三种干旱指数在干旱区沼泽湿地土壤水分遥感反演中的应用

Application of three drought indexes in soil moisture inversion using remote sensing in marsh wetlands of arid area

湿地水文条件对湿地生态系统结构和功能起着关键作用。借助卫星遥感技术,以干旱区疏勒河中下游沼泽湿地为研究对象,基于Landsat8 OLI遥感影像的温度植被干旱指数(TVDI)、垂直干旱指数(PDI)和归一化干旱监测指数(NPDI)3种干旱监测方法,结合野外湿地实测土壤水分数据进行比较和验证。结果表明:(1)TVDI、PDI和NPDI3种干旱指数在不同土层中均与土壤实测水分呈显著负相关(P<0.01),且NPDI指数与表层土壤水分的拟合效果最好。不同土层中,3种干旱指数与土壤水分的拟合优度大小均为NPDI>TVDI>PDI;(2)研究区同一湿地类型不同土层的土壤水分存在显著差异(P<0.05),且不同湿地类型的土壤水分总体上表现为随着土壤深度的增加呈递增态势;(3)研究区同一土层不同湿地类型的土壤水分差异显著(P<0.05),且不同土层中土壤水分的大小均为:沼泽化草甸>草本沼泽>季节性咸水沼泽>内陆盐沼。

Wetland hydrological conditions play a key role in the structure and function of the wetland ecosystem. In this study, we use three drought monitoring methods, Temperature Vegetation Dryness Index （TVDI）, Perpendicular Drought Index （PDI）, and Normalized PDI （NPDI） as well as soil moisture observation data in the field to study marsh wetlands of an arid area in the middle and lower reaches of the Shule River using a remote sensing technology based on the Landsat8 Operational Land Imager （OLI）. We obtained the following results in this study：1） TVDI, PDI, and NPDI were significantly negatively correlated with soil moisture in different soil layers （P 〈 0.01）, the goodness of fit among the three drought indexes was in the following order of magnitude NPDI 〉 TVDI 〉 PDI with soil moisture in different soil layers, and the fitting results using the NPDI index were the best with topsoil moisture; 2） there were numerous significant differences in soil moisture among different soil layers of the same marsh type （P 〈 0.05）, and an increasing trend in the soil moisture of different marsh types was observed with increasing soil depth; 3） the soil moisture was significantly different between different marsh types of the same soil layer （P 〈 0.05）, and the comparison of soil moisture in the different soil layers showed the following decreasing order of magnitude：marsh meadow 〉 herbaceous marsh 〉 seasonal saline marsh 〉 inland salt marsh.