Abstract: According to the data of organic matter (OM), total nitrogen (TN), available phosphrus (AP) and available potassium (AK) of topsoil samples (0~20 cm) collected from 135 sites in 2007, the spatial distribution characteristics of the main soil nutrients in three islands in Chongming，Chongming island， Changxing island and Hengsha island，were analyzed using the methods of geostatistics and overlay analysis in the software of ArcGIS 9.1. The results showed that the areas with higher OM and TN were mainly distributed in Chengqiao town and Bao town, and the values of both indices declined gradually towards northwest and northeast. The distribution trends of AP and AK were basically complementary. When comparing the values of 1980 and 2007 in terms of all these indexes, OM and TN did not change significantly, whereas AP increased rapidly and AK decreased. The results further revealed the unbalance in soil fertilization.

Key words: soil nutrients, spatio-temporal variation, GIS, Chongming, soil nutrients, spatio-temporal variation, GIS