Fluctuations Of Soil Salinity In Coastal Wetland After Reclamation

With the increasing demand of land, reclamation in the coastal area is a way to expand the area of agricultural lands. After the reclamation, the soil and hydrological conditions changed with disappearance of tidal interaction. This study focused on the soil, plant and atmosphere parts with long-term monitoring methods, trying to discuss the yearly, seasonal and daily soil salinity dynamics in native reed communities in reclamation area with different driving factors. This study will help to prevent the soil salinization in reclamation land in coastal area and enhance the management of the reclamation land.The main results of the study is as below:(1) After reclamation, the high precipitation facilitates soil salinity dropping each year at a specific rate in the area. The soil salinity at 10cm layer soil dropped averagely 7.94% each year in past 6 years, and averagely dropped 6.06% at 30cm layer soil each year between 2009 and 2012.(2) Due to the season influence, the soil salinity at two layers mainly increased in spring, summer and autumn and dropped in winter in most of the years. The rate increased in spring is slow but dramatic in summer and autumn. In winter, the soil salinity dropped within a short period and stayed steady for the rest of the time.(3) The daily lowest soil salinity happened before the dawn, and increased to the peak at 2 p.m. at the depth of 10 cm. The daily fluctuation of soil salinity at 10cm is stronger than at 30cm layer.(4) The evapotranspiration rate in spring and winter is highly correlated with the soil salinity dynamics, but not significant in summer and autumn. The soil salinity at both depth dropped significantly within 1-7 days after the big rain event. Soil salinity at the depth of 10 cm dropped sharply at the beginning of the big rain event and then kept stable while the soil salinity at the depth of 30cm dropped more constantly.