基于地统计学和GIS的太湖典型地区土壤属性制图研究——以土壤全氮制图为例

在地理信息系统(GIS)支持下，运用地统计学方法对太湖典型地区耕层土壤全氮含量的空间变异特征进行分析，探讨了适用于研究区域土壤全氮制图的最佳邻域，并在此基础上利用块段克立格(Block Kriging)法绘制了土壤全氮含量空间分布图。结果表明，土壤全氮的空间变异性在40km步长变化域上表现为明显的各向同性，超出这个范围，土壤全氮空间变异的各向异性明显增强，以40km步长变化域上土壤全氮的空间结构特征作为Kriging插值依据有助于提高制图精度。制图结果表明，研究区域土壤全氮含量在江阴和宜兴两市境内普遍较高，锡山和武进两市相对较低；且高值斑块区主要分布在地势低洼的圩田区，这是人为施肥和土壤特性共同影响的结果。Kriging估值标准差分布图可为评价和提高制图精度提供十分有用信息。

MAPPING SOIL PROPERTIES OF THE TYPICAL AREA OF TAIHU LAKE WATERSHED BY GEOSTATISTICS AND GEOGRAPHIC INFORMATION SYSTEMS--A CASE STUDY OF TOTAL NITROGEN IN TOPSOIL

Conventional soil mapping is generally based on the conceptual models which reflect the relationship between soil genetic factors and its spatial variability,and usually appears to be qualitative and subjective as it is difficult to gather suffi cient data to examine these models over large areas.However,with the development of geostatistics and Geographic Information Systems(GIS),methods of mapping soil properties have also been improved.In this paper,a geostatistic method combined with GIS was applied to characterize and map the spatial variability of total nitrogen(N)in topsoil in the typical area of Taihu Lake watershed.The results showed that the spatial variability of total N were apparent in isotropy within the maximum lag extent of 40 km and its anisotropy had little influence on kriging.The isotropic semivariogram through lags of 40 km indicated that the total N in the studied area had a relatively good autocorrelation,and the range of autocorrelation extended to about 16 km.The maps of the total N made by block kriging based on the fitted exponential model depicted that the soils in Jiangyin and Yixing county gen erally had more N than that in the other two counties and the hot spots of high N were apparent in low-lying polderland.High estimate standard deviations of the kriged estimates occurred where data were sparse and additional samples from the sparse places would increase the accuracy of the total N map which would be useful to conduct optimal fertilization and develop management practices to control the non point sources of N pollution.