Spatial variability characteristics of farmland soil organic matter in Pinggu District, Beijing, China

Based on the analysis of 989 topsoil sampling points in Pinggu District , Beijing, the county scale spatial characteristics of farmland soil organic matter (SOM) content were studied employing traditional statistics, geostatistics and geographic information system (GIS). The results of traditional statistics show that SOM content follows a lognormal distribution, with a arithmetic mean of 15.36 g?kg-1. SOM content was moderately variable in the area, with a coefficient of variation (C.V.) of 0.32. Based on the results of ANOVA, elevation and land use type both affect significantly the distribution of SOM content in study area. The geostatistical characteristics of SOM content were analyzed under GIS platform. The distribution of SOM content in the study area exhibit a one–order (linear) trend and anisotropy, the spatial autocorrelation distances (ranges) are large (17.0 km on the long axle and 12.6 km on the short axle) and the degree of spatial autocorrelation is moderate. A contour map of SOM content was obtained using ordinary Kriging interpolation, and the spatial distribution pattern was analyzed further. The SOM spatial pattern was approximately consistent with the spatial structure of topography and land use type.