夏季休牧对高寒矮嵩草草甸温室气体排放的影响

以高寒矮嵩草草甸为研究对象，利用密闭箱－气相色谱法，对夏季休牧8a的围栏草地(休牧草地)和全年放牧的草地(放牧草地)的温室气体排放通量、土壤特性和生物量进行了对比研究。结果表明：与放牧草地相比，休牧草地植被盖度较之高41％，单位面积生物量较之高53％。同时，土壤特性也有较大不同；休牧草地的植被－土壤系统CO₂排放通量比放牧草地低20.7％，测定期间两者CO₂排放通量以每天每公顷排放C的质量计分别为30.7和38.7 kg·(hm²·d)^-1；试验期间高寒矮嵩草草甸植被－土壤系统是大气CH₄的弱汇，休牧后草地土壤对CH₄的吸收能力增强，休牧和放牧草地CH₄的平均吸收强度分别为28.1和21.9 g·(hm²·d)^-1；休牧草地土壤N₂O排放通量比放牧草地低，两者排放通量分别为4.5和7.6 g·(hm²·d)^-1。可见，夏季休牧措施降低了草地对大气中温室气体浓度增加的贡献。

Impacts of no grazing in summer on greenhouse gas emissions from Kobresia humilis alpine meadow

Using close chamber-GC method, the impacts of no grazing in summer on greenhouse gas emissions from Kobresia humilis alpine meadow, soil properties, and biomass were measured in 2004. The results indicated that vegetation coverage was increased by 41%, biomass increased by 53% per hectare and soil properties changed significantly after eight years in no grazing grassland when compared to grazing grassland. CO₂ respiration from vegetation and soil of no grazing grassland was 20.7% lower than that from grazing grassland. The average emission rates were 30.7 kg·(hm²·d)^-1 for no grazing grassland and 38.7 kg·(hm²·d)^-1 for grazing grassland. Both Kobresia humilis alpine meadow with grazing and no grazing activities showed to be a sink of atmospheric CH₄ and the uptake rate of CH₄ was enhanced after the prohibition of grazing. The average uptake rates of CH₄ for no grazing grassland were 28.1 gCH₄·hm^-2·d^-1 and 21.9 gCH₄·hm^-2·d^-1 for grazing grassland. N₂O emission was lower from no grazing grassland than that from grazing grassland. The average emission rates of N₂O were 4.5 gN₂O-N·hm^-2·d^-1 and 7.6 gN₂O-N·hm^-2·d^-1 for no grazing grassland and grazing grassland, respectively. No grazing in summer weakened the contribution of grassland to the concentration of greenhouse gases in atmosphere compared to grazing grassland.