The Clinton administration yesterday proposed a fundamental change in how the nation manages its vast estate of national forests, recommending for the first time that ecological health officially take precedence over timber harvests and other commercial uses.

"What we are doing here is putting in place a new philosophy for how we look at and manage the national forests," said James R. Lyons, undersecretary of agriculture for natural resources and environment.

In practical terms, environmentalists and timber industry officials agreed, the new rules for devising land management plans for the 155 national forests would likely lock in or reduce the low timber harvest levels of recent years that have been driven by court decisions and administration policy.

In announcing the proposed regulations, which grew out of the recommendations of a scientific panel he appointed in 1997, Agriculture Secretary Dan Glickman said they would return the Forest Service "to its conservationist roots" by emphasizing sustainable use of the forests, rigorous outside scientific review of management plans, and increased public involvement in forest planning. Though administration officials stressed that economic and social sustainability of communities that depend on national forests is still a priority, spokesmen for the timber industry said the new rules would by administrative fiat overturn a basic function of the national forests enshrined in its founding statute of 1897.

"We feel [Forest Service Chief] Mike Dombeck is trying to change the basic mission of the Forest Service without consulting Congress," said Jim Geisinger, president of the Northwest Forestry Association. "I think where they're headed is turning the national forests into a system of biological reserves. If those regulations do become final, there's no reason not to turn over the forests to the National Park Service."

American Forest and Paper Association President W. Henson Moore said the administration had unilaterally decided to junk the Forest Service's legislative mandate for "multiple use" of its lands. "It's just not the way to make public policy," he said.

Environmental groups generally reacted warmly to the proposed rules, though they were disappointed by new restrictions on appealing land use plans. The proposal, said Mike Anderson of The Wilderness Society, "directs them towards a goal of ecosystem integrity, which is a long way from the multiple use focus of the past."

If implemented, the new rules would be the first comprehensive overhaul since 1982 of the often tortuous process of land management planning for the 192 million acres of federal forests and national grasslands. They reflect a continuing shift in public attitude that national forests should be managed more for recreation, wildlife and watershed protection and less for timber production, livestock grazing and mineral exploitation.

Though the forest system erected by President Theodore Roosevelt and his forester Gifford Pinchot was created to provide wood and water for a growing nation, large-scale timber production from those federal lands did not really begin until the post-World War II housing boom.

Timber harvests crested at about 12 billion board feet per year during the Reagan administration, but have fallen to about 3 billion during the Clinton administration.

Though numbingly technical, the process of land management planning for the national forests effectively determines how a large part of the public's estate is to be used. As Lyons said, "Planning is where the rubber meets the road."

The new planning process is designed to be more flexible, more open, less subject to challenge and more scientifically based. Unlike the old forest plans that locked in timber harvest numbers for a decade, the new ones will set two-year projections and allow for "adaptive management" to meet changing conditions. A key new element will be the involvement of national and regional science advisory boards to advise the Forest Service, and independent scientific reviews of the effectiveness of management plans in meeting ecological goals.