WHEN THE BOUGHS BREAK OPPRESSIVE HEAT SHEARING LIMBS FROM VALLEY TREES.

Byline: SUSAN ABRAM Staff Writer

VAN NUYS -- The residents of Elkwood Street joke that the name of their cul-de-sac should be Falling Limbs Lane.

Every summer, the muscular branches of the hulking liquidambars planted decades ago by the city have sagged lower as they've aged and gotten heavier. But this summer's unrelenting heat has sparked an epidemic of limbs that snap off with exhaustion, crashing onto front lawns and car hoods.

And that's where the joke ends.

``Every year, the limbs are falling more,'' Homer Johnson, a 54-year resident of Elkwood Street, said Friday, as he examined a limb -- as big around as a cantaloupe and as long as a yacht -- that fell near his curb a few nights earlier.

``As long as nobody gets hurt, that's the main thing,'' Johnson said.

The sound of tree branches falling in Los Angeles' urban forest is being heard loud and clear, along with residents' complaints, officials said.

The city's Bureau of Street Services has received 3,800 emergency calls for fallen tree limbs this summer, a 50-percent increase over last year, said William Robertson, director of Bureau of Street Services.

Most of those calls are from the San Fernando Valley, which has experienced a record-breaking heat wave.

``It's referred to as summer limb drop syndrome,'' Robertson said. ``Normally during the summer, there's branch failure. We're aware of it, and we prepare for it every year, but we've never experienced this (many) before.''

The city spends about $5 million annually for tree trimming, plus $1.3 million more to outside contractors. That level of service means a city- owned tree gets trimmed every eight years, Robertson said.

``The unfortunate thing is not only do we have the largest urban forest in the United States, but we are the most diverse,'' Robertson said. ``Many of those species require trimmings every two to three years. We can only trim so many trees so many years. We would love to trim a tree every three years.''

But other factors are contributing to the loss of limbs. Even trimming them every three years may not have helped this summer, said Ronald Lorenzen, street tree superintendent for Los Angeles.

``Heat is the No. 1 reason'' for limb failure, Lorenzen said. ``I don't ever remember a time when it's been day after day of 100-degree weather.''

Combined with a rainy winter and cool spring, the trees also have grown bushier, he said.

The San Fernando Valley has a large population of liquidambar, Lorenzen said, which is native to the southeastern United States, but also does well in Southern California.

Scientists have been studying summer limb drop for years, said local arborist Jan Scow. He said there are no clear answers, but only theories.

Others say trees lose their limbs in the heat because cells are shrinking from not getting enough water, causing bark and limbs to become brittle, said Linda Eremita, an arborist with TreePeople, an organization that educates the public about trees.

``It's been so hot that, if people haven't changed the amount of water they give to the tree, the tree is probably not getting enough water and cells could shrink.''

Because liquidambar, also known as sweet gum, is a tall tree, it is likely to catch more wind in its branches than shorter varieties.

Eremita also cautioned that trees should not be pruned when stressed. When a trees limbs fall, it is simply ridding itself of branches to preserve water in its trunk.

``The tree is kind of taking care of itself,'' she said. ``That's what it does in the forest. It's just doing what it should be doing, except we're in the city, so it could fall in on a person, or a car or a house.''

A spokesman for Mayor Antonio Villaraigosa said the office didn't know anything about the problem until it was contacted Friday by the Daily News.

``It hasn't been brought to our attention as high urgency, but as we're becoming aware of it, it will be put high on the list,'' said Darryl Ryan. ``We don't want branches falling on our residents.''

Ryan said street services crews are up to the challenge, even after the mayor promised that 300,000 potholes would be covered by the end of the next fiscal year.

``Street Services is an amazing bureau,'' he said. ``They love the work they do. They loved the pothole challenges of the mayor.''

But back on Elkwood Street, Homer Johnson remembers a time when the trees were kept neatly trimmed more often, when the only kind of shedding from the liquidambars were the star-shaped leaves in autumn, or the spiky seedpods that land on the pavement with a thwack.

At least eight limbs have snapped off the tree near Mark Paul Sebar's corner house on Elkwood Street. Two years ago, a branch fell on the hood of his white 1992 Lincoln Town Car, causing $2,000 damage.

``Look at the thickness of that branch up there,'' Sebar said as he pointed up to the top-heavy tree, where scars could be seen from where branches have fallen. ``That's a tremendous branch ready to fall.''

Neighbor Adrian McKay said she doubts Elkwood is the only San Fernando Valley neighborhood where trees are shedding limbs. She said she also understands that the city's resources are tight, and that it's been an extraordinary summer. But she worries about the limbs falling on people.

``If someone were to get hurt, the city would just call it an act of God,'' McKay said.

susan.abram(at)dailynews.com

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Photo:

(color) Mark Paul Sebar of Van Nuys surveys one of the many trees in his neighborhood that have lost their branches in the current heat wave.

Gus Ruelas/Staff Photographer