基于去除土壤散射干扰SAR数据的玉米残茬生物量反演

Retrieval of Corn Residue Biomass Based on SAR Data with Soil Scattering Interference Removed

作为保护性耕作的主要方式之一,作物留茬对农田生态系统的物质和能量循环有重要影响。及时、准确地获取作物残茬生物量分布状况对定量了解保护性耕作实施状况、评估残茬影响具有重要意义。本文利用AIEM-Oh模型和水云模型(Water Cloud Model,WCM)构建残茬后向散射模型,分离出去除土壤散射影响后玉米残茬后向散射系数;在此基础上选择适宜的雷达指数特征构建玉米残茬生物量反演模型,以Sentinel-1 SAR数据为主数据源,以梨树县为研究区实现其玉米残茬生物量估算。结果表明:基于残茬后向散射模型可以有效地消除土壤后向散射的干扰,选择合适特征参数构建的反演模型能够获得较好的残茬生物量反演效果。其中,基于双极化散射积(Product)的秋季生物量反演精度R2大于0.75,RMSE达85 g/m2以下。与去除土壤散射干扰前的生物量反演模型相比,去除土壤散射干扰后,采用常见指数特征的生物量反演精度R2增加至少0.15,RMSE减少至少17 g/m2。本研究验证了利用去除土壤散射干扰后残茬后向散射数据进行残茬生物量反演的可行性,为今后利用SAR遥感数据进行玉米残茬生物量的动态监测提供了有益的尝试。

As a main way of conservation tillage,crop residue has important influence on the cycle of material and energy in farmland ecosystem.Acquisition of the biomass information of corn residues timely and accurately is of great significance for understanding the implementation of conservation tillage and evaluating the impact of residues quantitatively.However,compared with crops,residues have lower coverage and contain less water,which makes it more difficult to acquire the biomass.To address this issue,we developed a residue backscattering model based on AIEM-Oh model and the Water Cloud Model(WCM)to remove the soil scattering interference.Using Sentinel-1 SAR images as the main data source,a regression model of corn residue biomass was constructed based on radar features selected to retrieve and map the corn residue biomass in Lishu County.Results show that the residue backscattering model can eliminate the interference of soil backscattering contribution effectively,and the inversion model based on the residue backscattering coefficient can improve the biomass inversion accuracy.The autumn biomass inversion model based on the dual-polarized scattering product(Product)has an R2 greater than 0.75,and an RMSE less than 85 g/m2,showing an increase of at least 0.12 in R2 and a decrease of 17 g/m2 in RMSE compared to the biomass inversion model before soil scattering contribution removed.This study verifies the feasibility of residue biomass inversion model based on backscattering data with soil scattering interference removed,and provides an attempt for the dynamic monitoring of corn residue biomass using SAR remote sensing data in the future.