太湖流域典型地区土壤磷素含量的空间变异特征

Characteristics of Spatial Variability of Total Phosphorus in Soil of the Typical Area of Taihu Lake Watershed

在地统计学和地理信息系统的支持下 ,以半方差函数为基本工具 ,分析了太湖流域典型地区土壤耕层全磷含量的空间变异特征 ,并运用块段克立格法进行线性无偏最优插值 ,制作了土壤耕层全磷含量的空间分布图。结果表明 :研究区域土壤全磷含量具有中等的空间相关性和良好的结构性 ,其自相关距离在 11km左右 ;土壤磷素含量的空间分布具有明显的斑块状特点 ,沿江平田区、地势低洼的圩田及低平田区磷素的含量相对较高 ,应作为农业面源磷污染的重点监控对象。

Nonpoint sources of P in agriculture soils have been identified as one of the main causes of freshwater eutrophication. Studies have showed that decades of P fertilization at rates exceeding the amount removed by crops have resulted in widespread accumulation of P in agriculture soils in Taihu Lake watershed, and the accumulation of P will increase the potential of sol P loss to surface waters. Therefore, studying the spatial variability of soil P at large scale will be helpful to develop management practices for controlling agriculture nonpoint P pollution. In this paper, a geostatistics method, with Geographic Information System (GIS), was applied to study the spatial variability of total soil P in the typical area of Taihu Lake watershed. The results showed that the spatial distribution features of the total soil P could be quantitatively described by semivariogram which could be fitted by exponential model. The ratios of nugget to sill at different lag intervals varied from 0.396 to 0.445, indicting that the total P in soil of the studied area had a relatively good spatial autocorrelation, and the range of autocorrelation extended to about 11km. The maps of the total soil P made by block kriging based on the fitted model depicted that the river shore land of northern part of Jiangyin county and low limnetic plan of the studied area generally had more P than the other places ,and much more attention should be paid to such places for the sake of protection of surface water quality.