Name:
Pinus ponderosa / Shrub Understory Central Rocky Mountain Woodland Alliance
Reference:
NatureServe Biotics 2019
Description:
This alliance is characterized by <i>Pinus ponderosa</i>-dominated woodlands with shrub-dominated understories, and "wooded steppes" with widely spaced, scattered <i>Pinus ponderosa</i> trees over generally shrubby but sparse understories. <i>Pinus ponderosa var. ponderosa</i> is the predominant conifer with <i>Pseudotsuga menziesii</i> or <i>Pinus flexilis</i> 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 <i>Amelanchier alnifolia, Arctostaphylos patula, Arctostaphylos uva-ursi, Artemisia arbuscula, Artemisia tridentata, Artemisia tripartita, Ceanothus velutinus, Cercocarpus ledifolius, Physocarpus malvaceus, Purshia tridentata, Rosa</i> spp. <i>Spiraea betulifolia, Symphoricarpos albus, Symphoricarpos oreophilus</i>, or <i>Vaccinium cespitosum</i>. Herbaceous vegetation varies from sparse to moderately dense, but typically has less cover than the shrubs. Species may include <i>Achnatherum hymenoides, Achnatherum occidentale, Calamagrostis rubescens, Carex geyeri, Carex inops, Elymus glaucus, Festuca campestris, Festuca idahoensis, Hesperostipa comata, Poa nervosa</i>, or <i>Pseudoroegneria spicata</i>. 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.
Accession Code:
urn:lsid:vegbank.org:commConcept:38732-{013BE656-BEBC-4FB4-9E8B-96CA44D941EB}
Plot-observations of this Community Concept:
0
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