Biodiversity, Biogeography, and Bioregions of Kern County

Kern 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.

The 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 many 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 California" include: 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 county.

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 100F 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.


Kern County Biogeography    Kern County Geology   Indigenous Peoples of Kern County

Interior chaparral and woodlands     Great Valley Grassland     Great Basin Desert     Mojave Desert     Sierran Forest

USDA Forest Service Ecological Subregions of California     2005 Wildflower Reports - Kern, Inyo, and Tulare Counties

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