The Pacific Northwest refers to northwestern North America which is bounded by the Pacific Ocean to the west and Rocky Mountains to the east.

Coastal Redwood Forest

These magnificent forests are characterized by the giant, endemic conifer Sequoia sempervirens (coastal redwood) (Cupressaceae). These are the world’s tallest trees reaching heights of 112 m and have growth rates close to the world’s maximum. This together with the fact that they have extremely long life spans, sometimes reaching over 2000 years, also results in the greatest biomass accumulation of any know ecosystem. These forests have been in existence for many millions of years, with fossils of Sequoia, dating back as far as the Jurassic Period. They were also much more extensive than they are today, and its generally believed that the last Ice Age limited Coastal Redwoods to their present narrow strip stretching from southern Oregon to Central California. Prior to this, the fossil record shows that they occurred throughout what is now the western United States and Canada, and along the coasts of Europe and Asia. Other endemic or near endemic conifers found in these forest include Chamaecyparis lawsoniana (Cupressaceae), Libocedrus decurrens (Cupressaceae), Torreya californica (Cephalotaxaceae), while other commonly associated conifers include Abies grandis, Picea sitchensis, Pinus contorta, Pinus jeffreyi, Pinus lambertiana, Pinus monticola, Pseudotsuga menziesii, Thuja plicata, Tsuga heterophyllum. Typical hardwood species include various endemic or near endemic species such as Arbutus menziesii (Ericaceae), Lithocarpus densiflora (Fagaceae), Quercus agrifoliai (Fagaceae), Umbellularia californica (Lauraceae)together with Alnus oregona, Acer macrophylla, Fraxinus latifolia, Quercus chrysolepis, Q. garryana and Q. kelloggii. Forests of the alluvial flats and moist lower slopes have the lushest under stories with many herbaceous species such as Anemone deltoides, Asarum caudatum, Disporum smithii, Hierochloe occidentalis, Oxalis oregana, Tiarella unifoliata, Trillium ovatum, Viola glabella and ferns such as Polystichum munitum. Stands in the middle and upper slopes differ somewhat in having understories characterised by evergreen shrubs such as Gaultheria shallon, Rhododendron macrophyllum and Vacccinium ovatum.

Californian Closed-Cone Pines and Cypress Forests

These forests form a unique series of plant communities scattered the length of California’s coast, mountains and islands. Many of the characteristic species are relict endemics such as Cupressus abramsiana, C. bakeri, C. forbesii, C. goveniana, C. macnabiana, C. macrocarpa, C. nevadensis, C. pigmaea, C. sagentii, C. stephensonii (Cupressaceae), Pinus muricata, P. radiata and P. torreyana (Pinaceae). In fact of California’s ten native cypress species eight are endemic.  Most of these are highly adapted to fire and their cones remain sealed after maturity, usually accumulating on the tree and only opening when heated by fire. Cypress species tend to occur in groves often within other communities such as chaparral, although no native species occur in the Central Valley or on the offshore islands. These groves support a variety of endemics some of which are confined to just one or a few groves. For example, Arctostaphylos otayensis (Ericaceae), Ceanothus otayensis (Rhamnaceae) and Lepechinia ganderi (Lamiaceae) are confined to the Otay Mountain grove; Nolina parryi (Ruscaceae) is confined to the Sierra Peak grove; Arctostaphylos hookeri (Ericaceae), and Haplopappus eastwoodae (Asteraceae) are confined to the Monterey Peninsula; Arctostaphylos silvicola (Ericaceae) is confined to the sandy soils of the Santa Cruz Mountains and Arctostaphylos pungens var. montana (Ericaceae) is largely confined to groves on serpentine soils. In other cypress groves endemics include Arctostaphylos nummularia (Ericaceae), Baccharis pilularis (Asteraceae), Chamaebatia australis (Rosaceae), Cneoridium dumosum (Rutaceae), Dudleya farinose (Crassulaceae), Eriodictyon californicum (Boraginaceae), Lathyrus splendens (Fabaceae), Lepechinia cardiophylla (Lamiaceae), Lithocarpus densiflorus (Fagaceae), Myrica gale (Myricaceae), Pseudotsuga macrocarpa (Pinaceae), Rosa californica (Rosaceae) and Xerophyllum tenax (Melanthiaceae).

The most widespread of the pine species is Pinus attenuata occurring nearly the whole length of California, but other species like Pinus radiata are more restricted. When first discovered in 1602 this species was confined to just three small areas near Monterey. All of these closed-cone pines are believed to be relicts of a more widespread Tertiary forest. Some of the endemic species found in these forests include Achillea borealis subsp. californica (Asteraceae), Ceanothus papillosus (Rhamnaceae), Galium angustifolium (Rubiaceae) and the conifer Libocedrus decurrens (Cupressaceae).  On the ultrabasic soils Pinus jeffreyi, P. monticola, P. lambertiana and other conifers occur in varying degrees of dominance, and in some of the more open of these stands, especially in the dryer areas, the associated grasslands include species such as Sitanion jubatum, Stipa lemmoni and the endemic Danthonia californica (Poaceae).

Klamath-Siskiyou Mixed Evergreen Forest

These typically include Pseudotsuga menziesii with one or more evergreen hardwoods such as Arbutus menziesii, Castanopsis chrysophylla, Lithocarpus densiflorus and Quercus chrysolepis. Stands are usually two-storied with Pseudotsuga forming a canopy up to 65 m and emerging above the hardwood canopy by up to 35 m. The shrub layer typically includes Arctostaphylos nevadensis, Berberis nervosa, Holodiscus discolor, Lonicera hispidula, Rhus diversiloba, Rosa gymnocarpa and Symphoricarpos mollis, while among the common herbs are Achlys triphylla, Chimaphila umbellata, Goodyera oblongata, Linnaea borealis, Smilacine stellata, Trientalis latifolia, Xerophyllum tenax, and the endemic Whipplea modesta (Hydrangeaceae). At higher elevations Abies concolor may dominate in virtually pure conifer stands and it is within this zone that the near endemic Pinus breweriana (Pinaceae) predominantly occurs. Common shrubs within this zone include Amelanchier pallida, Arctostaphylos nevadensis, Berberis dictyota, Cornus stolonifera, Corylus cornuta var. californuca, Paxistema myrsinites, Quercus sadleriana, Ribes lobbii, Rubus parviflorus and Symphoricarpos hesperis, while the many herbs include Achlys triphylla, Clintonia uniflora, Frageria californica, Stellaria jamesiana and endemics such as Adenocaulon bicolor (Asteraceae), Vancouveria hexandra (Berberidaceae) and Vicia americana var. oregona (Fabaceae).

References

Barbour, M. G. 1977. Terrestrial Vegetation of California. John Wiley and Sons.

Barbour, M. G. 1989. Californian upland forests and woodlands. Franklin, R. K. 1989. Pacific northwest forests. In: North American Terrestrial Vegetation. Eds. M. G. Barbour and W. D. Billings. Cambridge University Press.

Barbour, M., Pavlik, B., Drysdale, F. & Lindstrom, S. 1993. California’s Changing Landscape (Only Coastal Interface). California Native Plant Society. Sacramento.

Brown, D. E. 1982. Californian Evergreen Forest and Woodland. In: Desert Plants.  Biotic communities of the American southwest United States and Mexico. Ed. D. E. Brown. University of Arizona. 

Brown, D. E. 1982. Relict Conifer Forest and Woodland. In: Desert Plants.  Biotic communities of the American southwest United States and Mexico. Ed. D. E. Brown. University of Arizona.

Cooper, W, S. 1971. The broad-sclerophyll vegetation of California. In: World Vegetation Types.  Ed. S. R. Eyre. Macmillan.

Douglas, G. W. 1996. Endemic vascular plants of British Columbia and immediately adjacent regions. The Canadian Field-Naturalist, 110: 387-391.

Franklin, R. K. 1989. Pacific northwest forests. In: North American Terrestrial Vegetation. Eds. M. G. Barbour & W. D. Billings. Cambridge University Press.

Endo, S. 1952. A record of Sequoia from the Jurassic of Manchuria. Botanical Gazette, 113: 228-230.

Franklin, R. K. 1989. Pacific northwest forests. In: North American Terrestrial Vegetation. Eds. M. G. Barbour & W. D. Billings. Cambridge University Press.

Griffin, J. R. 1977. Oak Woodlands. In: Terrestrial Vegetation of California. Eds. M. G. Barbour and J. Major. John Wiley & Sons.

Lewis, H. 1972. The origin of endemics in the Californian flora. In: Taxonomy, Phytogeography and Evolution. Ed. D. H. Valentine. Academic Press.

Miller, C. N. 1977. Mesozoic conifers. Botanical Review, 43:217-280.

Philbrick, R. N. & Haller, J. R. 1977. The southern Californian islands. In: Terrestrial Vegetation of California. Eds. M. G. Barbour and J. Major. John Wiley & Sons.

Qian, H. 1999. Floristic analysis of vascular plant genera of North America north of Mexico: characterization and phytogeography. Journal of Biogeography, 26: 1307-1321.

Ricketts, T. h. et al. 1999. Terrestrial Ecosystems of North America - a conservation assessment. World Wildlife Fund, USA and Canada. Island Press, Washington.

Shevock, J. R. 1996. Status of rare and endemic plants. U. S. Forest Service, Pacific Southwest Region, San Francisco, California.

Sims, P. L. 1989. Grasslands.  In: North American Terrestrial Vegetation. Eds M. G. Barbour and W. D. Billings.  Cambridge University Press.

Stebbins, G. L. & Major, J. 1960. Endemism and speciation in the Californian flora. Ecological Monographs. 35: 1-35.

Vogl, R. J., Armstrong, W. P., White, K. L. & Cole, K. L. 1977. The closed-cone pine and cypress. In: Terrestrial Vegetation of California. Eds. M. G. Barbour and J. Major. John Wiley & Sons.

Westman, W. E. & Whittaker, R. H. 1975. The pygmy forest region of northern California: studies on the biomass and primary production. Journal of Ecology, 63: 493-520.

Zinke, P. J. 1977. The Redwood Forest and Associated North Coast Forest. In: Terrestrial Vegetation of California. Eds. M. G. Barbour & J. Major. John Wiley & Sons.