State environmental officials said this week that they will delay and radically change a plan to clear more than 500 acres of planted trees in the Manuel F. Correllus State Forest.

James Rassman, management forester for Southeastern Massachusetts, said the Department of Conservation and Recreation will reduce the scope of the work and change its priorities as it maps out a new plan for the 5,146-acre forest, which lies at the geographical and ecological heart of the Island.

Four months ago officials announced the massive clearing plan that includes dilapidated plantations of red and white pine. Forest officials said they wanted to move as quickly as possible to remove the plantations because the quality of some of the wood was marginal and declining rapidly, reducing the chance that a mainland logging company would bid on timber located on an offshore Island, far from the marketplace.

The project has been called the greatest single environmental restoration project in the history of New England by David R. Foster, the head of Harvard Forest, the research center of Harvard University that studied the forest extensively in 1999.

Mr. Rassman told the Gazette late last week that the state has learned a great deal from a closer examination of the red and white pine plantations this fall and winter, and from early negotiations with timber companies and transportation firms. The findings and the delay have proven to be a blessing in disguise, he said.

Among other things, officials learned that a significant amount of the wood is unmarketable, which reduces the size of the project and the urgency to do it quickly, Mr. Rassman said. He said this has given the Department of Conservation and Recreation a chance to think about how to deal with the planted trees in more creative ways.

"We want to do it right, rather than fast," Mr. Rassman said.

Starting in 1925, the state planted hundreds of thousands of red and white pine seedlings - along with other foreign species, such as Norway spruce and Scotch pine - on approximately 1,100 acres of what was once a vast, unproductive woodland of scrub and tree oak. But scientists of many disciplines now say the old forest is ecologically invaluable.

The value of the ecosystem has to do mainly with the offshore location of the forest, as well as its sandy soils, its historic record of being regularly swept by fire and almost completely spared the environmental disruption of agriculture. The state forest now hosts the densest concentration of rare plants and insects in the commonwealth, and perhaps in the Northeast, according to the state Natural Heritage and Endangered Species Program.

The trees were planted on a rolling, scrubby, fire-swept landscape known then as the Great Plain. The hope was that the Island could create and sustain a lumber industry. But inattention, disease and economics prevented the enterprise from ever developing, and for decades the plantations languished until the state began to invest in the restoration of the native scrub and tree oak woodland last year.

After spending a week surveying the plantations this fall, Mr. Rassman concluded that the red pine that covers about 350 acres are unfit even for the pulp market. "They're not dying. They're dead. And the value of the product has already gone by," Mr. Rassman said. Except in limited areas where the trees or small stands present either a fire hazard, a threat to public safety or an aesthetic nuisance, almost all the red pine will be left to decay back into the earth, or be cleared as part of normal maintenance of the forest.

With the removal of the red pine from commercial consideration, "I would say the project has become 40 per cent smaller," Mr. Rassman said.

Another substantial change in philosophy centers on the white pine. While the state still wants to clear away most, if not all, of the white pine plantations on 175 acres of state forest land, it now regards white pine as an indigenous part of the forest, and will not try to eliminate it as species.

"It's not just in these plantation blocks," said Mr. Rassman of the white pine. The plantation blocks, bounded by a grid of fire lanes, rise up in thickly clustered stands and shade out the native scrub and tree oaks that, when young, often support rare insects in the forest. The white pine plantations, all the same age and height, have also proven vulnerable to hurricanes - the state spent $50,000 to clear away fallen stands of white pines after Hurricane Bob raked the Island in August 1991.

"The white pine is now scattered throughout the forest; it's regenerated all over the place," Mr. Rassman said, adding that if the state set out to eliminate all the white pine, "I think you'll fail. And as long as it's not in plantation structure, I don't think it's that big of a risk."

The Department of Conservation and Recreation, Mr. Rassman said, remains committed to its mission to promote biodiversity in its properties, and consults regularly with Natural Heritage and Harvard Forest as it works out a comprehensive management plan for the state forest. He said the department expects to complete the plan within two years.

While it remains committed to removing the stands of white pine that Harvard Forest identified as a threat to the indigenous and rare insect communities, the department will also consult with the public and with Island conservation groups before it begins any significant work in the forest. No work will begin before next fall at the earliest, he said.

"If we're not going to get rid of all white pine, then we can ask which stands are important from an aesthetic standpoint," he said. "I'm sure some people riding bikes, people playing Frisbee golf and other things, would say that they're concerned with this or that [particular stand of trees]."

Mr. Rassman placed a new emphasis on removing stands of Norway spruce and Scotch pine, cited in the Harvard Forest study as a threat to the native biology. Many younger spruce and Scotch pines have recently been cleared from a frost bottom on the western side of the forest, where they threatened to overshadow and crowd out a particularly unique scrub-oak ecosystem in the cold, ancient river valleys.

Mr. Rassman said his department has had several conversations with mainland timber companies and others involved in the transportation business to find out if cutting and moving logs off-Island is economically feasible. He declined to discuss the talks.

But he said Vineyard officials have raised the possibility that a small Island biomass facility might one day be able to use state forest wood, as well as other renewable sources, to supply one or more Island enterprises with energy.

"That could solve so many problems, and that could leave us with the option of maintaining not necessarily the plantation structure, but some of the plantation species, like the white pine, as an on-Island renewable energy source," Mr. Rassman said, concluding:

"I'm in some conversations right now with some people that are looking into that, and what type of demand they would have with respect to various sizes of facilities, and would the state forest be able to provide that sustainably and in an environmentally sensitive manner, long-term."