A sensitive ecosystem

What's life like above treeline?

Courtney Meier (INSTAAR and Ecology and Evolutionary Biology, CU) and helper Gordon Bowman setting up plots for an ecology experiment, Niwot Ridge LTER, Colorado, July 2003. Photo: W. Bowman (INSTAAR).

The ecosystem visible from the TundraCam is alpine tundra, attuned to the harsh winters, dry conditions, and short growing season of the high-mountain climate. Climatic factors are extreme and require plants and animals to adapt to snow cover, high winds, and strong variations in weather from year to year. The western half of the Saddle site visible from the camera collects up to 10 meters (33 feet) of snow in some winters, while the eastern half is usually snow-free. The differences in precipitation and slope foster half a dozen very different plant communities in a fairly small area: fellfield, dry meadow, moist meadow, shrub tundra, wet meadow, and snowbed. Soils are Cryochrepts, a gravelly loam with a thin top layer of partially decomposed tundra litter, over granitic parent material.

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Michelle Huyser (Calvin College, Michigan), a participant in the Research Experiences for Undergraduates program run at the Mountain Research Station, measuring soil temperatures, as part of a project investigating plant species effects on soil microbial activity, Niwot Ridge LTER area, Colorado, June 2004. Photo: W. Bowman (INSTAAR).

Long-lived perennials dominate tundra plant communities. They can live for centuries - a few as long as 400 years. Plants are low to the ground to withstand the strong winds that sweep across the tundra. Many are cushion plants, which grow together in clumps that help protect them from cold. Most of their biomass is concentrated in the roots, safely below ground. Bees are scarce at high elevations and some plants reproduce by division rather than relying on flower pollination. Other plants can wait for years to seed. Still others seed incredibly quickly: the snow buttercup (Ranunculus adoneus) flowers through inches of snow and takes only a month to pass from its first appearance to seed production.

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Old-Man-of-the-Mountain (Hymenoxis grandiflora). Photo: William Bowman.

Alpine plants found on Niwot Ridge include western yellow paintbrush (Castilleja occidentalis), alpine forget-me-not (Eritrichum aretioides), alpine sunflower or Old Man of the Mountain (Hymenoxis grandiflora), and Arctic sandwort (Minuartia obtusiloba). Many alpine plants have complex relationships with wildlife. Alpine avens (Acomastylis rossii), a low-growing wildflower, secretes bitter tannins and other compounds that act as preservatives. Pikas collect “haypiles” of alpine avens leaves, along with other plants, to store as winter food. The compounds keep the haypiles from molding, and the tannins, which break down over time, may help protect the haypiles from other herbivores before the winter comes.


Ptarmigan. CC Meeting 2002. Photo: David Foster.

Only one bird, the white-tailed ptarmigan, lives on the tundra year-round. Summer visitors include water pipits, rosy finches, horned larks, and white-crowned sparrows. Small mammals, such as yellow-bellied marmots, golden-mantled ground squirrels, deer mice, voles, and pikas make their homes on the tundra. A few transient mammals visit the tundra as well, including snowshoe hares, porcupines, badgers, and weasels. Elk are the only large mammals at the Niwot Ridge site.

Life on the edge

Ice crystals on willow leaves near treeline following passage of a cold front that dropped 4 inches of snow on the first day of summer, above the INSTAAR Mountain Research Station in the Niwot Ridge LTER area, Colorado, 22 June 2004. Photo: W. Bowman (INSTAAR).

The tundra ecosystem is extremely sensitive to pollution and disturbance. Poor soils and a harsh climate leave little margin for tundra systems to restore themselves. Damage from erosion persists for centuries, and the extinction of any species affects many others.

Tundra Lab

Hikers approach the Tundra Lab in the saddle of Niwot Ridge. CC Meeting 2002. Photo: David Foster.

In 1990 the Mountain Research Station constructed the Alpine Tundra Laboratory with funding from the University of Colorado and the National Science Foundation. The Tundra Lab, the largest structure at the base of the weather tower that holds the TundraCam, houses year-round studies on Niwot Ridge.


Bill Osburn revisits vegetation plots he established 40 years ago on Niwot Ridge LTER, Colorado, July 2002. Photo: B. Bowman.

Scientists are studying the links between the tundra ecosystem, climate, and the region's complex terrain. Changes in climate and atmospheric deposition of nitrogen to these habitats are causing rapid changes in some portions of the system but not in others. Among other topics, researchers are looking at dissolved organic matter in alpine streams, the chemistry of alpine plants, loss of biodiversity from nitrogen fertilization, carbon cycling, interactions between animals and plants, and microbes in the soils.


Niwot Ridge Panorama

Niwot Ridge looking west towards (left to right) North and South Arapaho, Kiowa, Navajo, Apache, and Shoshoni Peaks. The flower in the foreground is Old-Man-of-the-Mountain (Hymenoxis grandiflora). Photo: B. Bowman.