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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。
Forests play an important role in regulating greenhouse gas emissions. With the rapid development of plantations, their greenhouse gas flux and response to fertilizers have drawn more and more attention. In order to understand the effect of N application on soil greenhouse gas fluxes during growing and non-growing season, Eucalyptus urophylla plantation in Dongmen forest farm in Guangxi Province was set low (84.2 kg N · hm-2) and medium (166.8 kg N · hm-2 and 333.7 kg N · hm-2, respectively. The fluxes of CO2, N2O and CH4 in soil were monitored by static box-gas chromatography. The results showed as follows: (1) The annual average CO2, CH4 and N2O flux of Eucalyptus plantations with different nitrogen application rates were 214 ~ 271 mg CO2 · m-2 · h-1 and -47 ~ -37 kg CH4 · m, respectively -2 · h-1 and 16 ~ 203 kg N2O · m-2 · h-1. The flux of soil CO2 was higher in the growing season than in the non-growing season, and the seasonal fluxes of CH4 and N2O did not show obvious seasonal changes. (2) Nitrogen addition significantly increased the annual average fluxes of CO2 and N2O in soils, and its promotion effect mainly concentrated in the growing season (4-6 months after nitrogen application, ie, from June to September), and the effect was weakened with time. (3) Nitrogen application significantly reduced the annual net harvest of CH4 in soil. Therefore, on the basis of maintaining the productivity of Eucalyptus plantation, in combination with the seasonal changes, the reasonable control of N rate will help reduce the greenhouse gas emissions from Eucalyptus plantation.