鼎湖山针阔叶混交林地表温室气体排放的日变化

Diurnal variations of fluxes of the greenhouse gases from a coniferous and broad-leaved mixed forest soil in Dinghushan

利用静态箱 -气相色谱法对鼎湖山针阔叶混交林地表 3种温室气体 CO2 、CH4 、N2 O通量进行了原位观测 .结果表明 ,鼎湖山针阔叶混交林地表为 CO2 、N2 O的排放源 ,为 CH4 的弱汇 ,通量日变幅分别是 4 88.99～ 70 0 .5 7,0 .0 4 9～ 0 .10 8mg/ (m2· h)和- 0 .0 2 5～ - 0 .0 5 3mg/ (m2 · h) ;地表凋落物分解释放 CO2 约占总排放的 1/ 3;凋落物层和林下灌木对 CH4 和 N2 O的通量无明显影响 ;CO2 、N2 O的 9∶ 0

The subtropical coniferous and broad-leaved mixed forest, a typical successional monsoon forest, is one of the major forests in the Subtropics in China. Therefore, it is very important to estimate the fluxes of the greenhouse gases from the forest soil in order to evaluate the impact of subtropical forests on the greenhouse gases emission/uptake. This study investigated the diurnal variations of fluxes of three greenhouse gases: CO_2、CH_4、N_2O from the coniferous and broad-leaved mixed forest soil. Static chamber-gas chromatograph technique was used to measure the fluxes of these greenhouse gases. By using the improved gas chromatography sampling system, the fluxes of all three greenhouse gases were analyzed with a single injection. In order to find out the effects of litter and seedling on the emission/uptake of these greenhouse gases, three treatments were set in the field: (1) bare soil surface (litter was removed previously); (2) litter+soil; (3) seedling+litter+soil. The experimental results demonstrated that the forest soil was a source of CO_2、N_2O and a weak sink of CH_4. The daily fluxes of CO_2、CH_4、N_2O from the soil surface were in the range of 488.99～700.57,0.049～0.108mg/(m^2·h) and -0.025～-0.053(mg/(m^2·h),) respectively. CO_2 from the litter decomposition accounted for about 1/3 of the total CO_2 emission from the soil surface, while the litter and seedling had no significant effect on the fluxes of CH_4 and N_2O. The fluxes of CO_2 and N_2O measured at 9∶00～11∶00 a.m. were significantly different from their daily averages, Therefore, caution must be taken if the CO_2 and N_2O fluxes measured at 9∶00～11∶00 a.m. are used for extrapolation.