Common (Translated Scientific) Name: Subalpine Fir - Engelmann Spruce / Clasping Twisted-stalk Swamp Forest

Colloquial Name: No Data Available

Hierarchy Level:  Association

Type Concept: This is a very broadly distributed association occurring in the major ranges of northern Utah, Wyoming, Idaho, eastern Washington and Montana into at least west-central Alberta. In drier climates it is a small-patch type, but with higher precipitation regimes; it can expand to large patches in valley locations. Elevations range from 1250 m in the north to 3355 m at the highest in the south. In the southern portion of this type''s distribution, parent materials are largely alluvium, soils are loamy to silty in texture, derived from the local country rock, which ranges from sandstone to basalt to granitics in the vicinity of major batholiths. In the north, sedimentary and metasediments are the rule with silty clay loams and loams predominating. Mottling and rust pockets are found in many soil pits, indicating high water tables or subirrigation for a portion of the year. Subirrigation is reflected by landscape positions on lower terraces and stringers of lower order streams, toeslopes and side-hill seeps. Most of the indicator forbs present are associated with the decidedly rich end of the soil-nutrient regime. The canopy for the most part is open, the modal cover ranging between 40-60%, dominated by Abies lasiocarpa and Picea engelmannii. Pinus contorta is the major seral species in the middle Rockies, whereas in the northern Rockies Pseudotsuga menziesii, Larix occidentalis, Pinus monticola, and Abies grandis are additional seral species. The dominant aspect of the undergrowth is an abundance of medium to tall forbs, though shrub cover can at times approach 50%; shrubs are a more important component in the northern distribution of the association. Shrubs with the highest constancy and cover include Ribes lacustre, Vaccinium membranaceum, Alnus viridis ssp. sinuata, Lonicera utahensis, Cornus sericea, and Menziesia ferruginea. The graminoid component is negligible. Of the forbs diagnostic for the association four, Streptopus amplexifolius, Senecio triangularis, Heracleum maximum and Mitella pentandra, are distributed across the breadth of the type, though there are numerous ancillary high-constancy forbs spanning the type''s range including Thalictrum occidentale, Geranium richardsonii, Osmorhiza berteroi, Maianthemum stellatum, Orthilia secunda, and Arnica cordifolia (or Arnica latifolia at higher elevations). Aconitum columbianum, Saxifraga odontoloma, Mertensia ciliata, and Mertensia arizonica are wet-site taxa occurring with relatively high constancy in the southerly portion of the association. The forb component of diagnostic species is more diverse from central Idaho northward.

Diagnostic Characteristics: No Data Available

Rationale for Nominal Species or Physiognomic Features: No Data Available

Classification Comments: This association is defined as a PNV vegetation type. If it were renamed as a dominance type, the species would include Picea engelmannii and Abies lasiocarpa. This association has a broad distribution and has been variously recognized by a stand having just a trace of the nominal species Streptopus amplexifolius, to any of a number of indicator species being present, singly or in combination, up to 5% canopy cover. There is considerable floristic diversity represented within the type given the broad geographical range, but the sites basically represent a rather narrow environmental spectrum, hygric to subhydric moisture regimes. All the globally similar associations have Picea engelmannii as an import canopy component, often having greater cover than Abies lasiocarpa, thus the adoption of the new dual designation of the upper canopy should be more meaningful. Streptopus amplexifolius should be retained to designate the undergrowth because it has relatively high constancy, a broad geographic distribution, priority of use, and there is no doubt of its association with wet sites. ~Abies lasiocarpa / Trautvetteria caroliniensis Swamp Forest (CEGL000339)$$ should be archived because it is virtually identical in terms of site parameters and composition to what has been defined elsewhere in the northern Rocky Mountains as ~Abies lasiocarpa - Picea engelmannii / Streptopus amplexifolius Swamp Forest (CEGL000336)$$. It is also unclear why various authors have recognized ~Abies lasiocarpa - Picea engelmannii / Galium triflorum Forest (CEGL000311)$$ as a separate entity; it would appear to have lower total forb cover, possibly because tree canopy cover is greater, though forb composition is virtually identical. It too should probably be synonymized with this association and archived.

Similar NVC Types: No Data Available

note: No Data Available