基于BEPS模型的雨养冬小麦农田土壤水分动态模拟

北部生态系统生产力模拟(BEPS,Boreal Ecosystem Productivity Simulator)模型能够模拟不同生态系统碳水循环过程,并通过气孔导度将二者有机地结合,在土壤水分模拟上具有更大的优势。为了使BEPS模型适用于较小空间尺度的雨养冬小麦农田生态系统的土壤水分模拟,根据冬小麦的降水截留过程、冠层的辐射传输过程、根系分布规律和区域土壤水文参数的获取方法对BEPS模型的水平衡模块进行参数方案调整。在此基础上,基于实现BEPS模型与遥感反演的农田土壤水分数据同化的目的,利用经上述调整方案后的BEPS模型,对郑州农业气象试验站2011—2015年冬小麦生长季的农田土壤水分进行动态模拟,并用观测数据进行验证。结果表明,调整后的BEPS模型能够较好地模拟雨养冬小麦农田土壤水分及动态变化,决定系数R2可达0.70以上,平均相对误差MRE总体低于25.0%,但对底层模拟能力较差;在以旬为步长条件下,拔节前模拟效果优于拔节后;土壤水文参数是影响模型模拟土壤水分垂直交换和分布的主要因素,可通过优化进一步提高土壤水分模拟能力。

Modelling Soil Moisture Dynamics in Rain-fed Winter Wheat Field Using the BEPS Model

BEPS (Boreal Ecosystem Productivity Simulator) is a model for simulating water and carbon cycling in boreal ecosystem by couplingthe water and the carbon in the stomatal conductivity. This paper investigated the suitability of BEPS for simulating soil moisture dynamics in small-scale rain-fed winter wheat fields. The BEPS model was parametrized using rainfall interception by crop, radiative transport process in canopy, root distribu-tion and soil hydrological properties. Using the parameterized model, we simulated the dynamic of soil water in a rain-fed winter wheat field at Zhengzhou Agrometeorological Station from 2011 to 2015, and the simulated re-sults were compared with measured data. The results showed that the parameterized BEPS was able to simulate soil moisture dynamic in the wheat field, with a R-squared coefficient of 0.70 and average relative error less than 25.0%. However, the model was less accurate in simulating change of water in deep soil. Usinga time step of 10 days, the model worked better before the jointing stage than after it. Soil hydrological properties were found to be the main factors affecting the movement of soil water in vertical direction, and the model could be further im-proved to more accurately simulate soil moisture dynamics.