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A3447 Pinus ponderosa / Herbaceous Understory Central Rocky Mountain Open Woodland Alliance
Type Concept Sentence: These Pinus ponderosa-dominated woodlands and savannas occur at the lower treeline/ecotone between grasslands, typically on warm, dry, exposed sites and are characterized by grassy understories that are generally fire-maintained. 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 / Herbaceous Understory Central Rocky Mountain Open Woodland Alliance
Colloquial Name: Central Rocky Mountain Ponderosa Pine / Herb Open Woodland
Hierarchy Level: Alliance
Type Concept: This alliance is characterized by Pinus ponderosa-dominated woodlands with grassy understories and savannas. Pinus ponderosa var. ponderosa is the predominant conifer with Pseudotsuga menziesii or Pinus flexilis occasionally present in the tree canopy. The understory is dominated by herbaceous vegetation composed of predominantly fire-adapted grasses and forbs that resprout following surface fires; shrubs, understory trees and downed logs are uncommon. Characteristic graminoids include Achnatherum spp., Carex inops, Elymus glaucus, Festuca campestris, Festuca idahoensis, Hesperostipa comata, 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 typically low, although occasionally forbs such as Wyethia mollis dominate the understory. Scattered shrubs may be present in some stands, but they have low cover (<10%) and do not characterize the understory. Species include Amelanchier alnifolia, Arctostaphylos patula, Arctostaphylos uva-ursi, Artemisia tridentata, Cercocarpus ledifolius, Physocarpus malvaceus, Purshia tridentata, Rosa spp., Symphoricarpos albus, or Symphoricarpos oreophilus. 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 and savannas occur at the lower treeline/ecotone between grasslands, typically on warm, dry, exposed sites. They 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 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. Surface textures are variable ranging from sand to loam and silt loam. Exposed rock and bare soil are common. Mixed fire regimes and surface fires of variable return intervals maintain these woodlands, depending on climate, degree of soil development, and understory density. Historically, many of these woodlands and savannas lacked the shrub component as a result of 3- to 7-year fire-return intervals. With fire suppression, tree canopies may become moderately dense and the grass component is reduced.
Diagnostic Characteristics: This alliance is characterized by an open tree canopy (10-40% cover) dominated by Pinus ponderosa with graminoids typically dominating the understory. Characteristic graminoids include Achnatherum spp., dry Carex species (Carex inops), Elymus elymoides, Elymus glaucus, Festuca campestris, Hesperostipa comata, Festuca idahoensis, or Pseudoroegneria spicata. More mesic sites may have Calamagrostis rubescens or Carex geyeri. Stands with understory dominated by forbs such as Wyethia mollis are also included in this alliance.
Rationale for Nominal Species or Physiognomic Features: No Data Available
Classification Comments: 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. The classification status of all associations formerly placed in Pinus ponderosa Forest Alliance (A.124) should be reviewed and verified.
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 a sparse to moderately dense herbaceous layer dominated perennial graminoids or occasionally by perennial forbs.
Floristics: This alliance is characterized by Pinus ponderosa-dominated woodlands with grassy understories and savannas. They are generally fire-maintained. Pinus ponderosa var. ponderosa is the predominant conifer; Pseudotsuga menziesii or Pinus flexilis may be present in the tree canopy but are usually absent. Herbaceous vegetation in the true savanna occurrences is predominantly fire-adapted grasses and forbs that resprout following surface fires; shrubs, understory trees and downed logs are uncommon. These more open stands support graminoids such as Achnatherum spp., Carex inops (and other dry sedges), Elymus elymoides, Elymus glaucus, Festuca campestris, Festuca idahoensis, Hesperostipa comata, Koeleria macrantha, Leucopoa kingii (= Festuca kingii), 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 typically low although occasionally forbs such as Wyethia mollis may dominate the understory. Scattered shrubs may be present in some stands, but they have low cover (<10%) and do not characterize the understory. Species may include Amelanchier alnifolia, Arctostaphylos patula, Arctostaphylos uva-ursi, Artemisia tridentata, Cercocarpus ledifolius, Physocarpus malvaceus, Purshia tridentata, Rosa spp., Symphoricarpos albus, or Symphoricarpos oreophilus.
Dynamics: Pinus ponderosa is a drought-resistant, shade-intolerant conifer which usually occurs at lower treeline in the major ranges of the western United States. Historically, surface fires and drought were influential in maintaining open-canopy conditions in these woodlands. With settlement and subsequent fire suppression, stands have become more dense. Presently, many stands contain understories of more shade-tolerant species, such as Pseudotsuga menziesii and/or Abies spp., as well as younger cohorts of Pinus ponderosa. These altered stand structures have affected fuel loads and altered fire regimes. Presettlement fire regimes were primarily frequent (5- to 15-year return intervals), low-intensity surface fires triggered by lightning strikes or deliberately set fires by Native Americans. With fire suppression and increased fuel loads, fires are now less frequent and often become intense crown fires which can kill mature Pinus ponderosa. Establishment is erratic and believed to be linked to periods of adequate soil moisture and good seed crops, as well as fire frequencies which allow seedlings to reach sapling size. Longer fire intervals have resulted in many stands having dense subcanopies of overstocked and unhealthy young Pinus ponderosa.
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. This alliance is characterized by woodlands with grassy understories and tree savannas. They are generally fire-maintained. These woodlands and savannas occur at the lower treeline/ecotone between grasslands, typically on warm, dry, exposed sites. 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 slopes or ridgetops and plateaus are most common. This alliance 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. Surface textures are highly variable in this alliance 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, depending on climate, degree of soil development, and understory density. Historically, many of these woodlands and savannas lacked the shrub component as a result of 3- to 7-year fire-return intervals.
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, ND, NV?, OR, SD, UT, WA, WY
Plot Analysis Summary:
http://vegbank.org/natureserve/ELEMENT_GLOBAL.2.899570
Confidence Level: Low
Confidence Level Comments: No Data Available
Grank: GNR
Greasons: No Data Available
Concept Lineage: Associations with herbaceous dominated 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 / Agropyron spicatum Association (Daubenmire 1952)
> Pinus ponderosa / Carex geyeri Habitat Type (Alexander et al. 1986)
> Pinus ponderosa / Elymus glaucus Forest (Hall 1973)
> Pinus ponderosa / Festuca campestris Habitat Type (Pfister et al. 1977)
> Pinus ponderosa / Festuca idahoensis (Cooper et al. 1985)
> Pinus ponderosa / Festuca idahoensis Habitat Type (Daubenmire and Daubenmire 1968)
> Pinus ponderosa / Pseudoroegneria spicata Habitat Type (Steele et al. 1981)
> Pinus ponderosa / Roegneria spicata Habitat Type (Daubenmire and Daubenmire 1968)
>< Interior Ponderosa Pine: 237 (Eyre 1980)
>< Westside Ponderosa Pine Forest (#84210) (Holland 1986b)
> Pinus ponderosa / Carex geyeri Habitat Type (Alexander et al. 1986)
> Pinus ponderosa / Elymus glaucus Forest (Hall 1973)
> Pinus ponderosa / Festuca campestris Habitat Type (Pfister et al. 1977)
> Pinus ponderosa / Festuca idahoensis (Cooper et al. 1985)
> Pinus ponderosa / Festuca idahoensis Habitat Type (Daubenmire and Daubenmire 1968)
> Pinus ponderosa / Pseudoroegneria spicata Habitat Type (Steele et al. 1981)
> Pinus ponderosa / Roegneria spicata Habitat Type (Daubenmire and Daubenmire 1968)
>< Interior Ponderosa Pine: 237 (Eyre 1980)
>< Westside Ponderosa Pine Forest (#84210) (Holland 1986b)
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