Name:
Pinus ponderosa / Herbaceous Understory Central Rocky Mountain Open Woodland Alliance
Reference:
NatureServe Biotics 2019
Description:
This alliance is characterized by <i>Pinus ponderosa</i>-dominated woodlands with grassy understories and savannas. <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 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 <i>Achnatherum</i> spp., <i>Carex inops, Elymus glaucus, Festuca campestris, Festuca idahoensis, Hesperostipa comata</i>, or <i>Pseudoroegneria spicata</i>. The more mesic portions of this alliance may include <i>Calamagrostis rubescens</i> or <i>Carex geyeri</i>, 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 <i>Wyethia mollis</i> 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 <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>. 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.
Accession Code:
urn:lsid:vegbank.org:commConcept:38733-{C669DE47-6282-40A8-8FF7-9F45F79BCAE9}
Plot-observations of this Community Concept:
0
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