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A2035 Pinus flexilis Intermountain Basins Forest & Woodland Alliance

Type Concept Sentence: Forests and woodlands of the central Great Basin, Columbia Plateau, middle and southern Rocky Mountains and Wyoming Basins solely dominated or codominated by the evergreen needle-leaved tree Pinus flexilis.

Common (Translated Scientific) Name: Limber Pine Intermountain Basins Forest & Woodland Alliance

Colloquial Name: Intermountain Basins Limber Pine Forest & Woodland

Hierarchy Level:  Alliance

Type Concept: These forests and woodlands occur from the central Great Basin, east and north to the Columbia Plateau, middle and southern Rocky Mountains and Wyoming Basins. Canopies are solely dominated or codominated by the evergreen needle-leaved tree Pinus flexilis. Other trees present to codominant include Abies concolor, Picea engelmannii, Populus tremuloides, and Pseudotsuga menziesii. The understory is sparse to moderately dense and composed of xeric shrubs, graminoids and cushion plants. The most common dominant shrubs include Arctostaphylos patula, Cercocarpus ledifolius, and Symphoricarpos oreophilus. Herbaceous layers are sparse but, given the broad geographic range of these forests and woodlands, are highly variable. The most common species are graminoids such as Achnatherum hymenoides, Bouteloua gracilis, Calamagrostis purpurascens, Carex rossii, Festuca campestris, Festuca idahoensis, Koeleria macrantha, Leucopoa kingii, and Pseudoroegneria spicata. Scattered forbs may include species of Achillea, Antennaria, Arenaria, Arnica, Astragalus, Erigeron, Eriogonum, Hymenopappus, Hymenoxys, Liatris, Sedum, Solidago, and Thermopsis. Sites include high-elevation ridges and rocky slopes above subalpine forests and woodlands, sometimes extending down into the montane zone. They are harsh, exposed to desiccating winds with rocky substrates and a short growing season that limit plant growth. Parent materials include dolomitic, limestone or granitic rocks. Occurrences can be found on all aspects but are more common on southwestern exposures on steep convex slopes and ridges between 2530 and 3600 m (8300-12,000 feet) elevation.

Diagnostic Characteristics: Pinus flexilis is the dominant and diagnostic species of this woodland group. The understory is variable, but is characterized by xeric shrubs and grasses found in subalpine zones in the intermountain basins and ranges of the West.

Rationale for Nominal Species or Physiognomic Features: No Data Available

Classification Comments: It may be difficult to determine which tree species are dominant in a mixed, montane or subalpine forest stand, especially when Pinus flexilis is seral on Pseudotsuga menziesii habitat type sites. Some stands included in this alliance are too sparse to be classified as woodlands, especially those growing on lava (Eggler 1941).

Similar NVC Types: No Data Available
note: No Data Available
Physiognomy and Structure: The structure of vegetation included in this alliance is variable and has a tree canopy that ranges from very open to dense with heights from to 3-20 m tall. The canopy is dominated by evergreen needle-leaved trees although broad-leaved deciduous species may codominate on some sites. Sparse to moderately sparse tall- and short-shrub layers may be present (1-3 m and <1 m tall, respectively). If present, both shrub layers may be dominated by broad-leaved or microphyllous deciduous shrubs. A sparse to moderately dense herbaceous layer dominated by perennial graminoids is present. Perennial forbs have sparse cover. Annual forbs and grasses may be seasonally present.

Floristics: Vegetation of this alliance has an open to moderately dense canopy 3-20 m tall. The stands are solely dominated or codominated by the evergreen needle-leaved tree Pinus flexilis. Other trees species that may be present to codominant vary by geography and elevation zones throughout the woodland''s range. Other trees present to codominant include Abies concolor, Picea engelmannii, Populus tremuloides, and Pseudotsuga menziesii. The understory is sparse to moderately dense and composed of xeric shrubs, graminoids and cushion plants. The most common dominant shrubs include Arctostaphylos patula, Cercocarpus ledifolius, and Symphoricarpos oreophilus. Other characteristic shrubs may include Arctostaphylos uva-ursi, Artemisia arbuscula, Artemisia nova, Artemisia tridentata, Jamesia americana, Juniperus communis, Mahonia repens, Purshia tridentata, Rhus trilobata, Shepherdia canadensis, and Yucca glauca. Herbaceous layers are sparse but, given the broad geographic range of these forests and woodlands, are highly variable. The most common species are graminoids such as Achnatherum hymenoides (= Oryzopsis hymenoides), Bouteloua gracilis, Calamagrostis purpurascens, Carex rossii, Festuca campestris, Festuca idahoensis, Koeleria macrantha, Leucopoa kingii (= Festuca kingii), and Pseudoroegneria spicata. Scattered forbs may include species of Achillea, Antennaria, Arenaria, Arnica, Astragalus, Erigeron, Eriogonum, Hymenopappus, Hymenoxys, Liatris, Sedum, Solidago, and Thermopsis.

Dynamics:  Although some of the conifers that are typically codominant in Pinus flexilis stands are late-successional species, they are not likely to displace Pinus flexilis. This is because most of these stands occur on harsh sites where Pinus flexilis is more competitive than most other conifer species. These stands are generally considered to be topographic or edaphic "climax" stands (Cooper 1975, Eyre 1980). Birds and small mammals often eat and cache the large, wingless pine seeds. Most important is the Clark''s nutcracker, which can transport the seeds long distances and cache them on exposed windswept sites (Lanner and Vander Wall 1980). This results in the regeneration of pines in clumps from forgotten caches (Eyre 1980, Steele et al. 1983).
Environmental Description:  These forests and woodlands occur throughout a great portion of the Intermountain West between 2530 and 3600 m elevation. Sites are xeric, harsh and exposed to desiccating winds with rocky substrates and a short growing season that limit plant growth. Parent materials include dolomitic, limestone or granitic rocks. Occurrences can be found on all aspects but are more common on southwestern exposures on steep convex slopes and ridges. A characteristic of these forests and woodlands is the prominence of bare ground and, therefore, litter accumulation is low. Steep slopes and often low ground cover often result in high rates of surface erosion.
Geographic Range: Stands included in this forest and woodland alliance occur intermittently throughout the intermountain regions of the central Great Basin, Columbia Plateau, middle and southern Rocky Mountains and Wyoming Basins.

Nations: US

States/Provinces:  CA, ID, MT, NV, UT, WY


Confidence Level: Moderate

Confidence Level Comments: No Data Available
Grank: G5

Greasons: No Data Available
Type Name Database Code Classification Code
Class 1 Forest & Woodland Class C01 1
Subclass 1.B Temperate & Boreal Forest & Woodland Subclass S15 1.B
Formation 1.B.2 Cool Temperate Forest & Woodland Formation F008 1.B.2
Division 1.B.2.Nb Rocky Mountain Forest & Woodland Division D194 1.B.2.Nb
Macrogroup 1.B.2.Nb.5 Subalpine Fir - Engelmann Spruce - Whitebark Pine Rocky Mountain Forest Macrogroup M020 1.B.2.Nb.5
Group 1.B.2.Nb.5.h Limber Pine - Great Basin Bristlecone Pine Intermountain Basins Subalpine Woodland Group G224 1.B.2.Nb.5.h
Alliance A2035 Limber Pine Intermountain Basins Forest & Woodland Alliance A2035 1.B.2.Nb.5.h
Association CEGL000804 Limber Pine / Curl-leaf Mountain-mahogany Woodland CEGL000804 1.B.2.Nb.5.h
Association CEGL005321 Limber Pine / Mountain Snowberry Woodland CEGL005321 1.B.2.Nb.5.h
Association CEGL005434 Limber Pine - (Quaking Aspen) / Greenleaf Manzanita Forest CEGL005434 1.B.2.Nb.5.h
Concept Lineage: This alliance is the combination of the 3 associations from the former alliances Pinus flexilis - Populus tremuloides Forest Alliance (A.425) and Pinus flexilis - Woodland Alliance (A.540). [proto-alliance A2035].

Predecessors: No Data Available

Obsolete Names: No Data Available

Obsolete Parents: No Data Available
Synonomy: ? Pinus flexilis / Agropyron spicatum Habitat Type (Girard et al. 1989)
= Pinus flexilis (Limber pine woodland) Alliance (Sawyer et al. 2009) [87.160.00]
? Pinus flexilis Habitat Type (Steele et al. 1983)
? Pinus flexilis Habitat Type (USFS 1992)
? Pinus flexilis Series (Girard et al. 1989)
? Pinus flexilis Series (Johnston 1987)
= Pinus flexilis Woodland Alliance (Evens et al. 2014)
= Pinus flexilis Woodland Alliance (CNPS 2017) [87.160.00]
>< Limber Pine Forest (#86700) (Holland 1986b)
? Limber Pine Woodland (Barrows et al. 1977) [included in Desert Montane and Forests and Woodlands]
>< Limber Pine: 219 (Eyre 1980)
= Limber pine series (Sawyer and Keeler-Wolf 1995)
>< Southern California Subalpine Forest (#86500) (Holland 1986b)
Concept Author(s): K.A. Schulz, in Faber-Langendoen et al. (2013)

Author of Description: M.E. Hall

Acknowledgements: No Data Available

Version Date: 03-14-14
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