基于Hydrus-1D模型的科尔沁沙地沙丘-草甸相间区土壤水分动态模拟

土壤水分是干旱半干旱地区生态环境的主要限制性因子,研究科尔沁沙地流动沙丘和草甸地土壤水分动态规律有助于荒漠化地区的生态恢复和保护。以2018年5月25日至10月31日为研究期,利用土壤各项实测参数和气象数据,评价Hydrus-1D模型在科尔沁沙地的适用性,并揭示科尔沁沙丘-草甸相间区土壤水分分布特征,重点分析研究区流动沙丘200 cm剖面和草甸地80 cm剖面土壤水分的动态规律。结果表明:研究区典型土地类型流动沙丘和草甸地土壤水分模拟值和实测值的决定系数均高于0.76,均方根误差0.01~0.02 cm³·cm^-3;在土壤剖面上具有明显的分层结构,流动沙丘分为3层,即0~20 cm为干沙层,20~120 cm为活跃层,120~200 cm为稳定层,其中40 cm土壤水分波动性最大;草甸地分为2层,即0~40 cm为活跃层,40~80 cm为稳定层,主要受降雨、蒸散发和地下水位影响;流动沙丘和草甸地降雨与表层土壤水分呈极显著相关,降雨量与地下水位变化仅草甸地呈显著正相关;在整个研究期内,流动沙丘土壤水分储量变化量为12.6 mm,土壤实际蒸发量为105.9 mm,200 cm深层渗漏量为173.9 mm,占总降雨量的59.5%;草甸地土壤水分储量变化量为8 mm,80 cm深层渗漏量为-27.2 mm(地下水补给量),土壤实际蒸发量为67 mm,植被蒸腾量为244 mm,地表径流量为0 mm。

Dynamic law of soil moisture in Horqin Sand Dune-Meadow Area based on Hydrus-1D Model and its applicability evaluation

Soil water as one of the main restraining factors of the ecological environment in arid and semi-arid area, which study on the dynamic changes of soil moisture under the moving sand dunes and meadows in Horqin Sandy Land contributes to the ecological restoration and desertification governance. Using measured soil parameters and meteorological data from May 25 to October 31, 2018, the applicability of Hydrus-1D model in study region was evaluated and the distribution characteristics of soil moisture in the interfacial area of Horqin sandy dune and meadow were revealed. The dynamic variation rules of soil moisture in the 2m profile of mobile dune and 1m profile of meadow were emphatically analyzed. The results show that: The determination coefficient of soil moisture simulation and measured value of typical land types in the study area is higher than 0.76, and the RMSE is between 0.01-0.02 cm³·cm^-3. There is a clear layered structure on the soil profile that the mobile sand dune is divided into three layers, named dry sand layer (0-20 cm), the active layer (20-120 cm), and the stable layer (120-200 cm), respectively, where 40 cm soil moisture is the most volatile. And the grassland is divided into two layers, that is, the active layer (0-40 cm) and the stable layer (40-80 cm), which is mainly affected by precipitation, evapotranspiration and groundwater level. Furthermore, surface soil moisture in mobile dunes and meadows is significantly correlated with rainfall, which is only positively correlated with groundwater level change in meadows. And during the whole study period, the change of soil moisture storage in mobile dune is 12.6 mm, the actual evaporation of soil is 105.9 mm and the deep leakage of 200 cm is 173.9 mm, accounting for 59.5% of the total rainfall. The change of soil moisture reserve in meadow land is 8 mm. The deep leakage at 80cm soil layer is -27.2 mm (groundwater recharge), the actual soil evaporation is 67 mm, the vegetation transpiration is 244 mm, and the surface runoff is 0 mm.