Soil development, mineralogy and organic matter stocks in a West Greenlandic tundra landscape

• We examined soils from different landscape positions in a glacially shaped valley. • Slope dynamics and water availability control soil development and carbon stocks. • Soil carbon stocks are spatially highly heterogenous and underestimated in models. • Solifluction and cryoturbation are as important for carbon storage as waterlogging. Arctic warming increases the thaw depth of permafrost affected soils, altering the local water cycle and accelerating soil-forming processes and decomposition of soil organic matter. The consequences vary greatly across the circumpolar region due to strong heterogeneity in soil-forming factors and soil properties. Despite numerous studies have been carried out in the tundra of West Greenland, detailed descriptions of soil development under contrasting soil-hydrological conditions are lacking, which impairs the accuracy of soil maps and Earth-system models. We address this knowledge gap by analysing soil profiles from three field transects located at slopes of a glacially shaped valley and on a moraine within the same valley, representing typical environmental and geomorphological settings of West Greenland. Dryer soils dominated at the top of the slopes, with solifluction and cryoturbation shaping soil properties, while water logging and accumulation of organic matter characterized the lower end of the slopes. In the vicinity of a braided-river, the terrain was flat but well-drained and soils were shallow but organic-rich, overlying coarse rubble. We show that soil development depends strongly on slope dynamics and hydrological conditions. We also show that soil organic carbon stocks are highly heterogeneous with 4 ± 6 Mg C ha −1 in shallow and poorly developed soils and 451 ± 160 Mg C ha −1 in the upper meter of peat-rich wetlands. The results highlight the great heterogeneity in soil moisture and vegetation types, driving marked differences in soil development and carbon stocks across typical West Greenlandic tundra.