Niwot Ridge/Green Lakes Valley LTER Site

The research site is in alpine tundra 45 km west of Boulder in the Front Range of Colorado. The investigations are conducted at elevations of 3000 to 3750 meters. Niwot Ridge extends eastward from the Continental Divide approximately 10 km, beginning as a rocky arete at Navajo Peak (4087 m), then changing to a narrow rocky-sided ridge topped by tundra. The ridge then broadens to a maximum width of almost 2 km before changing into krumholz and dwarf tree islands of Subalpine Fir and Engleman Spruce at treeline (3500 m). The Niwot Ridge/Green Lakes Valley LTER project is investigating the effects of disturbance on loss and cycling of elements in alpine tundra, and the response of vegetation (both terrestrial and lacustrine) to short term and long term fluctuations in climate characteristics. Tundra small mammal populations are monitored annually, as are seasonal changes in snowpack and plant phenology. Paleoecological studies focus on pollen, diatoms and insects. There are continuing studies of effects of altered snow cover, nutrients, and pH on the growth and phenology of Kobresia.

In this mid-latitude continental location, climate is strongly influenced by elevational and topographic conditions. Average annual precipitation is slightly greater than 900 cm, the majority coming as snow and, due to wind redistribution, is spatially non-uniform. Highly variable moisture conditions and topoclimatic characteristics determine vegetation community development and characteristics. Investigations are centered on the top of Niwot Ridge, an interiluve with tundra, in the wetland of Green Lakes Valley adjacent to the Ridge, and on the Martinelli Snowbank slope between. Niwot Ridge is the site of intensive climalotogical and biological investigations initiated more than 35 years ago; Martinelli is the site of disturbance studies, and the Green Lakes wetland adds a distinct and important habitat to our research. Long- term data sets are maintained on climate, snowpack, water and atmospheric chemistry, biological productivity, community composition, phenology, and long-term decomposition rates. Soil profiles have been described in each of the major vegetation types. Experimental studies are under way to determine effects of increased snowpack and of acid rain on alpine tundra.

The following are four key areas of investigation:

1. On the south-facing slope of Niwot Ridge an experimental study of distribution of elements and nutrient cycling in a mesic tundra meadow has been initiated. The study is located near an area of high snow accumulation known as the Martinelli Snowbank. The experimental design consists of latin square where natural disturbance has been imposed by intense pocket gopher activity. In addition to plant, animal and nutrient studies, we are investigating the role of organic acids in acid neutralizing processes within the soil, and aluminum mobility across the landscape, using a geochemical catena approach.
2. We are establishing a Niwot Ridge-Green Lakes Valley Geographic Information System (GIS) as part of the Joint Facility for Regional Ecosystem Analysis. The facility will support ARC/INFO GIS and LAS image analysis software. This facility is being established cooperatively by the University of Colorado and Colorado State University, and will link our site with the LTER site at the Central Plains Experimental Range and with the Center for Study of Earth from Space (CSES). We will develop a data base for our site from existing soil and vegetation maps, detailed field investigations, and from satellite imagery.
3. The wetland study aims to determine current accumulation rates of organic and inorganic nutrients in the system, major pathways of cycling within the system, and developmental history through pollen and diatom analysis. Aquatic biology studies focus on demography and food habits of key organisms, periphyton growth rates and composition rates. The site is a fen characterized by willow and sedge communities with ponds of standing water, and saturated or near-saturated soils. View of the Martinelli Slope site on the south-facing slope of Niwot Ridge soils. Snow cover is complete for eight winter months, with depths up to three meters. Water comes mainly from a persistent snowbank and from a rock glacier.
4. The paleoecology study is examining pollen and diatom assemblages from cores obtained in several nearby lakes and from ponds in the wetland. These paleoindicators are being used to reconstruct vegetation and climatic changes over the past 12,000 years.

The Niwot Ridge/Green Lakes LTER project encourages visiting scientists and collaborators to utilize these facilities for research that contributes to the LTER goals and objectives.

For further information contact Dr. Norman R. French, Institute of Arctic and Alpine Research (INSTAAR), Campus Box 450, University of Colorado, Boulder, CO 80309.

Recent Publications (Niwot)

Barry, R.G. 1986. Mountain climate data for long-term ecological research. Pp. 170-187 in Proceedings of International Symposium on the Qinghai-Xizang Plateau and mountain meteorology. March 20-24, 1984. Beijing, China. Science Press, Beijing. American Meteorological Society, Boston.

Bushnell, J.H. SO. Foster, and B.M. Wahle. Annotated inventory of invertebrate populations of an alpine lake and stream chain in Colorado. Great Basin Naturalist, 47(3):500-511.

Elias, S.A. and S.K. Short. 1987. New pollen and beetle analyses at the Mary Jane site, Colorado: evidence for late glacial tundra conditions. Geological Society of America Bulletin, 98:540-548.

Elias, S.A., S.K. Short, and P.U. Clark. 1986. Paleoenvironmental interpretations of the late Holocene, Rocky Mountain National Park, Colorado, U.S.A. Revue de Paleobiologie, 5(1)127-142.

Funk, D.W. and E.K. Bonde. 1986. Effects of artificial acid mist on growth and reproduction of two alpine plant species in the field. American Journal of Botany, 73(4): 524-528.

Swanson, F.J., T.K. Kratz, N. Caine, and R.G. Woodmansee. 1988. Landform effects on ecosystem patterns and processes. Bioscience, 38(2)92-98.  

Toetz, D. and M. McFarland. 1987. Lake loading ratios (N:P) and lacustrine nitrogen fixation. Water Resources Bulletin, 23(2):239-241.