Characteristics Analysis Of Soil Salinization In The Yellow River Delta Based On High Resolution Remote Sensing

Soil salinization is a serious global problem,and the problem of soil salinization in China is prominent.Yellow River delta is a typical coastal salinization area in China,and soil salinization seriously affects the land quality,resulting in grain yield decline,which brings great losses to the economy.Accurate and timely monitoring and studying the characteristics of soil salinization in the Yellow River delta can not only prevent deterioration,but also promote sustainable development of economy and ecology.Dongying is a typical area of the Yellow River delta.This paper took Dongying city in Shandong province as the study area.GF1-WFV remote sensing image was used to study the soil salinization in the Yellow River delta.The technique and method of extracting high resolution remote sensing information of soil salinization in the Yellow River delta were explored.According to the advantages of GF-1,such as high resolution,short revisit period and strong coverage ability,the spatial and temporal variation characteristics of soil salinization before and after irrigation,month by month,season by season and year by year in the study area were studied,and the following conclusions were obtained:?1?The correlation coefficient R² between the salinity index SI₁ and the measured total soil salinity was above 0.6,which met the requirements of soil salinization monitoring.SI₁was easy to calculate,so it was suitable for the analysis of temporal and spatial changes of soil salinization.It was feasible to use GF1-WFV remote sensing image for spectral index calculation to monitor soil salinization information.?2?During irrigation,saline soil was transformed into non-salinized soil.The area of non-salinized soil increased significantly,accounting for more than 97%of the total area.About one week after irrigation,non-salinized soil was transformed into mildly salinized soil and moderately salinized soil.The area of non-salinized soil decreased by 11%.The time of sowing and irrigation of wheat affected the spatial distribution of soil salinization.The change law obtained by monitoring soil salinization characteristics before and after irrigation by GF1-WFV remote sensing image was consistent with that obtained by field experiment,indicating that it was accurate and feasible to monitor soil salinization before and after irrigation by this means.This paper provided an accurate and efficient method for studying the characteristics of soil salinization before and after irrigation.?3?From Jan.to Dec.,soil salinization changes in the study area showed a trend of aggravation?Jan.-Mar.?-invariability?Mar.-June?-reduction?June-Oct.?-aggravation?Oct.-Nov.?-reduction?Nov.-Dec.?.The total area of salinized soil in the study area had two peak values?from the end of Feb.to June and Nov.?and three low values?from Jan.to the beginning of Feb.,from the end of Sept.to Oct.and Dec.?.The change of saline soil area was consistent with the change of total salinized soil area,while the change of non-salinized soil area was contrary to the change of total salinized soil area.The areas of mildly salinized soil,moderately salinized soil and severely salinized soil basically remain stable within one year.?4?The severity of soil salinization in different seasons in the study area was spring>summer>autumn>winter.The total area of salinized soil was above 80%in spring,above60%in summer,below 50%in autumn and below 50%in winter.With the passage of the seasons,soil salinization in the Yellow River delta began to decrease gradually from the central area on both sides of the Yellow River to the coastal areas.The direction of soil salinization increasing or decreasing in the study area was mainly dominated by the transformation between non-salinized soil and saline soil.?5?From 2014 to 2018,the salinized soil with the largest area was saline soil,accounting for 65%-90%of the total area of the study area,with an annual change rate K of0.44%.Soil salinization in the study area had been stable since 2001,mainly saline soil,and the soil salinization had been serious for a long time.The spatial distribution of soil salinization in the study area had remained unchanged for many years.The degree of soil salinization in the western and southern areas farther from the sea was less than that in the eastern and northern areas closer to the sea.The degree of soil salinization in the areas along the Yellow River was less than that in the areas far from the Yellow River.