University of California

Oak Tree Conservation


Redding, CA – Kent Manuel, Redding’s city planner, eyes a bedraggled line of dying blue oak trees.

“This is a stand of trees that the city asked the developer to retain in its native state to buffer the highway over here so you couldn’t see the loading docks and this rather large parking lot,” he says.

But several years after the project was built, the trees began toppling over. The strip of oaks wasn’t wide enough, and the tall, skinny trees were too exposed to withstand the winds.

“We really should have preserved a much larger area or perhaps considered not using the native vegetation as a way to buffer this development from the street,” says Manuel. “It simply is a failure at this point. Good intentions, but it didn’t work.”

It’s not likely that Manuel, his staff, Redding’s planning commissioners or some of Redding’s developers will make the same or similar mistakes again. They attended an oak tree conservation workshop funded by the federal Renewable Resources Extension Act, administered by the University of California Division of Agriculture and Natural Resources. In all, four workshops were held in 2004 – three in Calaveras County that looked at rural residential development and rangeland, and one in Redding that focused on the impact of urban development on oaks. In all, the workshops attracted 117 people. Besides developers and planners, the workshop attendees included building inspectors, representatives from homeowner’s associations and fire-safe councils, landowners, and arborists.

Richard Harris, a UC Extension forestry specialist, organized the workshops at the request of the Integrated Hardwood Range Management Program. The University of California established that program in 1986 to help the state conserve its hardwood rangelands.

Unlike conifers, oak trees aren’t protected by state regulations. Since 1950, people have cut down and burned more than one million acres of oak woodlands to plant crops, expand cities, and build rural subdivisions. Today, 10 million acres remain, approximately two-thirds of the state’s original native stands; 80 percent is in the hands of private landowners.

Forests Forever, an advocacy group, says that 20,000 acres of oaks are disappearing every year, due to residential, commercial and industrial development; agricultural conversion; sudden oak death disease; cattle grazing; fire suppression; and invasive grasses that choke out oak seedlings. Although some counties require tree replacement or some form of oak preservation, others do not.

Even though county regulations exist, says Harris, they may not be enforced. The answer to protecting oak trees and preventing fragmentation of oak woodland, he says, “is better enforcement of protections on the local level.”

Redding, a city with such a plethora of oak trees that it could be renamed “Oakville”, passed an ordinance in 1990 to protect its oaks.

Even though Redding has 85,000 people, its parklands and the Sacramento River, which runs straight through town, give the city a daily connection to nature lacking in most urban areas. People who work downtown can go fishing on the river’s banks during lunch. During migration season, fish swarm up the river. For weeks afterwards, salmon carcasses release their nutrients into the waters while, nearby, fish eggs, buried in fine gravels, mature.

Redding’s pride and joy are its oak trees. Despite the 1990 tree ordinance, the city was losing some oaks that it thought it had protected adequately. When Harris offered a workshop tailored to management of urban oak trees, Manuel jumped at the opportunity.

“It was important that we took several of our planning commissioners as well as many of our planning staff, because we saw some failures that had occurred, and we were wondering why they had happened,” says Manuel.

During the one-day course, they attended lectures and discussions in the morning, and, in the afternoon, took a field trip to several sites to assess the city’s failures and successes.

“Through that course, we picked up enough tips and quite a bit of science so that we can all do our jobs better,” says Manuel.

One of the city’s success stories is the area around an attractive low-income housing development, Shadowbrook Apartments, built along Churn Creek, which runs nine miles through Redding. “This is an example of the best method to preserve trees in the Redding area,” says Manuel, as he points out a 500-foot wide buffer that protects the creek.

“There can be no development in this area,” he says. “The apartment complex next to it was set back far enough so that it’s not going to impact the native vegetation.”

Just steps away from high-density housing, residents can take peaceful walks among trees where chirping birds flit from branch to branch, and squirrels scamper along tree limbs. The city is building a 100-mile system of trails along all of its city creeks that feed into the Sacramento River. “It’s been incredibly popular,” notes Manuel. “There are so many people out there walking these trails and greenways, you’d just be amazed. People flock to those neighborhoods, just because of the trails.”

An important lesson learned in the workshop is that saving stands of trees is usually preferable to saving individual trees, says Manuel. Another lesson is that there’s no rule of thumb. Ensuring healthy oaks depends on the types of soils in which they’re living, on the tree’s structure, its vigor and history, and the type of exposure they have to wind and rain.

However, there are a few basics that will increase the chances of an oak tree’s survival, says Manuel:

if you retain the oaks’ native root structure,

if you don’t impact the soils two diameters out from the root zone,

if the area around the oaks out to their drip line (the outer edge of the trees’ canopy) is planted with no plants, or drought-tolerant plants,

and if the area around the oaks is not irrigated -- summer watering will kill an oak tree, which has adapted naturally to California’s dry summer climate.

Sometimes, construction constraints are such that some oaks are likely to die slowly. In that case, the city advises developers to acknowledge that the oaks will live for no more than 10 or 20 years, and to plant other drought-tolerant trees that will take their place.

Still, the hardiness of some oaks confounds Manuel. “We can show you numerous examples of blue oaks, which are highly sensitive to compaction of the soil and loss of aeration to their roots, that have had pavement put around them, and they are as healthy as they have ever been,” he says. “It defies all logic.”

-- Jane Ellen Stevens
April 2005

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