Print Report
A3327 Quercus garryana - Pinus ponderosa / Carex geyeri Woodland Alliance
Type Concept Sentence: This alliance covers stands that are dominated by Quercus garryana mixed with Pinus ponderosa and/or Pseudotsuga menziesii. The understory may include dense shrubs or just herbaceous species. This alliance is geographically concentrated on the eastside of the Cascade Range of Oregon and Washington with disjunct stands in southern central Oregon and northern California.
Common (Translated Scientific) Name: Oregon White Oak - Ponderosa Pine / Geyer''s Sedge Woodland Alliance
Colloquial Name: East Cascadian Oregon White Oak - Pine Woodland
Hierarchy Level: Alliance
Type Concept: This alliance consists of stands dominated by Quercus garryana mixed with Pinus ponderosa and/or Pseudotsuga menziesii. Isolated, taller Pinus ponderosa or Pseudotsuga menziesii over Quercus garryana trees sometimes characterize this alliance. Clonal Quercus garryana stands can create dense patches across a grassy landscape creating open woodlands or savannas. The understory may be dense shrubs or be dominated by grasses, sedges or forbs. Shrubs prominent in some stands include Artemisia nova, Artemisia tridentata, Chrysothamnus viscidiflorus, and Purshia tridentata. Understories are generally dominated by herbaceous species, especially graminoids. Mesic sites have an open to closed sodgrass understory dominated by Calamagrostis rubescens, Carex geyeri, Carex rossii, Carex inops, or Elymus glaucus. Drier savanna and woodland understories typically contain bunchgrass steppe species such as Festuca idahoensis or Pseudoroegneria spicata. Common exotic grasses that often appear in high abundance are Bromus tectorum and Poa bulbosa. This alliance occurs in the foothills of the eastern Cascades in Washington and Oregon within 65 km (40 miles) of the Columbia River Gorge, further east into the Columbia Plateau ecoregion, and there are disjunct occurrences in Klamath County, south-central Oregon and Siskiyou County, north-central California. These woodlands occur at the lower treeline/ecotone between Artemisia spp. or Purshia tridentata steppe or shrubland and Pinus ponderosa and/or Pseudotsuga menziesii forests or woodlands. Fire plays an important role in creating vegetation structure and composition in this habitat. Decades of fire suppression have led to invasion by Pinus ponderosa along lower treeline and by Pseudotsuga menziesii. Soil, fire and drought play roles in maintaining an open tree canopy in part of this dry woodland habitat. It is drier and colder than more maritime stands of ~Quercus garryana - Pseudotsuga menziesii / Toxicodendron diversilobum Forest & Woodland Alliance (A3328)$$.
Diagnostic Characteristics: Forests and woodlands dominated by a mix of Quercus garryana and Pinus ponderosa or Pseudotsuga menziesii.
Rationale for Nominal Species or Physiognomic Features: No Data Available
Classification Comments: This alliance concept parallels that of ecological system ~East Cascades Oak-Ponderosa Pine Forest and Woodland (CES204.085)$$, where associations have floristic components of the Intermountain Basins or Rocky Mountains. There is some floristic overlap with west-side white oak associations. The two alliances in this group are distinguished by the differing floristics in the shrub and herb layers between "eastside" and "westside." There is certainly some overlap, and geographically east versus west of the mountains is not a sharp line. We could consider finding a stronger eastside diagnostic species for the name of this alliance.
Similar NVC Types: No Data Available
note: No Data Available
Physiognomy and Structure: Vegetation within this alliance is characterized by a sparse and irregular layer of cold-deciduous trees, 8-25 m in height. A sparse cold-deciduous or evergreen shrub layer may be present. Drought-tolerant graminoids and herbs usually form a continuous ground cover less than 1 m in height.
Floristics: This alliance consists of stands dominated by Quercus garryana mixed with Pinus ponderosa and/or Pseudotsuga menziesii. Isolated, taller Pinus ponderosa or Pseudotsuga menziesii over Quercus garryana trees sometimes characterize this alliance. Clonal Quercus garryana stands can create dense patches across a grassy landscape creating open woodlands or savannas. The understory may be dense shrubs or be dominated by grasses, sedges or forbs. Shrubs prominent in some stands include Artemisia nova, Artemisia tridentata, Chrysothamnus viscidiflorus, and Purshia tridentata. Understories are generally dominated by herbaceous species, especially graminoids. Mesic sites have an open to closed sodgrass understory dominated by Calamagrostis rubescens, Carex geyeri, Carex rossii, Carex inops, or Elymus glaucus. Drier savanna and woodland understories typically contain bunchgrass steppe species such as Festuca idahoensis or Pseudoroegneria spicata. Common exotic grasses that often appear in high abundance are Bromus tectorum and Poa bulbosa.
Dynamics: 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. Dry season fire historically controlled the abundance of invading conifers and maintained the savanna structure of these communities (Thilenius 1968). Fire suppression and grazing can lead to cloning of Quercus garryana and the development of more closed-canopy stands. Quercus garryana is shade-intolerant and is eventually killed when overtopped by coniferous forest. Although many Quercus garryana communities are seral to conifer forest, the extreme seasonal drought where this alliance occurs allows the Quercus garryana to maintain dominance.
Environmental Description: Vegetation within this alliance is found in low-elevation (120-900 m) valleys and slopes of the Pacific Northwest. Precipitation ranges from 40-150 cm annually, with a protracted warm, dry period in midsummer. Dry-season fire is common and serves to maintain the open canopy of these savannas. These are among the most drought-tolerant communities of the maritime Pacific Northwest, and occur east of the Cascade Range where river canyons allow adequate penetration of Pacific moisture. This alliance represents the most xeric expression of the Quercus garryana alliances, where soil drought prohibits continuous canopy cover. Stands of the alliance are found at the lowermost boundary of woodland and forest vegetation, on hot, dry sites, particularly in the Columbia River Gorge, on southerly aspects. Soils are moderately deep, rocky silt loams to loams, derived from mixed colluvium of basaltic materials with a minor component of loess. Adjacent vegetation often includes Quercus garryana woodlands, Quercus garryana, Pseudotsuga menziesii, Pinus ponderosa, or Abies grandis forest communities at the upper elevation, and valley grasslands or Artemisia steppe at lower, drier sites.
Geographic Range: This alliance occurs 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. Disjunct occurrences are found in Klamath County in south-central Oregon and Siskiyou County in north-central California where more sagebrush and bitterbrush occurs in the understory, along with other shrubs.
Nations: CA?,US
States/Provinces: BC?, CA, OR, WA
Plot Analysis Summary:
http://vegbank.org/natureserve/ELEMENT_GLOBAL.2.899451
Confidence Level: Low
Confidence Level Comments: No Data Available
Grank: GNR
Greasons: No Data Available
Concept Lineage: None of the old Quercus garryana alliances relate cleanly to this new alliance.
Predecessors: No Data Available
Obsolete Names: No Data Available
Obsolete Parents: No Data Available
Synonomy: >< Quercus garryana (Oregon white oak woodland) Alliance (Sawyer et al. 2009) [71.030.00]
>< Oregon White Oak Series (Sawyer and Keeler-Wolf 1995)
>< Oregon White Oak Series (Sawyer and Keeler-Wolf 1995)
- Chappell, C., R. Crawford, J. Kagan, and P. J. Doran. 1997. A vegetation, land use, and habitat classification system for the terrestrial and aquatic ecosystems of Oregon and Washington. Unpublished report prepared for Wildlife habitat and species associations within Oregon and Washington landscapes: Building a common understanding for management. Prepared by Washington and Oregon Natural Heritage Programs, Olympia, WA, and Portland, OR. 177 pp.
- Faber-Langendoen, D., J. Drake, M. Hall, G. Kittel, S. Menard, C. Nordman, M. Pyne, M. Reid, M. Russo, K. Schulz, L. Sneddon, K. Snow, and J. Teague. 2013-2019b. Screening alliances for induction into the U.S. National Vegetation Classification: Part 1 - Alliance concept review. NatureServe, Arlington, VA.
- Franklin, J. F., and C. T. Dyrness. 1973. Natural vegetation of Oregon and Washington. General Technical Report PNW-8. USDA Forest Service, Pacific Northwest Forest and Range Experiment Station, Portland, OR. 417 pp.
- Sawyer, J. O., T. Keeler-Wolf, and J. Evens. 2009. A manual of California vegetation. Second edition. California Native Plant Society, Sacramento CA. 1300 pp.
- Sawyer, J. O., and T. Keeler-Wolf. 1995. A manual of California vegetation. California Native Plant Society, Sacramento. 471 pp.
- Thilenius, J. F. 1968. The Quercus garryana forests of the Willamette Valley, Oregon. Ecology 49:1124-1133.