Physiognomy and Structure: These are forests dominated by needle-leaved evergreen with open to high cover (20-100%). Understory layers are typically depauperate.

Floristics: Canopies are dominated by Abies lasiocarpa and/or Picea engelmannii and stand structure may take on a ribbon or tree island form. Abies lasiocarpa, Pinus flexilis, and Pinus aristata are minor components in the canopy and very infrequent in the understory. The shrub layer is sparse and species-poor although Ribes montigenum and Vaccinium scoparium may be present. Herbaceous species may be absent or sparse and typically include the forbs Geum rossii and Trifolium dasyphyllum.

Dynamics:  Abies lasiocarpa forests develop on sites with limited, short growing seasons and relatively deep winter snowpacks. Tree growth is very slow in these habitats, and forests are rapidly colonized by much more rapidly growing shade-intolerant species, such as Pseudotsuga menziesii, Pinus contorta, or Populus tremuloides, following fire, clearcut logging, or windthrow disturbance. Abies lasiocarpa is among the most shade-tolerant trees in the Rocky Mountains, but seedlings compete poorly in greater than 50% full sunlight (Burns and Honkala 1990a). Snow avalanches occur frequently at upper elevations, and can result in a mosaic of varying stand ages on sites affected by this disturbance type.