Effects of Land Use and Soil characteristics on Changes in Soil Organic Carbon (Case Study: Ala Area- Semnan)

Rising atmospheric carbon dioxide is one of the main causes of climate change and its devastating environmental consequences, such as global warming. Soils are the third largest carbon storehouse, and the amount of carbon storage is strongly influenced by the land use management. The aim of this study was to investigate the changes in carbon storage in different land uses included Punica granatum orchard, Medicago sativa farm, rangeland, Hordeum vulgare farm and fallow, under impact of soil properties such as sand, clay, silt, nitrogen, phosphorus, potassium, organic carbon, pH and EC, in Ala area of Semnan. In the selected land uses 30 soil samples were taken in both 0 - 5 and 5 - 30 cm soil depths in three. In order to investigate the effect of land use type in two soil depths studied on soil carbon content, analysis of variance and Duncan's test was used to compare the means. Pearson correlation was used to investigate the relationship between soil properties as independent variables and soil organic carbon as a dependent variable. Also, multiple regression analysis was performed to determine relationship type between the variables. According to the results, the type of land use in both soil depths has a significant effect on soil carbon storage. The highest average soil carbon storage in 0 - 5 and 5 - 30 cm soil depths in alfalfa and pomegranate orchard land uses are 16.14 and 68.11 t/ha, respectively. The lowest amount of carbon storage in 0 - 5 and 5 to 30 cm soil depths related to rangeland use are 6.23 and 16.58 hectare/ha, respectively. Pearson correlation coefficient between organic carbon and soil factors of nitrogen and phosphorus were statistically significant with r of 0.8 and 0.59, respectively. Since the correlation between organic carbon and phosphorus is low, it was omitted in the regression analysis. Finally, the percentage of soil organic carbon was obtained based on the percentage of soil nitrogen. In general, land use change from pasture to arable land and pomegranate orchard can have a significant effect on increasing soil carbon storage in the study area. Soil properties other than nitrogen have no significant effect on soil organic carbon.