Spatial variability of soil organic carbon in relation to site properties: a case study in Tongyu County, Jilin Province

Spatial variability of SOC concentrations in relation to site properties, including topography, soil types, land uses, soil texture, pH and other variables, was, investigated by using conventional statistics, geostatistics and geographical information system (GIS) analyses, taking Tongyu County, Jilin Province as a study area. 191 topsoil samples were taken in September 2006. Statistical significant (P<0.01) positive correlation between SOC and total Nitrogen(TN), negative correlation between SOC and sand content, relative elevation were observed, with low correlation between SOC and pH, electronic conductivity (EC). There was no significant difference among the main land use types, which indicated that land use type was not a main determinant of spatial distribution of SOC in this area. SOC in Aeolian soil and solonetz were the lowest and SOC in chemozem, meadow soil and wetland soil were relatively higher. The experimental variogram of SOC has been fitted with an exponential model. Geostatistical analysis showed that SOC had a moderate spatial autocorrelation, which was mainly induced by structural factors. The spatial distribution pattern of SOC concentrations interpolated by Kriging showed that SOC increased from west to east in the study area and exhibited the strip distribution with nearly north-south orientation, which is approximately consistent with the spatial structure of topography