以负值为主,15-50 cm以正值为主,表明N₂O的周转在土壤剖面中层（7-30cm）最快.综上,N₂O浓度在土层中的分布情况为从上到下先增加后减少,主要产生位点于30 cm土层并从该层向其上下层扩散输送;结果可为菜地土壤N₂O产生位点的定位及其转化过程的研究提供参考.（图4表2参33）更多还原

【Abstract】 The concentrations of nitrous oxide（N₂O） at 7, 15, 30, and 50 cm soil depths under bare fallow, rotation vegetable field（rotation of Garland chrysanthemum-Tung choy-Bok choy） were monitored using a special in situ soil gas collection device and gas chromatography, to explore the production site, diffusion flux, and net turnover rate of N₂O in soil profiles.The results showed that the concentration profile of N₂O was dramatically spatially and temporally variable. Average N₂O concentration at depths of 7 cm, 15 cm, 30 cm, and 50 cm from rotation vegetable field were 1.9, 8.7, 9.2, and 26.7 times that in the corresponding soil layer from the bare fallow field, respectively. Average N₂O concentration increased with soil depth within the range of 0–30 cm soil layer, then decreased at the depth of 30–50 cm. These indicated that large nitrogen fertilizer application promoted N₂O production at the top soil layers. The diffusion fluxes ranged from-354 to 420 μg N m^-2h^-1 in bare fallow and 482 to 1 510 μg N m^-2h^-1 in rotation field, respectively. It was concluded that N₂O was mainly absorbed by soil at the 30–50 cm layer according to negative N₂O diffusion fluxes value at the same soil layer. The diffusion fluxes at the 7–15 cm layer in the rotation field, which was as high as 1 510 μg N m^-2h^-1, were higher by 68.1%, 2.5%, and 36.6% than those at 0–7 cm, 15–30 cm, and 30–50 cm soil layers, respectively. Therefore, the key site of N₂O production was at depths of 7–30 cm in the soil profile. Net N₂O turnover rates from bare fallow and rotation vegetable were negative at the 0–15 cm soil layer but positive at the 15–50 cm. It was concluded that the fastest N₂O turnover occurred in the middle layer of the soil profile（7–30 cm）. In conclusion, the distribution of N₂O concentration first increased and then decreased with the increase in N₂O concentration.N₂O was mainly produced at the depth of 30 cm and was diffused to ambient. These results could be used as references for understanding N₂O production sites and transformation process in vegetable field ecosystems.更多还原