Background As the economic center of the Bohai Bay region, Tianjin Binhai New Area has the problem of soil salinization, which is outstanding. It is one of the factors restricting its sustainable development of social economy and ecological environment construction. Understanding the state of soil moisture and salinity differentiation and its spatial distribution are the basis for soil prevention and sustainable use of land resources. It is of great significance to carry out research on soil salinization in Binhai New Area, Therefore, The paper takes Tianjin Binhai New Area as the study area.

Methods The paper used GF-1 as the data source and obtained the land use types of the study area by the method of supervised classification. Soil samples of 0-20 cm and 20-40 cm in the study area were obtained from field investigation and the data of soil moisture and salinity were obtained through laboratory analysis. The paper combined classical statistics with geostatistics and GIS technology to study spatial variability and spatial distribution of soil moisture and salinity in different soil depth and land use types.

Results 1) Soil salinity content showed a great variability and soil moisture showed a moderate variability in each soil layer. With soil depth increasing, the variability of soil moisture and salinity gradually decreased. Soil salinity variability was greater than soil moisture. 2) Soil salinity showed moderate spatial relation in the depth of 0-20 cm soil layer and strong spatial relation in 20-40 cm soli layer. Soil moisture showed strong spatial relation. With the increase of soil depth, the spatial correlation of soil moisture and salinity increased. The spatial correlation of soil moisture was greater than soil salinity. 3) As soil depth increasing, soil salinity and moisture content increased. The soil salinity decreased from northeast to southwest, showing a spatial distribution of strips and local patches. With the distance from the Bohai Sea increasing, the soil salinity decreased. From the northeastern to the southwest, the overall soil moisture content decreased first and then increased.

Conclusions The spatial variability of soil salinity in the study area is greater than soil moisture and the variability is strengthened with the increase of soil depth. The vertical trend of soil moisture and salinity is consistent with the overall area in different land use. The results can provide theoretical basis for improvement of saline-alkali land、vegetation restoration and land use optimization in Binhai New Area.