Print Report

A0106 Pseudotsuga menziesii - Notholithocarpus densiflorus Forest Alliance

Type Concept Sentence: This forest alliance consists of mixed stands of Pseudotsuga menziesii and Notholithocarpus densiflorus with other conifers or broadleaf evergreen trees. These forests occur along low- to moderate-elevation mountain slopes and valley margins in the mountains of northern California and southern Oregon.

Common (Translated Scientific) Name: Douglas-fir - Tanoak Forest Alliance

Colloquial Name: Douglas-fir - Tanoak Forest

Hierarchy Level:  Alliance

Type Concept: This alliance consists of mixed stands of Pseudotsuga menziesii and Notholithocarpus densiflorus, with other conifers or broadleaf evergreen trees, such as Acer macrophyllum, Arbutus menziesii, Calocedrus decurrens, Chamaecyparis lawsoniana, Chrysolepis chrysophylla, Pinus ponderosa, Pinus lambertiana, Quercus chrysolepis, Quercus kelloggii, Taxus brevifolia, Tsuga heterophylla and Umbellularia californica. Conifer cover is significant. Common shrubs include Gaultheria shallon, Mahonia nervosa, Rhododendron macrophyllum, Toxicodendron diversilobum, Vaccinium ovatum, and Vaccinium uliginosum. Trees are >75 m in height and the canopy is intermittent to continuous, two-tiered in older stands. The shrub layer is sparse to intermittent, and the herbaceous layer is sparse or abundant. This forest alliance occurs in the mountains of northern California (as far south as Santa Cruz) and southern Oregon, including the Klamath Mountains and the western portion of the southern Cascades and northern Sierra Nevada at elevations ranging from 100-1500 m. Habitats are raised stream benches, terraces, slopes, and ridges of all aspects. Soils are deep, well-drained, and mostly derived from sandstones and schists.

Diagnostic Characteristics: Mixed stands of Pseudotsuga menziesii and Notholithocarpus densiflorus, with other conifers or broadleaf evergreen trees, such as Acer macrophyllum, Arbutus menziesii, Calocedrus decurrens, Chamaecyparis lawsoniana, Chrysolepis chrysophylla, Pinus ponderosa, Pinus lambertiana, Quercus chrysolepis, Quercus kelloggii, Taxus brevifolia, Tsuga heterophylla, and Umbellularia californica. Pseudotsuga menziesii and Notholithocarpus densiflorus both 25-60% relative cover in the tree canopy.

Rationale for Nominal Species or Physiognomic Features: No Data Available

Classification Comments: This concept seems pretty broad when reviewing the list of USNVC and MCV (Sawyer and Keeler-Wolf 1995) associations. We should consider if another alliance should be defined based on the lack of Notholithocarpus, but the names of the associations that lack Notholithocarpus may still have a component of tanoak. Possibly a Pseudotsuga - Umbellularia - Quercus (chrysolepis, agrifolia) alliance would be worth exploring. From Sawyer et al. (2009): "Bingham (1999) found that stands where Pseudotsuga menziesii and Notholithocarpus densiflorus shared dominance segregated significantly in species composition and environmental conditions from those where Pseudotsuga menziesii shared dominance with other trees [see the Abies concolor - Pseudotsuga menziesii, Pinus ponderosa - Pseudotsuga menziesii, Pseudotsuga menziesii alliances in other groups]."

Shrublands with Chrysolepis chrysophylla var. minor dominant are placed in ~Californian Maritime Chaparral Group (G258)$$. No hardwoods are codominant with Pseudotsuga menziesii in ~Pseudotsuga menziesii / Baccharis pilularis Forest (CEGL003165)$$, and it is recommended to move this to another Pseudotsuga menziesii alliance (J. Evens pers. comm. 2013).

Similar NVC Types: No Data Available
note: No Data Available
Physiognomy and Structure: This alliance is characterized by a multi-tiered structure, with a closed canopy of giant (>50 m tall) conifers and a shorter tree canopy of sclerophyllous hardwoods (20-50 m tall). There is a complex shrub layer. The herbaceous understory is usually sparse, but can be diverse and lush in light gaps or mesic sites.

Floristics: Communities within this alliance usually contain an open canopy of Pseudotsuga menziesii, which is usually 50 m or more in height. Notholithocarpus densiflorus (= Lithocarpus densiflorus) typically forms a sclerophyllous subcanopy. Other coniferous trees such as Chamaecyparis lawsoniana, Pinus lambertiana, Pinus ponderosa, and Sequoia sempervirens may be present in the upper tree layer, depending upon location and stand history. Broad-leaved cold-deciduous and sclerophyllous trees such as Umbellularia californica, Chrysolepis chrysophylla (= Castanopsis chrysophylla), Cornus nuttallii, Arbutus menziesii, Quercus chrysolepis, and Acer macrophyllum may also be present in the hardwood subcanopy. The needle-leaved evergreen Taxus brevifolia may also be part of the subcanopy, particularly in moist ravines. The forest understory is usually species-rich and well-developed. Common shrub species in stands of this alliance include Acer circinatum, Corylus cornuta var. californica, Gaultheria shallon, Lonicera hispidula, Quercus sadleriana, Rhododendron occidentale, Symphoricarpos albus, Toxicodendron diversilobum, Vaccinium ovatum, and Vaccinium uliginosum. The herbaceous layer is usually sparse and dominated by shade-tolerant forbs, including Achlys triphylla, Asarum caudatum, Maianthemum stellatum, Oxalis oregana, Trientalis borealis ssp. latifolia (= Trientalis latifolia), Trillium ovatum, and Xerophyllum tenax. Graminoid species include Bromus vulgaris, Elymus glaucus, Festuca occidentalis, and Luzula parviflora.

Dynamics:  Vegetation within this alliance is more widespread and stands are denser than historically, due largely to fire suppression. Notholithocarpus densiflorus, which resprouts following fire, is favored over Pseudotsuga menziesii with increasing fire frequency. With increasing stand age, Pseudotsuga menziesii overtops Notholithocarpus densiflorus and assumes canopy dominance. Ancient stands of this alliance are often of giant forest stature (>50 m in height) in the Klamath/Siskiyou region (Chappell et al. 1997). Due to the longevity of Pseudotsuga menziesii and the shade tolerance of Notholithocarpus densiflorus, these communities may be quite persistent in the absence of fire or other disturbance (Hunter 1997).
Environmental Description:  The vegetation within this alliance occurs in the maritime-influenced mountains of northern California and southern Oregon. This region has mild to warm winter temperatures, hot summers, and receives 75-250 cm of annual precipitation in a Mediterranean pattern of winter rain followed by summer drought. Drought stress is ameliorated somewhat by fogs in coastal stands. These forests occur along low- to moderate-elevation (100-1500 m) mountain slopes and valley margins, with an increasing affinity for moist topographic positions away from the coast and southward. These communities were probably subject to a moderately severe fire regime in presettlement times, due to late summer lightning and burning by indigenous peoples.
Geographic Range: This forest alliance occurs in the maritime-influenced mountains of northern California (as far south as Santa Cruz) and southern Oregon, including the Klamath Mountains and the western portion of the southern Cascades and northern Sierra Nevada.

Nations: US

States/Provinces:  CA, OR


Confidence Level: Low

Confidence Level Comments: No Data Available
Grank: G4

Greasons: No Data Available
Type Name Database Code Classification Code
Class 1 Forest & Woodland Class C01 1
Subclass 1.B Temperate & Boreal Forest & Woodland Subclass S15 1.B
Formation 1.B.1 Warm Temperate Forest & Woodland Formation F018 1.B.1
Division 1.B.1.Nc Californian Forest & Woodland Division D007 1.B.1.Nc
Macrogroup 1.B.1.Nc.1 California Live Oak - California Laurel - Western Cypress species Forest & Woodland Macrogroup M009 1.B.1.Nc.1
Group 1.B.1.Nc.1.c Douglas-fir - Tanoak - Pacific Madrone Forest Group G208 1.B.1.Nc.1.c
Alliance A0106 Douglas-fir - Tanoak Forest Alliance A0106 1.B.1.Nc.1.c
Association CEGL000071 Douglas-fir - Giant Chinquapin / Pacific Rhododendron Forest CEGL000071 1.B.1.Nc.1.c
Association CEGL000072 Douglas-fir / Pacific Poison-oak Woodland CEGL000072 1.B.1.Nc.1.c
Association CEGL000073 Douglas-fir - California Laurel / Pacific Poison-oak Forest CEGL000073 1.B.1.Nc.1.c
Association CEGL000074 Douglas-fir / Tanoak - Giant Chinquapin Forest CEGL000074 1.B.1.Nc.1.c
Association CEGL000075 Douglas-fir / Tanoak / Salal Forest CEGL000075 1.B.1.Nc.1.c
Association CEGL000076 Douglas-fir / Tanoak / Canyon Live Oak Forest CEGL000076 1.B.1.Nc.1.c
Association CEGL000077 Douglas-fir / Tanoak / Western Azalea Forest CEGL000077 1.B.1.Nc.1.c
Association CEGL000078 Douglas-fir / Tanoak / Pacific Poison-oak Forest CEGL000078 1.B.1.Nc.1.c
Association CEGL000079 Douglas-fir / Tanoak / Bog Blueberry Forest CEGL000079 1.B.1.Nc.1.c
Association CEGL000080 Douglas-fir / Tanoak / California Huckleberry Forest CEGL000080 1.B.1.Nc.1.c
Association CEGL000087 Douglas-fir - Western Hemlock / Tanoak - California Laurel Forest CEGL000087 1.B.1.Nc.1.c
Association CEGL000518 Bigleaf Maple - Douglas-fir - California Laurel / Western Swordfern Forest CEGL000518 1.B.1.Nc.1.c
Association CEGL000926 Douglas-fir / Canyon Live Oak Woodland CEGL000926 1.B.1.Nc.1.c
Association CEGL003165 Douglas-fir / Coyotebrush Forest CEGL003165 1.B.1.Nc.1.c
Association CEGL003166 Douglas-fir / California Live Oak Forest CEGL003166 1.B.1.Nc.1.c
Association CEGL003167 Douglas-fir / California Laurel / California Buckthorn Forest CEGL003167 1.B.1.Nc.1.c
Association CEGL003168 Douglas-fir / California Laurel / Western Swordfern Forest CEGL003168 1.B.1.Nc.1.c
Association CEGL003174 California Laurel / Western Swordfern Forest CEGL003174 1.B.1.Nc.1.c
Concept Lineage: This new alliance includes all of A.106, plus portions of A.108 and others

Predecessors: No Data Available

Obsolete Names: No Data Available

Obsolete Parents: No Data Available
Synonomy: = Pseudotsuga menziesii - Lithocarpus densiflorus (Douglas fir - tanoak forest) Alliance (Sawyer et al. 2009) [82.500.00]
= Pseudotsuga menziesii-Notholithocarpus densiflorus Forest Alliance (CNPS 2017) [82.500.00]
= Douglas fir-tanoak series (Sawyer and Keeler-Wolf 1995)
>< Douglas-fir - Tanoak - Pacific Madrone: 234 (Eyre 1980)
>< Mixed Evergreen Forest (#81100) (Holland 1986b)
>< Tan-Oak Forest (#81400) (Holland 1986b)
>< Upland Douglas-fir Forest (#82420) (Holland 1986b)
>< Western Broadleaf and Needleleaf Forests: 29: California Mixed Evergreen Forest (Quercus-Arbutus-Pseudotsuga) (Küchler 1964)
Concept Author(s): D. Sarr, in Faber-Langendoen et al. (2013)

Author of Description: M.S. Reid

Acknowledgements: No Data Available

Version Date: 12-18-14
  • Atzet, T., and D. L. Wheeler. 1984. Preliminary plant associations of the Siskiyou Mountains Province, Siskiyou National Forest. USDA Forest Service, Pacific Northwest Region, Portland, OR.
  • Bingham, B. B., and J. O. Sawyer. 1991. Distinctive features and definitions of young, mature, and old-growth Douglas-fir/hardwood forests. Pages 363-378 in: L. F. Ruggierro, K. B. Audry, A. B. Cary, and M. H. Huff, editors. Wildlife and vegetation of unmanaged Douglas-fir forests. PNW-GTR-285. USDA Forest Service, Pacific Northwest Research Station, Portland, OR.
  • Bingham, B. B., and J. O. Sawyer. 1992. Canopy status and tree condition of young, mature and old-growth Douglas-fir/hardwood forests. Pages 141-149 in: R. R. Harris, D. E. Erman, and H. M. Kerner, editors. Bio-diversity of northwestern California. Wildland Resource Center Report No. 29. University of California, Berkeley, CA.
  • CNPS [California Native Plant Society]. 2015-2017. A manual of California vegetation [online]. California Native Plant Society, Sacramento, CA. [http://vegetation.cnps.org/].
  • 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.
  • Cheng, S. 2004. Forest Service research natural areas in California. General Technical Paper PSW-GTR-188. USDA Forest Service, Pacific Southwest Research Station, Albany, CA.
  • Evens, J. M., and E. Kentner. 2006. Classification of vegetation associations from the Mount Tamalpais Watershed, Nicasio Reservoir, and Soulajule Reservior in Marin County, California. Report for the Marin Municipal Water District. California Native Plant Society, Sacramento.
  • Eyre, F. H., editor. 1980. Forest cover types of the United States and Canada. Society of American Foresters, Washington, DC. 148 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.
  • Fites, J. 1993. Ecological guide to mixed conifer plant associations of the northern Sierra Nevada and southern Cascades. Publication R5-ECOL-TP-001. USDA Forest Service, Pacific Southwest Region, San Francisco, CA.
  • Franklin, J. F., K. Cromack, W. Denison, A. McKee, C. Maser, J. Sedell, F. Swanson, and G. Juday. 1981. Ecological characteristics of old-growth Douglas-fir forests. General Technical Report PNW-118. USDA Forest Service, Pacific Northwest Research Station, Portland, OR.
  • 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.
  • Gudmonds, K. N., and M. G. Barbour. 1987. Mixed evergreen forest stands in the northern Sierra Nevada. Pages 32-37 in: T. R. Plumb and N. H. Pillsbury, editors. Multiple-use management of California''s hardwood resources. General Technical Report PSW 100. USDA Forest Service, Pacific Southwest Research Station, Berkeley, CA.
  • Holland, R. F. 1986b. Preliminary descriptions of the terrestrial natural communities of California. Unpublished report prepared for the California Department of Fish and Game, Nongame-Heritage Program and Natural Diversity Database, Sacramento. 156 pp.
  • Hunter, J. C. 1997. Fourteen years of change in two old-growth Pseudotsuga-Lithocarpus forests on northern California. Journal of the Torrey Botanical Society 124(4):273-279.
  • Jimerson, T. M. 1993. Preliminary plant associations of the Klamath province, Six Rivers and Klamath national forests. Unpublished report. USDA Forest Service, Eureka, CA.
  • Jimerson, T. M., E. A. McGee, D. W. Jones, R. J. Svilich, E. Hotalen, G. DeNitto, T. Laurent, J. D. Tenpas, M. E. Smith, K. Hefner-McClelland, and J. Mattison. 1996. A field guide to the tanoak and Douglas-fir plant associations in northwestern California. Technical Paper R5-ECOL-TP-009. USDA Forest Service, Pacific Southwest Region, San Francisco, CA.
  • Keeler-Wolf, T. 1990a. Ecological surveys of Forest Service Research Natural Areas in California. General Technical Report PSW-125. USDA Forest Service, Pacific Southwest Research Station, Berkeley, CA. 165 pp.
  • Keeler-Wolf, T., M. Schindel, and S. San. 2004. Point Reyes National Seashore, Golden Gate National Recreation Area, San Francisco Water Department Watershed Lands, Mount Tamalpais, Tomales Bay, and Samuel P. Taylor State Parks. Appendix B. Point Reyes National Seashore, Golden Gate National Recreation Area, and surrounding wildlands plant community classification and mapping project. Final report. California State Department of Fish and Game, Sacramento, CA.
  • Küchler, A. W. 1964. Potential natural vegetation of the conterminous United States. American Geographic Society Special Publication 36. New York, NY. 116 pp.
  • Lee, C. 2004. Vegetation alliances and associations of the Whiskeytown National Recreation Area. Master’s thesis, Humboldt State University, Arcata, CA.
  • McDonald, P. M., D. Minore, and T. Atzet. 1983. Southwestern Oregon-Northern California hardwoods. Pages 29-32 in: R. M. Burns, technical coordinator. Silvicultural systems for the major forest types of the United States. Agricultural Handbook 445. USDA Forest Service, Washington, DC.
  • McMurray, N. 1989. Lithocarpus densiflora. In: Fire Effects Information System [Online]. USDA Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory (Producer). [http://www.fs.fed.us/database/feis/]
  • Mize, C. W. 1973. Vegetation types of lower elevation forests in the Klamath region, California. Master''s thesis, Humboldt State University, Arcata, CA.
  • Sawyer, J. O. 2006. Northwest California: A natural history. University of California Press, Berkeley, CA.
  • Sawyer, J. O. 2007. Forests of northwestern California. Pages 253-295 in: M. G. Barbour, T. Keeler-Wolf, and A. Schoenherr, editors. Terrestrial vegetation of California, third edition. University of California Press, Berkeley, CA.
  • 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 D. A. Thornburgh. 1977. Montane and subalpine vegetation of the Klamath Mountains. Pages 699-732 in: M. G. Barbour and J. Major, editors. Terrestrial vegetation of California. John Wiley and Sons, New York.
  • Sawyer, J. O., and T. Keeler-Wolf. 1995. A manual of California vegetation. California Native Plant Society, Sacramento. 471 pp.
  • Simpson, L. G. 1980. Forest types on ultramafic parent materials of the southern Siskiyou Mountains in the Klamath Region of California. Master''s thesis, Humboldt State University, Arcata, CA.
  • Uchytil, R. J. 1991b. Pseudotsuga menziesii var. menziesii. In: Fire Effects Information System [Online]. USDA Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory (Producer). [http://www.fs.fed.us/database/feis/]
  • Whittaker, R. H. 1960. Vegetation of the Siskiyou Mountains, Oregon and California. Ecological Monographs 30:279-338.
  • Zinke, P. J. 1977. The redwood forest and associated north coast forests. Pages 679 in: M. G. Barbour and J. Major, editors. Terrestrial vegetation of California. Wiley-Interscience, reprinted by the California Native Plant Society 1988, Sacramento, CA.