内蒙古温带半干旱羊草草原N_2O通量及其影响因素

The N_2O fluxes in Leymus Chinense grassland of Inner Mongolia, China

利用静态箱 -气相色谱法于 2 0 0 1～ 2 0 0 3年对内蒙古锡林河流域羊草草原进行了连续 2年的野外定位试验 ,获得羊草草原原状群落与土壤N2 O年排放通量分别在 3 91～ 4 71μgm- 2h- 1以及 5 5 0～ 10 0 3μgm- 2 h- 1范围内变动 ,证明内蒙古温带半干旱羊草草原生态系统是大气中N2 O的源 ;系统分析了羊草草原N2 O通量的季节变化、源汇特征以及关键的环境因子对草地N2 O通量的影响等 ,建立了N2 O通量与环境因子间的回归方程 ;并利用两年连续完整的观测数据对羊草草原N2

Using the static chamber method, the fluxes of nitrous oxide from the undisturbed community and soil layer were measured through the continuous experiment in situ from 2001 to 2003 in Leymus Chinense grassland in Xilin river basin of Inner Mongolia, China.The seasonal variation, characteristics of sources and sinks, and the effects of main environmental factors on N 2O fluxes were analyzed. The regression models between the N 2O fluxes and the environmental factors were also established using the statistical method, at the same time, the annual total emission flux of N 2O was estimated. The main results are as follows:(1) The seasonal variations of N 2O fluxes in undisturbed community and soil layer were very obvious with higher emissions in spring and summer, then autumn but maintaining a relatively low emissions level in winter, furthermore, negative fluxes were found sometimes in winter. (2) The annual mean N 2O flux of undisturbed community ranged from 3.91 μgm -2h -1 to 4.71 μgm -2h -1 and that of soil layer ranged from 5.49 to 10.03 μgm -2h -1.The average N 2O flux of undisturbed community was lower than that of soil layer in the same statistical period, the relative thick litter layer obviously reduced the emission of N 2O to a certain degree. (3) To compare the N 2O fluxes of the whole year, the N 2O fluxes from undisturbed community and soil layer were significantly positive correlated with the air temperature and surface soil temperature at non-growing season, whereas they had a weak correlation with the soil moisture. The changes of air temperature and the other closely relative temperature factors could account for 72%～88% of the variation of undisturbed community and soil layer N 2O fluxes in non-growing season. What’s more, the correlations between N 2O flux and the soil temperature at 5cm and 10cm depth were higher than that between N 2O flux and surface soil temperature. But in growing season, negative correlations were found between N 2O flux and the air temperature and the soil temperature at 0cm, 5cm and 10cm depth, especially the correlations between N 2O flux and air temperature reached the significance level of 0.05. The results of multi-variable stepwise regression indicated that the change of 0～10cm and 10～20cm soil moisture could account for 72～85% of the variation of undisturbed community and soil layer N 2O fluxes in growing season.