Spatio-temporal Variability Of Coastal Soil Salinity In Reclaimed Zone And Influence On Land Use

Since Reform and Opening, Zhejiang province has experienced rapid development of industrialization and urbanization, and the demand for lands increases sharply, leading to rapid loss of farmland, therefore the government have to find a way to solve the conflict between demand and supply by exploiting the reserved land resource in the coastal reclamation. Research on soil salt spatio-temporal variability and its influence on land use will benefit the achievement of sustainable agriculture development and ecology cycle.The coastal reclamation region, which is located in the north of Shangyu in Zhejiang province (in south of Hangzhou gulf), is the study area. In this region, the method of decision tree based on C4.5 algorithm was applied to interpreting the remote sensing images data which were gained in the year of 2001 and 2010. Meanwhile, RS GIS and Geostatistics analysis software was applied to make comparison of the soil salt temporal-spatial change between 2001and 2010, in purpose of seeking for the characteristics and trend of its spatio-temporal change, drawing the conclusion of its influence on land use. The study results include four parts as follows:1. The normalized difference vegetation index(NDVI) and spectral values of each band of remote sensing image are chose as the classification index, and classification method of the decision tree based on the C4.5 algorithm the can not only use the spectrum information of ground objects, but also combined it with ground objects’other information, so differences in all kinds of land can be accurately distinguished in result of raising the accuracy of classification.2. In the subareas which was reclaimed before 1991, crops with poor salt tolerance are dominant and in the subareas which were reclaimed after 1991, fishery is the primary pattern of land use. At the same time, the distribution of land use pattern is influenced by soil salinity. Paddy land, vegetable field and orchard mainly distribute in subarea with low salinity, and fishery and dry land in which cotton is primarily cultivated mainly distribute in subarea with high salinity.3. The result of regional division research on spatio-temporal variability of soil salinity shows that, in subareas with longer reclamation history, the soil salinity is low, and spatial variability is weak, and temporal variability is strong; in subareas with longer reclamation history, the condition is opposite. In the same subarea, soil salinity reduces with time in some degree and its spatial autocorrelation is diminished.4. By stacking the land type figure and the soil salinity figure, the results show that regions with different soil salinty are suitable for different land use patterns, and the spatial distribution of land use pattern is influenced by spatio-temporal variability of soil salinty, and land use pattern varies with soil salinity.