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Catalog Record: Biogeochemistry of a treeline watershed, NW Alaska
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USGS
Primary

Biogeochemistry of a treeline watershed, NW Alaska

The extensive boreal biome is little studies relative to its global importance. Its high soil moisture and low temperatures result in large below-ground reservoirs of carbon (C) and nitrogen (N). Presently, such high-latitude ecosystems are undergoing the largest temperature increases in global warming. Change in soil temperature or moisture in the large pools of soil organic matter could fundamentally change ecosystem C and N budgets. Since 1990, we have conducted treeline studies in a small (800 ha) watershed in Noatak National Preserve, northwestern Alaska. Our objectives were to (1) gain an understanding of treeline dynamics, structure, and function; and (2) examine the effects of global climate change, particularly soil temperature, moisture, and N availability, on ecosystem processes. Our intensive site studies show that the treeline has advanced into turdra during the past 150 years. Inplace and laboratory incubations indicate that soil organic-layer mineralization rates increase with a temperature change >5 degrees C. N availability was greatest in soils beneath alder and lowest beneath willow or cottongrass tussocks. Watershed output of inorganic N as NO3 was 70 percent greater than input. The high inorganic-N output likely reflects soil freeze-thaw cycles, shallow flowpaths to the stream, and low seasonal biological retention. Concentrations and flux of dissolved organic carbon (DOC) in streamwater increased during spring melt and in autumn, indicating a seasonal accumulation of soil and forest-floor DOC and a shallower flowpath for meltwater to the stream. In sum, our research suggests that treeling transitionzone processes are quite sensitive to climate change, especially those functions regulating the C and N cycles.

Complete
2002-06-30
2008-06-01

Data and Resources

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    Report :: Publication

    http://www.fort.usgs.gov/products/publications/pub_abstract.asp?PubID=729

Status: Complete
Start Date: 2002/06/30
Type: Project
End Date: 2008/06/01
Primary Contacts
Name: Robert Stottlemeyer
Email: robert_stottlemyer@USGS.gov
Other Contacts
Name: Robert Stottlemeyer
Email: robert_stottlemyer@USGS.gov
Primary Organizations
Type
US Geological Survey
Federal

Regions
Alaska, North Slope

Direct Record Link
http://catalog.northslope.org/catalog/entries/2248-biogeochemistry-of-a-treeline-watershed-nw-alaska
Direct Full Map Link
http://catalog.northslope.org/catalog/entries/2248-biogeochemistry-of-a-treeline-watershed-nw-alaska/map