Print Report
A0540 Pinus flexilis Rocky Mountain Woodland Alliance
Type Concept Sentence: This woodland alliance occurs intermittently from timberline to lower montane and foothill zones throughout much of the Rocky Mountains as well as disjunct populations in surrounding regions with stands solely dominated or codominated by the evergreen needle-leaved tree Pinus flexilis.
Common (Translated Scientific) Name: Limber Pine Rocky Mountain Woodland Alliance
Colloquial Name: Rocky Mountain Limber Pine Woodland
Hierarchy Level: Alliance
Type Concept: Woodlands included in this alliance occur intermittently from timberline to lower montane zones throughout much of the Rocky Mountains on escarpments and other geographic breaks. The vegetation is characterized by an open canopy typically 3-10 m tall, but individuals may reach 15 m. 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 and include Pinus albicaulis, Picea engelmannii, Populus tremuloides, or Pseudotsuga menziesii in the subalpine, and Pinus contorta, Pinus ponderosa, or Pseudotsuga menziesii in the montane zone. The understory vegetation is typically sparse because sites are dry and have a large cover of rock. A sparse shrub layer may be present that includes tall shrubs such as Artemisia tridentata, Cercocarpus ledifolius, Jamesia americana, Rhus trilobata, and Shepherdia canadensis. Arctostaphylos uva-ursi, Juniperus communis, Mahonia repens, Ribes cereum, and Yucca glauca are the most frequent low shrubs. The herbaceous layer often dominates the understory and is composed primarily of graminoids such as Achnatherum hymenoides, Bouteloua gracilis, Calamagrostis purpurascens, Carex rossii, Festuca idahoensis, Festuca campestris, Leucopoa kingii, and Koeleria macrantha. Sites are typically xeric on exposed, windswept rocky slopes and ridges from montane to subalpine. Elevations range from 1385-3350 m. These open woodlands occur on all aspects, but are most common on dry south- and west-facing slopes. Soils are typically shallow, skeletal and coarse-textured, such as gravelly, sandy loams or loams, but may include alkaline clays. Exposed bedrock is common and many stands have over 50% bare soil.
Diagnostic Characteristics: Communities in this alliance are defined by dominance of needle-leaved evergreen trees. Pinus flexilis is the most constant and dominant canopy species within communities in this alliance, although Populus tremuloides may codominate in some stands. Other trees species that may be present to codominant include Picea engelmannii, Pinus albicaulis, Pinus contorta, Pinus ponderosa, Populus tremuloides, and Pseudotsuga menziesii. Environmental settings are typically xeric on exposed, windswept rocky slopes and ridges.
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).
Pending further study, this alliance may be divided into two alliances based on geographic, floristic or environmental factors. However, little information is available for some of the associations included here. Furthermore, some association concepts included here have extremely broad ranges whereas others have very narrow distributions. Therefore, assigning associations to different alliances based on geographic range is not clear.
Pending further study, this alliance may be divided into two alliances based on geographic, floristic or environmental factors. However, little information is available for some of the associations included here. Furthermore, some association concepts included here have extremely broad ranges whereas others have very narrow distributions. Therefore, assigning associations to different alliances based on geographic range is not clear.
Similar NVC Types: No Data Available
note: No Data Available
Physiognomy and Structure: Vegetation included in this alliance has an open tree canopy that is typically to 3-10 m tall. The canopy is dominated by evergreen needle-leaved trees. 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 that are usually less than 3 m tall. A sparse to moderately dense herbaceous layer dominated by perennial graminoids may be present. Perennial forbs have sparse cover. Annual forbs and grasses may be seasonally present.
Floristics: Stands have an open canopy typically 3-10 m tall, but individuals may reach 15 m. 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. In the subalpine, Pinus albicaulis, Picea engelmannii or Pseudotsuga menziesii may be present, and in the montane zone, Pinus contorta, Pinus ponderosa, or Pseudotsuga menziesii are frequently present. The understory vegetation is typically sparse because sites are dry and have a large cover of rock. A sparse shrub layer may be present. The taller shrubs may include Artemisia tridentata, Cercocarpus ledifolius, Jamesia americana, Rhus trilobata, Shepherdia canadensis, Symphoricarpos oreophilus, and immature tree species. The most frequent low shrubs are Arctostaphylos uva-ursi, Artemisia arbuscula, Artemisia nova, Juniperus communis, Mahonia repens, and Yucca glauca. The herbaceous layer often dominates the understory. The most common species are graminoids such as Achnatherum hymenoides (= Oryzopsis hymenoides), Bouteloua gracilis, Calamagrostis purpurascens, Carex rossii, Festuca idahoensis, Festuca campestris, Leucopoa kingii (= Festuca kingii), Koeleria macrantha, and Poa fendleriana. 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). Because Pinus flexilis occurs over a broad range of elevations, it can also be important as a post-fire seral species on drier sites in the Rocky Mountains (Cooper 1975, Peet 1988). Peet (1978a) reported apparent competitive displacement with Pinus flexilis in Colorado. He noted that Pinus flexilis may dominate xeric sites from low to high elevations, except where Pinus aristata or Pinus albicaulis occur. 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: Woodlands included in this alliance occur intermittently from subalpine to lower montane zones throughout much of the Rocky Mountains. They occur on windswept mid to upper portions of steep to moderate slopes and ridgetops. Elevations range from 1385-3050 m. Climate is semiarid, cold temperate. Annual precipitation patterns and amounts are variable, but locally the sites are typically xeric on exposed, windswept rocky slopes and ridges. These open woodlands occur on all aspects, but are most common on dry south- and west-facing slopes. Soils are typically shallow, skeletal and coarse-textured, such as gravelly, sandy loams or loams, but may include alkaline clays. Stands grow best on calcareous soils derived from limestone or sandstone, but parent material is variable and includes a variety of igneous, sedimentary, and metamorphic rocks. Depending on the stand, bedrock may include a mixture of andesite, basalt, lava, limestone, dolomite, granite, gneiss, quartzite, rhyolite, schist, sandstone, serpentine, or shale. Exposed bedrock is common and many stands have over 50% bare soil. Soil pH is typically neutral or slightly alkaline, but ranges from acidic to alkaline.
Geographic Range: Communities of this alliance occur from the southern Rocky Mountains north to the Canadian Rocky Mountains, west into the Great Basin and Columbia Plateau and east into the Wyoming Basins.
Nations: CA,US
States/Provinces: AB, CO, ID, MT, NM, NV, OR, UT, WY
Plot Analysis Summary:
http://vegbank.org/natureserve/ELEMENT_GLOBAL.2.857460
Confidence Level: Moderate
Confidence Level Comments: No Data Available
Grank: GNR
Greasons: No Data Available
Concept Lineage: A.540, in part
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 Habitat Type (Steele et al. 1983)
? Pinus flexilis Habitat Type (USFS 1992)
? Pinus flexilis Series (Johnston 1987)
? Pinus flexilis Series (Girard et al. 1989)
? 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)
? Southern California Subalpine Forest (#86500) (Holland 1986b)
? Pinus flexilis Habitat Type (Steele et al. 1983)
? Pinus flexilis Habitat Type (USFS 1992)
? Pinus flexilis Series (Johnston 1987)
? Pinus flexilis Series (Girard et al. 1989)
? 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)
? Southern California Subalpine Forest (#86500) (Holland 1986b)
- Barrows, J. S., E. W. Mogren, K. Rowdabaugh, and R. Yancik. 1977. The role of fire in ponderosa pine and mixed conifer ecosystems. Final report, Cooperative report between the National Park Service and Rocky Mountain Forest and Range Experiment Station, Fort Collins, CO. 101 pp.
- Cooper, S. V. 1975. Forest habitat types of northwestern Wyoming and contiguous portion of Montana and Idaho. Unpublished dissertation, Washington State University, Pullman. 190 pp.
- Eggler, W. A. 1941. Primary succession on volcanic deposits in southern Idaho. Ecological Monographs 11(3):278-298.
- 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.
- Girard, M. M., H. Goetz, and A. J. Bjugstad. 1989. Native woodland habitat types of southwestern North Dakota. Research Paper RM-281. USDA Forest Service, Rocky Mountain Forest and Range Experiment Station, Fort Collins, CO. 36 pp.
- Holland, R. F. 1986b. Preliminary descriptions of the terrestrial natural communities of California. Unpublished report prepared for the California Department of Fish and Game, Nongame-Heritage Program and Natural Diversity Database, Sacramento. 156 pp.
- 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.
- Lanner, R. M., and S. B. Vander Wall. 1980. Dispersal of limber pine seed by Clark''s nutcracker. Journal of Forestry 78(10):637-639.
- MTNHP [Montana Natural Heritage Program]. No date. Unpublished data on file. Montana Natural Heritage Program, Helena, MT.
- Peet, R. K. 1978a. Latitudinal variation in southern Rocky Mountain forests. Journal of Biogeography 5:275-289.
- Peet, R. K. 1988. Forests of the Rocky Mountains. Pages 64-101 in: M. G. Barbour and W. D. Billings, editors. North American Terrestrial Vegetation. Cambridge University Press, New York.
- Steele, R., S. V. Cooper, D. M. Ondov, D. W. Roberts, and R. D. Pfister. 1983. Forest habitat types of eastern Idaho - western Wyoming. General Technical Report INT-144. USDA Forest Service, Intermountain Forest and Range Experiment Station, Ogden, UT. 122 pp.
- USFS [U.S. Forest Service]. 1992. Draft habitat types of the Little Missouri National Grasslands. Medora and McKenzie ranger districts, Custer National Forest. Dickinson, ND.