灌溉对藏北高寒草甸生物量和温室气体排放的影响

温室气体不仅是引起气候变化的主要因素,并对气候具有重要的反馈作用,鉴于近年来藏北地区温度明显升高,降水逐步增加,通过对藏北高寒草甸进行灌溉,以模拟未来降水增加对该生态系统生长旺季温室气体排放的影响。结果表明:土壤水分增加显著促进草地地上生物量积累;灌溉促进高寒草甸CO2和N2O排放,但降低CH4吸收量;CO2和CH4排放量日变化与土壤湿度呈显著的线性相关关系(P<0.05),N2O与土壤湿度呈显著的二次项相关关系(P<0.05),三种温室气体排放均与土壤温度无显著相关关系(P>0.05)。综合上述研究结果认为,未来随着降水增加,藏北高寒草甸温室气体排放通量将明显增加,并对该地区气候变化产生正反馈作用;应结合高寒草地光合作用、土壤碳氮含量,对未来藏北高寒草甸温室气体净通量进行深入研究,以确定藏北高寒草甸温室气体排放在气候变化中扮演的角色。

Effects of Irrigation on Biomass and Greenhouse Gas Emissions of Alpine Meadow in Northern Tibet

In recent years, northern Tibet has experienced significant warming and precipitation rises. Greenhouse gases(GHGs) are not only the main cause of climate change, but they also have an important feedback effect on climate. In this study, we conducted an in situ irrigation experiment in an alpine meadow(4500 m above the sea level) to simulate the effects of future rainfall increases on GHG emissions and biomass in northern Tibet. Three treatments:control(CK), low water(DS), and high water(GS) were set up. A static chamber and gas chromatography method were used to measure the GHG emissions. Results showed that a increase in soil moisture led to significant increases in grassland biomass, carbon dioxide(CO₂) emission, and nitrous dioxide(N₂O) emission, but decrease in methane(CH₄) uptake. A linear positive correlation between CO₂/CH₄ emissions and soil moisture was found(P<0.05). Nitrous oxide emissions had a significant quadratic relationship with soil moisture(P<0.05). However, there was no correlation between CO₂/CH₄/N₂O emissions and soil temperature. Taken together, significantly increased GHG emissions will have a positive feedback effect on climate change in the alpine meadows of northern Tibet under future precipitation scenarios. A further research on the interaction between GHG fluxes and plant photosynthesis, soil carbon, and soil nitrogen is necessary to determine the contribution of alpine meadows to climate change.