Physiognomy and Structure: No Data Available

Floristics: In the tree layer, Abies grandis is dominant, averaging 42% cover. There are two main seral dominants, Pinus ponderosa (18% cover) and Pseudotsuga menziesii (17% cover). Small amounts of Larix occidentalis (10%), Picea engelmannii, and Abies lasiocarpa do occur. Acer glabrum (10%) dominates the shrub layer in old-growth stands. Common shrubs are Physocarpus malvaceus, Symphoricarpos albus, Spiraea betulifolia, Sorbus scopulina, Lonicera utahensis, Rosa gymnocarpa (4%), Vaccinium membranaceum (= Vaccinium globulare) (7%), and Paxistima myrsinites. In the herbaceous layer, shade-tolerant forbs such as Adenocaulon bicolor and Prosartes trachycarpa (= Disporum trachycarpum) help indicate this association, especially when the tree canopies become dense and the shrubs become depauperate. Cover of common herbaceous species includes Arnica cordifolia (6%), Galium triflorum (3%), Osmorhiza berteroi (= Osmorhiza chilensis) (3%), Thalictrum occidentale (4%), and Bromus vulgaris (2%). Calamagrostis rubescens also occurs in the herbaceous layer.

Steele et al. (1981) recognize two phases of this type. The first phase, a Physocarpus malvaceus - Physocarpus malvaceus phase, represents a warm dry variant of the association. Physocarpus is the dominant shrub, although it may have low coverage in dense stands. A layer of Calamagrostis rubescens is common in this phase. The second phase is the Acer glabrum - Acer glabrum typic phase. This phase is found on the more moist aspects. Acer glabrum dominates the shrub layer, and Calamagrostis rubescens seldom develops high coverages.

Dynamics:  Damping-off fungus takes a heavy toll of Abies grandis seedlings during wet seasons, and insolation and drought cause mortality during the dry summer months. Seedlings are well established by the third year.

Fire hazard is normally low to moderate under normal weather conditions (Fischer and Bradley 1987). Although this type does not occur in Fischer and Bradley''s study, this type is equivalent to their Group Eleven - warm, moist grand fir, western red-cedar, and western hemlock habitat types. The threat of fire is highest in the summer, when the moist maritime climate no longer prevails. During severe summer drought, heavy fuel loading from high plant productivity can set the stage for severe, widespread fires. Stands are replaced and sites revert to pioneer species. Summertime fuel moisture conditions in young stands are not nearly as high as in older, more dense stands, and the effects of fire are often more severe than they are in older stands. Surface fires often scar the base of the grand fir, creating favorable entry points for decay organisms. The initial floral component, seeds stored on site, and the accidents of natural seeding and seedling establishment may structure the community following the fire more than the characteristics of the fire itself. Although generally true for all fire groups, it is more pronounced in this fire group. The use of fire for site preparation will usually result in increased spring and summer browse for big game in addition to successful regeneration of seral tree species.