城市背景下草地蒸散发及土壤水分变异特性——以扬州区域性草地植被为例

Variation Characteristics of Evapotranspiration and Soil Moisture in Urban Grassland: A Case Study on the Regional Grassland Vegetation in Yangzhou City

为揭示城市背景下区域土壤水分变异特性及其利用效率,以扬州大学扬子津校区农水与水文生态实验场(P1)及扬州大学江阳路南校区草坪(P2)为研究区,基于实测的水文、气象数据,采用彭曼-蒙蒂斯(Penman-Monteith)公式估算草地生长期内蒸散发量,采用FAO推荐的经修正的彭曼-蒙蒂斯(Penman-Monteith)公式推求参考作物蒸散发量,并对水分有效性进行评价;采用有限差分方法结合非饱和土壤水分运动方程构建一维土壤水分运动模型,通过对观测土壤水分的数值模拟检验模型的适用性,对表层(0～10 cm)土壤水分进行模拟。结果表明:计算时段(2016-10-05-2017-10-04)内,P1、P2的ET_0为1 115.0 mm,略低于该时段的降雨量(1 200.0 mm);计算时段(2017-07-01-2017-09-31)内,P1点的ET累积值为129.7 mm,占同期降雨量的24.2%,P2点ET累积值为122.2 mm,占同期降雨量的22.9%;同期的水分有效性参数m_a分别为0.39、0.37;P1、P2两点土壤水分模拟结果与实测数据之间的均方根误差(RMSE)分别为0.012、0.021,纳什效率系数(NSE)分别为0.830、0.928,表明两点的计算与实测序列的误差较小,构建的一维土壤水分运动模型具有较高的计算精度。研究成果以期为城市化背景下草地植被的土壤水分循环以及基于绿色植被的海绵城市建设提供研究基础。

In order to reveal the regional soil moisture variation characteristics and its utilization efficiency under city background,with the Irrigation,Drainage and Hydrology Ecological Experimental Field in Yangzijin Campus of Yangzhou University(P1),and the grassland in Jiangyang Road South Campus of Yangzhou University(P2)as the study area,based on the observed hydrological and meteorological data,the Penman Monteith formula was adopted to estimate the grass evaporation quantity in the growth period,the revised Penman-Monteith formula recommended by FAO was to use calculate the reference crop evaporation amount and evaluate the moisture effectiveness;The finite difference method was used to build a one-dimensional soil water movement model combined with the unsaturated soil water movement equation.The applicability of the model was tested by the numerical simulation of the observed soil water,and the surface(0~10 cm)soil water was simulated.The results showed that the ET0of P1 and P2 was 1 115.0 mm during the calculation period(from October 5,2016 to October 4,2017),which was slightly lower than the rainfall during this period(1 200.0 mm).During the calculation period(2017-07-01-2017-09-31),the cumulative ET value at point P1 was 129.7 mm,accounting for 24.2%of the corresponding rainfall;the cumulative ET value at point P2 was 122.2 mm,accounting for 22.9%of the corresponding rainfall.During the same period,the water availability parameters,ma,were 0.39 and 0.37,respectively.The root-mean-square error(RMSE)between the simulation results of soil moisture and the measured data were 0.012 and 0.021,respectively,and the Nash efficiency coefficient(NSE)were 0.830 and 0.928,respectively,indicating that the error between the calculation and the measured sequence of the two points was small,and the constructed one-dimensional soil moisture movement model had a high calculation accuracy.The research results are expected to provide research basis for soil water cycle of grassland vegetation and sponge city construction based on green vegetation under the background of urbanization.