Thesis

: Soil salinity and groundwater depth are the two important factors affecting the vegetation growth and distribution in the Yellow Ｒiver Delta． Through field investigation and statistical analysis ， this paper studied the relationships between the typical vegetations ( Suaeda heteroptera － Tamarix chinensis ， Ｒobinia pseudoacacia ， Phragmites australis ， and cotton ) ， soil salinity ， and groundwater depth in the Delta． In the study area ， groundwater depth had significant effects on soil salinity ， with the average influence coefficient being 0． 327． When the groundwater depth was 0． 5－1． 5 m ， soil salinization was most severe． The vegetation growth in the Delta was poorer ， with the NDVI in 78% of the total area being less than 0． 4． Groundwater depth and soil salinity had significant effects on the vegetation distribution． Soil salinity had significant effects on the NDVI of Ｒ． pseudoacacia ， S． heteroptera － T． chinensis ， P． australis ， and cotton ， while groundwater depth had significant effects on the NDVI of S． heteroptera － T． chinensis ， but lesser effects on the NDVI of P． australis ， cotton and Ｒ． pseudoacacia ．