Large scale evaluation of methane budget over frozen boreal forest by synthesis of field observation, process modeling and satellite remote sensing

甲烷(CH4)是一种强温室气体，湿生态系统是CH4的来源。然而，在CH4汇和源分布不均的多年冻土湿地和北方森林，CH4的收支及其机制尚不清楚。我们观测到了阿拉斯加北部森林的CH4通量。通过应用涡旋协方差、梯度、REA和小室等多种测量方法，得到了准确的CH4通量结果。确定了干植被条件下的汇CH4通量，雨后潮湿条件下的汇CH4通量，明确了站点CH4通量的季节变化规律，分析了环境因子与CH4通量的关系，并将其用于改进过程基地模式“VISTER”的参数。应用支持向量机回归(SVR)方法对阿拉斯加地区23个测点的区域尺度CO2通量进行了遥感估算，并与已有模型进行了比较，得到了较为可靠的结果。

Methane (CH4) is a strong greenhouse gas and wet ecosystem is CH4 source. However, CH4 budget and the mechanism underlying are still unknown at wetlands and boreal forests on permafrost, where CH4 sink and source distributed heterogeneously. We observed CH4 flux at boreal forest in Alaska. We obtained accurate CH4 flux results by applying multiple measurement methods such as eddy covariance, gradient, REA and chambers. Those approved the sink CH4 flux under dry vegetation conditions while an obvious source under wet conditions after rain, and the seasonal variations at the site were clearly determined.Relationships among environmental factors and CH4 flux were analyzed which were used to improve parameters of a process base model "VISIT". Support vector regression (SVR) was applied to estimate regional scale CO2 flux using satellite remote sensing and measured CO2 flux at 23 tower sites over Alaska, and the reliable results comparing to previous models were obtained.