Title: Rangeland degradation in Mongolia: Changes in vegetation composition and biomass, and potential effect on soil carbon

Mongolian rangelands are degrading due to changes in land management and climate change. Grazing-induced disturbances will further exacerbate the problem and potentially increase the soil organic carbon (SOC) rate of loss. We lack understanding on what ecosystem processes are involved and how they interact and how they are expressed in different ecological zones of Mongolia in order to be able to mitigate the problems. To address these challenges, a series of experiments was designed, comparing open pastures and enclosures in different ecological zones of Mongolia, focusing on vegetation and soil properties. In addition, an effort was made to analyze Icelandic soil data to compare vegetation cover and SOC accumulation. The results suggest that grazing reduces vegetation cover by 9.1%, biomass by 23.1%. Species diversity decreased and species composition changed with grazing. Species cover, biomass, species diversity, and species numbers differed significantly between ecological zones, suggesting an influential site effect, here interpreted as climatic effect. SOC differed significantly between land reclamation treatments and soil depths. The highest values were found in the grass treatment and the topsoils in all treatments. Continuous grazing affects biodiversity, vegetation composition, biomass and cover. However, the effects differ between climatic zones. Vegetation cover and SOC appear to be positively correlated, suggesting that overgrazing will reduce soil fertility and hence the grazing resources.