Characteristics of spatial distribution of soil organic matter and total nitrogen as well as the influencing factors in three islands in chongming

According to the data of soil organic matter(SOM) and total nitrogen(TN) contents in the samples collected from 135 points in topsoil in 2007,the characteristics of spatial distribution and the influencing factors of SOM and TN in three islands in Chongming were analyzed using the software ArcGIS 9.1 with geostatistics and overlay analysis.The results showed that the contents of SOM (18.97%±9.27)g·kg-1 and TN(0.93±0.47)g·kg-1 were relatively low in general.The coefficient of variation(CV) of SOM and TN was 0.509 6 and 0.488 6,respectively.The semivariogram of total soil nitrogen was simulated by the spherical model,and the semivariogram of organic matter,Gaussian.The ratio of nugget to sill of total nitrogen and organic matter was 0.625 and 0.653,respectively,indicating that the spatial autocorrelation of SOM and TN was moderately interdependent,respectively.From the areas with higher SOM and TN contents distributing in Chenqiao and Bao town to the vicinity,the values of SOM and TN decreased gradually.Xisha,Dongtan and Beihu were low-value areas.The spatial distributions of SOM and TN were related to the history of reclamation and fertilization,as well as the effect of urbanization.