The northern spotted owl, an elusive denizen of virgin forests in the Northwest, has emerged to silence chain saws in big sections of ancient timber stands of Washington and Oregon.

Prodded by environmental groups, the U.S. Forest Service intends this fall to approve a ban on logging and other development in 347,700 of the 1.3 million acres of old-growth forest within 13 national forests in the two states, government and environmental officials said Wednesday.The plan, aimed at protecting the spotted owl and other wildlife from the effects of logging in their unique forest habitat, has drawn sharp criticism from the timber industry.

Timber spokesmen contend that the spotted owl needs no such protection, and that the move is just one of several environmental steps to cripple or shut down the industry, which is in the midst of a record cutting year.

Old-growth timber, which is anywhere from 200 to 600 years old, is prized by the industry for its higher-quality grain. Old-growth species include cedar, hemlock, Douglas fir and spruce.

The owl-protection plan is scheduled to be signed soon by Forest Service chief F. Dale Robertson, said Grant Gunderson, an agency wildlife biologist.