HELENA, Mont. — Plum Creek Timber is expected to declare about 7,200 acres of wildlife habitat off-limits to development under an $8 million deal with the Montana wildlife agency.

The Department of Fish, Wildlife and Parks intends to buy a conservation easement for the Plum Creek land in western Montana's Swan Valley, a deal set to become final on Thursday, the agency's Steve Knapp said.

Seattle-based Plum Creek, one of the nation's largest owners of private timberland, would continue to own the property in the northern Swan Valley and would manage it as timberland in accordance with a state plan to protect wildlife habitat.

"Without this conservation acquisition, the lands would likely be sold for development," according to a briefing paper that Fish, Wildlife and Parks commissioners received in December, when they authorized buying the easement.

A Plum Creek spokeswoman declined to comment Thursday. "We're not prepared to announce anything because nothing's been finalized yet," Kathy Budinick said.

The easement is the first step in what state officials hope will ultimately be a project conserving nearly 11,000 acres of Plum Creek land in the Swan Valley, at a potential total cost of $27 million to $30 million. Besides placing roughly 7,200 acres under the conservation easement, the state wildlife agency anticipates buying as much as 3,680 acres owned by the timber company.

The agency will rely largely on federal funding, plus dollars from the nonprofit Trust for Public Land.

The lands, intermingled with the Swan River State Forest, support grizzly bears, black bears, deer, elk and moose, and include streams that support bull trout and westslope cutthroat trout. Besides protecting habitat for those species, the conservation easement helps ensure continued public access to outdoor recreation, as would the land purchases, state officials said.

Plum Creek drew the ire of some Swan Valley residents a few years ago when the company prepared to sell some of its valley timberland as residential property. At the time, Plum Creek owned about 80,000 acres in that scenic swath of Montana. Locals said real-estate sales would end some traditional land uses and change the valley's character.

Plum Creek has been selling "nonstrategic" timberlands in the United States and expects sales in its real-estate segment to total between $280 million and $300 million for 2006, the company reported early this week.