Changes in salinity and vegetation growth under different land use types during the reclamation in coastal saline soil.

The ecological construction in coastal saline-alkali areas urgently needs to be explored in terms of water-salt regulation management and functional irrigation. In this paper, the extremely severe saline soil in the eastern coastal area of the North China Plain was selected for vegetation rehabilitation by drip irrigation. Through two-year field experiments, the spatial and temporal soil salinity-water dynamics of three land use types (LUTS) under two irrigation strategies (IIS) were systematically studied. The results revealed: (1) The soils in the understory grassland and shrub land root zones remained stable for desalination, with the average ECe decreasing to 0.69 dS/m and 0.71 dS/m under autumn irrigation at surface, and 0.66 dS/m and 0.85 dS/m under winter irrigation. And a slight salt accumulation occurred in the bare land in stage IV. (2)The soil surface moisture increased, and the bulk density decreased significantly with drip irrigation. The final moisture of understory grassland and shrub land was 3.85 and 2.97 times that of the bare land layer at 0-10 cm, 2.55 and 1.97 times at 10-20 cm, and 1.61 times and 1.47 times at 20-40 cm, respectively. (3)Due to quick salt rinsing, Salix matsudana and Hibiscus maintained a high survival rate, and the germination of understory vegetation further increased the vegetation coverage. Meanwhile perennial understory herbs gradually became the dominant species, which positively effects on the maintenance of soil low-salt environment. (4)There were significant differences in SWC and ECe between autumn and winter irrigation treatment during stage I and stage II, indicating that irrigation strategies only impact on soil water-salt movement in the early stage. While there was no significant difference between understory grassland and shrub land, indicating that the research about the effects of vegetation cover type on water-salt transport should take a longer time scale.