Dense-foliage tamarisk (Tamarix chinensis) varieties are widely planted for landscape construction projects in the highly saline coastal soil of northern China. Because these plants are salt-secreting halophytes, their growth in arid land usually leads to soil salinization and water loss. In this work, a tamarisk plantation was established in a coastal area within a semi-arid region of China, and the water content, salinity levels and spatial distribution patterns in the soil were analysed in 1 × 1 m grids of a 10×10 m sample plot in July 2014 and July 2016. Four layers of soil within the 0–80 cm profile were sampled, and the soil water, salt, Na+ and Cl− contents and pH were determined. In 2016, the soil water content had decreased slightly, and the soil salt content had increased by 0.49 g kg⁻¹, representing a 7.0% increase compared with the value in 2014. Both the soil Cl⁻ and Na⁺ content increased from 2014 to 2016, accounting for a greater fraction of the total salt, and the mean soil pH also increased by approximately 0.4. The spatial variation was weaker in the deeper layers but moderate in the surface layer. After tamarisk establishment, the spatial variation in soil salinity declined and showed a trend toward homogeneity. The secreted salt and litterfall from the tamarisk might explain the higher soil salinity and increased homogeneity, which suggests that tamarisk growth will lead to increased soil salinity and a more homogeneous salt distribution throughout the soil.