The Oaks of Mendocino County

August 6, 2006

By: Greg Giusti

How many different forest types can you think of? What comes to mind? Redwoods, pines, Douglas-fir, maybe if youíre an adventurous hiker type even the high elevation true fir forests. How many of you thought of oak forests? If you didnít, donít feel bad. The oaks have been the over-looked forest for some time. Just as there are different kinds of pines and firs, there are several species of oaks that can be found growing in pure stands or as associates in mixed forests.

Of all the forest types found in California the oak forests are considered to have the highest degree of biological diversity of all forest types. As many as 335 species of terrestrial vertebrates (amphibians, reptiles, birds and mammals), plus a number of fish species and an estimated 6000 species of invertebrates (insects, spiders) are believed to exist in the oak forests.

The oaks are generally grouped together into two main categories, the white oak group and the red oak group. The white oaks (valley, blue, and Oregon) are characterized as being deciduous, loosing their leaves in the winter, and having their acorns mature within the same year (much like a walnut or almond). The red group (coast, canyon, interior and Shreve live oaks, and the California black oak) can be evergreen (live oaks) or deciduous (black oak) and their acorns require two years to mature.

There are 20 species of oaks in California. Of those 11 grow in a tree form, and 9 grow in a bush form, many of these are sub-species or variations of the parent form. There are 8 recognized species found in Mendocino County and like the rest of the state, the trees are found in both pure and mixed stands. Their location is often determined by soil types, soil moisture, and directional orientation.

The valley oak, Quercus lobata, is a true California endemic, found no where else in the world. Their pioneer name, ìmush oakî implies the relatively soft nature of the wood and the limits of its utility. These are the very large, majestic trees that dot the valley landscapes in Ukiah, Anderson, Potter and Round Valleys. In fact, Round Valley represents the northern most extent of the species along the coast.

The blue oak, Q. douglassi, often referred to as ìpost oakî connotes the pioneer use of this tree for fence posts. During the summer, the blue color of the leaves is very obvious and is a handy field key that identifies the species. The blue oak is another California endemic and is common on the upland, drier slopes of Mendocino County.

The live oaks provide much of the evergreen hardwood cover found throughout the county. The coast live oak ranges from the southern part of the state to just north of Hopland, while the Shreve and interior species are found over much of the county in many of the same locations as the blue oak. As its name implies, the Canyon Live Oak is common along river gorges.

The black oak (Q. Kelloggi) is a majestic tree that provides brilliant fall color is often found growing at higher elevations with other hardwoods and conifers such as madrone, maples, alders and Douglas fir. The large tree is a prolific acorn producer and was an important food staple of Native Americans.

Descriptions and distributions of Californiaís oak resources can be found by visiting the University of Californiaís oak web-site at http://danr.ucop.edu/ihrmp/

Greg Giusti is the UC Forest Advisor for Mendocino County and is a Registered Professional Forester.

You can now view Tree Tips on the web. Go to www.nwwg.org, click on Resources and click on Tree Tips.