Effects of landscape age on small watershed carbon and nutrient fluxes in Arctic Alaska

    Dissolved organic matter (DOM) production and transport are key components of terrestrial and aquatic carbon (C) and nitrogen (N) cycling in arctic tundra systems. Responses of arctic terrestrial and aquatic primary productivity to climate change could be influenced by differences in organic nutrient availability and transport on diverse landscape types. Previous arctic research has shown that landscape age, and associated differences in geochemistry, has a significant effect on terrestrial DOM production, soil respiration, and soil N mineralization. However, whether differences in terrestrial biogeochemical cycling translate into differences in dissolved pools of C and N in soils and streams is unknown. To investigate this question, we compared growing-season soil and stream solute composition in small watersheds on glacial drift of four ages near Toolik Lake, AK. We sampled saturated and unsaturated soil water across a hillslope toposequence that included upper, middle, and riparian locations in each watershed. In all sites, soil water bicarbonate was significantly higher in riparian samples, while soil water dissolved organic carbon (DOC) and total dissolved nitrogen (TDN) were significantly higher in the upslope transects indicating significant transformations of C and N within the hillslope. High pH sites on younger glacial drift had significantly higher stream and soil water bicarbonate concentrations. Unlike previous laboratory results, there was no consistent pattern of DOC or TDN with landscape age. Our results suggest that under current permafrost and soil conditions, there is more variability in dissolved organic C and N availability within the hillslope than among landscapes of different ages.