Simulating Methane Emissions from the Littoral Zone of a Reservoir by Wetland DNDC Model

Wetland-DNDC模型模拟密云水库消落带甲烷排放（英文）

The littoral zone of freshwater ecosystems is believed to be a hotspot for methane （CH4） emissions, but in situ measurements are rare. This paper reports a study of CH4 fluxes from the Miyun Reservoir near Beijing in China based on an integrated observational and modelling approach. CH4 fluxes were measured at three sites with different water levels containing nine representative vegetation communities. A process-based model, Wetland-DNDC, was tested against observations for its applicability in simulating CH4 fluxes from the littoral zone of the reservoir. The R^2 values, which showed correlation between the modeled and observed results, were 0.89, 0.81 and 0.49 for the deep water, shallow water and seasonally flooded sites, respectively. The modeled data indicated that the observed CH4 fluxes were mainly driven by water level fluctuations, soil temperature and soil organic matter content. The modeled average annual flux from the littoral zone of Miyun Reservoir was 15.1 g CH4·m^-2, which was comparable with other studies in China. Our study suggests that Wetland-DNDC is a suitable choice as a model for CH4 flux simulation from littoral zone of reservoirs or lakes, although improvements in the vegetation module could enhance the model＇s accuracy and applicability.

淡水生态系统消落带是甲烷排放研究的热点区域,但相关数据的积累十分薄弱。本研究利用静态箱法和过程模型(Wetland-DNDC),研究了密云水库消落带CH_4排放通量。在消落带的三个水位梯度:即永久淹水深水区、永久淹水浅水区和季节性淹没区,选取九种典型植被进行CH_4排放通量的野外监测和模型模拟。结果表明:在三个水位梯度上,Wetland-DNDC模拟值与实测值拟合度分别为0.89、0.81和0.49(p<0.001)。Wetland-DNDC模型抓住了水位波动、土壤温度和土壤有机质含量等因子对消落带CH_4排放的影响规律,成功地在时间、空间和数量级上对消落带CH_4排放通量进行了模拟,为评估水库温室气体排放提供了新方法。在密云水库生长季模拟的消落带CH_4总排放量为15.1 g CH4·m^(-2),在数量级上,与国内其他类型湿地消落带CH_4排放具有可比性。据此推算Wetland-DNDC模型适用于水库或湖泊消落带区域甲烷排放的模拟,对植被模块进行改进可以进一步提高模型模拟的准确性。