The relationship between different salt crust thickness and soil physical properties in Ebinur Lake wetland and its influencing factors
To investigate the Ebinur lake wetland soil physical properties under salt crusts and their interactions, we selected representative samples of 30 sites from different areas in wetland and with different salt crust thickness, on the depth of 0-20 cm, 20-40 cm, and 40-60 cm, analyzed the physical properties of soil, including porosity, particle size, and water content by combining field investigation and laboratory tests, and discussed the influences of properties on salt crust thickness. The results show that: 1) The grain size of soil covered by salt crust is mainly in the range of 1.00-0.05 mm during the declining and the growing periods, while at the mature stage it is mainly in the range of 0.01-0.001 mm. The bulk density of soil is ranked from the highest one of the salt crust in the growing period (1.81 g/cm³), to that of the mature period (1.58 g/cm³) and to the lowest one of that in the declining period (1.34 g/cm³). The soil porosity decreases gradually from the declining period (50.8%), mature period (40.7%) to the growing period (32.6%). Soil moisture content from high to low is in the order of growing period (32.5 g/kg), mature period (21.7 g/kg), and the declining period (16.2 g/kg). Soil saturated water content and soil moisture content are in the order of the declining period, mature period, and the growing period from high to low.2) Salt crust thickness is significantly positively correlated with both capillary porosity and soil particle size in the range of 0.05-1 mm for soil in the depth of 0~20cm soil (P<0.01), while negatively correlated with soil bulk density (P<0.05). The correlation between salt crust thickness and soil physical properties gradually decreases with the increase of depth.3) The factors influencing salt crust thickness mainly include the capillary porosity as the first principal component (78.1%) and the soil particle size as the second principal component (16.5%). The increase of porosity can promote the formation and accumulation of salt crust, and make the salt crust thicker, while the increase of grains in the size of 0.001 to 0.01 mm can inhibit the formation and accumulation of salt crust, and make salt crust thinner. Overall, salt crust changes the physical characteristics of soil (water content, porosity, and grain size); on the other hand, the physical properties of soil affect the thickness of salt crust.