The Arctic LTER research site is in the foothills region of the North Slope of Alaska 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 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 communities. The North Slope is divided into the Coastal Plain (6,000 km2), the Foothills (95,000 km2), and the Mountains (40,000 km2).