基于光学和雷达多源遥感的于田绿洲土壤盐渍化时空分析

Spatial and temporal analysis of soil salinity in Yutian Oasis by combined optical and radar multi-source remote sensing

目前土壤盐渍化是全球重要的环境问题,探明于田绿洲土壤盐渍化的时空变化规律,挖掘雷达遥感探测土壤盐分的优势,对干旱区绿洲的土壤盐渍化时空变化进行监测评估。以于田绿洲为研究区,基于PALSAR-2、Sentinel-1极化合成孔径雷达数据和Landsat 8 OLI等多源数据集,筛选雷达影像的最优后向散射特征与主成分分析后的光学影像组合,最后利用随机森林方法进行图像分类,定量提取于田绿洲土壤盐渍化信息,对土壤盐渍化时空变化进行分析。结果表明:(1)在同时使用随机森林分类方法下,各年的光学影像总体精度平均为80.36%,Kappa系数平均为0.77;光学影像结合雷达影像的分类精度比光学影像分类精度高,总体精度平均为85.62%,Kappa系数平均为0.82。(2)2015—2021年于田绿洲产生土壤盐渍化的区域主要分布于研究区北部的绿洲边缘和荒漠交错带。(3)2015—2021年盐渍地面积年均变化量为-1120.55 hm^(2)·a^(-1),变化率为-10.67%。于田绿洲盐渍化程度总体呈下降趋势,盐渍化以轻中度盐渍地为主。

Soil salinization is currently a prominent global environmental problem.Spatiotemporal variation of soil salinization in Yutian Oasis was explored,and the advantages of radar remote sensing in excavated soil salinity were investigated to monitor and evaluate the temporal and spatial variabilities of soil salinization in arid oasis.Based on Phased Array type L-band Synthetic Aperture Radar 2(PALSAR-2),Sentinel-1 polarimetric synthetic aperture radar data,and Landsat 8 Operational Land Imager(Landsat 8 OLI)multi-source dataset,the optimal backscattering characteristics of radar images were selected,and optical images were combined based on principal component analysis.Finally,the random forest method was used to classify the images.Quantitative extraction of soil salinization information in Yutian Oasis and the spatial and temporal variation of soil salinization were analyzed.Results showed that(1)under the random forest classification approach,the total accuracy of optical images in each year was 80.36%,and the kappa coefficient was 0.77.The classification accuracy of optical images combined with radar images was higher than that of optical images,the total accuracy was 85.62%,and the kappa coefficient was 0.82.(2)From 2015 to 2021,the area of salinized soil in Yutian Oasis was mainly distributed in the north of the study area,interlaced edge of the oasis,and desert.(3)The average annual variation of saline land area from 2015 to 2021 was-1120.55 hm^(2)·a^(-1),and the change rate was-10.67%.The salinization of Yutian Oasis generally showed a downward trend and was mainly mild to moderate saline land.