DEVELOPMENT THINNING STATE'S OAK WOODLANDS.

Byline: Jon Engellenner Scripps-McClatchy Western Service

As science increasingly focuses on threatened species, California's oak woodlands are being viewed more broadly - as an endangered habitat. Despite the calm aura of the foothills, once the domain of cattle ranches, riotous growth is taking its toll.

Experts say the threat from the burgeoning population isn't so much the chopping down of trees as the chopping up of habitats where oaks and their dependent species already struggle for survival against a host of natural forces.

``Statewide, development is the No. 1 cause of the losses of oak woodlands,'' said Amy Larson, executive director of the California Oak Foundation, an educational group headquartered in Oakland.

About 15 percent of California's oak woodland has been lost to development in the past 40 years. Since 1973, the rate of decline has been about 15,000 acres per year in a domain that is at least 80 percent privately owned.

Although many of the state's counties have come up with oak protection guidelines, they tend not to focus on the suburbanization of the foothills, critics say.

``The problem with these policies is they don't address the development issue, and that issue is the biggest threat to oak woodlands,'' Larson said.

To date, 38 of the state's 58 counties have completed or are working on oak protection rules. About one-third of those efforts contain voluntary guidelines with no regulation or protection, Larson said.

The foothill species - valley oaks, blue oaks and interior live oaks - are hallmarks of the hills that harbor the state's most diverse environment. Within California's 8 million acres of oak-covered hill country are more than 300 forms of vertebrate wildlife, 5,000 insect species and 2,000 different plants.

But slow regeneration and suburban growth pose a threat to the once-abundant resource, especially in places like Placer and El Dorado counties, ranked among the six fastest-growing state counties over the past five years.

In El Dorado, Placer and Nevada counties, about 183,000 acres - much of it oak-studded rangeland - was taken out of agricultural production between 1984 and 1992, according to a study by the Sierra Business Council.

In an exhaustive, three-year research report released June 7, the hardwoods were listed as the most threatened forest type in the Sierra. That document, the Sierra Nevada Ecosystem Project report, lists urban development and overgrazing as key threats to oak woodlands.

But it is not the first scientific look at the oaks, 19 species of which dot the rim of the Central Valley, the Coast Range and the westerly strip of Southern California. A five-agency study of the oak habitat has been under way for a decade.

``By far, the biggest issue is human development, especially commercial and residential growth,'' said Rick Standiford of the multiagency Integrated Hardwood Range Management Program in Berkeley, now in its 11th year. He wrote the Ecosystem Project report's chapter on foothill oaks. ``The whole climate has developed from large ranches that supplied a lot of open spaces.

``Now it's turning toward houses on 5 to 40 acres.''

The study of the oak habitat, despite all the research, is an inexact science. Soil, weather, wildlife and human-impact conditions vary widely among locations. These factors make elusive the answers to questions about what is hampering oak regeneration.

One thing is clear, according to the hardwood range management program: Based upon growth projections and planned projects, another 250,000 acres of oak woodland will fall to development pressure in the coming years.

People alone don't threaten the oak woodland habitat, researchers say. It is what they bring with them: Dogs and cats that harass and kill wildlife; horses that trample and compact the soil; kids who eradicate songbirds with their BB guns; and water hoses that take their toll on drought-dependent trees.

But if the Sierra foothills are under siege, they also are getting some respect, local sources say. Heated debates over tree protection ordinances indicate that many see a broad value in oaks.

``The marketplace recognizes it,'' said Standiford, whose group has generated 66 studies and 150 scientific articles on oak woodlands. ``If you have 40 trees to the acre, the property is worth 30 percent more right off the ground.''

The state's counties are under a state Board of Forestry mandate to adopt local guidelines for oak rangeland protection.

Sacramento and Placer are among 11 counties with full-blown tree ordinances. Many cities, including Sacramento, Roseville and Rocklin, also have tree ordinances.

The crucible of the Rocklin ordinance was a high-profile fight three years ago over saving two moss-backed blue oaks that stood in the way of a planned supermarket.

The compromise was an architecturally altered Albertson's and the preservation of just one of the trees, now dwarfed and isolated by concrete and asphalt.

The same ordinance is under pressure to become more development-friendly. At issue are tree-saving rules that would cost developers of a commercial site on Granite Drive about $250,000, said George Magnuson, Rocklin mayor.

``When you look at a zoning that would cost you a quarter of a million for tree mitigation, why would you want to build there?'' he asked.

``There are empty retail spaces all along Granite Drive that are not empty because of the oak tree ordinance,'' said Diane Bell, who fought three years ago to save the oaks at Albertson's. ``The ordinance is a scapegoat.''

Rocklin, like most other communities, requires protection or replacement of oaks of a certain size. But the tree-by-tree approach is under serious scrutiny.

``What we're losing is the habitat,'' said Joe Madeiros, a botany instructor at Sierra College in Rocklin. An advocate of setting aside plots for oak regeneration rather than saving heritage trees, he said too much stressB is placed on designing subdivisions with an oak in each yard.

``The trees die from every cause, but lawns are the biggest killer,'' he said. ``All you have to do is to drive around town and look at the oaks that were `saved.' They are either dead or dying.

``There's no quicker way to kill them than to put water on their feet.''

Foothill oaks are a hardy lot, showing cactus-like resistance to drought and an ability to grow to full size after being nipped and nibbled by livestock and a host of natural pests. Some of those pests are grasses imported from the Mediterranean by early California settlers.

``These alien grasses are severe overspenders of water, especially in the late spring, and the oaks can't compete,'' said John W. Menke, a University of California at Davis, instructor and researcher. The native grasses, he noted, had more gradual thirsts. ``I think that is the principal reason we see low regeneration.''

Under the right conditions, when a hole is bored in the foothill hardpan for the tree's taproot, an oak can grow to 6 feet in four years, according to Doug McCreary, of the Sierra Foothill Research and Extension Center in the Yuba County community of Browns Valley. But there also can be 25-year-old oaks that are only a foot tall. McCreary's 10 years of research tell him that people don't have ``a huge, direct impact on the regeneration process,'' except when somebody grazes several horses on a small parcel.

The main concern is the breaking up of large tracts once held by ranchers that provide corridors for wildlife movement.

``The biggest risk is to the wildlife habitat that gets so fragmented by people living on these 5-acre parcels,'' said UC Davis' Menke.