Environmental Description:  Alpine vegetation occurs above the treeline. Treeline varies depending on latitude and the "mountain mass" (i.e., large mountain masses retain more heat and tend to have higher treeline elevations, whereas smaller and more isolated mountain masses tend to have lower treeline elevations). In addition to elevation, exposure to wind is a key factor in the type of vegetation; in snowy regions, it impacts on the depth and duration of snow cover and, hence, protection of the vegetation, length of growing season, and soil moisture conditions.

Climate: For alpine vegetation, the "tundra" climate of high altitudes does not necessarily correspond to that of high latitudes (i.e., Arctic tundra). Although both regions have low mean annual temperature and short growing seasons, and experience a seasonal change in sun angle (high in the summer, low in the winter), the light regimes are quite different. Alpine regions never experience 24 hours of day or night; day length varies with latitude. And although permafrost occurs on high mountains, it does not produce the kinds of landforms found in the Arctic because few flat sites are available. Conversely, avalanches and rockslides are common in alpine regions, but do not occur in the Arctic (Quinn 2008). Some alpine regions can have very deep snow (several meters), whereas the Arctic generally has low snow cover.

Temperatures in the Arctic and Antarctic vary with the season, which has periods of 24-hour light (summer) and dark (winter). The number of days with those extremes varies with latitude, ranging from 1 day at the Arctic and Antarctic circles (66½°N and S latitude) to 6 months at the poles. Temperatures vary both with latitude and degree of continentality. Mean temperatures of the warmest summer months vary considerably but generally average between 4.5° and 13°C. In the winter, they average from -20° to -30°C. Annual precipitation, which often falls as snow, is typically <25 cm, but some localities may have as much as 50 cm.

Soil/substrate/hydrology: Most alpine soils are regularly disturbed by freezing, erosion and downslope slides, and contain a mix of rocks and fine particles (Quinn 2008). Three major types of soils occur in the alpine regions: (1) Poorly developed rocky or stony soils (or Entisols) are sometimes called Lithosols when formed on bare rock of slopes and ridges and Regosols when formed on unconsolidated rock-like talus, scree, or rubble (soil orders from Soil Survey Staff (1999)) [see Brady and Weil (2002) for comparison of U.S. soil orders with Canadian and FAO systems]. Both types are shallow, dry and azonal. (2) Alpine turf and meadow soils (or Inceptisols) are up to 75 cm deep and exhibit distinct horizons; and (3) bog soils (Histosols) are found in depressions or where seepage saturates the ground to a depth of 1 m or more (Quinn 2008).

In many polar tundra areas, the deep layers of the soil are permanently frozen (permafrost), and only the surface layer is thawed and becomes biologically active during the summer (Whittaker 1975). Soils may be dry to seasonally saturated. Permafrost is ground that is permanently frozen, and is widespread in the Arctic, covering large parts of Canada and Russia. It is discontinuous in the Boreal Forest & Woodland region to the south. It can extend down more than 600 m, depending on mean annual temperature, type of soil and rock, proximity to the ocean and topography. In the summer, only the soil surface may thaw, up to 20-60 cm. On slopes, the thawed soil may begin to move, a process called solifluction (Quinn 2008). Permafrost also creates specific landscape features collectively called patterned ground, forming circles, polygons, nets, hummocks, steps or stripes (Quinn 2008).