Landscaping the Great Outdoors. National parks focus on natural design. ENVIRONMENT

VISITORS to Yellowstone National Park or Mt. St. Helens volcano who stand agape at nature's handiwork generally are oblivious to the human handiwork involved in maintaining scenic vistas. That's just as it should be, the landscape architects of the National Park Service and US Forest Service say. Although these experts do not move mountains, they sometimes groom them; and they figure that the job has been done right when it seems as though nature did it.

While timber production, fire control, and recreation necessarily intrude on nature, visual considerations do represent constraints. David Porter, a landscape architect with the Gifford Pinchot National Forest in Washington, says, ``We don't just go in and take out trees. Before we manipulate vegetation in an area, we analyze the basic landscape: the linear features, color forms, and sight lines. Ideally, any alterations must blend with existing features to have visual harmony when the work is done.''

Federal land stewards operate by a hierarchy of visual objectives from preservation to maximum modification - the former in designated wilderness from which by law ``the imprint of man'' must be absent, the latter in areas managed primarily for timber or recreation.

Throughout the West, timber is routinely logged by clearcutting, the removal in a single operation of all trees in a stand. In areas where visual quality is an issue, ``Instead of 40 acres, we may permit only five to seven acres to be clearcut,'' Mr. Porter explains. ``Then we may contour the edges to emulate natural openings such as meadows.'' Ideally, forest roads are laid out along natural contours.

Besides maintaining inherent visual qualities, the Forest Service engages in scenic enhancement projects, such as opening up tree cover along a highway, and rehabilitation, or removing scars from the land. For example, tree stumps may be sawed flush with the ground and slash (logging debris) removed to create a glade-like effect.

When properly done, Porter says, site modifications are ``virtually indistinguishable to the passing motorist or casual hiker.'' Along Washington's White Pass Highway, for example, clearings one-to-two acres in size look like natural features. And few visitors realize that Black Butte, a large volcanic cone visible from Oregon's Santiam Highway, has been extensively logged.

At parks and monuments, National Park Service landscape architect Tom DeHaven says, the task is ``fitting in recreational development like parking, roads, and campgrounds with the least amount of visual disruption.'' All introduced elements are taken into account, including people. Ray Murray, a Park Service planner in San Francisco, says the popularity of brightly colored outdoor clothing has created headaches park founders never dreamed of. ``Some trails have to be designed to keep hikers on hillsides from seeing people in parking lots or campgrounds below who are wearing bright reds, blues, and yellows. Visitors feel such views spoil the outdoor experience,'' he says.

As more people than ever before take to the woods and waters, some expect the whole outdoors to be a wilderness. Planners trying to meet the visual expectations of typical visitors, not outdoor purists, recognize that some visual intrusions are impossible to mask, Porter says. Also, citizens often complain about eyesores on private or state holdings over which federal agencies have no control.

Murray notes that ``people in general have gotten used to a much higher standard of visual quality in everything from food to the printed word.'' As a result, users are ``much more likely to notice when we mess up,'' Porter says. According to him, the ideal of unobtrusive design can, in fact, work against agencies from a public relations perspective in that ``people often judge our work not by what we do best but what we do worst.''

Conversely, urban values get imposed on the wilds. ``Sometimes at places like Yellowstone, you get complaints from city-dwellers about the `calling cards' that horses leave on trails and you have to explain that national parks aren't managed, or manicured, like city parks,'' Mr. DeHaven says.

Ultimately, the public's conflicting ideas of how nature ought to look make landscaping the great outdoors as much a balancing act as a design problem, Murray says. He sometimes envies conventional landscape architecture with its emphasis on artifice, but says that integrating visual elements from station wagons to stags to snowcaps has its own special challenges and rewards.