西藏纳木错高寒草原、高寒草甸和沼泽化草甸主要温室气体通量对比研究

青藏高原高寒草地占我国天然草地的40%，研究其温室气体源汇强度及驱动因子具有重要意义。采用静态箱-气相色谱法，在西藏纳木错地区开展高寒草原、高寒草甸和沼泽化草甸的生态系统呼吸、CH₄和N₂O通量观测，生长季内的观测表明：高寒草原和高寒草甸生态系统呼吸分别为（283.7±14.4） mg·m^-2·h^-1和（275.7±20.6） mg·m^-2·h^-1，低于有机质丰富的沼泽化草甸，为（591.6±53.2） mg·m^-2·h^-1。高寒草原和高寒草甸均是CH₄的汇，其生长季均值分别为（-84.9±7.6） μg·m^-2·h^-1和（-39.2±4.6） μg·m^-2·h^-1；而沼泽化草甸是CH₄的源其均值为（149.2±34.2） μg·m^-2·h^-1。高寒草原、高寒草甸和沼泽化草甸均为N₂O的源，生长季排放量分别为（7.3±2.8），（3.0±1.1）和（2.2±4.3） μg·m^-2·h^-1。土壤水分总体控制着高寒草地CH₄通量的时空变化，在土壤水分含量约大于30%的沼泽化草甸表现为CH₄的排放源，而在土壤水分含量低于30%的高寒草原和草甸表现为CH₄的汇；生长季水分含量越高，对CH₄的吸收越弱。

Research on Key Greenhouse Gas Fluxes across Alpine Steppe,Alpine Meadow and Swamp Meadow in Nam Co,Tibetan Plateau

The alpine grassland of Tibetan Plateau accounts for 40% of natural grassland in China. It is, therefore, important to qualify the greenhouse gas fluxes of the alpine grassland and their driving factors. Observations of ecosystem respiration, CH₄ and N₂O fluxes across alpine steppe, alpine meadow and swamp meadow were conducted using static chamber and gas chromatograph method in the Nam Co region of Tibetan Plateau. One growing season's measurement showed that the ecosystem respiration of alpine steppe and meadow were 283.7±14.4 mg·m^-2·h^-1 and 275.7±20.6 mg·m^-2·h^-1, respectively, and both were significantly lower than that of swamp meadow (591.6±53.2 mg·m^-2·h^-1), which was rich in soil organic carbon. Both alpine steppe and meadow were sinks of CH₄ (-84.9±7.6 and -39.2±4.6 μg·m^-2·h^-1, respectively), while the swamp meadow was a resource of CH₄ (149.2±34.2 μg·m^-2·h^-1). All three ecosystems were a resource of N₂O. The emissions of N₂O during growing season were 7.3±2.8, 3.0±1.1 and 2.2±4.3 μg·m^-2·h^-1, respectively. Comparison of CH₄ flux among three grassland types indicated that the spatial-temporal variation of CH₄ flux depended on the soil moisture. The swamp meadow with more than 30% soil moisture contents was a resource of CH₄, while both alpine steppe and meadow with less than 30% soil moisture contents were the sinks of CH₄ and the strength of the sink decreased with soil moisture increasing during growing season.