Alpine Nivation Hollow Payson’s sedge / black alpine sedge -northern singlespike sedge / Drummond’s rush (Carex paysonis/ Carex nigricans-Carex scirpoidea/ Juncus drummondii)

Description

Vegetation at the site has a simple structure of extremely dense, low-growing sedge turf with a few snow-tolerant forb species. The vegetation is dominated by one to two mat-forming sedges including Payson’s sedge (Carex paysonis), black alpine sedge (Carex nigricans), and northern singlespike sedge (Carex scirpoidea). Overall, due to harsh site conditions, there is lower species diversity although forbs do occur. Forbs at this site include Rocky Mountain groundsel (Packera streptanthifolia), Eschscholtz’s buttercup (Ranunculus eschscholtzii), and arrowleaf ragwort (Senecio triangularis). Other species that occur at the site in high frequency include alpine timothy (Phleum alpinum), alpine bluegrass (Poa alpina), creeping sibbaldia (Sibbaldia procumbens), subalpine fleabane (Erigeron peregrinus), meadow bistort (Polygonum bistorta), varileaf cinquefoil (Potentilla diversifolia), and Rocky Mountain goldenrod (Solidago multiradiata). Growing season is very short, but all species are perennial and able to have very quick springtime assimilation. Other species may occur infrequently and in very low cover representing more incidental occurrence. Species found at this ecological site are designated as facultative wetland, facultative and facultative upland. Therefore, most species are neutral towards or have only a slight affinity to wetland areas. Specifically, Juncus mertensiana is a wetland obligate species and occurs infrequently and in very low cover, at this site. Carex paysonis occurs in high cover throughout most sites, and is a facultative upland species meaning that it is usually in non-wetland conditions, but may occur in wetlands. Carex nigricans can dominate sites, and is a facultative wetland designated species, which means that it is a hydrophyte, which usually occurs in wetlands but also may occur in non-wetland areas. Carex scirpoidea and Juncus parryi can have high coverage at sites, though not in high frequency through all sites, are considered facultative species, which means they can occur in wetland and non-wetland areas.

The vegetative communities of these snowbeds all have a presence of Carex paysonis in varying degree of cover, making it a diagnostic species for snowbeds on the whole. There are four general types each dominated by a different species: the Carex paysonis-dominated, the Carex scirpoidea-dominated, the Carex nigricans-dominated, and the Juncus parryi-dominated. The Carex paysonis-dominated had Juncus drummondii and Sibbaldia procumbens frequently and in fair cover (10 percent). Carex nigricans and Antennaria species were infrequent but had fair cover (10 percent). There was only one site visited with Carex scirpoidea dominant, but it also had Carex paysonis present (5 percent) and Juncus mertensianus (1 percent). The Carex nigricans-dominated type had high cover of Carex paysonis (35 percent) as well as the shrub Salix arctica (33 percent). The Juncus parryi-dominated type had Arenaria capillaris, Erigeron peregrinus, and Sibbaldia procumbens in very low cover. Also present at these sites were Carex species in very low cover including Carex phaeocephala, Carex rossii, and Carex rupestris.

Carex nigricans has fair forage palatability for cattle, sheep, and horses, defined as moderately relished and consumed to a moderate degree. It is moderate in energy and protein value, which means it retains usable energy and digestible protein values moderately well during fall and winter (Hansen, 1995).

Carex nigricans subalpine sedge meadows were found to be very resistant to light and heavy human trampling (Cole, 1985). Both light and heavy human trampling resulted in canopy coverage of Carex nigricans to be above 50 percent post-trampling after 0-800 passes. Grasses were found to be generally resistant to trampling, while forbs were variable in resistance to trampling.

Submodel

Description

Climate change can have a profound effect on snowbed vegetation communities. The harsh site conditions and very short growing season of Nivation hollows dictate that only highly adapted species are able to thrive. Highly adapted species are not generalist species and therefore do not compete well against other species if dramatic changes occur. These species have special growth conditions, their sensitivity to and inability to respond rapidly to changes in annual snowfall patterns make them particularly vulnerable in a warmer climate. These snowbed communities would be negatively impacted by climate change and will be invaded by species from adjacent plant communities, particularly shrubs (Bjork and Molau, 2007). The amount of time this would take is unknown at this time.

Submodel