Spatial Distribution of Soil Organic Matter in Surface Soils of Three Climatic Zones in Isfahan Province

Organic matter and its related soil properties are among the most important indicators of soil quality. Despite the importance of soil organic carbon, no comprehensive study has been done on organic carbon changes in soils of the Isfahan Province. The objective of this research was to investigate factors affecting soil organic carbon in soils of this province. A total of 248 surface soil samples were collected from different climatic zones of the province. Soil properties were measured by standard laboratory methods. Long-term temperature and precipitation data for 21 synoptic stations in the Isfahan Province were collected. Regression equation between each climatic parameter and elevation was established. These significant equations were used to estimate temperature and precipitation in the sampling points. Principal component analysis (PCA) was used to find the most effective factors which controlled soil variability in the study area. Multiple linear regression analysis was developed to estimate soil organic carbon in the study area. The results showed that four principal components control soil organic carbon in the study area, namely, climate and soil texture, soil salinity, gypsum, and calcium carbonate percentage. Climate and soil texture were identified by multiple linear regression as the most important factors influencing the soil organic carbon in the study area. There was significant statistical difference in the soil organic carbon percentage among different climatic zones. Due to considerable climatic differences and low amounts of soil organic carbon in the Isfahan Province, long-term planning and management practices are needed to prevent carbon loss and soil degradation, especially in arid and semi-arid regions.