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Oaks

First I passed through a wild canyon, then over hills covered with oats, with here and there trees – oaks and pines.
Some of these oaks were noble ones indeed. How I wish one stood in our yard at home. I lay beneath its shade a little while before going on.

William Henry Brewer, Chief Botanist: California Geological Survey, 1861

 

Oak Setting

 

Oak Trees

 

Growing only in California and mainly in the transverse ranges below 2,500 feet elevation, the Valley Oak (Quercus lobata) is the largest of all oak trees in North America and distinctive to our bioregion. (Quercus means oak, and lobata means deeply lobed.)

They can rise more than 100 feet above the ground, have trunks six or seven feet in diameter and grow to 600 years in age. Trees with three to four foot diameter trunks are typically 150 to 250 years old. The branches have an irregular, spreading and arching appearance that produce evocative silhouettes in Santa Ynez Valley and the surrounding mountains.

A staple food of the Chumash, Valley Oak acorns were mixed with other types to improve taste. They were ground, leeched of tannins and made into a cake or flat bread. Oak Apples (wasp galls) were also collected, stored and used for tinder.
No less than seven wasps lay their eggs on (or in) the leaves or stems of Valley oaks in the spring. The tree then forms these interesting galls, which the larvae are raised on.

Early settlers used a variety of names for the Valley Oak including: White oak, bottom oak, swamp oak, water oak and mush oak. The Spanish called the tree 'roble' because it reminded them of the white oaks found in Europe.

 

The Valley Oak, as with oil and otters, has been at the center of occasional controversy in the bioregion. One example is the All American Plains Project (AAPL) which involved the operation of a large, buried, crude oil pipeline designed to carry 300,000 barrels per day of locally produced petroleum to refinery destinations outside Santa Barbara County.

Mitigations were proposed to minimize impacts. A mitigation is an action that seeks to make up for environmental damage and biological loss by planting or restoring a much larger area elsewhere. While it had been forecast that 500, or as few as 250 oak trees would be lost, the actual number removed by construction was approximately 2,300. Three separate oak species were impacted: valley oaks (82), coast live oaks (1,303), and blue oaks (878).

It soon became evident that the restoration plan was failing and another plan had to be formulated. The University of California's Sedgwick Reserve near Santa Ynez launched a program in 1992. The management plan includes large scale oak tree planting experiments, research on factors affecting oak habitat restoration, and public outreach.

How difficult is it for an oak tree to grow?
Out of more than 8,000 acorns planted in five plantings since 1996, approximately 800 were alive as of Spring 2004. And these were afforded the highest level of protection.

 

Why are oaks important?
Oak woodlands serve important ecological functions, playing a critical role in protecting soils from erosion and landslides, regulating water flow in watersheds, and maintaining water quality in streams and rivers. Especially, they have higher levels of biodiversity than virtually any other terrestrial ecosystem in California. At least 300 terrestrial vertebrate species (Block, Morrison, and Verner 1990), 1,100 native vascular plant species (CalFlora Database 1998), 370 fungal species and an estimated 5,000 arthropod species (Swiecki et al. 1997a) are associated with California oak woodlands.

Our oak woodlands have been greatly reduced over the past 230 years. European and later American settlers eroded woodland cover for fuel-wood and charcoal production. Widespread destruction to clear land for more profitable agriculture has further contributed to the loss. Thanks to this, many plant and animal species have also been removed; while many non-native plant and animal species have become so widespread that their eradication is impossible. Although native species are still present in these degraded ecosystems, non-native annual grasses and forbs now dominate what is known as the herbaceous layer.

Download educator's background in PDF format at the top of this page for discussion questions.
Citations are listed in the Reference Section.