Tuesday, November 14, 2006

Dissolved Organic Matter Dynamics from Pedons to Watersheds in the Coastal, Temperate, Rainforest of Southeastern Alaska.

David D'Amore1, Rick Edwards1, Jason Fellman2, and Eran Hood2. (1) USDA Forest Service, Pacific Northwest Research Station, 2770 Sherwood Lane Ste 2A, Juneau, AK 99801, (2) Univ of Alaska, Fairbanks, AK 99775

The pacific coastal temperate rainforest is a dynamic area of terrestrial and aquatic interactions.  Abundant rainfall and steep topography influence the flux of nutrients from soils to surface water.  This system is sensitive to the potential impacts of climate change such as increased precipitation or temperature that regulate the storage, cycling and export of dissolved organic matter (DOM).  We measured DOM export from 60 watersheds during spring and fall, and followed the short-term export of dissolved organic matter intensively at several small catchments to understand both large and small scale processes. Pedon-level fluctuations in temperature and water table influence seasonal changes in the storage, cycling, and export of DOM.  Wetland soils are significant sources of DOM to rivers in southeastern Alaska.  This connection is much stronger in the fall when wetland soils are hydrologically better connected.  Soil water table fluctuations and mineralization of C,N, and P in soil organic matter leads to varied patterns of soil retention, loss and associated DOM quality in soils.  Whereas wetlands provide substantial DOM storage and subsequent export, moderately well-drained soils also have fluxes of DOM due to the accumulation of deep organic deposits on the soil surface.  Fluctuations in temperature and precipitation associated with climate change will influence nutrient cycles and export of DOM that will lead to shifts in the biogeochemistry of aquatic systems.  Understanding both small scale changes in specific soil types at the pedon level will inform observations of large-scale watershed level. Both of these scales of study are critical to understanding the potential impacts of small climate shifts on the ecosystems in the dynamic coastal systems of the Pacific Northwest coast.