Hangzhou Bay Tideland Soil Properties Spatial Variations

Studies on Spatio-temporal Change and Variability of Properties of Coastal Saline Soils in Hangzhou Gulf The studies were conducted on the south of I-Iangzhou Gulf at Town Xinpu, which, as the experiment and education base of Zhejiang University, was brought into being by dyking 4 times from as early as 1815 to 1973. This paper analyses the spatio-temporal change and variability of properties of coastal saline soils in Hangzhou Gulf at different times, using classical statistics and geostatistics. 100 sampling points, arranged to meet the requirements of equality and contrast, were taken at different areas and depths. The content of CaCO3, total amount of salts, pH, organic matter, available Cu, Mn and Zn etc. Based on the results of the analysis, this paper probes the long-run spatio-temporal change and variability of properties of coastal saline soils in Hangzhou Gulf It is shown as follows: The amount and distribution of CaCO3 are important to fertility, erosion, available water-holding capacity and genesis of a soil. Content of carbonates is used to define carbonatic, particle size, calcareous soil classes, and calcic and petrocalcic horizons. And specifically the CaCO3 content is a diagnostic standard by which to classify different soils. Spatio-temporal change and variability of the CaCO3 content is discussed along as well as vertically to the dykes. It is found that the CaCO3 content shows great difference in the those directions. Along the dykes, the variability models are different at the surface, while, at other depths, 60 are similar. At the same depths results show larger fractional dimension values and changes vertically to the dykes than those along them implying, comparatively, spatial variability caused by random factors is more prominent along the dykes. It is also found that at the surface, the CaCO3 content has the greatest variability coefficients. As it goes deeper, the variability coefficients decrease gradually, indicating the uniformity of soil properties. In addition decalfication rates are calculated, results showing a general decrease along the depths with that at the surface the greatest. As reckoned, it will take 350 years for the surface soil to be fully decalcified. The total amount of salts is an important characteristic of saline soils, an impeding factor to the growth of plants. As to the areas dyked at the same time, the total amount of salts increase with the depth, due to the difference of intensity of washing and cultivation. As to the areas dyked at different times, newly dyked areas show greater total amount of salts. Compared to the content of CaCO3, total amount of salts are a much more changeable factor. Though it is not the same at different depths, the total amount of salts changes generally uniformly. In general, it is found that the total amount of salts shows difference between the direction along and that vertical to the dykes. Along the dykes random factors play a greater role in causing spatial variability. The variograms exhibit certain periodicity, implying stripes at the surface. Vertically to the dykes, the variograms show a greater tendency in increase, indicating structural difference, which time plays an important part in bringing into being. Along the dykes limit distances are small and fractional dimension values, large, spatial variability is caused mainly by...