Name:
Pinus ponderosa var. ponderosa Central Rocky Mountain Open Woodland Group
Reference:
NatureServe Biotics 2019
Description:
This inland Pacific Northwest group 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 group includes two physiognomic phases: true woodlands of <i>Pinus ponderosa</i> with shrubby or grassy understories, and "wooded steppes" with widely spaced, scattered <i>Pinus ponderosa</i> 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. <i>Pinus ponderosa var. ponderosa</i> is the predominant conifer; <i>Pseudotsuga menziesii</i> or <i>Pinus flexilis</i> may be present in the tree canopy but are usually absent. The understory can be shrubby, with <i>Amelanchier alnifolia, Arctostaphylos patula, Arctostaphylos uva-ursi, Artemisia tridentata, Cercocarpus ledifolius, Physocarpus malvaceus, Purshia tridentata, Rosa</i> spp., <i>Symphoricarpos albus</i>, or <i>Symphoricarpos oreophilus</i> as common species. In transition areas with sagebrush steppe, <i>Artemisia tridentata ssp. tridentata, Artemisia tridentata ssp. wyomingensis, Artemisia tripartita</i>, and <i>Purshia tridentata</i> may be common in fire-protected sites such as rocky areas. Deciduous shrubs, such as <i>Physocarpus malvaceus, Spiraea betulifolia</i>, or <i>Symphoricarpos albus</i>, can be abundant in more northerly sites or more moist climates. Herbaceous vegetation in the true savanna occurrences is predominantly fire-resistant grasses and forbs that resprout following surface fires; shrubs, understory trees and downed logs are uncommon. These more open stands support grasses such as <i>Achnatherum</i> spp., dry <i>Carex</i> species (<i>Carex inops</i>), <i>Elymus elymoides, Festuca campestris, Festuca idahoensis, Hesperostipa</i> spp., or <i>Pseudoroegneria spicata</i>. These woodlands and savannas occur at the lower treeline/ecotone between grasslands or shrublands and more mesic coniferous forests, 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 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. The more mesic portions of this group may include <i>Calamagrostis rubescens</i> or <i>Carex geyeri</i>, species more typical of ~Central Rocky Mountain Douglas-fir - Pine Forest Group (G210)$$. 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. Historically, many of these woodlands and savannas lacked the shrub component as a result of 3- to 7-year fire-return intervals.
Accession Code:
urn:lsid:vegbank.org:commConcept:40009-{B3B75BE0-F3EC-4436-91D2-81505D87ADE4}
Plot-observations of this Community Concept:
0
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