Spatial variability of soil particle size distribution, organic carbon and aggregate stability in range lands of eastern Sabalan, Ardabil Province, Iran

The purpose of this study was to compare the spatial variability of soil physical quality variables in range lands of eastern Sabalan in Ardabil Province, Iran. Totally, 98 Soil samples were regularly collected in 200 × 200 m2 grid and the position of points was recorded with Global Position System. Particle size distribution of sand, silt and clay and mean weight diameter (MWD) of wet aggregates were measured in disturbed soil samples. Measured soil variables were transferred to the Geographic Information System (GIS) and GS + softwares. After determining geostatistical parameters, the suitable maps were prepared for soil variables using interpolation methods. Spatial structure (ratio of nugget effect to sill) parameter was determined strong for clay, silt and sand variables and moderate for MWD and OC variables. The best experimental semivariograms were obtained exponential model for MWD and OC, and spherical model for clay, sand and silt variables. Based on mean absolute error (MAE) and mean bias error (MBE) criteria, kriging method estimated better than inverse distance weighting (IDW) method for sand, clay, OC and MWD variables. The IDW method had higher accuracy in estimating silt relative to kriging method. The spatial variability maps indicated that the soil structural stability is poor (MWD= 0.51 mm) due to the high content of sand (67.25%) and low content of OC (1.48%) in the studied region.

Keywords:

range lands , soil physical quality , spatial structure , kriging