Niwot Ridge encompasses a wide variety of vegetation communities. Lodgepole pine and aspen stands are found on the lower east- and south-facing slopes of Niwot Ridge. Lodgpole pine is replaced by subalpine spruce-fir forests at higher elevations. Limber pine occurs in rocky terrain throughout forested areas. In the transition zone or ecotone between the closed subalpine forest and alpine tundra, meadows are interspersed with islands of stunted coniferous trees (krummholz) and taller patch forest. Above treeline the alpine tundra is made up primarily of herbaceous plant communities, with shrubs occurring in some areas. The highest most rugged western portions of the ridge are dominated by unvegetated scree and sparse vegetation (fellfield).
Due to an uneven distribution of moisture, herbaceous vegetation communities vary considerably throughout the alpine tundra. Moisture availability differences are caused by interactions among wind, snow, and high topographic relief, which create a mosaic of snow-free and snow accumulation areas where the amount and timing of meltwater release varies. Summer precipitation is also highly variable, both temporally and spatially, usually arriving in brief convective storms. During the early 1970s, Pat Webber and Diane May used ordination techniques to broadly define six vegetation communities, or noda, in the Niwot Ridge Saddle, a major research area: fellfield, dry meadow, moist meadow, wet meadow, shrub tundra, and snowbed.
Fellfield vegetation communities include low-statured cushion plants, such as Silene acaulis, and mat-forming plants, like Trifolium dasyphyllum. Dry meadow tundra is characterized by high cover of the sedge Kobresia myosuroides. The moist meadow is dominated by the forb Geum rossii and the grass Deschampsia cespitosa. Wet meadow is characterized by the sedge Carex scopulorum and the forb Caltha leptosepala. Shrub tundra contains high willow (Salix glauca, S. planifolia) cover. Snowbed areas are dominated either by the forb Sibbaldia procumbens or the sedge Carex pyrenaica.
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This material is based upon work supported by the National Science Foundation under Cooperative Agreement #DEB-1637686. Any opinions, findings, conclusions, or recommendations expressed in the material are those of the author(s) and do not necesarily reflect the views of the National Science Foundation.
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