Soil organic carbon stocks in permafrost-affected soils in West Greenland

Little is known about soil organic carbon (SOC) stocks in permafrost-affected soils in Greenland. Generally, occurrence and stocks of SOC in permafrost-affected soils of the Arctic were underestimated for many years. Compared to the assumed dimension of the influence of carbon dynamics on climate change this knowledge should be substantially widened. A total of 155 soil samples were used to get abetter understanding about SOC stocks, depth function and spatial distribution of SOC in permafrost-affected soils in a characteristic deglaciated valley in West Greenland southeast of Kangerlussuaq. The valley is characterized by a high variability of active layer thickness and pedo-variance mainly caused by topography. The average SOC stock of the Umimmalissuaq valley is 9.9 kg m(-2) in the upper 30 cm and around 30 kg m(-2) in the first meter, which is remarkably higher than regional predictions with 6-15.9 kg m(-2) in the first 100 cm. To account for spatial heterogeneity landscape units are developed which are most useful for grouping and predicting SOC stocks. The SOC store measured 14.2 kg m(-2) in the upper 30 cm, 11.5 kg m(-2) on north-facing slopes, and 8.4 kg m(-2) on south-facing slopes. Little SOC stocks with around 6 kg m(-2) were found under abrasion fields particularly on hilltops and moraine ridges. Soils on south-faring slopes usually have very low SOC stocks in deeper soil horizons except of organic rich horizons in rarely occurring paleosols. North-facing soils and valley bottom slopes generally have high SOC stocks of around 19 kg SOC m(-2) in soil horizons with a depth of 30-100 cm. In general, the main influencing parameter on SOC stocks is the soil organic matter input from the vegetative cover. The vegetative cover is mainly a result of topographic position and aspect related to the ice margin and katabatic winds. Soil moisture and high active layer may influence SOC stocks positively. (C) 2016 Elsevier B.V. All rights reserved.