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A3454 Pseudotsuga menziesii Southern Rocky Mountain Forest & Woodland Alliance

Type Concept Sentence: Forests and woodlands primarily of the southern Rocky Mountains with canopies dominated by Pseudotsuga menziesii.


Common (Translated Scientific) Name: Douglas-fir Southern Rocky Mountain Forest & Woodland Alliance

Colloquial Name: Southern Rocky Mountain Douglas-fir Forest & Woodland

Hierarchy Level:  Alliance

Type Concept: These forests and woodlands are primarily distributed in the southern Rocky Mountains, and as far east as Texas. They include evergreen forests dominated by Pseudotsuga menziesii. Canopy associates vary widely depending on geographic location and may include Abies lasiocarpa, Juniperus scopulorum, Pinus contorta, Pinus flexilis, Pinus ponderosa, Pinus strobiformis, and Populus tremuloides. Understories are most often shrub-dominated, but in some associations a layer of graminoids takes prominence. Common dominant shrubs may include Arctostaphylos patula, Arctostaphylos uva-ursi, Artemisia tridentata, Cercocarpus montanus, Holodiscus dumosus, Juniperus communis, Paxistima myrsinites, Physocarpus monogynus, Quercus gambelii, and Quercus x pauciloba. Herbaceous dominants may include Festuca arizonica, Jamesia americana, Muhlenbergia montana, Muhlenbergia straminea, and Poa fendleriana. Elevations range from less than 1000 m in the northern Rocky Mountains to nearly 2900 m in the Southern Rockies and plateaus of the southwestern U.S. Lower elevation stands typically occupy protected northern exposures or mesic ravines and canyons, often on steep slopes. At higher elevations, these forests occur primarily on southerly aspects or ridgetops.

Diagnostic Characteristics: Canopies are dominated or codominated by Pseudotsuga menziesii in association with other conifer species. These forests and woodlands are distinguished from other Pseudotsuga menziesii alliances in having a species composition that is more associated with the southern Rocky Mountains.

Rationale for Nominal Species or Physiognomic Features: No Data Available

Classification Comments: No Data Available

Similar NVC Types: No Data Available
note: No Data Available

Physiognomy and Structure: These forests are characterized by a multi-tiered needle-leaved evergreen tree canopy up to 50 m high, with 20-100% cover. Cold-deciduous, broad-leaved species occasionally codominate. Downed wood may also be abundant in older stands. Shrub cover is dominated by ericaceous or cold-deciduous species and can be dense. The herbaceous understory is primarily composed of graminoids.

Floristics: These forests and woodlands are dominated by Pseudotsuga menziesii in the canopy and almost always in the tree regeneration layer. Pinus ponderosa is an important seral species occurring in many associations, either as older seral remnants or codominating in the canopy. Other trees that can be present to abundant (typically seral) include Populus tremuloides (in the southern Rockies and south into New Mexico and Arizona), Pinus strobiformis (in New Mexico and Arizona), and Pinus contorta (throughout much of the alliance''s range). Species of Abies and Picea do not commonly occur in this alliance, but are present in some stands. Understories in Pseudotsuga menziesii forests are varied; many associations have well-developed shrub layers, varying in height from <2 m (typically) to up to 5 m. Dominant or diagnostic species may include Acer grandidentatum, Amelanchier alnifolia, Arctostaphylos patula, Jamesia americana, Physocarpus monogynus, Quercus arizonica, Quercus gambelii, Quercus rugosa, Quercus X pauciloba, and Quercus hypoleucoides. Arctostaphylos uva-ursi and Mahonia repens are present to important throughout the range. The herbaceous layer can be sparse or, if the shrub layer is not abundant, can be relatively species-rich, usually graminoid-dominated. Important or dominant species include the graminoids Bromus ciliatus, Calamagrostis rubescens, Carex geyeri, Carex rossii, Festuca arizonica, Festuca occidentalis, Luzula parviflora, Muhlenbergia montana, and Muhlenbergia straminea (= Muhlenbergia virescens); and the forbs Arnica cordifolia, Osmorhiza berteroi, Thalictrum occidentale, Viola adunca, and species of many other genera, including Arenaria, Erigeron, Fragaria, Galium, Lathyrus, Lupinus, Penstemon, Vicia, and others.

Dynamics:  Successional relationships in this alliance are complex. Pseudotsuga menziesii seedlings compete poorly in deep shade. At drier locales, seedlings may be favored by moderate shading, such as by a canopy of Pinus ponderosa, which helps to minimize drought stress. In some locations, much of these forests has been logged or burned during European settlement, and present-day stands are second-growth forests dating from fire, logging, or other stand-replacing disturbances (Mauk and Henderson 1984, Chappell et al. 1997). Pseudotsuga menziesii forests were probably subject to a moderate-severity fire regime in presettlement times, with fire-return intervals of 30-100 years. Many of the important tree species in these forests are fire-adapted (Populus tremuloides, Pinus ponderosa, Pinus contorta) (Pfister et al. 1977), and fire-induced reproduction of Pinus ponderosa can result in its continued codominance in Pseudotsuga menziesii forests (Steele et al. 1981). Seeds of the shrub Ceanothus velutinus can remain dormant in forest stands for 200 years (Steele et al. 1981) and germinate abundantly after fire, competitively suppressing conifer seedlings. Some stands may have higher tree-stem density than historically, due largely to fire suppression. Fire suppression has also led to the succession of Pinus ponderosa woodlands or Quercus spp. woodlands to Pseudotsuga menziesii forests.

Environmental Description:  These Pseudotsuga menziesii forests and woodlands occur under a comparatively dry and continental climate regime. Elevations range from less than 1000 m in the northern Rocky Mountains to nearly 2900 m in the Southern Rockies and plateaus of the southwestern U.S. Lower elevation stands typically occupy protected northern exposures or mesic ravines and canyons, often on steep slopes. At higher elevations, these forests occur primarily on southerly aspects or ridgetops. Annual precipitation ranges from 50-100 cm with moderate snowfall and a greater proportion falling during the growing season. Monsoonal summer rains contribute a significant proportion of the annual precipitation in Arizona, New Mexico, and Colorado. Soils are highly variable across the range of this alliance and are derived from diverse parent materials. Pseudotsuga menziesii forests are reported by most studies (Pfister et al. 1977, Steele et al. 1981, Mauk and Henderson 1984, Lillybridge et al. 1995) to show no particular affinities to geologic substrates. Rock types are typically sedimentary rocks in the Central and Southern Rockies and the Colorado Plateau. The soils are typically slightly acidic (pH 5.0-6.0), well-drained, and well-aerated. They can be derived from moderately deep colluvium or shallow-jointed bedrock, and are usually gravelly or rocky.

Geographic Range: This alliance primarily occurs in the southern Rocky Mountains, but extends west into the Great Basin, and east to Trans-Pecos Texas, and north into Alberta, Canada.

Nations: CA,US

States/Provinces:  AB, AZ, CO, MT, NM, NV, TX, UT, WY




Confidence Level: Moderate

Confidence Level Comments: No Data Available

Grank: GNR

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.1 White Fir - Douglas-fir - Blue Spruce Forest Macrogroup M022 1.B.2.Nb.1
Group 1.B.2.Nb.1.c White Fir - Douglas-fir Southern Rocky Mountain Dry Forest Group G226 1.B.2.Nb.1.c
Alliance A3454 Douglas-fir Southern Rocky Mountain Forest & Woodland Alliance A3454 1.B.2.Nb.1.c
Association CEGL000423 Douglas-fir / Greenleaf Manzanita Woodland CEGL000423 1.B.2.Nb.1.c
Association CEGL000424 Douglas-fir / Kinnikinnick Forest CEGL000424 1.B.2.Nb.1.c
Association CEGL000433 Douglas-fir / Arizona Fescue Forest CEGL000433 1.B.2.Nb.1.c
Association CEGL000438 Douglas-fir / Five-petal Cliffbush Forest CEGL000438 1.B.2.Nb.1.c
Association CEGL000443 Douglas-fir / Mountain Muhly Forest CEGL000443 1.B.2.Nb.1.c
Association CEGL000444 Douglas-fir / Screwleaf Muhly Forest CEGL000444 1.B.2.Nb.1.c
Association CEGL000446 Douglas-fir / Oregon Boxleaf Forest CEGL000446 1.B.2.Nb.1.c
Association CEGL000449 Douglas-fir / Mountain Ninebark Forest CEGL000449 1.B.2.Nb.1.c
Association CEGL000452 Douglas-fir / Gambel Oak Forest CEGL000452 1.B.2.Nb.1.c
Association CEGL000455 Douglas-fir / Wavyleaf Oak Forest CEGL000455 1.B.2.Nb.1.c
Association CEGL000545 Quaking Aspen - Douglas-fir / Common Juniper Forest CEGL000545 1.B.2.Nb.1.c
Association CEGL000898 Douglas-fir / Alderleaf Mountain-mahogany Woodland CEGL000898 1.B.2.Nb.1.c
Association CEGL000902 Douglas-fir / Rockspirea Scree Woodland CEGL000902 1.B.2.Nb.1.c
Association CEGL000911 Douglas-fir Scree Woodland CEGL000911 1.B.2.Nb.1.c
Association CEGL002808 Douglas-fir / (Mountain Big Sagebrush, Wyoming Big Sagebrush) Woodland CEGL002808 1.B.2.Nb.1.c
Association CEGL002809 Douglas-fir / Muttongrass Woodland CEGL002809 1.B.2.Nb.1.c

Concept Lineage: A.157 and A.552

Predecessors: No Data Available

Obsolete Names: No Data Available

Obsolete Parents: No Data Available

Synonomy: >< Pinus ponderosa - Pseudotsuga menziesii Woodlands (Chappell et al. 1997)
>< Aspen: 217 (Eyre 1980)
>< IA1a. Douglas Fir - Pine Forest (Allard 1990)
>< Interior Douglas-fir: 210 (Eyre 1980)

Concept Author(s): M.S. Reid and D. Sarr, in Faber-Langendoen et al. (2013)

Author of Description: M.E. Hall

Acknowledgements: No Data Available

Version Date: 08-14-17

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  • Chappell, C., R. Crawford, J. Kagan, and P. J. Doran. 1997. A vegetation, land use, and habitat classification system for the terrestrial and aquatic ecosystems of Oregon and Washington. Unpublished report prepared for Wildlife habitat and species associations within Oregon and Washington landscapes: Building a common understanding for management. Prepared by Washington and Oregon Natural Heritage Programs, Olympia, WA, and Portland, OR. 177 pp.
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