Environmental Description:  Plant associations within this upper subalpine to lower alpine mesic meadow alliance occur in the central Rocky Mountains including the Yellowstone Plateau, south into the Colorado Plateau west to high ranges in the Great Basin and possibly Sierra Nevada. Elevations range from 2500 to 3900 m. Climate is temperate. Summers are warm and winters are cold with freezing temperatures and heavy snow. The precipitation has a bimodal distribution, with about 70% of it occurring from October to April and 30% falling during the summer, often as high-intensity convection storms in the southern extent (Hall 1971). Associations are found in mesic to wet meadows, floodplains, and near seeps and streambanks on medium-textured, mineral soils (Hall 1971, Mattson 1984).

Stands on the Aquarius Plateau are located on gentle slopes (7%) on any aspect, midway between temporarily flooded basins and rock outcrops (Hall 1971). They may also occur on other somewhat mesic sites such as below talus slopes and along streams. Soil is a shallow, acidic (pH 5), nutrient-poor clay loam or loam derived from the basaltic lava that caps the plateau (Hall 1971). The ground surface has a cryptogamic crust of lichens, liverworts, and mosses. Although the soil profile is considered relatively shallow (54 cm), it is the deepest soil associated with the six herbaceous communities described in this meadow (Hall 1971). Water relations appear to be the dominant environmental factor that controls species composition (Hall 1971). This community is classified as dry-mesic (21% soil moisture) which is an intermediate grouping in a soil moisture gradient that ranges from hydric to rocky-xeric (51-5%) (Hall 1971).

Nachlinger (1985) did a detailed soil description on stands in the Sierra Nevada where sites were well-drained, typically occurring on gentle slopes ranging from 4-10° with southeast, south or west aspects. The water table generally is greater than 1 m below the surface (Nachlinger 1985). The A horizon averages 34 cm and is very dark brown to dark gray brown. Structure and texture vary from massive or single grain, loamy sand or sandy loam to massive or weak, angular blocky sandy clay loam, clay loam, or clay. She also reports an acid pH (4.7) in the A horizon. The B horizon is thick averaging 53 cm. It is most often dark brown sandy clay loam with a strongly acidic pH of 5.4 (Nachlinger 1985).

Adjacent vegetation on a large scale is subalpine forest dominated by species of Abies, Picea, or Populus tremuloides. On a smaller scale adjacent vegetation described by Hall (1971) includes mesic, wet-mesic or hydric meadows dominated by Danthonia intermedia, Deschampsia cespitosa, or Carex aquatilis, respectively. More xeric sites are dominated by Festuca brachyphylla.