Soil organic carbon stock as affected by land use/cover changes in the humid region of northern Iran

This study was conducted to determine the changes in the soil carbon stocks as influenced by land use in a humid zone of Deylaman district (10,876 ha), a mountainous region of northern Iran. For this, land use maps were produced from TM and ETM+ images for 1985, 2000 and 2010 years; and this was supplemented by field measurement of soil carbon in 2010. The results showed that the mean soil organic carbon (SOC) density was 6.7 +/- 1.8 kg C m(-2), 5.2 +/- 3.4 kg C m(-2) and 3.2 +/- 1.8 kg C m(-2) for 0-20 cm soil layer and 4.8 +/- 1.9 kg C m(-2), 3.1 +/- 2 kg C m(-2) and 2.7 +/- 1.8 kg C m(-2) for 20-40 cm soil layer in forest, rangeland and cultivated land, respectively. During the past 25 years, 14.4% of the forest area had been converted to rangeland; and 28.4% of rangelands had been converted to cultivated land. According to the historical land use changes in the study area, the highest loss of SOC stocks resulted from the conversion of the forest to rangeland (0.45x10(4) Mg C in 0-40 cm depth layer); and the conversion of rangeland to cultivated land (0.37x10(4) Mg C in 0-40 cm), which typically led to the loss of soil carbon in the area studied. The knowledge on the historical land use changes and its influence on overall SOC stocks could be helpful for making management decision for farmers and policy managers in the future, for enhancing the potential of C sequestration in northern Iran.