Drought, Smog Now Suspected in Dieback of Brush

Scientists trying to determine what is killing large patches of wild vegetation in the Santa Monica and San Gabriel mountains, worsening the seasonal brush-fire threat, are increasingly looking at the effects of drought, perhaps aggravated by smog.

Los Angeles County Fire Department officials said the dieback of mountain brush may have created as much as a million tons of dead vegetation to feed fires on mountain slopes this summer.

The cause may be clearer after a data-gathering flight by an ER-2, a modified version of the U-2 spy plane, which the National Aeronautics and Space Administration is making available, said Phillip Riggan, a researcher for the U.S. Forest Service in Riverside.

A NASA spokesman at Moffett Field near San Jose said the flight will take place during the last week in May or the first two weeks of June. Processing the data will take two to three weeks, the spokesman said.

Concern Over Dead Brush

Los Angeles County Fire Department officials have said they are worried about the death of wild vegetation from unknown causes, which has been reported in mountain areas from Ventura County to San Diego County. Fire officials said as much as 30% of the brush has succumbed in some areas, with some patches of dead brush reaching 500 acres.

County Fire Chief John W. Englund, whose office also carries the title of county forester, wrote to the state Department of Forestry earlier this month warning that the dieback is creating a serious fire hazard in the mountains.

Fires in affected areas this summer “will be high in intensity because of the increased dead fuels and will require increased fire-suppression efforts for containment,” he said.

Fire authorities were particularly concerned by the loss of wild lilac, a difficult-to-burn shrub which acts as a natural damper on the spread of brush fires.

Pest, Disease Unlikely

Riggan said scientists are leaning away from earlier suspicions that the vegetation, weakened by drought, had lost its resistance to some insect or disease.

“The symptoms don’t appear to indicate an airborne fungus, or root rot or any kind of bug,” he said. “Several plant pathologists have investigated, and as yet they have not found any organisms that are doing this.”

Investigators at a Forest Service laboratory in San Francisco are examining dead vegetation for signs of such organisms, Riggan said.

But “whatever this is,” he said, “it’s so widespread, and attacking so many species, that it doesn’t fit the classic patterns of a root rot, which tends to hit smaller pockets, or of a fungus, which usually affects only one species.”

There is a growing suspicion that the dieback is the result of the lack of rain this year, after several years of heavy winter rainfalls, he said. The rainy years encouraged growth of the brush, which may now be “overextended”--grown too large to cope with a dry year.

Smog May Be Factor

In informal observations, he said, he has noticed that the heaviest loss appears to be in areas where the vegetation is most exposed to polluted air, raising the possibility that drought-weakened brush has lost a resistance to smog that protected healthier brush in wetter years.

“The worst damage we see is on the front range of the San Gabriels, where there’s heavy air pollution,” he said. “There’s less damage in the Santa Monicas, where there’s less air pollution.”

The Forest Service, the California Department of Forestry and the Los Angeles County Fire Department are working together on the problem, Riggan said, although they do not agree on all details.

Riggan estimated that 100,000 acres of brush are affected in Los Angeles County. The county Fire Department’s specialist in vegetation management, Capt. Scott Franklin, believes the total is twice as high, said a department spokesman, Capt. Gordon Pearson.

200,000 Acres Estimated

“Franklin’s preliminary estimate is that we’re looking at 200,000 acres of brush that could be impacted by as much as five tons of material per acre,” Pearson said.

“That’s a million tons of dead brush.”

The ER-2 will soar over the mountains at 60,000 feet, a NASA spokesman said. Regular, infrared and heat-sensitive photography will be used on a six-mile-wide strip of the San Gabriel Mountains from Claremont to the Newhall area.

Then the plane will photograph the Santa Monica Mountains from the San Diego Freeway west into Ventura County.

The ER-2 is basically a U-2 equipped with what NASA calls “earth resources” monitors instead of intelligence-gathering equipment.