Name:
Arenaria capillaris / Polytrichum piliferum Herbaceous Vegetation
Reference:
Western Ecology Working Group of...
Description:
This vegetation type has been described only from the alpine and upper subalpine of Glacier National Park in Montana, east of the Continental Divide. This community occurs across a range of topographic positions, which apparently have in common an extended period of snow cover. Slopes are predominantly gentle to moderately steep (7-45%) with easterly to northerly exposures, which would be lee slopes in the presence of prevailing southwesterly wind. Snow drifts occur in the lee of raised relief features and depressions; drifts provide abundant early growing-season moisture, but sites may desiccate markedly in late summer. The observed elevation range is 2090 to 2390 m (6855-7840 feet). Parent materials include argillite, quartzite, arenites and limestone and can constitute up to 40% surface rock, most of which is stable though imparting a distinct fell-field aspect to these sites; frost churning is obviously occurring in the rockier frost rubble sites. Frost action is also manifested as cracks and soil creep in the open mineral soil. Total vascular cover varies considerably, from 25% to 80%, most of it being low-growing forbs, among which <i>Arenaria capillaris</i> consistently has the greatest cover and is indicative of persisting snow cover. Another chionophilous forb, <i>Sibbaldia procumbens</i>, exhibits less cover and is inconsistently present. Other forbs with moderate to high constancy include <i>Eriogonum flavum, Arnica rydbergii, Antennaria umbrinella, Silene parryi, Pedicularis contorta, Potentilla diversifolia, Polygonum bistortoides, Solidago multiradiata, Selaginella densa var. scopulorum (= Selaginella scopulorum)</i>, and <i>Agoseris glauca</i>. The graminoid component is relatively unimportant, with <i>Carex phaeocephala, Luzula spicata</i>, and <i>Poa cusickii</i> being consistently present (more than 60%). Bryophytes, among which <i>Polytrichum piliferum</i> is highly constant and highly variable in cover, and lichens comprise a component highly variable in cover, from being unrepresented to a combined cover of 75%.
Accession Code:
VB.CC.32171.CEGL005855
Plot-observations of this Community Concept:
0
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