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A3643 Abies lasiocarpa - Picea engelmannii Rocky Mountain Dry-Mesic Forest Alliance
Type Concept Sentence: This alliance is characterized by forests and woodlands with broad distributions throughout the southern, central and northern Rocky Mountains and eastern Cascades dominated by Abies lasiocarpa and/or Picea engelmannii.
Common (Translated Scientific) Name: Subalpine Fir - Engelmann Spruce Rocky Mountain Dry-Mesic Forest Alliance
Colloquial Name: Rocky Mountain Dry-Mesic Subalpine Fir - Engelmann Spruce Forest
Hierarchy Level: Alliance
Type Concept: This alliance is characterized by forests and woodlands with broad distributions in the upper montane or subalpine zone throughout the southern, central and northern Rocky Mountains and eastern Cascades dominated by Abies lasiocarpa and/or Picea engelmannii. Canopies may be open to closed. Common associated conifers can include Abies concolor, Larix occidentalis, Picea pungens, Pinus albicaulis, Pinus aristata, Pinus contorta, Pinus flexilis, Pinus strobiformis, and Pseudotsuga menziesii. Understories are highly variable across the range of this alliance and can be dominated by grasses, dry sedges, mesic forbs or shrubs. Common shrub species can include Acer glabrum, Amelanchier alnifolia, Jamesia americana, Juniperus communis, Lonicera utahensis, Mahonia repens, Paxistima myrsinites, Physocarpus monogynus, Ribes montigenum, Ribes pinetorum, Rosa woodsii, Salix scouleriana, Shepherdia canadensis, Spiraea betulifolia, Symphoricarpos oreophilus, Vaccinium myrtillus, and Vaccinium scoparium. Herbaceous layers may be forb-dominated as well. Species may include Arnica cordifolia, Arnica latifolia, Astragalus miser, Chamerion angustifolium, Erigeron eximius, Eucephalus engelmannii, Frasera speciosa, Goodyera repens, Orthilia secunda, Pedicularis racemosa, Polemonium pulcherrimum, and Solidago multiradiata. The most common graminoids include Carex geyeri, Carex rossii, Luzula parviflora, and Poa nervosa. This alliance occurs above the warmer and drier montane forests of the West, which are typically mixed-coniferous forests, but may extend down into the montane zone where there is cold-air drainage. Parent materials and soils are variable. Sites include gentle to very steep mountain slopes, ridgetops, plateaus, basins, alluvial terraces and benches. All aspects are represented, but northerly and easterly aspects predominate, and southerly aspects are found only at higher elevations. Soils are variable, but often gravelly or rocky, relatively shallow with thick duff layers and sometimes high moss or lichen cover.
Diagnostic Characteristics: Needle-leaved evergreen forests and woodlands of the subalpine elevation zones of the Rocky Mountains with dry to mesic moisture regimes. Canopies are dominated by Abies lasiocarpa and/or Picea engelmannii. Understories are highly variable across the range of this alliance and can be dominated by grasses, dry sedges, mesic forbs or shrubs.
Rationale for Nominal Species or Physiognomic Features: No Data Available
Classification Comments: This alliance is based upon a series concept in which Abies lasiocarpa and/or Picea engelmannii may not be the dominant tree canopy species but are always present in the regeneration layer, and it is assumed would dominate the site should "climax" conditions be reached.
Similar NVC Types: No Data Available
note: No Data Available
Physiognomy and Structure: These are forests and woodlands dominated by needle-leaved evergreen trees up to 30 m in height and with open to closed canopy cover (20-100%). Although cold-deciduous trees are relatively rare, they can be prominent in some early-successional stands. Stands may have such high tree density that little light reaches the forest floor and understory layers are depauperate. In stands with somewhat more open canopies, a moderately dense shrub layer may be present, dominated by ericaceous or, less commonly, cold-deciduous species. The ground layer is dominated by perennial forbs or sod-forming graminoids, and herbaceous cover increases with increasing light availability and/or soil moisture. A nonvascular layer of predominantly mosses may be present. Old-growth stands will have hummocky topography, downed logs and snags, and lichens or fungi may cover rotting woody debris.
Floristics: These subalpine forests are characterized by a canopy typically dominated by Abies lasiocarpa and/or Picea engelmannii. In early- to mid-successional stands, other conifers can be dominant or codominant, but Picea engelmannii and Abies lasiocarpa are the most abundant seedlings and saplings. In the Northern Rockies and Cascades other important conifers can include Larix occidentalis, Pinus contorta, Pinus flexilis, and Pseudotsuga menziesii. On the east side of the Continental Divide, only Pseudotsuga and Pinus contorta are important, but in northwestern Wyoming and Utah, Pinus flexilis or Pinus albicaulis can codominate stands at higher elevations. In the southern stands of Colorado and Arizona, other important canopy species may include Abies concolor, Abies lasiocarpa var. arizonica, Picea pungens, Pinus aristata, Pinus flexilis, and Pinus strobiformis. The shrub layer is often sparse, but where canopies are more open can be dominated by ericaceous, cold-deciduous or evergreen species such as Acer glabrum, Amelanchier alnifolia, Jamesia americana, Juniperus communis, Lonicera utahensis, Mahonia repens, Paxistima myrsinites, Physocarpus monogynus, Ribes montigenum, Ribes pinetorum, Rosa woodsii, Salix scouleriana, Shepherdia canadensis, Spiraea betulifolia, Symphoricarpos oreophilus, Vaccinium myrtillus, and Vaccinium scoparium. The herbaceous layer can be either depauperate or species-rich, and is most often dominated by perennial forbs. Important to dominant species include Arnica cordifolia, Arnica latifolia, Astragalus miser, Chamerion angustifolium (= Epilobium angustifolium), Erigeron eximius, Eucephalus engelmannii (= Aster engelmannii), Frasera speciosa, Goodyera repens, Orthilia secunda, Pedicularis racemosa, Polemonium pulcherrimum, and Solidago multiradiata. The most common graminoids include Carex geyeri, Carex rossii, Luzula parviflora, and Poa nervosa. One association has a depauperate understory, with only mosses having significant cover, such as Hypnum revolutum.
Dynamics: Picea engelmannii can be very long-lived, reaching 500 years of age. Abies lasiocarpa decreases in importance relative to Picea engelmannii with increasing distance from the region of Montana and Idaho where maritime air masses influence the climate. Fire is an important disturbance factor, but fire regimes have a long return interval and so are often stand-replacing. Picea engelmannii can rapidly recolonize and dominate burned sites, or can succeed to other species such as Pinus contorta or Populus tremuloides. Due to great longevity, Pseudotsuga menziesii may persist in stands of this alliance for long periods without regeneration. Old-growth characteristics in Picea engelmannii forests will include treefall and windthrow gaps in the canopy, with large downed logs, rotting woody material, tree seedling establishment on logs or on mineral soils unearthed in root balls, and snags. Picea engelmannii is susceptible to infestations by the spruce beetle (Dendroctonus rufipennis) or the spruce budworm (Choristoneura occidentalis), which can cause high mortality during outbreaks. In the Southwest, Arceuthobium microcarpum is a common cause of mortality for the species. 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). In Oregon and Washington, many communities are bottomland, moist, upper montane forests that rarely burn. Fire is important in many of the more open sites, as well as those on steep slopes. Snow avalanches occur frequently at upper elevations, and can result in a mosaic of varying stand ages on sites affected by this disturbance type.
Environmental Description: These upper montane or subalpine forests occur in much of the Rocky Mountains and eastern Cascades where they are often the matrix forests and woodlands. They occur above the warmer and drier montane forests of the West, which are typically mixed-coniferous forests. In the Cascade Range, they occupy areas with pronounced rainshadow effects from mountains to the west, where precipitation is more limited than in the surrounding areas. Average temperatures are fairly uniform across the alliance''s range, with mean July and January temperatures of 12° and -10°C, respectively (Burns and Honkala 1990a). Snowpacks can be deep, but often melt quickly, and summers are cool. Summer frosts are characteristic, especially on sites where cold air pools. Elevations of occurrence increase with decreasing latitude, ranging from less than 970-1800 m in the Cascades, from 900 m to well over 3200 m in the Northern Rockies of Montana, Idaho and Wyoming, and up to 3350 m in the Colorado Rockies. Sites where these forests and woodlands are found include gentle to very steep mountain slopes, high-elevation ridgetops and upper slopes, plateau-like surfaces, basins, alluvial terraces, and well-drained benches. In some locations where there is cold-air drainage, these forests may extend down in elevation into the montane zone, where they will occupy dry stream terraces, toeslopes, or mesic sites with cooler temperature regimes such as northern aspects. Parent materials and soils are variable across the distribution of the alliance. Parent materials include ash, tuff, lava, basalt, granitics, quartzite, dolomite, rhyolite, and other sedimentary rock types. Stands can also occur on colluvium or alluvium. Soils are typically not deep, poorly developed, and can have significant amounts of rock and gravel in the profile. Subalpine soils, such as found associated with these forests, often show evidence of podzolization processes, especially in the north, and poorly decomposed organic layers are common.
Geographic Range: This alliance occupies the subalpine elevation zones of the central, southern and northern Rocky Mountains, east to the Cascades and west to the Wyoming Basins.
Nations: US
States/Provinces: AZ, CO, ID, MT, NM, NV, OR, UT, WA, WY
Plot Analysis Summary:
http://vegbank.org/natureserve/ELEMENT_GLOBAL.2.899701
Confidence Level: Moderate
Confidence Level Comments: No Data Available
Grank: GNR
Greasons: No Data Available
Concept Lineage: A.164, A.168, A.559.
Predecessors: No Data Available
Obsolete Names: No Data Available
Obsolete Parents: No Data Available
Synonomy: >< Abies lasiocarpa-Picea engelmannii Series (Johnston 1987)
>< Picea series (Pfister et al. 1977)
>< Engelmann Spruce - Subalpine Fir: 206 (Eyre 1980)
>< Western Needleleaf Forests: 15: Western Spruce-Fir Forest (Picea-Abies) (Küchler 1964)
>< Western Needleleaf Forests: 21: Southwestern Spruce-Fir Forest (Picea-Abies) (Küchler 1964)
>< Picea series (Pfister et al. 1977)
>< Engelmann Spruce - Subalpine Fir: 206 (Eyre 1980)
>< Western Needleleaf Forests: 15: Western Spruce-Fir Forest (Picea-Abies) (Küchler 1964)
>< Western Needleleaf Forests: 21: Southwestern Spruce-Fir Forest (Picea-Abies) (Küchler 1964)
- Burns, R. M., and B. H. Honkala, technical coordinators. 1990a. Silvics of North America: Volume 1. Conifers. Agriculture Handbook 654. USDA Forest Service, Washington, DC. 675 pp.
- Eyre, F. H., editor. 1980. Forest cover types of the United States and Canada. Society of American Foresters, Washington, DC. 148 pp.
- Faber-Langendoen, D., J. Drake, M. Hall, G. Kittel, S. Menard, C. Nordman, M. Pyne, M. Reid, M. Russo, K. Schulz, L. Sneddon, K. Snow, and J. Teague. 2013-2019b. Screening alliances for induction into the U.S. National Vegetation Classification: Part 1 - Alliance concept review. NatureServe, Arlington, VA.
- Horton, L. E. 1971. Vegetation and ecological relationships, west slope of the Teton study area, Targhee National Forest. USDA Forest Service, Intermountain Region. Unpublished mimeographed report. 50 pp. plus appendices.
- Johnson, C. G., Jr., and S. A. Simon. 1987. Plant associations of the Wallowa-Snake Province Wallowa-Whitman National Forest. Technical Paper R6-ECOL-TP-255A-86. USDA Forest Service, Pacific Northwest Region, Wallowa-Whitman National Forest. 399 pp. plus appendices.
- Johnston, B. C. 1987. Plant associations of Region Two: Potential plant communities of Wyoming, South Dakota, Nebraska, Colorado, and Kansas. R2-ECOL-87-2. USDA Forest Service, Rocky Mountain Region. Lakewood, CO. 429 pp.
- Küchler, A. W. 1964. Potential natural vegetation of the conterminous United States. American Geographic Society Special Publication 36. New York, NY. 116 pp.
- Pfister, R. D., B. L. Kovalchik, S. F. Arno, and R. C. Presby. 1977. Forest habitat types of Montana. General Technical Report INT-34. USDA Forest Service, Intermountain Forest and Range Experiment Station, Ogden, UT. 174 pp.