Lateral and Vertical Variations of Soil Organic and Inorganic Carbon Content in Aridisols and Entisols of a Rangeland

The influence of biological and physicochemical soil properties on the variations in soil organic and inorganic carbon (OC and IC) contents at the soil surface was studied. Three-dimensional plots of variations in OC, IC and the correlated properties were obtained. Soils of the study area were classified as Aridisols and Entisols used as a rangeland. Soil samples were collected from 38 representative points with a wide range of physicochemical soil properties; in addition, three important microbiological indicators-dehydrogenase enzyme activity (DHA), soil basal respiration, and bacterial population-were analyzed. Variation partitioning analysis was carried out to assess the determining factors influencing soil OC and IC variations in soil surface. Additionally, the principal component analysis (PCA) was applied to explore the patterns of determinant soil variables. Variation partitioning demonstrated that the physicochemical soil properties were the determining variables in explaining the variations of both OC and IC. A remarkable portion of the variations remained unexplained by any of the two explanatory sets according to this analysis. Soil OC was not significantly related to the biological soil properties. Soil OC was inversely related to IC, clay, and sodium contents in the soil profiles. Soil type-specific vertical trends were observed for soil OC and IC. Soil conditions and pedogenic processes were deduced to have a major role in OC and IC spatial variations according to the results of soil type-specific trends of variation. The results of this study can be useful for better soil management and OC and IC prediction, or spatial distribution patterns modeling.