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Plant Focus

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Quercus look is one of the least-known oaks of the arid mountains of the Middle East. It grows on Mount Hermon and in the Anti-Lebanon...

2018 Pre-Conference Tour #2: North Coast

Forty enthusiastic IOS members ventured from UC Davis through Sonoma wine country toward the north California coast. Abbey Hart of UC Davis Arboretum was our capable Tour coordinator. Abbey, Emily Griswold, and other arboretum staff spent weeks of diligent effort to book Tour sites, pre-check them, confirm hotels, keep costs reasonable, and generally accomplish the remarkable feat of keeping order with the diverse interests and enthusiasm of all participants. We visited sites of enormous habitat contrast that included many species of native oaks and the giant redwoods, unique in all the world.  

On several Pre-Tour occasions, our intrepid IOS guide, Stewart Winchester, emphasized the edaphic influence of serpentine on the distribution and growth habit of California oaks.

Stewart Winchester, intrepid Tour guide

We stopped at Sugarloaf Ridge State Park to see diminutive, aptly-named Quercus durata. Merely a meter tall, it shares its serpentine outcrop niche with Ceanothus jepsonii and Umbellularia californica. Serpentine soil is shallow, rocky, and extremely deficient in essential plant nutrients: calcium, nitrogen, and phosphorus.

Leather oak (Quercus durata) in Sugarloaf Ridge State Park

Undaunted, our little leather oak amigo has evolved through the eons to also tolerate high soil concentrations of magnesium and toxic heavy metals.

Quercus durata gathers just enough soil moisture in this edaphic wasteland, so toxic to most plants, to generously offer IOS members its gift of a few acorns among its tiny, leathery leaves when we saw this plant again in Mendocino County.

Only a few hundred meters distant, obviously on more fertile hillside soils, we saw much larger Q. douglasii, Q. lobata, and, adorned with reddish fruits, Arbutus menziesii. Tragically, many of these madrones are in decline or dying from Phytopthora ramorum, the foliar pathogen that attacks so many Mediterranean climate broadleaf evergreen genera. Fortunately, the dominant White Oaks, California's finest, resist this pernicious foliar infection.

Tour participants hard at work beneath the U.S. National Champion Quercus lobata

The soil fertility contrast of Sugarloaf Ridge State Park serpentine to fertile Mendocino Valley alluvium, where valley oak dominates, is difficult to comprehend. The following day, we had our opportunity, however. We collected large acorns under the magnificent, 153-foot tall National Champion Q. lobata. Beneath the frame of this monarch California oak, we felt in awe. Our compulsion to gather the abundant acorns was overwhelming. We gathered them from the ground beneath this venerable tree just as Native Americans did before us for hundreds of years. Its habitat and nutritional value was obvious: this single oak is an entire ecosystem. A big thank you to Ben Fetzer for allowing us access to the farm and to his family for their efforts preserving this magnificent oak.

Apart from our Tour companions, a person could linger to quietly observe this benevolent creature's multitude of wildlife friends. Its 4-inch bark is pock-marked with thousands of holes made by acorn woodpeckers to sequester their abundant acorn reserves.

Woodpeckers have converted the bark of this Quercus lobata into a pantry for acorns

So get this: it not only provides the acorn currency of life within its niche, it offers wildlife a storehouse to bank its wealth even after it generously gives all its mast away. How humbling is that?  

To wrap up our North Coast Pre-Tour, on the afternoon of October 20th we visited the Hopland Research and Extension Center (HREC), where we were kindly welcomed and guided by Kerry Heise and Emily Allen. HREC is one of nine such centers operated by the UC Division of Agriculture and Natural Resources. The Center’s 5,358 acres are a living laboratory for study of more than 600 plant species within the four major vegetation types, namely grass, woodland-grass, dense woodland, and chaparral. Within the Coast Range foothills of the Mayacamas Mountains, this is an expansive UC resource of rugged terrain and exceptional research value for such study areas such as oak regeneration, and now the aftereffects of widespread range and woodland fire.

Quercus douglasii at Hopland Research and Extension Center, in an area recently affected by fire © Bryan Denig

 An abundant crop of blue oak (Q. douglasii) acorns littered the ground beneath these larger oaks recovering from the fire. Shreve oak (Q. parvula var. shrevei) grows near the main buildings. We walked along a path where we saw Q. berberidifolia, and ended with a group photo.

Group photo at Hopland Research and Extension Center © Abbey Hart

Stewart informed us, trees inspired us, and we had delightful company with each other on the bus. But the coast redwoods and valley oaks evoked our sense of wonder. Savanna images of oak sentinels centuries old have that effect on our psyche: they help us to connect our heads with our hearts, don’t they? In that way we share a seamless bond with all who have encountered them for centuries before we were born.

Dwarfed by giant redwoods...

Post script

Unlike oaks, we’re highly mobile. We communicate like no other creature on Earth. We know objective information about oak ecosystem health and threats. Will we use these capabilities for oaks’ benefit so that generations after us will see we were accountable stewards?

How might you identify and prioritize in your own mind what you can do to respond to development threats to oaks near your own home? Engage friends, children, grandchildren, students, Scouts, co-workers, parents, city planners, and maintenance staff.....

Passivity, IOS friends, is not an option if oaks have more that entertainment value. What small actions or steps might you and your family/friends do to educate youngsters of all ages about oaks? They have gifted us for eons far beyond our comprehension. Now they need our love and attention like never before, and our imaginative ACTION. What might each of us resolve to DO in 2019 to lend oak habitat and trees a bit of help?


A detailed Tour report will be published in the 2019 issue of International Oaks (Proceedings of the 9th International Oak Society Conference). You can view more photographs of this Tour in a photo gallery here.

Photographs © Mark Krautmann unless specified