Niwot Ridge is located approximately 35 km west of Boulder, Colorado, with the entire study site lying above 3000 m elevation. There is a cirque glacier (Arikaree Glacier), extensive alpine tundra, a variety of glacial landforms, glacial lakes and moraines, cirques and talus slopes, patterned ground, and permafrost. The research area is bounded on the west by the Continental Divide, with runoff on the two sides being destined for the Colorado and Mississippi Rivers. The alpine study area is reached by an unimproved road from the Mountain Research Station (2895 m) which leads to within 2 km of the main tundra research site, the Saddle (3528 m). The D-1 research site (3739 m), for which climate records are continuous from 1952, lies a farther 3 km from the road head. The Martinelli study area (3380 m) is located 1 km southwest of the Saddle, in the forest-tundra ecotone. The Green Lakes Valley lies immediately south of the western half of Niwot Ridge. It includes the Arikaree Glacier at its head (3798 m), and the wetland, Green Lake 4, and Albion research sites. The Green Lakes Valley and Martinelli sites are all within the City of Boulder Watershed which is closed to public access. Niwot Ridge, including the main alpine study site, is part of the Roosevelt National Forest and has been designated a Biosphere Reserve (United Nations Educational, Scientific and Cultural Organization, UNESCO) and an Experimental Ecology Reserve (USDA Forest Service). A context-sensitive topographic relief map can be used to access the scenic views of the areas indicated above, as well as several others.
The Saddle site is an Alpine Tundra site, located 5.6 km from the Continental Divide. Topographic setting: ridge-top, but in a shallow saddle between east and west knolls. There is a 10,000 sqft tundra laboratory at Niwot Ridge which serves as a staging area for research in all weather conditions. In addition, there is an 80 sqft subnivean laboratory equipped with snow melt lysimeters that drain into dedicated tipping buckets. These laboratories have year-round motorized access 120-volt line power. There is an Aerometrics wet--chemistry precipitation collector as part of the National Atmospheric Deposition Program (NADP), which has operated continuously since 1984 and is the highest site in the entire NADP network. The timing, duration, and amount of snow cover has been manipulated since 1994 with a 2.6x60 m snowfence, providing a proxy for climate change. There are several meteorological stations at the Saddle site. Climate data completeness good from 1981 to present. Climate parameters measured include temperature, relative humidity, solar radiation, barometric pressure, wind speed and direction, precipitation, soil moisture and temperature. NOAA measures surface ozone as well.
Soils are Cryochrepts and are approximately 2.0 m in depth over granitic parent material. Soil C in the top 100 mm of soil ranges from 130 to 200 g/kg and soil N pools range from 9 to 15 g/kg [Burns, 1980].
Vegetation at the experimental sites on Niwot Ridge is classified as dry, moist and wet meadow communities and the dominant plant species are the gramminoid Kobresia myosuroides, the forb Acomostylis rossii, and the gramminoid Deschamsia caespitosa in protected microsites.