Title: Comparison of carbon and nitrogen stocks under grazed and un-grazed areas

Grazing is an important part of the grassland ecosystem dynamics and plays a key role in carbon and nitrogen storage in the system. The exclusion from grazing is considered one of the major practical implications to restore the ecosystem and prevent grassland degradation. The study focused on the effects of grazing on vegetation and soil properties in subarctic grassland in Iceland, comparing a grazed and an un-grazed area. The aim of this pilot study was to examine the effects of exclusion from grazing on the main compartments (soil, vegetation and sward/litter) of carbon and nitrogen storage in the system. The area excluded from grazing had less total carbon and nitrogen storage in the system down to 30 cm depth in soil and the distribution of the carbon and nitrogen stocks among the system compartments was slightly different. The results showed that the carbon and nitrogen stocks in vegetation and sward/litter were slightly higher in the un-grazed area as compared to the grazed area, which indicated the recovery of the ecosystem after exclusion from grazing, whereas the carbon and nitrogen in soil was significantly higher in the grazed area as compared to the ungrazed area. The study did not answer whether the difference observed in soil carbon and nitrogen stocks was due to the effects of grazing or environmental factors such as soil moisture. In addition, the soil was the largest reservoir of carbon and nitrogen in both study areas. Therefore, further research to investigate the effects of exclusion from grazing are needed not only to understand the ecology of this fragile ecosystem but also to enhance sustainability of grazing management.