HR: 0800h
AN: B41D-0751    [Abstracts]
TI: A Multi-scale, Multi-method Approach to Examining the Effects of Landscape Age on Dissolved Organic Carbon and Nitrogen Movement in Arctic Alaska
AU: * Whittinghill, K A
EM: whit0924@umn.edu
AF: University of Minnesota, 100 Ecology 1987 Upper Buford Circle, Saint Paul, MN 55108, United States
AU: Hobbie, S E
EM: shobbie@umn.edu
AF: University of Minnesota, 100 Ecology 1987 Upper Buford Circle, Saint Paul, MN 55108, United States
AU: Finlay, J C
EM: jfinlay@umn.edu
AF: University of Minnesota, 100 Ecology 1987 Upper Buford Circle, Saint Paul, MN 55108, United States
AB: Studies of arctic terrestrial carbon cycling have emphasized gaseous carbon fluxes, with less attention to dissolved carbon fluxes. However, recent work suggests that dissolved fluxes could be significant components of arctic terrestrial carbon budgets. Nitrogen availability exerts a strong control on terrestrial C balance through effects on plant productivity. Although most nitrogen in arctic systems is found in the organic form, little is known about the controls on dissolved organic nitrogen (DON) production and transport at high latitudes. We examined regional patterns of dissolved organic carbon (DOC) and DON production and concentrations over a glacial age chronosequence in northern Alaska. We used soil incubations, lysimeters, and stream sampling to study the relative importance of glacial age and associated differences in geochemistry at the plot, hillslope and watershed scale. Landscape age significantly affected DOC and DON production in soil incubations and DOC and DON concentrations in soil water at the plot scale. The importance of landscape age diminished at the more integrative hillslope and watershed scales, perhaps due to the influence of hillslope vegetation or riparian soils. DOC and DON concentrations were more correlated in laboratory incubations without vegetation and than at the hillslope and watershed scale. Two possible influences on dissolved carbon production that vary with landscape age are differences in exchangeable calcium and pH, which decrease over time as a result of weathering. In a factorial soil manipulation experiment with samples from multiple sites across the glacial age chronosequence, both decreasing pH and increasing exchangeable calcium concentrations significantly reduced the production of dissolved organic carbon. Our results suggest that landscape age is an important control on dissolved fluxes of carbon and nitrogen, but the effect is dependent on the scale of measurement.
DE: 0414 Biogeochemical cycles, processes, and modeling (0412, 0793, 1615, 4805, 4912)
DE: 0428 Carbon cycling (4806)
DE: 0469 Nitrogen cycling
DE: 0486 Soils/pedology (1865)
SC: Biogeosciences [B]
MN: 2007 Fall Meeting