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Treeline biogeochemistry and dynamics, Noatak National Preserve, northwestern Alaska

Studies by the U.S. Geological Survey in Alaska, 2000. Professional Paper 1662

By:
, ,
Edited by:
F.H. Wilson, J.P. Galloway

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Abstract

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.

Additional Publication Details

Publication type:
Article
Publication Subtype:
Journal Article
Title:
Treeline biogeochemistry and dynamics, Noatak National Preserve, northwestern Alaska
Series title:
Studies by the U.S. Geological Survey in Alaska, 2000. Professional Paper 1662
Year Published:
2002
Language:
English
Publisher:
U.S. Geological Survey
Publisher location:
Reston, VA
Contributing office(s):
Fort Collins Science Center
Description:
p. 113-121
Larger Work Type:
Report
Larger Work Subtype:
Other Report
First page:
113
Last page:
121
Number of Pages:
9