Out of the Ashes . . . Life : Last year’s Topanga Canyon fire led to a bold, successful experiment: letting nature regenerate itself.

The brush fire that burned 404 acres at the north end of Topanga Canyon last Sept. 6 ignited more than just chaparral.

It fired a philosophical dispute among some Topanga Canyon residents and conservationists over whether Los Angeles County should reseed the canyons and ridges with rye grass to prevent erosion and flooding downstream from the scorched area.

Some canyon residents were alarmed when county officials decided in October that they would not take special steps to replant the burned slopes. Mindful of the potential for flood damage, the homeowners had counted on soil-stabilizing rye grass being planted above their dwellings.

Giving Native Growth a Chance

Instead of reseeding, officials decided to let native grasses and wildflowers germinate on their own in the fire zone.

The result is a riot of mustard grass, lupine, poppies and other colorful wildflowers near the Top O’ Topanga overlook where only blackened earth existed a few months ago. Motorists on Topanga Canyon Boulevard say the growth is the thickest and most colorful in the Santa Monica Mountain range this year.

Although officials’ decision not to plant rye grass in the fire zone was seen by some as a bold one, county fire officials said their action was the result of a new, scientific approach to vegetation management.

“It wasn’t a gamble. Everything was pretty much calculated,” said Capt. Gordon Pearson, a county Fire Department spokesman.

Not Jeopardizing Homes

“We’re not interested in putting people’s homes in jeopardy. After they’ve experienced a fire, Lord knows they don’t need any more problems,” Pearson said.

In the past, however, emergency reseeding of burned hillsides above populated areas appears to have been almost automatic. County fire officials trace their use of rye grass for controlling erosion in brush-fire areas back to 1911.

More recently, fire officials and flood-control experts have used a mechanical seed-spreader suspended from a helicopter to quickly cover rough terrain with a measured 32 seeds per square foot.

Such quick reseeding allows rye grass to get a good foothold after the first gentle rains of the winter season, according to officials.

But environmentalists argued that the tough rye grass often took hold too well on hillsides after fires.

Native Growth Choked Out

They complained that the hardy ground cover choked out the more fragile native grasses and wildflowers before they were given a chance to grow back naturally.

Two years ago, the environmentalists’ postion was given a boost when longtime county Deputy Forester Klaus Radtke took a critical view of wholesale reseeding efforts in a published mountain-area safety study. He concluded that aerially seeded rye grass is less effective on steep slopes than are native grasses.

Several directors of the Topanga-Las Virgenes Resource Conservation District championed the natural regrowth after last fall’s fire.

They set up an inspection of the burned area that brought together county fire and flood-control officials, local environmentalists and federal conservationists. The inspection uncovered indications that the fire had not been hot enough to destroy native seeds lying just beneath the soil’s surface.

During the tour, Jill Swift, then a director of the conservation district, argued that rye grass removes significant amounts of nutrients from the soil, retarding the regrowth of native plants for years after the rye itself has died.

Decision Draws Praise

David Gottlieb, a district director, recently praised the Fire Department’s reseeding decision. “The area has regenerated wonderfully,” he said.

Gottlieb said rye grass reseeding will continue to retain a place in mountain-fire ecology, however. He said extremely hot brush fires literally scorch the soil and kill native seeds buried near the surface.

When that happens, rye grass reseeding is prudent, he said. This year, however, “the lupine and the mustard and the other growth out there is wonderful,” Gottlieb said.

Bob Johnson, head deputy forester for Los Angeles County, confirmed that the Fire Department will continue to turn to reseeding when the situation warrants it.

“We have not abandoned reseeding,” he said. “It’s getting more scientific. We’re taking a very critical look at areas before we do it. We’ll be scrutinizing every site.”

Johnson said foresters and fire officials are using “brush cover” maps and are analyzing terrain in an effort to determine the actual danger of downstream flooding after brush fires.