Majestic Oaks Fail to Renew; Researchers Look for Clues

Scientists peering beneath the shade of California’s majestic blue oak trees are hoping to unravel one of their mysteries and save the species.

The researchers at 38 experimental stations deep in the silence of Los Padres National Forest oak groves are trying to figure out why the seedling stage of the trees--in which they are a few feet tall, with two-inch diameter trunks--is virtually non-existent.

The oak is the tree most often seen in California, and there are up to 50,000 of them in Los Padres, 150 miles northwest of Los Angeles.

Saving the oaks is important, forest ecologist Mark Borchert said, because they provide an important source of food for wildlife.

There is a “very elaborate organization built around acorns,” he said.

20% of Acorns Sprout

The experiment in the forest’s American Canyon area north of Santa Barbara took root in 1984, when 3,040 blue oak acorns were sown. Roughly that many acorns were planted again last year. About 20% sprouted from each planting.

The experiment is expected to shed some light on why there are so few seedlings from blue oaks, the species that used to dominate Northern and Central California hillsides.

Something is hindering the development of the trees, and it may take generations to come up with answers, Borchert said.

One culprit may be a winged predator, he said, noting that scrub jays plant acorns and, remembering where they buried them, return later to eat most of them. But some acorns make it and sprout.

It takes oaks about 60 to 80 years to reach the seedling stage. The trees take several hundred years to reach maturity, and they often live thousands of years.

Many people blame nibbling deer and cattle for the oak seedling loss, but that theory is discounted because in Sequoia National Park, where cattle have been excluded since the park was established more than 100 years ago, there has been virtually no oak regeneration, Borchert said.

Fences Do Not Help

Also, there has been very little regeneration in an area fenced off for more than 30 years near the University of California, Berkeley, where studies are being conducted to determine how big an oak has to get before it can survive nibbling by deer and cattle, he said.

In the fenced Los Padres National Forest test areas, there also has been little regeneration, Borchert said.

Borchert said his 38-enclosure experiment is a duplication of experiments done elsewhere, including one on a much smaller scale in Monterey County on valley oaks, whose numbers have been drastically reduced on the flatlands by development and agriculture, and similar experiments in England, where oak regeneration also is a problem.