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Releaf for Stanford's century-old arboretum
STANFORD -- Planners, grounds managers and biologists have developed a plan to rejuvenate the Stanford arboretum after 300 giant eucalyptus have fallen prey to a fast-moving pest.
The plan, favorably reviewed by the Board of Trustees in February, will gradually transform the arboretum to a forest of oaks and other California native species. The arboretum, the wooded area on either side of Palm Drive between Campus Drive and El Camino Real, is the site of football tailgate parties, the Stanford family mausoleum, and a marsh and vernal pools that are ecological components of the university's flood control system.
The Stanford Planning Office formulated the plan in response to the die-off of Tasmanian blue gums (Eucalyptus globulus), the predominant species in the arboretum.
During the past year, the eucalyptus long-horned borer has fatally attacked about 300 of the century-old trees, said Herb Fong, manager of grounds. And it's not over yet.
"As fast as we're cutting them down, new ones are dying," Fong said.
Stanford planners -- in consultation with representatives of the Biology Department, Center for Conservation Biology, Facilities-Grounds, Athletics, Friends of the Arboretum and California Department of Forestry -- considered several revegetation strategies.
They decided to plant California oaks, bays, buckeyes and maples, while maintaining the remaining healthy eucalyptus and other existing exotics.
"We aim to enhance visual amenity and ecological stability," said Drew Oman, landscape architect and manager of the arboretum project. "Together, we can make a beautiful, natural area that supports diverse and abundant life for the second hundred years."
As part of his original plans for the university, Sen. Leland Stanford envisioned the arboretum as a "zoo for trees" -- with specimen trees of every type able to thrive at Stanford. Between 1888 and 1893, the year Stanford died, many hearty, fast- growing eucalyptus were planted as "nurse trees" to shade and aid in establishing the more tender varieties. Stanford's original intention was to remove the nurse trees once the others had stabilized.
During the financial crisis that followed his death, however, the arboretum was neglected. Most specimen trees failed, while the heartier eucalypts flourished.
Those planning the arboretum revitalization upheld Stanford's vision for maintaining wooded open space, but departed from his notion of trees from around the world in favor of species native to California.
To keep costs down and grow a stand of trees of many ages, the planners will stagger the arboretum plantings over the next 30 years. They plan to begin revegetation near the perimeter of the arboretum to screen the roads, then move to high-use areas and along several creeks, and finally replant the central regions.
The effort got under way Saturday, April 11, when a small group from the Friends of the Arboretum planted two dozen oaks and bay laurels along the creek near the intersection of Lasuen Way and Campus Drive, not far from the marsh.
In recent months, Fong's crews and an outside contractor have removed about 300 trees that were casualties of the eucalyptus borer, which eats layers of tissue just below the bark. These cells serve as the tree's transport mechanism, moving sugars produced by photosynthesis down to the roots, and water and nutrients up to the foliage.
Healthy trees can combat the borer and similar pests by producing extra sap and drowning them. The aging arboretum trees, weakened by prolonged drought and last year's repeated hard frosts, are unable to offer much resistance, Oman said.
In their native Australia, eucalyptus are aided by wasps that eat the borer. Inadvertently brought to San Diego in 1990, where it was unchecked by its usual predators, the borer reproduced rapidly and spread throughout California.
"We have the largest stand of infested trees in the area," Oman said. "They already are serving as a source of infestation for eucalyptus trees throughout our sector of the peninsula."
Fong said that the Department of Forestry will introduce Australian wasps in the Stanford arboretum this spring and summer as part of a test program to see if they can successfully adapt to the region and slow down the borer. A similar program in Southern California has proved relatively successful, he said.
As part of the removal process, crews have reduced the giant eucalyptus logs to mountains of chips, killing beetle larvae in the process, Fong said.
Borer-infested logs are quarantined and anyone who transports them from the arboretum may contribute to spreading the pest. Unfortunately, a lot of the wood "walked away" before it could be sent through giant chippers, Fong said. The contractor is selling the chips to a cogeneration plant that will use them to produce energy.
Fong's logging operation has cost about $30,000 for his crews and another $20,000 for an outside contractor. He said the contractor would be brought back as necessary to help remove additional trees he expects will die this spring and summer.
Oman encouraged people to enjoy the arboretum, but cautioned that the dying eucalyptus may drop limbs and can be dangerous.
He also noted that the region can become tinder dry, posing a severe fire risk. He urged all users not to smoke in the area and to keep vehicles on the roads where exhaust systems will not ignite the grasses.
Copies of the Arboretum Plan are available from the Planning Office.
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