Soil Organic Carbon Stocks and Nitrogen Content Comparison in Different Slope Positions in Native Grasslands and Adjacent Cultivated Soils (Case Study: Kermanshah Mountain Rangelands, Iran)

Global warming has been largely driven by increasing atmospheric GHG (Green House Gasses), particularly carbon dioxide caused by fossil fuels burning. The current trend can not be stopped except by reducing fossil fuel consumption or storing organic carbon in soil or earthchr('39')s biological systems such as forests, rangelands and agricultural systems. This study was conducted to determine the effect of slope position as well as land use effect on organic carbon storage and nitrogen content in a mountainous area in the middle of Zagros chain mountain ranges in Kermanshah. The results showed that slope position has significant effect on aboveground biomass, SOC (Soil Organic Carbon) and Soil Nitrogen Content (SNC). Comparison of different rangeland slopes showed that the lowest slope position (20-30%) had the highest amount of SOC, SNC and aboveground biomass. The presence of scattered trees in the shoulder position added significant amount of soil organic carbon and total nitrogen content to the soil beneath the trees, resulting from the input of tree litter and positive effect of trees canopy on herbaceous layer. Comparison of natural rangeland in all slope positions and adjacent cropland showed higher amount of SOC and SNC in grasslands. Comparison of croplands and adjacent rangelands with the same slope shows a significant increase in organic carbon content (P>0.05) and soil nitrogen percentage in the rangelands. This situation is also seen in other rangeland slope classes.