中文摘要：

为揭示不同放牧强度下不同草原类型气体交换的变化规律,在8月中旬采用Li-6400便携式光合仪和密闭式箱法,分别对内蒙古草甸草原、典型草原和荒漠草原不同放牧强度下气体交换进行分析研究。结果表明：不同草原类型之间的生态系统净CO2交换（NEE）、生态系统总呼吸（ER）和生态系统总初级生产力（GEP）均存在显著差异（P〈0.05）。草甸草原的NEE和GEP随放牧强度增加呈现降低趋势,ER则呈现上升趋势;典型草原的NEE和GEP随放牧强度增加呈现上升趋势,ER则呈现下降趋势;荒漠草原的NEE和GEP除对照区外,随放牧强度增加呈现上升趋势,而ER呈降低趋势。放牧通过对草原生态系统植物、土壤等产生影响,从而影响生态系统气体交换。

英文摘要：

In order to reveal the variation of gas exchange under different grazing intensities and grassland types in Inner Mongolia,gas exchange under different grazing intensities for three main grassland types（meadow steppe,typical steppe and desert steppe） were measured by using infrared analyzer（IRGA;LI-6400,Li-Cor,Lincoln,NE,USA） with a transparent chamber（0.5 m×0.5 m×0.5 m） in middle August.Results indicated that ecosystem net CO2 exchange（NEE）,ecosystem respiration（ER） and gross ecosystem productivity（GEP） were significantly different between types（P0.05）.NEE and GEP decreased and ER increased in meadow steppe with grazing intensities increasing.NEE and GEP increased and ER decreased in typical steppe with grazing intensities increasing;NEE and GEP increased and ER decreased in desert steppe with grazing intensities increasing compared to control.Grazing affected ecosystem gas exchange through influencing plants and soil of grassland ecosystem.