Carbon availability in soils of thermo-erosional valleys– a case study from a valley on Herschel Island,West Canadian Arctic

Permafrost is a perennially frozen ground often occurring in periglacial environments. Due to its frozen state, organic carbon accumulates in the soils. By temperature rise and thaw of the active layer, these stocks become vulnerable to microbial decomposition. To predict the future of organic carbon in the Arctic, it is necessary to expand the knowledge on its spatial distribution across arctic environments. This study examined the spatial distribution of organic carbon and its availability within a valley, which is subjected to thermo-erosion on Herschel Island, Yukon Territory. By analyses of soil samples variations in soil organic carbon, total nitrogen and the carbon-to-nitrogen ratio (C/N) were investigated. Ecological units, hillslope position and distance to shore helped to identify spatial differences between sites. The analyses showed that highest values for soil organic carbon, total nitrogen and C/N occurred on uplands, followed closely of the values in the valley bed. On slopes the values of soil organic carbon, total nitrogen and C/N were lower. Further, differences of the soil organic carbon, total nitrogen and C/N stocks occurred across the valley locations with distance to the shore. Upstream the soil organic carbon, total nitrogen and C/N stocks were higher to those downstream. Sites on slopes and downstream are characterized by continuous surface disturbances due to permafrost degradation, thermo-erosion and hillslope processes. This study could demonstrate that even in local scales organic carbon stocks and its availability differs spatially depending on environmental parameters.