Dissolved organic matter and stream biogeochemistry in watersheds underlain with discontinuous permafrost in subarctic Alaska (Invited)
Abstract
In the subarctic, watersheds are commonly underlain with discontinuous permafrost, which has a dominant control on catchment hydrology and the resulting input of dissolved organic matter (DOM) into streams. Wildfires also are common in subarctic Alaska, have been increasing in frequency and severity with recent warming, and have the potential to alter the delivery of DOM to streams. We have been studying DOM and nutrients in a number of streams draining subcatchments with varying extents of underlying permafrost in the Caribou-Poker Creeks Research Watershed in interior Alaska. DOM concentration is greatest in streams draining watersheds with large extents of underlying permafrost, whereas nitrate concentration tends to be highest in streams draining lower permafrost catchments. DOM in soil water and ground waters feeding streams varies markedly in quantity (1.5 - 35 mgC/L), composition and lability. DOM in springs flowing from shallow soil flowpaths tends to be enriched in tyrosine and tryptophan like molecules, and a large proportion of this DOM appears to be readily decomposed by microorganisms. Following a wildfire in the CPCRW, stream DOM concentration significantly declined compared with a control stream, suggesting that the fire either resulted in a loss of soil organic matter or altered hydrologic flowpaths through catchments. With climatic warming, permafrost thaw and changing fire frequency will interact to determine DOM concentration and composition in streams of the subarctic, and will have important impacts on the coupling between DOM decomposition and nutrient cycling.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2010
- Bibcode:
- 2010AGUFM.B32C..02J
- Keywords:
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- 0428 BIOGEOSCIENCES / Carbon cycling;
- 0470 BIOGEOSCIENCES / Nutrients and nutrient cycling;
- 0475 BIOGEOSCIENCES / Permafrost;
- cryosphere;
- and high-latitude processes