The
Rocky Mountain Floristic Region
is a
floristic region
within the
Holarctic Kingdom
in western
North America
(
Canada
and the
United States
) delineated by
Armen Takhtajan
.
[1]
The region extends from
Kodiak Island
in Alaska to the
San Francisco Bay Area
and
Sierra Nevada
in
California
. It consists of two provinces, the Vancouverian, which comprises the coastal part of the region for its entire length, including the Pacific Coast Ranges, and the Rocky Mountain, which includes the Rocky Mountains and associated ranges. There are no
endemic
plant families in the region but many endemic genera and species.
Geography
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The region spans from
Kodiak Island
of
Alaska
approximately to the
San Francisco Bay Area
and
Sierra Nevada
of
California
, running between the shore of the
Pacific Ocean
on the west and the
Great Plains
on the east, along the
Rocky Mountains
and
Pacific Coast Ranges
. It is bordered by the Canadian Province of the
Circumboreal Region
in the north, by the North American Prairies Province of the
North American Atlantic Region
in the east and by the
Californian Province
of the
Madrean Region
in the south. The borders with the Canadian and Californian Provinces are vague.
Flora
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Although the Rocky Mountain Region has no
endemic
vascular plant
families
and only one endemic
Marchantiophyta
family (
Gyrothyraceae
), it has many endemic
genera
(such as
Sidalcea
,
Luetkea
,
Whipplea
,
Vancouveria
,
Lithophragma
,
Tellima
,
Tolmiea
,
Luina
) and numerous endemic
species
. The genera
Arnica
,
Castilleja
,
Erigeron
, and
Lomatium
have their major center of diversity here. The region possesses the greatest diversity of
conifers
in the
New World
. The remaining wildland of the province is covered mostly by
temperate coniferous forests
(such as
Northern California coastal forests
,
Maritime Coast Range Ponderosa Pine forests
,
Klamath-Siskiyou forests
,
British Columbia mainland coastal forests
,
Fraser Plateau and Basin complex
,
Northern Pacific coastal forests
) dominated by
Pinus ponderosa
,
Pinus contorta
and
Pseudotsuga menziesii
, as well as the
alpine tundra
above timberline. The region is subdivided further into the Vancouverian Province and Rocky Mountain Province.
The Vancouverian Province comprises the coastal part of the region for its entire length, including the
Pacific Coast Ranges
. Such plant species and genera as
Sequoia sempervirens
,
Sequoiadendron giganteum
,
Darlingtonia californica
,
Vancouveria
and
Whipplea
are endemic to it. The boundary with the Californian Province is not well-defined.
The Rocky Mountain Province includes the Rocky Mountains and associated ranges. Due to more heavy
glaciation
during the
Pleistocene
, its flora, especially in the north, has a far lower degree of endemism than that of the Vancouverian Province. Much of it is shared with the Canadian Province and the Circumboreal Region in general.
[2]
53°45′N
126°07′W
/
53.75°N 126.12°W
/
53.75; -126.12
References
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]