中文摘要：

森林在调控温室气体排放方面有重要作用,随着人工林的迅速发展,其温室气体通量和对施肥的响应逐渐引起广泛关注。为了解施氮对桉树人工林生长季和非生长季土壤温室气体通量的影响,在广西东门林场尾巨桉人工林样地设置低（84.2 kg N·hm-2）、中（166.8 kg N·hm-2）、高（333.7 kg N·hm-2）3个施氮水平和不施氮对照,采用静态箱-气相色谱法监测土壤CO2、N2O和CH4通量。结果表明：（1）不同施氮处理的桉树人工林土壤CO2、CH4和N2O年均排放通量分别为214~271 mg CO2·m-2·h-1、-47~-37 kg CH4·m-2·h-1和16~203 kg N2O·m-2·h-1;土壤CO2排放通量在生长季高于非生长季,CH4和N2O通量未表现出明显季节变化。（2）施氮显著增加了土壤CO2和N2O年均排放通量,其促进效应主要集中在生长季（施氮后的4个月,即6—9月）,且随时间增加,效应减弱。（3）施氮显著降低了土壤CH4年均吸收通量。因此,在维持桉树人工林生产力的基础上,结合季节变化,合理调控施氮量将有助于减少桉树林土壤温室气体排放。

英文摘要：

Forests play a key role in regulating greenhouse gas fluxes. With the increasing of plantation area, much attention has been paid to greenhouse gas flux and its response to fertiliza- tion. In order to identify the effects of nitrogen fertilization on the greenhouse gas fluxes of soil- atmosphere interface in growing and non-growing seasons in Eucalyptus plantations, low, middle and high nitrogen fertilization treatments （84.2, 166.8 and 333.7 kg N · hm-2） and no fertiliza- tion （control） were established in Eucalyptus plantations in Guangxi, southern China. Green- house gas fluxes of soil-atmosphere interface were measured by using the static chamber-gas chro- matograph method. The results showed that the annual mean fluxes of CO2, CH4 and N2O were 214-271 mg CO2 · m-2 · h-1 , -47--37 kg CH4 ~ m-2 · h-1 and 16-203 kg N2O · m-2 · h-1 in Eucalyptus plantations, respectively. The fluxes of soil CO2 emission were higher in growing sea- son than in non-growing season, but no significant seasonal variations were observed for the fluxes of CH4 and N2O. Nitrogen fertilization significantly increased the annual mean fluxes of soil CO2 and N2O emission, especially in the growing season （April to September）. The annual mean flu- xes of soil CH4 uptake showed a decreased trend with nitrogen fertilization, which suggested soil CH4 uptake was inhibited by nitrogen fertilization. Our results suggested that reasonable nitrogen fertilization according to the seasonal variation of greenhouse gas emission should not be neglected for decreasing soil greenhouse gas emission in Eucalyptus plantations.