Tuesday, June 5, 2007
436

The Impact of Permafrost and Groundwater Flowpaths on the Quantity and Quality of Dissolved Organic Matter in Boreal Forest Streams

Kelly L. Balcarczyk and Jeremy B. Jones. Institute of Arctic Biology, University of Alaska Fairbanks, 311 Irving, Fairbanks, AK 99775

In the boreal forest of interior Alaska the presence or absence of permafrost has a large effect on catchment hydrology and vegetation, and consequently impacts the quantity and quality of dissolved organic matter (DOM) transported to streams.  The goal of our research was to examine the impact of permafrost and the resulting subsurface flowpaths through watersheds on the quantity and quality of DOM delivered to streams.  We sampled groundwater and streams from five sub-catchments in Caribou-Poker Creeks Research Watershed that were underlain with varying extents of permafrost (4 – 54%).  An end-member mixing model indicated that three primary groundwater sources fed stream flow in the sub-catchments.  These groundwater sources differed markedly in the quantity (1.5 – 35 mgC/L) and quality (dissolved organic carbon:dissolved organic nitrogen ranging from 6 – 36; SUVA ranging from 3.3 – 6.1 L mg-1 m-1) of DOM.  At the sub-catchment scale, permafrost affects the contributions of these groundwater sources which, in turn, determine the bioavailability of DOM in streams.  Streams in low permafrost watersheds had a lower quantity but higher quality of DOM than streams in high permafrost watersheds.  Consequently, permafrost loss due to climate change may result in higher quality DOM in boreal forest streams.