Biodiversity, Biogeography, and
Bioregions of Kern County
County is unique in its diverse geography. The county covers 8,172 square
miles and is located 2/3 of the way down the state. It is almost
completely square 60 mi long by 135 mi. wide with right angle set-backs on the west
end. It is the third largest county in California and covers an area
larger than many states combined.
county falls within the Austral Region of Merriam's
classification scheme of Life Zones and contains
Hudsonian, Canadian, Transition, Upper Sonoran,
and Lower Sonoran zones based on altitude and
aspect. The three floristic provinces found in
California converge in the Northeastern corner of
Kern County along the crest of the Sierra Nevada:
Californian, Great Basin Desert, and the Mojave
Desert subprovince of the Sonoran Desert. With the
convergence of the major floristic provinces a
broad transition zone of five major ecoregions congregate
in the Southern Sierra and Kern Valley: Grassland,
Interior Chaparral, Conifer Forest, Mojave Desert,
and Great Basin Desert. This juxtaposition of so
habitats causes an intermingling of plants and
animals in configurations unparalleled in any
region North of the Mexican border.
What are bioregions?
A 1978 report on the biological
diversity of California stated their were 6 general biological communities
found within California. Great Basin Desert, Mojave Desert, Great Valley
Grassland, Sierran Forest, Coastal Chaparral, and Coastal Redwood Forest.
According to this schema, Kern County contains 5 of the six with only
Coastal Redwood missing from the county. There are other more recent
schemes that have a greater diversity of bioregions.
If you look at the county map the bluish green portion
contains what has been described as mostly great valley grassland.
Although, dedicated scientists are working to reclassify much of the south
and western San Joaquin Valley as the San Joaquin Desert, due to its low
annual precipitation and its predominant vegetation being alkali scrub and
alkali sink with very little native grassland. Valley habitats are the most disturbed
within the county with agriculture plowing most of the native land under.
The valley is surrounded by mountains which are mostly considered the
Sierran bioregion. East of the Sierran crest a very small portion of Great
Basin Desert is found in the northeast corner of the county. The rest of the desert is
considered Mojave Desert bioregion. Nestled within the foothills of our
mountains is the final bioregion of the county, Coastal Chaparral. So what
exactly makes a bioregion?
Bioregions are described by the
major category of vegetation they contain. Great Valley Grassland contains grasses and
shrubs native to the region. When you examine the
floral diversity in the region, you will find that many native
grasses have been extirpated and replaced with exotic grasses accidentally
or deliberately introduced in the early
1800's by sheep and cattle ranchers.
Bioregions become a difficult term to use because
many scientists and politicians use different classification
schemes. But, no matter who describes
the biogeography of California, the Kern County area is home to many
geographic and biological influences.
Geographic subdivisions found within the county
according to "The Jepson Manual: Higher Plants of
CALIFORNIAN PROVINCE; Kern County has 4 of the 6
regions including the: San Joaquin Valley portion
of Great Central Valley, Inner South Coast Ranges
of the Central Western California, Transverse
Range of Southwestern California, Tehachapi -
southern Sierra Nevada Foothills - southern High
Sierra Nevada of the Sierra Nevada Mountain Range,
and DESERT PROVINCE; Mojave Desert. Many plants of
the GREAT BASIN PROVINCE are found in the
northeast along the eastern slopes of the Sierra
Nevada mountains, although Jepson does not
describe the province as actually being in the
Ecological diversity is also affected by the rapid
elevation changes in the county. With a difference
from 206' to 8824' above sea level within 50
miles, the number of climate zones is remarkable
as well. The highest parts of the county fall
within the coldest zones. The high elevation
mountains generally fall within climate zones 2-3,
which equates to a frost free growing period of
150-160 days each year. The Central Valley climate
zones 7-9 which consist of hot dry summers and
cold wet winters. A thermal belt where frost is
uncommon is found in zone 9, all of the other
zones have periods of frost each winter. The
desert portion of the county consists of climate
zone 11. Wide swings in temperature, wind, frost,
and prolonged periods where the temperature
exceeds 100ºF are consistent conditions within
this region. The sunniest place in the United
States is found in Inyokern. Both the Mojave
Desert and the Central Valley fall under the
Mediterranean regime of winter precipitation.
Historically the southern San
Joaquin Valley contained the largest freshwater marsh and lake system west
of the Mississippi River prior to damming the rivers and lakes. The Tulare Lake Basin
in Kern, Kings, and Tulare Counties, contained over
1 million acres of lakes and marshes. Millions of waterfowl, fish,
amphibians, and reptiles made their homes within the basin.
The Buena Vista basin was smaller yet offered similar sanctuary to
wildlife and the Yokuts people that lived along the shores of Buena Vista,
Kern, and Goose Lakes.
This photograph was taken in May 2001 from Kelso Valley on the eastern
fringe of the Piute Mountains. Visible in the photo are plants from Mojave
Desert, Great Valley Grassland, Coastal Chaparral, and Sierran Forest, and
Great Basin Desert Ecosystems.