This BioProvince (as defined by Armen Takhtajan) extends from the Gulf of Alaska to California covering some 25 degrees of latitude but is never more than about 350 km wide. Kodiak Island in Alaska forms its northern limit and from there it continues eastward and southward as a narrow strip near the coast through British Columbia including Vancouver Island and Haida Gwaii (Queen Charlotte Islands). In Washingtom and Oregon it broadens out to include the Cascade Mountains as well as the Coastal Range and Olympic Mountains. It then follows the Coastal Range through California nearly as far as San Francisco and then departs slightly from the coast and extends to the southern tip of the Sierra Nevada. However, the western foothills of the Sierra Nevada, sometimes up to more than 1000 m, lie within the Californian BioProvince. The geology is complex but the climate is characterised by moist, maritime conditions with prolonged cloudy periods. There are only very narrow diurnal tempertures fluctuations and the winters are mild but wet with up to 80% of precipitation occurring between October and March. Summers, on the other hand, are cool but relatively dry. Fog formation is an important form of precipitation especially in the Californian uplands. Endemism is comparatively high with about 30 endemic genera and many endemic species of vascular plants but there are no endemic families. There is however an endemic family of liverworts (Gyrothyraceae).
One of the more distinctive areas within this BioProvince is the Klamath Mountain Range which is a series of Palaeozoic and Mesozoic formations distinct from the surrounding younger rocks of the Coastal Range and Cascades. There are many local endemic plants within this area; amoung these are Kalmiopsis leachiana (Ericaceae), Iris bracteata, I. innominata and I. thompsonii (Iridaceae) and about a dozen species of Asteraceae including Antennaria suffrutescens, Arnica cernau, A. spathulata, Aster brickellioides, A. paludicola, A. siskiyouensis, Brickelia greenei, Erigeron cervinus, E. delicatus, E. flexuosus, Hieracium bolanderi, H. greenei and Microseris howellii. The conifer Pinus breweri (Pinaceae) is also nearly confined to the Klamath Range. Sierra Nevada also has a lot of local endemism with several monotypic genera, such as Bolandra (Saxifragaceae), Carpenteria (Hydrangeaceae), Orochaenactis (Asteraceae) and Phalacoseris (Asteraceae) and over 100 endemic species. Endemics are particularly well represented among the Asteraceae with species such as Aster peirsonii, Chaenactis alpigena, C. nevadensis, Erigeron petiolaris, E. miser, Eriophyllum nubigenum, Haplopappus eximius, H. peirsonii, H. whitneyi, Hulsea brevifolia, Madia yosemitana, Orochaenactis thysanocarpha, Phalacroseria bolanderi, Senecio clarkianus and S. pattersonensis.
The following accounts for this BioProvince have been written or will be written with particular reference to endemic and locally important species. Accounts available are displayed in green or yellow. Those displayed in red are either in the pipeline or awaiting expert contributions.
|Endemic Vascular Plant Flora|
|Endemic Flora (Haida Gwaii)|
|Endemic Flora (Olympic Pen.)|