Flora

A wide variety of vegetation types is found on Niwot Ridge, considering the relatively small area that it occupies. Subalpine forest can be found on the lower, gentler eastern slopes, whereas the higher, more rugged western portions of the ridge are dominated by nearly unvegetated surfaces. Subalpine meadows, krummholz (stunted trees), and patch forest occur in the transition zone between closed forest and alpine tundra.

The interactions among wind, snow, and high relief result in a mosaic of snow-free and snow accumulation areas with consequent wide variability in the amount and timing of meltwater release. Summer precipitation is also highly variable, both temporally and spatially, usually arriving in brief convective storms. Thus, the moisture available to alpine plants is very unevenly distributed.

The major research area is the Saddle. Its western half is a snow accumulation area (up to 10 m in some years); its eastern half remains free of snow for most of the winter. Thus, the Saddle contains several quite different vegetation communities within a fairly small area. During the early 1970s, Pat Webber and Diane May used ordination techniques to broadly define six vegetation communities, or noda, in the Saddle: fellfield, dry meadow, moist meadow, shrub tundra, wet meadow, and snowbed.

Fellfield contains low-statured cushion plants, such as Silene acaulis, and mat-forming plants, such as Trifolium dasyphyllum. Dry meadow is characterized by high cover of the sedge Kobresia myosuroides. Moist meadow is dominated by the forb Geum rossii and the grass Deschampsia cespitosa. Shrub tundra contains high willow (Salix planifolia/Salix glauca) cover. Wet meadow is characterized by abundant Carex scopulorum, a sedge, and Caltha leptosepala, a forb. Snowbed is dominated either by the forb Sibbaldia procumbens or the sedge Carex pyrenaica.

Belowground allocation and processes may be particularly important in alpine vegetation, as evidenced by high root:shoot ratios in alpine plant species.

Fauna

Animal life inhabiting the Niwot Ridge area ranges from microarthropods to elk (Cervus canadensis) and moose (Alces alces.

The only year-round avian resident in the Colorado alpine is the white-tailed ptarmigan (Lagopus leucura). Common summer residents include the American pipit (Anthus rubescens), rosy finch (Leucosticte spp.), horned lark (Eremophila alpestris), and white-crowned sparrow (Zonotrichia leucophrys).

Of the 32 species of mammals observed in alpine tundra on Niwot Ridge, approximately 20 are herbivores, and of these 12 are small herbivores, ranging in size from mice and voles to marmots. The small mammal herbivore community at Niwot Ridge includes the deer mouse (Peromyscus maniculatus), western jumping mouse (Zapus princeps), bushy-tailed woodrat (Neotoma cinerea), voles (Microtus longicaudus, M. montanus, Phenacomys intermedius, and Clethrionomys gapperi), least chipmunk (Tamius minimus), golden-mantled ground squirrel (Spermophilus lateralis), northern pocket gopher (Thomomys talpoides), pika (Ochotona princeps), and yellow-bellied marmot (Marmota flaviventris). The snowshoe hare (Lepus americanus) and porcupine (Erithizon dorsatum) are transient species in alpine tundra.

Other small mammals that have been observed on Niwot Ridge include shrews (Sorex vagrans and S. nanus), badger (Taxidea taxus), and weasels (Mustela spp.).

Sources of information on this page were:

Halfpenny, J.C., and C.H. Southwick. 1982. Small mammal herbivores of the Colorado alpine tundra. Pp 113-123 In: Halfpenny, J.C. (ed.). Ecological Studies in the Colorado Alpine. Institute of Arctic and Alpine Research Occasional Paper 37. 147 pp.

May, T.A. 1980. Animal ecology: Overview. Pp 430-435 In: Ives, J.D. (ed.). Geoecology of the Colorado Front Range: A Study of Alpine and Subalpine Environments. Westview Press: Boulder, CO. 484 pp.