青藏高原高寒湿地温室气体排放对水位降低和氮沉降的响应

湿地生态系统在二氧化碳、甲烷等温室气体（Greenhouse gases, GHGs）的吸收和排放中具有重要作用。国内外学者针对中高纬度地区湿地在全球变化下GHGs通量方面已经做了较多工作，但高寒湿地却是研究的薄弱环节。青藏高原高寒湿地是亚洲水塔，三江之源，近几十年来经历着明显的干化作用，水位下降明显。对于湿地生态系统，水位下降意味着二氧化碳排放的增加，甲烷排放的减少，但它们的综合温室效应如何仍不清楚。本研究以海拔3200m的青海海北乱海子高寒湿地为对象，利用原状土柱（0.6m×0.6m×0.6m），进行水位降低（对照，水位降低20cm）和模拟氮沉降(对照，增加30kg N ha-1yr-1)的交互实验，结合湿地沿水位梯度GHGs排放的长期监测，通过对GHGs通量日变化、季节变化和年际变化的测定，探讨水位降低和氮沉降对湿地GHGs排放的影响，为评估未来高寒湿地对GHGs的贡献提供理论依据。

Wetland ecosystems play a critically important role in the greenhouse gases (GHGs) uptake and emission because their soil store large amounts of carbon and nitrogen. Although many studies have been conducted on GHGs flux from middle- and high-latitude wetlands around the world, studies in alpine wetland are still lack. The alpine wetlands in Qinghai-Tibetan Plateau are Asian water-tower and the Three Rivers source, but in recent decades, the wetlands are subjected to obvious drying, and the water table was lowered seriously. Water table drawdown will presumably lead to an increase in CO2 emission and a decrease in CH4 emission in wetland ecosystem, but its integrated greenhouse effect is not very clear. In our study, we extracted intact peat monolith from the Luanhaizi alpine wetland (altitude 3200 m) in Haibei, Qinghai province, and constructed a facility to manipulate water table (control, -20cm) and simulate N deposition (control, +30kg N ha-1yr-1), yielding a full-factorial experimental design. Additionally, an in situ long-term automated measurement of GHGs flux has also been conducted along a water table gradient since 2008. We quantified the diurnal, seasonal and inter-annual variability of GHGs fluxes and investigated the effect of water table lowering and N addition on GHGs emissions, which may provide important information for evaluating the role of wetland in GHGs emissions in the future.