Spatial variability of soil organic carbon on different slope positions of loess hillslopes in Toshan area, Golestan Province

In this study, classical statistics and geostatistical methods were used to determine changes in spatial heterogeneity of soil organic carbon (SOC) in relation to topography and different slope positions in loess hillslopes in Toshan region located in Golestan Province. In this investigation, three different geostatistical methods i.e Kriging, Cokriging and Inverse distance weighted have been used and evaluated. Hence, 234 soil samples at regular grid were collected from different parts of a slope. In this research, the evaluation criteria were Mean Error and Root Mean Square Error with the Cross Validation method. The results showed that ordinary cokriging method with clay as covariate estimated better results in evaluation of SOC in whole parts of hillslope with RMSE values of 0.2552 in comparison with Kriging and Inverse distance weighted methods. Interpolation map of organic carbon from whole part of hillslope showed lower SOC concentrations with increasing elevation and slope gradient. Spatial correlation ratio of SOC was different in various slope positions and these patterns were closely related to the structure of topography.