Carbon dynamics in an alluvial fan in the eastern Canadian Arctic

Alluvial fans are common features of mountainous landscapes in circumpolar regions and are characterized by a suit of hillslope processes that drive sediment distribution. At present there is little known about the biogeochemistry of these systems. Thus, this study aimed to understand alluvial fan soil carbon (C) dynamics. Surface and permafrost soil was retrieved in the apex, mid-section, and foot of a fan on Bylot Island in the Canadian Arctic. Soil characteristics such as grain size distribution, ice content and major ions, electric conductivity, as well as total C and nitrogen (N) contents were determined. Moreover, soil organic carbon (SOC) pools were assessed using density fractionation in combination with acid hydrolysis. Despite the strong influence of hillslope processes on physical sediment characteristics, hillslope location had no effect on SOC and N stocks. However, fractionation analysis showed that hillslope processes facilitate the degradation of soil C prior to its burial and integration into permafrost soil, where over 90% of the SOC pool associated with the mineral-fraction is resistant to degradation. Hence, SOC pools at the foot of alluvial fans may be considered relatively stable.