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A3446 Pinus ponderosa / Shrub Understory Central Rocky Mountain Woodland Alliance

Type Concept Sentence: These are Pinus ponderosa-dominated woodlands with shrub-dominated understories and "wooded steppes" with widely spaced, scattered Pinus ponderosa trees over generally shrubby but sparse understories that occur at the lower treeline/ecotone on warm, dry, exposed sites. This inland Pacific Northwest alliance occurs in the foothills of the central Rocky Mountains in the Columbia Plateau region and west along the foothills of the Modoc Plateau and eastern Cascades into southern interior British Columbia. It also occurs east across Idaho into the eastern foothills of the Montana Rockies.

Common (Translated Scientific) Name: Ponderosa Pine / Shrub Understory Central Rocky Mountain Woodland Alliance

Colloquial Name: Central Rocky Mountain Ponderosa Pine / Shrub Woodland

Hierarchy Level:  Alliance

Type Concept: This alliance is characterized by Pinus ponderosa-dominated woodlands with shrub-dominated understories, and "wooded steppes" with widely spaced, scattered Pinus ponderosa trees over generally shrubby but sparse understories. Pinus ponderosa var. ponderosa is the predominant conifer with Pseudotsuga menziesii or Pinus flexilis occasionally present in the tree canopy. The understory is characterized by shrubs that form an open to moderately dense layer. If shrub cover is sparse (<10% cover), then it exceeds herbaceous cover. Common shrubs include Amelanchier alnifolia, Arctostaphylos patula, Arctostaphylos uva-ursi, Artemisia arbuscula, Artemisia tridentata, Artemisia tripartita, Ceanothus velutinus, Cercocarpus ledifolius, Physocarpus malvaceus, Purshia tridentata, Rosa spp. Spiraea betulifolia, Symphoricarpos albus, Symphoricarpos oreophilus, or Vaccinium cespitosum. Herbaceous vegetation varies from sparse to moderately dense, but typically has less cover than the shrubs. Species may include Achnatherum hymenoides, Achnatherum occidentale, Calamagrostis rubescens, Carex geyeri, Carex inops, Elymus glaucus, Festuca campestris, Festuca idahoensis, Hesperostipa comata, Poa nervosa, or Pseudoroegneria spicata. This inland Pacific Northwest alliance occurs in the foothills of the central Rocky Mountains in the Columbia Plateau region and west along the foothills of the Modoc Plateau and eastern Cascades into southern interior British Columbia. It also occurs east across Idaho into the eastern foothills of the Montana Rockies. These woodlands occur at the lower treeline/ecotone between shrublands and more mesic coniferous forests, typically on warm, dry, exposed sites that are often too dry and with widely spaced vegetation to carry fire. These interior Pacific Northwest woodlands receive winter and spring rains, and thus have a greater spring "green-up" than the drier woodlands in the Central Rockies. Elevations range from less than 500 m in British Columbia to 1600 m in the central Idaho mountains. Occurrences are found on all slopes and aspects; however, moderately steep to very steep slopes or ridgetops and plateaus are most common. Soils are shallow, often gravelly or coarse textured, and well-drained with periods of drought during the growing season. Some occurrences may occur as edaphic climax communities on very skeletal, infertile and/or excessively drained soils, such as pumice, cinder or lava fields, and scree slopes. Mixed fire regimes and surface fires of variable return intervals maintain these woodlands typically with a shrub-dominated or patchy shrub layer, depending on climate, degree of soil development, and understory density.

Diagnostic Characteristics: This alliance is characterized by an open to moderately dense tree canopy dominated by Pinus ponderosa with shrubs characterizing the understory. If grasses are abundant, then a distinct shrub layer is present with at least 10% cover. Other sites are so xeric that only scattered shrubs are present in understory. Characteristic shrubs include Arctostaphylos patula, Arctostaphylos uva-ursi, Artemisia tridentata, Cercocarpus ledifolius, Physocarpus malvaceus, Purshia tridentata, Spiraea betulifolia, Symphoricarpos oreophilus, or Symphoricarpos albus, Amelanchier alnifolia, and Rosa spp. common species. Herbaceous species are variable and not diagnostic.

Rationale for Nominal Species or Physiognomic Features: No Data Available

Classification Comments: This alliance is broadly defined and includes two physiognomic phases: true woodlands and "wooded steppes" with widely spaced, scattered over generally shrubby but sparse understories. It may be possible to split this alliance into two and assign associations accordingly, but it is not possible at this time. It may be possible to split this alliance into dry-mesic and mesic-wet upland forests and woodlands, but it needs further review.

Taxonomists (Kartesz 1999) recognize two varieties of Pinus ponderosa, a Pacific form, Pinus ponderosa var. ponderosa, and an interior form, Pinus ponderosa var. scopulorum. Associations dominated by either variety are included in this alliance.

Similar NVC Types: No Data Available
note: No Data Available
Physiognomy and Structure: This alliance includes open to moderately dense woodland and savanna stands of needle-leaved evergreen trees 10-30 m in height. The understory is characterized by tall- or short-shrub layers (>10% cover) of sclerophyllous or cold-deciduous species. A sparse to moderately dense herbaceous layer dominated by perennial forbs is important in some stands.

Floristics: This inland Pacific Northwest alliance is characterized by Pinus ponderosa-dominated woodlands with shrub-dominated understories, and "wooded steppes" with widely spaced, scattered Pinus ponderosa trees over generally shrubby but sparse understories. The former are generally fire-maintained, while the later are often too dry and with widely spaced vegetation to carry fire. Pinus ponderosa var. ponderosa is the predominant conifer; Pseudotsuga menziesii or Pinus flexilis may be present in the tree canopy but are usually absent. The understory is characterized by shrubs; common species include Amelanchier alnifolia, Arctostaphylos patula, Arctostaphylos uva-ursi, Artemisia arbuscula, Artemisia tridentata, Artemisia tripartita, Ceanothus velutinus, Cercocarpus ledifolius, Physocarpus malvaceus, Purshia tridentata, Rosa spp. Spiraea betulifolia, Symphoricarpos albus, Symphoricarpos oreophilus, or Vaccinium cespitosum. In transition areas with sagebrush steppe, Artemisia tridentata ssp. tridentata, Artemisia tridentata ssp. wyomingensis, and Artemisia tripartita, and Purshia tridentata may be common in fire-protected sites such as rocky areas. Deciduous shrubs, such as Physocarpus malvaceus, Spiraea betulifolia, Symphoricarpos albus, or Spiraea betulifolia, can be abundant in more northerly sites or more moist climates. Herbaceous vegetation varies from sparse to moderately dense, but typically has less cover than the shrubs. Species may include Achnatherum hymenoides, Achnatherum occidentale, Calamagrostis rubescens, Carex geyeri, Carex inops, Elymus glaucus, Festuca campestris, Festuca idahoensis, Hesperostipa comata, Poa nervosa, or Pseudoroegneria spicata. The more mesic portions of this alliance may include Calamagrostis rubescens or Carex geyeri, species more typical of alliances in ~Central Rocky Mountain Douglas-fir - Pine Forest Group (G210)$$. Forb cover is sparse but may be diverse and include species of many other genera, such as Antennaria, Arenaria, Erigeron, Eriogonum, Heterotheca, Lupinus, and Lathyrus.

Dynamics:  These woodlands occur at the lower treeline/ecotone between shrublands and more mesic coniferous forests, typically on warm, dry, exposed sites Some occurrences may occur as edaphic climax communities on very skeletal, infertile and/or excessively drained soils, such as pumice, cinder or lava fields, and scree slopes that are too dry and with widely spaced vegetation to carry fire. Other sites have mixed fire regimes and surface fires of variable return intervals that maintain these woodlands, typically with a shrub-dominated or patchy shrub layer, depending on climate, degree of soil development, and understory density.
Environmental Description:  This inland Pacific Northwest alliance occurs in the foothills of the central Rocky Mountains in the Columbia Plateau region and west along the foothills of the Modoc Plateau and eastern Cascades into southern interior British Columbia. It also occurs east across Idaho into the eastern foothills of the Montana Rockies. These woodlands occur at the lower treeline/ecotone between shrublands and more mesic coniferous forests, typically on warm, dry, exposed sites that are often too dry and with widely spaced vegetation to carry fire. Generally, these woodlands occur in areas which receive 25-60 cm of precipitation annually, with some seasonal drought. These interior Pacific Northwest woodlands receive winter and spring rains, and thus have a greater spring "green-up" than the drier woodlands in the Central Rockies. However, sites are often too droughty to support a closed tree canopy. Elevations range from less than 500 m in British Columbia to 1600 m in the central Idaho mountains. Occurrences are found on all slopes and aspects; however, moderately steep to very steep slopes or ridgetops and plateaus are most common. This group generally occurs on most geological substrates from weathered rock to glacial deposits to eolian deposits. Characteristic soil features include good aeration and drainage, coarse textures, circumneutral to slightly acidic pH, an abundance of mineral material, and periods of drought during the growing season. Some occurrences may occur as edaphic climax communities on very skeletal, infertile and/or excessively drained soils, such as pumice, cinder or lava fields, and scree slopes. Surface textures are highly variable in this group ranging from sand to loam and silt loam. Exposed rock and bare soil consistently occur to some degree in all the associations. Mixed fire regimes and surface fires of variable return intervals maintain these woodlands, typically with a shrub-dominated or patchy shrub layer, depending on climate, degree of soil development, and understory density.
Geographic Range: This alliance is found in southern British Columbia south along the Cascades and central Rocky Mountains of Washington, Oregon and the Modoc Plateau of northeastern California. In the northeastern part of its range, it extends across the Central Rocky Mountains west of the Continental Divide into northwestern Montana, south to the Snake River Plain in Idaho, and east into the foothills of western Montana (but not into central or eastern Montana). In Oregon, it is most common in south-central Oregon, in lands managed by the Lakeview District of the BLM, and by the adjacent Fremont and Deschutes national forests. It also occurs on the marginal lands coming south out of the Blue Mountains, on the edge of the northern Basin and Range.

Nations: CA,US

States/Provinces:  AB, BC, CA, CO, ID, MT, NM, NV?, OR, SD, UT, WA, WY


Confidence Level: Low

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.2 Ponderosa Pine - Douglas-fir - Limber Pine Central Rocky Mountain Dry Forest Macrogroup M501 1.B.2.Nb.2
Group 1.B.2.Nb.2.a Ponderosa Pine Central Rocky Mountain Open Woodland Group G213 1.B.2.Nb.2.a
Alliance A3446 Ponderosa Pine / Shrub Understory Central Rocky Mountain Woodland Alliance A3446 1.B.2.Nb.2.a
Association CEGL000062 Ponderosa Pine / Greenleaf Manzanita - Snowbrush Ceanothus Woodland CEGL000062 1.B.2.Nb.2.a
Association CEGL000063 Ponderosa Pine / Greenleaf Manzanita - Antelope Bitterbrush Woodland CEGL000063 1.B.2.Nb.2.a
Association CEGL000064 Ponderosa Pine / Snowbrush Ceanothus - Antelope Bitterbrush Woodland CEGL000064 1.B.2.Nb.2.a
Association CEGL000178 Ponderosa Pine / Big Sagebrush - Antelope Bitterbrush Woodland CEGL000178 1.B.2.Nb.2.a
Association CEGL000179 Ponderosa Pine / Wyoming Big Sagebrush / Needle-and-Thread Woodland CEGL000179 1.B.2.Nb.2.a
Association CEGL000180 Ponderosa Pine / Mountain Big Sagebrush / Hooker''s Bluegrass Woodland CEGL000180 1.B.2.Nb.2.a
Association CEGL000189 Ponderosa Pine / Mallow Ninebark Forest CEGL000189 1.B.2.Nb.2.a
Association CEGL000193 Ponderosa Pine / Antelope Bitterbrush / Long-stolon Sedge Forest CEGL000193 1.B.2.Nb.2.a
Association CEGL000194 Ponderosa Pine / Antelope Bitterbrush / Ross'' Sedge Woodland CEGL000194 1.B.2.Nb.2.a
Association CEGL000195 Ponderosa Pine / Antelope Bitterbrush / Idaho Fescue Woodland CEGL000195 1.B.2.Nb.2.a
Association CEGL000196 Ponderosa Pine / Antelope Bitterbrush / Indian Ricegrass Woodland CEGL000196 1.B.2.Nb.2.a
Association CEGL000197 Ponderosa Pine / Antelope Bitterbrush / Bluebunch Wheatgrass Woodland CEGL000197 1.B.2.Nb.2.a
Association CEGL000198 Ponderosa Pine / Antelope Bitterbrush / Western Needlegrass Woodland CEGL000198 1.B.2.Nb.2.a
Association CEGL000200 Ponderosa Pine / Gooseberry Currant Woodland CEGL000200 1.B.2.Nb.2.a
Association CEGL000202 Ponderosa Pine / Shinyleaf Meadowsweet Forest CEGL000202 1.B.2.Nb.2.a
Association CEGL000203 Ponderosa Pine / Common Snowberry Forest CEGL000203 1.B.2.Nb.2.a
Association CEGL000205 Ponderosa Pine / Mountain Snowberry Forest CEGL000205 1.B.2.Nb.2.a
Association CEGL000845 Ponderosa Pine / Little Sagebrush Woodland CEGL000845 1.B.2.Nb.2.a
Association CEGL002606 Ponderosa Pine / Antelope Bitterbrush / Geyer''s Sedge Woodland CEGL002606 1.B.2.Nb.2.a
Association CEGL002688 Ponderosa Pine - Western Juniper / Big Sagebrush - Antelope Bitterbrush Woodland CEGL002688 1.B.2.Nb.2.a
Association CEGL005646 Ponderosa Pine / Curl-leaf Mountain-mahogany Central Rocky Mountain Woodland CEGL005646 1.B.2.Nb.2.a
Association CEGL005648 Ponderosa Pine / Antelope Bitterbrush Central Rocky Mountain Woodland CEGL005648 1.B.2.Nb.2.a
Association CEGL005841 Ponderosa Pine / Dwarf Bilberry Woodland CEGL005841 1.B.2.Nb.2.a
Concept Lineage: Associations with shrub characterized understories from Old Alliance I.A.8.N.b. Pinus ponderosa Forest Alliance (A.124) and Old Alliance II.A.4.N.a. Pinus ponderosa Woodland Alliance (A.530) are included in this alliance. A.124 (in part), A.530 (in part)

Predecessors: No Data Available

Obsolete Names: No Data Available

Obsolete Parents: No Data Available
Synonomy: > Pinus ponderosa / Arctostaphylos patula - Ceanothus velutinus / Pteridium aquilinum (Sherman 1969)
> Pinus ponderosa / Artemisia arbuscula Habitat Type (DeVelice et al. 1986)
> Pinus ponderosa / Artemisia tridentata ssp. vaseyana / Poa nervosa (Hopkins 1979a)
> Pinus ponderosa / Physocarpus malvaceus Habitat Type (Steele et al. 1981)
> Pinus ponderosa / Purshia tridentata / Agropyron spicatum (Lillybridge et al. 1995)
> Pinus ponderosa / Purshia tridentata / Festuca idahoensis - Pseudoroegneria spicata (Daubenmire 1968a)
> Pinus ponderosa / Purshia tridentata (Clausnitzer and Zamora 1987)
> Pinus ponderosa / Symphoricarpos oreophila Habitat Type (Steele et al. 1981)
? Pseudotsuga menziesii - Pinus ponderosa / Carex geyeri (Cole 1977b)
>< Interior Ponderosa Pine: 237 (Eyre 1980)
>< Pacific Ponderosa Pine: 245 (Eyre 1980)
? Ponderosa Pine / Bitterbrush - Manzanita / Fescue (Volland 1985)
? Ponderosa Pine / Bitterbrush / Fescue (Hopkins 1979a)
Concept Author(s): K.A. Schulz, in Faber-Langendoen et al. (2013)

Author of Description: K.A. Schulz

Acknowledgements: We have incorporated significant descriptive information previously compiled by M. Manning and Marion Reid.

Version Date: 01-08-14
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