Distributions of carbon in calcareous soils under different land uses in western Iran

Concentrations of Natural stable and unstable carbon in ecosystems have been used extensively to help to understand a wide range of soil processes and functions. This study was conducted to explore the effects of land use changes on different carbon fractions (F₁, F₂, F₃ and F₄), permanganate oxidizable carbon (POXC), soil organic carbon (SOC) and total organic carbon (TOC) associated with soils in calcareous soils of western Iran. Four popular land uses in the selected site including natural forest, range land, dryland farming and irrigated farming systems were employed as the basis of soil sampling. The results showed a strong relationship between land use conversion and SOC stocks changes. The greatest mean values for carbon content and the least mean values of CaCO₃ in bulk topsoil (0–15 cm) in the forest land were observed. Dryland farming had the least both active and passive pools of C in comparison with the other land uses. The positive and significant correlations was observed between SOC, Total C and POXC contents and different C fractions. Taking C and POXC pools into account, a more definitive picture of the soil C is obtained than when only total C is measured. The influence of land use changes on overall soil carbon stocks could be helpful for making management decision for farmers and policy makers in the future, for enhancing the potential of C sequestration in western Iran.