Evaluation of Spatial variability of soil quality in Wildlife Refugee of Karkhe in southwestern Iran

Soil properties are continuous variables whose values at any location can be expected to vary according to direction and distance of separation from neighboring samples. The spatial variability and variation of soil properties should be quantified for a better understanding of the influence of such factors as management and pollution, and [mally for leading to more efficient management. Geostatistics provide descriptive tools such as variogram to characterize the spatial pattern of continuous soil attributes. This study addressed the spatial variability of soil properties at the regional scale using geostatistical method. The study was carried out in Wildlife Refugee of Karkhe in riparian forests of Karkhe river southwestern Iran. The soil was sampled in 2009 using 200 sampling point along parallel transects (perpendicular to the river). The distance between transects were 0.5 km. The sampling procedure was hierarchically, we considered maximum distance between samples as 0.5 km, but the samples were taken at 250m, 100m, 50m, 10m and 5m at different locations of sampling. At each transect point, three 50 cmx50 cmx25 cm samples were taken for analyses at each sampling campaign. Soil bulk density, total nitrogen and C/N were analyzed using geostatistics (variogram) in order to describe and quantify the spatial continuity. Soil properties showed spatial variability with the highest coefficient of variation being observed for C/N and the lowest for soil bulk density. The variograms revealed the presence of spatial autocorrelation. Soil bulk density was moderately spatially dependent, while Nt and C/N showed the weak spatial dependence. The range of influence was 810, 1200 and 3300 m respectively for C/N, Nt and bulk density. The contour maps produced by kriging, showed a heterogeneous and patchy structure for the estimated values of Nt and C/N. The kriging map also showed the highest increase in the area next to river for soil bulk density.