HR: 0800h
AN: B41D-0754 [Abstracts]
TI: Regional DOC Fluxes for the Tongass National Forest in Southeast Alaska
AU: * Edwards, R T
EM: rtedwards@fs.fed.us
AF: USDA Forest Service, PNW Research Station, 2770 Sherwood Lane, Suite 2A, Juneau, AK
99801, United States
AU: D'Amore, D V
EM: ddamore@fs.fed.us
AF: USDA Forest Service, PNW Research Station, 2770 Sherwood Lane, Suite 2A, Juneau, AK
99801, United States
AU: Hood, E
EM: eran.hood@uas.alaska.edu
AF: University of Alaska Southeast, Department of Environmental Sciences, 11120 Glacier
Highway, Juneau, AK 99801, United States
AB:
The Tongass National Forest (Tongass) is the largest national forest in the United States and contains most of
the remaining high value Coastal Temperate Rainforest in North America. The Tongass covers 68,748 km2
of southeast Alaska with 42,000 km of coastline. Annual rainfall ranges from 1.5 to 8 meters. The Tongass
contains about 8% as much total carbon as forests in the lower 48 states and 90% of the Tongass lies within 5
km of saltwater, creating a high potential for terrestrial influence on the near-shore environment. Riverine carbon
from the Tongass flows into a web of estuaries and channels within the Alexander Archipelago. In contrast to
riverine inputs to the open ocean, Tongass carbon is likely retained near the coastline for longer duration and
may exert a larger influence on coastal productivity. An important impact of climate change on the carbon cycle is
in the transfer of dissolved organic carbon (DOC) from terrestrial to aquatic ecosystems. We have combined a
regional survey of riverine DOC concentrations with estimates of climatic and hydrologic factors to estimate the
present DOC flux to the marine ecosystem of southeast Alaska. The preliminary flux estimate yields an annual
runoff of 960 gigagrams DOC y-1 from the Tongass (140 kg C ha-1 y-1). Streamwater dissolved
organic carbon concentrations vary widely with catchment properties such as wetland extent and slope, with
values ranging from <0.1 mg l-1 to 20 mg l-1. Wetland soils cover 30% of the Tongass and are the
primary source of DOC and associated variability in concentration in coastal watersheds. The large variation in
DOC flux among watersheds with differing geographic composition suggests that the pattern of terrestrial
influences on marine process will also vary as will the sensitivity of exports to changes in soil retention and
processing caused by climate change.
DE: 0428 Carbon cycling (4806)
DE: 0442 Estuarine and nearshore processes (4235)
DE: 0470 Nutrients and nutrient cycling (4845, 4850)
DE: 0486 Soils/pedology (1865)
DE: 0497 Wetlands (1890)
SC: Biogeosciences [B]
MN: 2007 Fall Meeting