The Arctic LTER site includes the entire Toolik Lake watershed and the adjacent watershed of the upper Kuparuk River,
down to the confluence of these two watersheds. Additional sites include the 1000 km2 Anaktuvuk River (AR) Burn site 40 km NNW of Toolik Lake, Oksrukuyki watershed and thermokarst disturbances within helicopter range of Toolik Field Station (thermokarsts are slumps in the landscape caused by local thawing of ice in permafrost). This area is typical of the northern foothills of the Brooks Range, with no trees, a complete snow cover for 7 to 9 months, winter ice cover on lakes and streams, and no stream flow during the winter.
Tussock tundra vegetation of sedges and grasses mixed with dwarf shrubs and low evergreens is the dominant vegetation type but there are extensive areas of drier heath tundra on ridge tops and other well-drained sites as well as areas of river-bottom willow and lowland wet-sedge communities (Walker et al. 1994; http://www.uaf.edu/toolik/gis/). The climate at the site is typical of arctic regions, with a mean annual air temperature of about -7°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. Permafrost underlies the site to a depth of ~200 m. An active layer thaws each summer to a depth of 30-50 cm (Hobbie et al. 2014). The glacial tills that cover the hills near Toolik have three different ages, ~300,000 y, ~60,000 y, and 11,500-25,000 y (Hamilton 2003). These landscapes control surface water chemistry, with the oldest lakes and streams being very dilute with low amounts of inorganic ions and alkalinity (Kling et al. 1992, 2000). Soils are more acidic in the older surfaces and less acidic in the youngest surface because of differences in leaching of the carbonate-rich glacial till (Walker et al. 1989, 2003). One consequence is that a different vegetation covers these surfaces; for example there is little or no birch in the non-acidic tundra (Gough et al. 2000).
The Arctic LTER project began in 1987 with the overall goal of the project to understand all of the ecosystems that comprise the landscape around Toolik Lake, their structure, function, and interactions, to allow prediction of effects of change. The specific focus of our work evolves continuously and changes with each cycle of funding, as understanding and grows and new opportunities are recognized.
The site has become the location for a large number of research projects and the resulting accumulation of a large quantity of ecological research. It is quite probably the best known arctic research site. This is due to the combination of logistics provided by NSF support which includes helicopter transportation, the availability of the LTER database with all the information since 1975, and availability of climate information from the LTER and the TFS. The LTER data set provides researchers with climate data, soil chemistry information, vegetation distribution information, and other ecological information needed on any project. Another factor that attracts many non-LTER scientists is the availability of the long-term experiments of warming the tundra, fertilizing the tundra, lakes and streams, reducing the available solar radiation, and excluding grazing. Scientists are allowed to sample and measure the effects of more than 30 years of experimental treatments.