| With the development of economic, ecological environment and security issues are paid more attentions, as well as the prediction of ecological security and the construction of ecological security-warning on the base of predict research. Located in the west-pacific coastline and the estuary of China's largest river, Chongming Island considered as the last ecological land in Shanghai, and it plans to become a real ecological island in 21 century for leaving space to the ecological protection and sampling sites selection to the world level project, according to the latest planning and development orientation. So soil pollution monitor, surveillance and comprehensive evaluation of fertility which are closely related to the ecological security are become one of the most important part in ecological security-warning program. Soil is a nature complex that has complex morphology and evolution, carried out spatial variability research of soil nutrition has great significance to the farmland fertilization, nutrition efficiency and reduction of environmental pollution which induced by over fertilization.Soil was a natural synthesis with complicated configuration and evolvement process. The study on soil spatial variability of soil nutrients is very important to promote the development of soil science. It is not improving the resource utilization ratio of soil nutrients, but also reducing the environmental pollution.Based on the soil land use and development conditions,on the one hand ,the study discussed how to optimize the distribution of sampling sites by using geostatistics and GIS technology. On the other hand, according to the process of soil formation and land use, the research also analysis fertility evaluation with method of combining Nemero index. On the basis of spatial distribution of soil nutrient, we hope that we can provide evidence for rational fertilization, environmental protection and ecological construction in Chongming.In the research, first of all, by analyzing spatial variability of soil heavy metals, spatial interpolations were made by universal kriging and inverse distance weighted methods. The results are as following:The range of Zn is 2000m which has no variation of the angle; the anisotropy of Hg is not significant, its range is 2500m; the anisotropy of As, Cu and Pb are the same 50°, their range are 55000m, 35000m and 5000m; the Cr, Cd, Ni variation of angle of 300 degrees, variable range is 7500m, 40000m, 16000m. As variable-range and anisotropy are the most important parameters, it is necessary to develop the second sample plan in order to obtain a more accurate spatial variability of soil nutrients. Secondly, this paper studied the spatial variability and distribution of available Cu, Mn, Zn, B, Mo, Fe in the soil surface of Chongming island. According to the analysis of soil trace elements, the best lag size and scale were chosen. The results showed that: six indicators all shown strong variability. Thirdly, based on the Spatial Variability research on the 18 chemical indexes, this paper performed Supervised Classification to the ETM image produced in 2002 by ERDAS. 6 Principal component factors were selected by using PCA and factor axis; 3-band graphic was obtained by composing bands; and 7 classes were eventually reclassified via ArcGIS. After introducing the pedogenic development factors which were selected as evaluated objects to conduct comprehensive evaluation of the soil by combining Membership function and Nemero Index, five levels of soil maturity were discerned by the evaluation in each zone separately.Based on the above, this paper obtained the following conclusions:1. The feature of soil behaves as an obvious spatial heterogeneity and different observational scales of soil nutrient and heavy metal elements'distributions are suitable to be analyzed and predicted by geostatistical models. As a magnificent method in analyzing the spatial variation of soil, difference among the interpolations of different elements that being estimated at different sampling scales come up under the help of geostatistics with GIS. In this article, according to the sampling data of traditional"S"-sampling method, detailed analysis on the spatial distribution was performed, especially on the anisotropy and range of each element, with the gradient of terrain and land use factors, to present a reformative schema of sampling. The result shows a discernable advantage of the second sampling schema that the variations are more precise to reflect the status of interesting area. Therefore, the method that to draw up a schema of second sampling referring to the results observed from the first sampling sites is feasible and indispensable.2. In the research on soil nutrients, the crucial issue is to choose an appropriate model, scale and relevant parameters for interpolation. The model and parameter suggested automatically by ArcGIS software itself could hardly provide a satisfactory portray of the features of soil data. By iterate the lag sizes of different scales, the effective parameters and model could be found out with the minimum value of nugget effect. Introduced multi-scaled models to interpolation in this research, And these models are proved consequently to improve not only the accuracy of interpolation but also the similarity of the variation features of soil nutrients.3. Chongming island is formed by rush, and its development process is quite complicated. The changes at different degrees take place every year. It is important to understand Chongming's soil fertility. With the investigation to the limiting factors of soil development, classification and division to 18 chemical index of soil, as well as did comprehensive evaluation to the soil fertility; soil fertility of research area is objectively reflected. This approach needs more data and related technology by comparing with traditional method, but under the existing condition, this approach is feasible and has good results to this research area.
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