Physiognomy and Structure: No Data Available

Floristics: Abies lasiocarpa is the dominant tree species, with some codominance of Picea engelmannii. Pseudotsuga menziesii and Populus tremuloides are major seral species. Both tall- and low-shrub layers are present. Rubus parviflorus and Acer glabrum are the most common species. Other frequently occurring shrubs are Holodiscus dumosus, Lonicera involucrata, Lonicera utahensis, Ribes pinetorum, Paxistima myrsinites, and Robinia neomexicana. The herbaceous cover is rich in species diversity, suggestive of mesic conditions. Bromus ciliatus, Geranium richardsonii, Goodyera oblongifolia, and Orthilia secunda (= Ramischia secunda) are commonly found. Also present are Arnica cordifolia, Artemisia franserioides, Clematis columbiana (= Clematis pseudoalpina), Prosartes trachycarpa (= Disporum trachycarpum), Chamerion angustifolium (= Epilobium angustifolium), Erigeron eximius (= Erigeron superbus), Oreochrysum parryi (= Haplopappus parryi), Lathyrus spp., Ligusticum porteri, Osmorhiza depauperata, Pteridium aquilinum, Packera cardamine (= Senecio cardamine), Maianthemum racemosum (= Smilacina racemosa), Maianthemum stellatum (= Smilacina stellata), Thalictrum fendleri, Viola canadensis, and Zigadenus elegans.

Moir and Ludwig (1979), who originally described this type, recognize two phases. The first is a Vaccinium myrtillus phase, characterized by Vaccinium being codominant with Rubus parviflorus. This phase is similar to the Abies lasiocarpa / Vaccinium myrtillus, Rubus parviflorus phase habitat type, and occurs on cooler sites with deeper snowpack. The second phase is an Acer glabrum phase. Acer is consistent in the tall-shrub stratum, and Vaccinium myrtillus is absent in the low-shrub stratum with Abies concolor as a major seral species, whereas Abies concolor is only accidental or minor in the Vaccinium myrtillus phase.

Dynamics:  Abies lasiocarpa is almost uniformly susceptible to Fomes annosus and Melampsorella caryophyllacearum (yellow witches'' broom rust). Picea is susceptible to Engelmann spruce bark beetle (Dendroctonus rufipennis), which may limit or temporarily suppress its codominance with the Abies according to Jones (1974).

Crane (1982) places this association in fire group fourteen, which are the mesic, low to mid-elevation subalpine fir habitat types in southwestern Colorado. There does not appear to be any specific information on fire frequency for forests in this fire group. Fire disturbance is relatively light, burning irregularly in patchy distribution on this moist type according to Moir and Ludwig (1979).

Following a stand-replacing fire, the community reverts to a grass and forb stage, followed shortly by aspen resprouting rapidly. The grass stage will be prolonged by repeated fires. The most likely conifers in an early stand are Douglas-fir and Engelmann spruce, although fir may be present. As the aspen grows into mature trees, the slower-growing conifers will remain understory trees. A low surface fire will kill some of the aspen but will not stimulate much sprouting. If the Douglas-fir has developed thickened bark, it should easily withstand a low surface fire. However, many of the spruce and most of the firs may be killed. The main effect of a low surface fire is to open the stand for seedling establishment and to lessen the importance of aspen. A severe fire would return the site to grass and forbs. If no fires occur, a mixed stand will develop on the site. Eventually, Douglas-fir could be lost from the site because of shading, resulting in a climax of fir and possibly spruce. This climax forest will maintain itself and low surface fires should only remove duff and allow regeneration.