There's a guy called "Deep Root" at a telephone somewhere in Montana who's driving the U.S. Forest Service out of its tree.

"Deep Root" is either a present or former -- he likes to keep these details vague -- Forest Service manager who is leading a crusade to tell the world about what he considers a conspiracy between the logging industry and his superiors in Washington to build thousands of miles of roads through pristine back- woods areas and thus open tens of thousands of acres of virgin trees to the clear-cutters.

Deep Root says this cozy arrangement between government and industry costs the taxpayers hundreds of millions of dollars and renders large areas of forest ineligible for protection as wilderness areas.

For weeks now his calls have been coming in to The Washington Post bureau here and to the Denver offices of The New York Times, Newsweek, NBC and other national media. Invariably, they are collect calls from -- as the operator puts it -- "an experienced forest manager in Montana."

Although he won't identify himself, Deep Root makes it clear that he is an insider who knows a great deal about the Forest Service. All he wants, he says, is to draw some attention to "this conspiracy."

His targets are not at all pleased. Shortly after Deep Root started placing his calls, Forest Service officials here started calling reporters to make inquiries about their nemesis. "Did he happen to leave a return number?" one Forest Service type asked me casually in the midst of a long conversation.

"The guy is a regular public-relations expert," complains Hank Deutsch, the Forest Service's spokesman here, who has been busy all fall trying to follow Deep Root's trail and rebut his charges.

"He knows just whom to call at every newspaper and magazine," says John Benneth, of the Industrial Forestry Association, a trade group, who is also trying to rebut Deep Root.

One reason the Forest Service and the industry have been so thin-barked about Deep Root's accusations is that he is chipping at an extremely sensitive branch of national forest operations: the timber sales program.

About half the wood cut down each year by America's logging companies comes from national forests. The Forest Service asks lumber companies to bid on a particular stand of trees and then sells the clump to the highest bidder (in some cases, there is only one bidder).

This timber-selling program produced a net gain for the Treasury of about $1.4 billion between 1978-83, by the Forest Service's accounting. But some specific sales bring in less than it costs the government to run the sale. The Forest Service's costs include marking the cuttable trees and building roads to bring logging machinery through the forests.

The General Accounting Office said the government actually lost money on 42 percent of its sales in 1982. The Wilderness Society, a private environmental group, computed that the government spends $98 for every $2 it earns on timber sales in one Alaska forest -- yet the government has made long-term agreements with big timber companies to continue those sales.

The Forest Service says these "deficit sales" provide extensive benefits for recreation, wildlife and forest fire prevention even if the wood is sold at a loss.

The logging industry complains that the problem is largely an accounting dispute. "If the government's costs and benefits were computed accurately," Benneth says, "a large number of what are called below-cost sales would show up as quite profitable for the (Forest) Service."

But the policy has sparked a wildfire of opposition from environmental liberals like the Wilderness Society to cut-the-fat conservatives like the Grace Commission. Adherents to a new "free market" school of environmentalism called "The New Resource Economics" cite the timber sales as a reason for transferring most public lands and forests to the private sector.

"There's no way a private business would develop a policy of clear- cutting forest land and selling the wood at a loss," says John Baden, a "New Resource" economist. "Only government could treat a forest that irresponsibly."

Deep Root says he and many of his fellow Forest Service veterans are also upset about the timber sales, primarily because each sale requires the building of a logging road that can have a major environmental and legal impact on forest land.

"I love it when they say they need to cut a stand of timber on some remote mountainside for the good of wildlife," the whistle blower says sarcastically. "Does anybody mention the wildlife impact of hacking a big road right through the habitat and sending these 30-ton logging rigs back and forth?"

Under the Wilderness Act of 1964, primitive areas of National Forest are eligible for designation as "wilderness" -- and thus forever off-limits to economic development -- only if they are "roadless." Each new mile of logging road, therefore, removes tens of thousands of acres from the pool of potential wilderness land.

"There's absolutely no question that the reason for all these roads in virgin areas is to make sure the land can never be included in a wilderness," he told me.

Citing Forest Service blueprints for the next decade, Deep Root says the service is planning "a road-building binge" designed to thwart members of Congress working to expand wilderness areas in the Rocky Mountain west.

Forest Service Chief Max Peterson says, "The U.S. Forest Service isn't on a road-building binge." He points out that construction money spent and miles of road completed have both declined slightly over the past four years.

Deep Root and his environmental allies reply that road-building has increased in areas they consider "potential wilderness lands."

Like the sheriff of Nottingham, who held an archery contest on the theory that the mysterious Robin Hood could not resist the challenge, some government officials think they might draw Deep Root to Washington next spring for a House subcommittee's hearings on the deficit sales and road-building in virgin forests. "If this fellow in Montana is really an expert, you'd think he'd want to show up and testify," says the Forest Service's Deutsch.

Deep Root is coy about his intentions. "There will be a lot of people to make my case if I can't go," he says. "But of course, I'd like to be there."