Pacific Northwest Research Station

The Juneau Aquatic and Land Interactions Team

2008 Science Accomplishments

Scientists quantify carbon fluxes in southeast Alaska

A field crew gathers water samples to determine the amount of dissolved carbon cycling through a watershed in southeast Alaska. Credit: Rick Edwards

Coastal temperate rain forests sequester large amounts of carbon because cool, wet conditions inhibit decomposition. They are also sources of carbon. The Tongass National Forest exports as much dissolved organic carbon per year in water as would be removed through harvesting 1.6 million board feet of timber-enough to frame 100,000 homes. Much of this carbon is transferred to aquatic systems where it likely plays a key role supporting production of species such as salmon, shrimp, crab, and others. What isn't incorporated into aquatic food webs enters long-term storage within the marine system.

As the climate warms, the rate at which carbon is released from the soils of coastal temperate rain forests could increase. Station scientists continue to measure rates and controls of major fluxes to better understand the carbon cycle and the interplay between terrestrial and aquatic systems. This information will be used to develop forest carbon management strategies and be applied to regional and national carbon sequestration goals.

Partners: University of Alaska Southeast, U.S. Cooperative State Research, Education, and Extension Service

To learn more, contact Rick Edwards at rtedwards@fs.fed.us.

Glacier-fed watersheds differ from those without glaciers and have climate change implications

Watersheds in southeast Alaska will be significantly altered as the climate warms. Currently, 86 percent of the water discharged from the Tongass National Forest comes from large continental watersheds containing glaciers and permanent snowfields. The seasonality of discharge, chemistry, and temperature of glacial rivers is very different from nonglacial rivers in the Tongass. As warming continues, the loss of glacial inputs and changes in the timing of runoff related to changes in snowpack and snow-to-rain ratios will dramatically affect stream habitats and the annual pattern of carbon and nutrient inputs to the marine system.

Watersheds that do not contain glaciers exhibit two peaks annually, a spring snowmelt peak and a fall peak. As the snow line rises, discharge will begin to track precipitation, as is observed in the lowest watersheds, and the spring melt peak will disappear. These changes in annual hydrology will interact with nutrient cycles to change the shape and productivity of river habitats.

This research is leading to better modeling of present and changing hydrology of Alaska's streams. Improved models of future runoff will help managers design stream restoration and fish enhancement projects and be used to model potential fish distribution under various climate scenarios.

Partners: University of Alaska Southeast, U.S. Cooperative State Research, Education,
and Extension Service

To learn more, contact Rick Edwards at rtedwards@fs.fed.us.