Arctic LTER Site Description: Overview.
The Arctic LTER research site (68°N and 149°W) is in the foothills region of the North Slope of Alaska (Fig. 1)
and includes the entire Toolik Lake
watershed and the adjacent watershed of
the upper Kuparuk River, down to the
confluence of these two watersheds. This
area is typical of the northern
foothills of the Brooks Range, with
continuous permafrost, no trees, a
complete snow cover for 7 to 9 months,
winter ice cover on lakes, streams, and
ocean, and cessation of river flow
during the winter. Tussock tundra
vegetation of sedges and grasses mixed
with dwarf birch and low willows
form the dominant vegetation type
with areas of drier heath tundra on ridge tops and other well-drained sites as well as areas of river-bottom willow communities.
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The climate at the site is typical of arctic regions, with a mean annual air temperature of about -10°C and low precipitation (45% of the 20-40 cm of precipitation falls as snow). During the summer the daily average air temperature is 7-12°C with the sun continuously above the horizon
from mid-May to late July (Fig. 2). The snow-free season can lasts from late May to mid-September, with below-freezing temperatures and snow showers possible at any time.
 The entire region is underlain by continuous permafrost (depth of ~200 m at Toolik), which exerts a major influence on the distribution, structure, and function of both terrestrial and aquatic ecosystems. Since only 28-46 cm of the soil surface thaws annually, plants have limited rooting depth and soils saturate quickly with runoff immediate and flashy. The cold, wet soils also inhibit decomposition although respiration of soil microbes can continue down to –7.5°C.
There has been a pronounced warming over the past 30 years in arctic Alaska. Chapman and Walsh (1993) state that this warming has been as much as 2° in the winter and 1° in the
summer. Over the same period, the plant communities in the acidic tussock tundra at Toolik show a shift towards dominance of woody plants, especially the dwarf birch (Betula nana). In contrast, pollen from the sediments of lakes near Toolik show the plant communities being stable for some 6,500 years and with a peak of birch pollen abundance before that time. The last glacial advance that reached Toolik was around 10,000 years ago.
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