These moderate-to-high-elevation systems are found throughout the Rocky Mountains, dominated by herbaceous species found on wetter sites with very low-velocity surface and subsurface flows. Occurrences range in elevation from montane to alpine at 1,000 to 3,353 meters (3,280-11,000 feet). This system typically occurs in cold, moist basins, seeps and alluvial terraces of headwater streams or as a narrow strip adjacent to alpine lakes (Hansen et al., 1995). Wet meadows are typically found on flat areas or gentle slopes, but may also occur on sub-irrigated sites with slopes up to 10 percent. In alpine regions, sites are typically small depressions located below late-melting snow patches or on snowbeds. The growing season may only last for one to two months. Soils of this system may be mineral or organic. In either case, soils show typical hydric soil characteristics, including high organic content and/or low chroma and redoximorphic features. This system often occurs as a mosaic of several plant associations, often dominated by graminoids such as tufted hairgrass (Deschampsia caespitosa), and a diversity of montane or alpine sedges such as small-head sedge (Carex illota), small-winged sedge (Carex microptera), black alpine sedge (Carex nigricans), Holm’s Rocky Mountain sedge (Carex scopulorum) shortstalk sedge (Carex podocarpa) and Payson’s sedge (Carex paysonis). Drummond’s rush (Juncus drummondii), Merten’s rush (Juncus mertensianus), and high elevation bluegrasses (Poa arctica and Poa alpina) are often present. Forbs such as arrow-leaf groundsel (Senecio triangularis), slender-sepal marsh marigold (Caltha leptosepala), and spreading globeflower (Trollius laxus) often form high cover in higher elevation meadows. Wet meadows are associated with snowmelt and are usually not subjected to high disturbance events such as flooding.
A variety of plant communities are found within this system in Montana. Composition and zonation of wet meadow plant communities represent the competitive abilities, moisture and nutrient requirements, and stress tolerance of anoxic conditions of individual plant species. Variability of water-table depth and reduced soil conditions, soil pH, and saturation duration, strongly influences the distribution and assemblage of species within a wet meadow. Obligate wetland species occur within a fairly restricted range of water-table depth, whereas many common species such as tufted hairgrass, Baltic rush (Juncus balticus) and Kentucky bluegrass (Poa pratensis) occur over wide ranges. Overlap in ranges of water-table depth for individual species suggests that small changes in hydrology could potentially result in shifts in dominance by different species, and ultimately replacement or loss of certain species.
Many alpine wet meadows throughout the state are dominated by tufted hairgrass, forming a dense stand of tussocks. The tufted hairgrass Temporarily Flooded Herbaceous Alliance has been found at elevations as high as 10,100 feet, but is much more common at lower elevations where it often occupies low gradient areas and slopes less than 15 percent, facing north to northeast (Cooper et al., 1997). This alliance is thought to be found in relatively undisturbed sites (Hansen et al., 1995), while more disturbed sites are dominated by Kentucky bluegrass (Poa pratensis), fowl bluegrass (Poa palustris), redtop (Agrostis stolonifera) and Baltic rush.
In southwestern Montana, wet meadow communities are dominated by species more characteristic of the Middle Rocky Mountains ecoregion, such as Holm’s Rocky Mountain sedge (Cooper et al, 1999). Drier sites, especially those where soils and/or hydrology have been disturbed, may be characterized by Baltic rush and clustered field sedge (Carex praegracilis) communities. In the Northern Rocky Mountains, shortstalk sedge or Payson’s sedge are dominant (Lesica, 2002), often found on slopes that range from zero to eight percent where the growing season lasts only for one to two months. In these northern occurrences, other common graminoids include small-head sedge, lens sedge (Carex lenticularis), smallwing sedge, black alpine sedge, beaked sedge (Carex utriculata), Drummond’s rush, Merten’s rush, arctic bluegrass, and alpine bluegrass. Common forbs include woolly pussytoes (Antennaria lanata), spreading globeflower, slender-sepal marsh marigold, arrow-leaf groundsel, elephant’s head (Pedicularis groenlandica), small flowered anemone (Anemone parviflora), alpine bistort (Polygonum viviparum), Buek’s groundsel (Packera subnuda), and Rocky Mountain goldenrod (Solidago multiradiata). Sibbaldia (Sibbaldia procumbens) often occurs in open areas within the turf or open peat. At more montane elevations, extensive shrubby cinquefoil (Dasiphora fruticosa) shrublands are frequently found adjacent to this system.
At montane elevations, zonation of wet meadow complexes is evident with sedges such as inflated sedges (Carex utriculata and C. vescicaria), wooly sedge (Carex pellita), Nebraska sedge (Carex nebrascensis) and water sedge (Carex aquatilis) occupying the wettest zone of the meadow complex. These sedge-dominated communities are typically surrounded by spikerushes (Eleocharis spp.), followed by a zone of grasses and forbs such as Baltic rush, bluejoint reedgrass (Calamagrostis canadensis), slimstem reedgrass (Calamagrostis stricta), pink elephant’s head and water ragwort (Senecio hydrophilus).
Cooper, Stephen V, Peter Lesica, and Deborah S. Page-Dumroese. Plant Community Classification for Alpine Vegetation on the Beaverhead National Forest, Montana. Ogden, UT (324 25th Street, Ogden 84401: U.S. Dept. of Agriculture, Forest Service, Intermountain Research Station, 1997. Print.
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