California is on the edge of a massive tectonic plate. A highly active fault line runs along the western portion of the state, joining the North American and Pacific plates. The infamous 1906 and 1988 earthquakes were powerful reminders of where California is positioned on Earth. A consequence of being on the edge of a tectonic plate is the presence of a diverse set of mountain ranges with a bizarre range of geologic phenomena. This has created a landscape with countless combinations of microclimates, soils, and moisture dynamics that have pushed plants in innumerable evolutionary paths. California’s mountain ranges create rain shadows that keep our desert landscapes dry. They are responsible for the alluvial soils of the central valley and drastic elevation changes that bring rain and snowmelt from mountaintops to lower elevations.
The Central Valley is a large, 450 mile-long depression in the center of our state that is surrounded by the Sierra Nevada’s to the east and Coast Ranges to the west. Bordering this massive valley are the foothills that support Oak dominated grasslands, known as savannas, which form the transition between high mountain forests and Central Valley prairie. The valley itself is broken up and defined by two major rivers. The northern half, or the Sacramento Valley, is defined by the Sacramento River that runs as far north as the Klamath Mountains. The southern half, or the San Joaquin Valley is defined by the San Joaquin River that is fed from high elevations in the Sierra Nevada. Ultimately, these two rivers meet in the Delta, flowing through San Francisco Bay and into the Pacific Ocean. Depths of up to ten thousand feet of sediment fill the Central Valley due to the last five million years of runoff from the surrounding mountains. As sediment has built up over this time, waterways have slowly organized into distinct streams and rivers that innervate the heart of our State. Lining these watercourses are woodlands, commonly known as gallery forests, which often support the greatest magnitude of life in the Central Valley. The Sacramento riparian woodland alone is home to 39 mammal, 6 frog, 7 lizard, 6 snake, and over 69 bird species.
Fig A: Albert Bierstadt’s A View From Sacramento
The Central Valley has been under developmental scrutiny for centuries. Beginning in the 18th century, settlers and speculators alike sought after the rich soils found in the valley. Today, it is home to the multibillion-dollar agricultural industry that California’s economy relies on. Californians would pay more for their produce if such prime growing regions were not so accessible. Unfortunately, this fertile land is also the site of considerable biodiversity. Overgrazing and introduced grasses pose a serious threat to dwindling populations of native plants in the Central Valley. The subsequent agricultural boom has impacted the land and waterways, and increased the incentive to further develop this region. Albeit, the anthropogenic effect on this region has yielded considerable rewards for Californians. In addition to access to some of the best produce in the world at affordable prices, the Central Valley has created an industry that puts nearly eight percent of Californians to work and pulls in roughly five percent of California’s labor income.
-Alluvial soil: clay, silt, or gravel deposited where rivers or streams terminate. It is generally very fertile and desirable for growing crops.
-Rain shadow: dry areas of lower elevation that are adjacent to high mountains where rain is blocked for much of the year.
VI. Species on Display
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- Sumner, Daniel. "The Measure of California Agriculture." Agricultural Issues Center, University of California. (2008)
-Campbell, Neil, Jane Reece, et al. Biology. 8th. San Francisco: Pearson Education, 2008. Prin
-Calflora: Information on California plants for education, research and conservation.
[web application]. 2008. Berkeley, California: The Calflora Database [a non-profit organization].
Available: http://www.calflora.org/ (Accessed: Oct 20, 2008).
-All photographs: Creative Commons Attribution