Variations in the CT-measured pore structure and hydraulic characteristics of coastal saline soils with different reclamation periods

Purpose Rational utilization of coastal tidal flat resources is important for the sustainable development of coastal areas. The objective of this study is to reveal the variations in the soil structure and hydraulic characteristics of saline soil for different reclamation periods in coastal areas and to provide a theoretical reference for the efficient utilization of water and soil resources in coastal reclamation areas. Materials and methods Twenty-seven undisturbed soil cores with three soil profiles (0-20 cm, 20-40 cm, and 40-60 cm) were collected from paddy fields in three coastal reclamation areas in Jiangsu Province, China, which were reclaimed from 1940 to 1960, from 1960 to 2000, and after 2000 (labeled Y1, Y2, and Y3 respectively), to analyze the intrinsic relationships between the soil pore structure and hydraulic characteristics. Results and discussion Sixty to eighty years of reclamation significantly improved the pore density and complexity of the soil pore system (p < 0.05), which was reflected in the pore density of the Y3 treatment being 3.7 and 2.4 times that of the Y1 and Y2 treatments, respectively, while the fractal dimension (FD) was 1.11 and 1.06 times that of the Y1 and Y2 treatments, respectively. A longer reclamation period increased porosity and improved pore network connectivity. At the same time, reclamation activities enhanced the soil water infiltration capacity, and the soil saturated hydraulic conductivity (Ks) of the Y2 and Y3 treatments was 4.90 and 3.63 times that of the Y1 treatment, respectively. Compared with pores in deeper layers, surface pores were more abundant, and the water infiltration capacity was stronger in shallower layers. The pore number density, porosity, FD, structural connectivity parameters, and bulk density (BD) were significantly correlated with Ks. Conclusions Long-term artificial reclamation activities can improve the condition of the soil pore system by increasing pore density and porosity, optimizing pore shape, and improving the complexity and connectivity of the pore network, thus enhancing the water infiltration performance of the soil and improving the utilization efficiency of water and soil resources.