Title: Assessment of soil organic carbon stock variation in cropland, restored and eroded lands in Gunnarsholt, Iceland

Soil organic carbon is an important component of soil organic matter that serves as a useful indicator of soil condition. It also explains the soils’ potential to serve as sinks for inorganic carbon in climate change mitigation. Land restoration is a promising tool for carbon sequestration in soils. This study assessed the variation of soil organic carbon content among cropland, restored land and eroded land in Iceland. The cropland and restored land were both revegetated around 1976 and the site for the cropland converted in 2009. The study employed the loss-on-ignition method to estimate soil organic matter content. The soil organic carbon – loss-on-ignition relationship conversion factor was determined using regressions and used to calculate soil organic carbon. The results showed that soil organic carbon concentration was higher in the restored land than in the cropland and the eroded land, in the top 5 cm depth of soil. However, the highest soil organic carbon concentration was observed in the cropland compared to both the restored land and the eroded land for the 5-15 cm depth. For the top 15 cm depth, no significant difference was observed between the cropland and the restored land in soil organic carbon concentration. The total soil organic carbon stocks in the top 15 cm depth was highest in cropland compared to the restored land and the eroded land. The soil organic carbon contents for the eroded land were significantly lowest for both depths. The findings suggest that land restoration has great potential to improve soil organic carbon content.