Name:
Quercus garryana - Pinus ponderosa - Pseudotsuga menziesii Forest & Woodland Group
Reference:
NatureServe Biotics 2019
Description:
This narrowly restricted group appears at or near lower treeline in foothills of the eastern Cascades in Washington and Oregon, within 65 km (40 miles) of the Columbia River Gorge. It also appears in the adjacent Columbia Plateau ecoregion. Most occurrences of this group are dominated by a mix of <i>Quercus garryana</i> and <i>Pinus ponderosa</i> or <i>Pseudotsuga menziesii</i>. Isolated, taller <i>Pinus ponderosa</i> or <i>Pseudotsuga menziesii</i> over <i>Quercus garryana</i> trees characterize parts of this group. Clonal <i>Quercus garryana</i> can create dense patches across a grassy landscape or can dominate open woodlands or even savannas. The understory may include dense stands of shrubs or, more often, be dominated by grasses, sedges or forbs. Shrub-steppe shrubs may be prominent in some stands and create a distinct tree / shrub / sparse grassland habitat, including <i>Artemisia nova</i> (in Oregon only), <i>Artemisia tridentata, Chrysothamnus viscidiflorus</i>, and <i>Purshia tridentata</i>. Mesic sites have an open to closed sodgrass understory dominated by <i>Calamagrostis rubescens, Carex geyeri, Carex inops, Carex rossii</i>, or <i>Elymus glaucus</i>. Drier savanna and woodland understories typically contain bunchgrass steppe species such as <i>Festuca idahoensis</i> or <i>Pseudoroegneria spicata</i>. Common exotic grasses that often appear in high abundance are <i>Bromus tectorum</i> and <i>Poa bulbosa</i>. Disjunct occurrences in the Klamath Mountains and southernmost Cascades typically have high cover of sagebrush and bitterbrush in the understory, along with other shrubs. In the Columbia River Gorge, this group appears as small to large patches in transitional areas in the Little White Salmon and White Salmon river drainages in Washington and Hood River, Rock Creek, Moiser Creek, Mill Creek, Threemile Creek, Fifteen Mile Creek, and White River drainages in Oregon. <i>Quercus garryana</i> can create dense patches often associated with grassland or shrubland balds within a closed <i>Pseudotsuga menziesii</i> forest landscape. Commonly the understory is shrubby and composed of <i>Ceanothus integerrimus, Holodiscus discolor, Symphoricarpos albus</i>, and <i>Toxicodendron diversilobum</i>. These woodlands occur at the lower treeline/ecotone between <i>Artemisia</i> spp. or <i>Purshia tridentata</i> steppe or shrubland and <i>Pinus ponderosa</i> and/or <i>Pseudotsuga menziesii</i> forest or woodland. Elevations range from 460 to 1920 m. Sites are typically warm with southern exposures with seasonal soil drought or desiccating winds. Substrates usually have bedrock, sand, or pumice soils which are excessively well-drained. Fire plays an important role in creating vegetation structure and composition in this habitat. Decades of fire suppression have led to invasion by <i>Pinus ponderosa</i> along lower treeline and by <i>Pseudotsuga menziesii</i> in the gorge and other oak patches on xeric sites in the east Cascade foothills. In the past, most of the habitat experienced frequent low-severity fires that maintained woodland or savanna conditions. The mean fire-return interval is 20 years, although variable. Soil drought plays a role, maintaining an open tree canopy in part of this dry woodland habitat.<br /><br />Westside: This group also occurs of the west side of the mountain ranges from the Cascades to the North Coast Ranges in California. It is limited to the southern portions of the North Pacific region where it occurs in southwestern British Columbia, in the Puget Trough and Willamette Valley south into the Klamath Mountains and into northern California, southward through the lower southern Cascades and western Modoc Plateau and the middle and inner North Coast Ranges into Mendocino County. The vegetation ranges from savanna and woodland to forest dominated by deciduous broadleaf trees, mostly <i>Quercus garryana</i>. Codominance by the evergreen conifer <i>Pseudotsuga menziesii</i> is common, and <i>Pinus ponderosa</i> is important in some stands. In the south, common associates also include <i>Quercus kelloggii</i> and <i>Arbutus menziesii</i>. The predominant oaks with the higher frequency fires include <i>Quercus kelloggii</i> and <i>Quercus garryana</i>, with <i>Quercus garryana var. garryana</i> codominant in the central and northern Coast Ranges, Klamath Mountains and Modoc Plateau. However, <i>Quercus garryana var. fruticosa</i> often codominates in the northwestern Coast Ranges. More isolated patches of shrubby, clonal <i>Quercus garryana var. semota</i> (similar to but apparently distinct from <i>var. fruticosa</i>) occur farther south into the Sierra Nevada southward to the Paiute and Tehachapi mountains (southern branches of the Sierra Nevada), but these are without <i>Pinus ponderosa</i> or <i>Pseudotsuga menziesii</i> and appear to behave more as montane chaparral stands. The perennial bunchgrass component includes <i>Danthonia californica</i> (close to the coast), <i>Elymus glaucus, Festuca californica</i>, and <i>Festuca idahoensis</i>. A variety of native forbs also occur. Other characteristic species include <i>Ceanothus cuneatus, Juniperus occidentalis</i>, and <i>Toxicodendron diversilobum</i>. Succession in the absence of fire tends to favor increased shrub dominance in the understory, increased tree density, and increased importance of conifers, with the end result being conversion to a conifer forest. This group merges into ~Californian Broadleaf Forest & Woodland Group (G195)$$. This group occurs as both small patch and large patch in its dynamics. This west side version of this group is associated with dry, predominantly low-elevation sites and/or sites that experienced frequent presettlement fires. Elevations range from 600-1600 m (1800-4850 feet) on steep, rocky slopes where snow and cold temperatures occur. In the Willamette Valley, soils are mesic yet well-drained, and the stands are mostly large patch. In the Puget Lowland and Georgia Basin, this group is primarily found on dry sites, typically either shallow bedrock soils or deep gravelly glacial outwash soils. It occurs on various soils in the interior valleys of the Klamath Mountains, and on shallow soils of "bald hill" toward the coast. Even where more environmentally limited, the group is strongly associated with a historic low-severity fire regime. With frequent annual burning (at lower elevations and on warmer sites), this group is an open to dense woodland of large oaks with well-developed grassy understories of native perennial bunchgrass. Succession in the absence of fire tends to favor increased shrub dominance in the understory, increased tree density, and increased importance of conifers, with the end result being conversion to a conifer forest. This group merges into ~Californian Broadleaf Forest & Woodland Group (G195)$$. This group occurs as both small patch and large patch in its dynamics.
Accession Code:
urn:lsid:vegbank.org:commConcept:40003-{E65A3477-E77F-424D-B319-607E1F6FC62C}
Plot-observations of this Community Concept:
0
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