Monitoring Spatiotemporal Dynamics of Soil Salinization Across the Qingtongxia Irrigation District Using Multi-Temporal Landsat Tm/Oli Data and Multi-Parameter Optimization

Abstract

The Qingtongxia Irrigation District, situated on the alluvial plain of the Yellow River in the Ningxia Hui Autonomous Region, faces severe soil salinization caused by both natural and anthropogenic factors. This issue reduces crop yields, exacerbates ecological and land degradation, and severely limits sustainable development of agriculture in the region. To address this challenge, this study proposed a precise soil salinization retrieval method based on multi-information fusion, enabling quantitative analysis of the spatiotemporal evolution and patterns of soil salinization.This study integrated remote sensing imagery with ground sampling data to develop several soil salinity prediction models including Multiple Linear Regression (MLR), Stepwise Regression (SR), Partial Least Squares Regression (PLSR), Support Vector Regression (SVR), and Random Forest Regression (RFR). The results indicated that the RFR model outperformed the other models in terms of salinity prediction accuracy. To further improve precision, certain data smoothing techniques, such as Moving Average (MA), Savitzky-Golay (SG), Median Filtering (MF), and Gaussian Filtering (GF), were applied to compare the model performance under different treatments. The findings revealed that the RFR model combined with GF smoothing achieved the highest predictive accuracy, making it well suited for precise surface salinity retrieval in the Qingtongxia Irrigation District. Using an optimized model, this study estimated the spatial distribution of soil salinity from 1989 to 2023. The results demonstrated a general decline in soil salinity across most areas, with notable reductions along the central northeast-southwest axis and in the western and eastern regions, while a few localized areas in the north exhibited increased salinity. This study provides a scientific foundation for predicting, preventing, and managing soil salinization in Qingtongxia Irrigation District, contributing to the sustainable application of soil resources, ensuring food security, and supporting sustainable agricultural development.

Keywords: Qingtongxia Irrigation District, Soil Salinization, Remote Sensing Retrieval, Spatiotemporal Distribution