Reagan's campaign 'trail' winds through the great outdoors

President Reagan is trying hard to convince average voters that he cares just as much about the environment as they do. This week, his schedule gives new meaning to the phrase ''campaign trail.'' On Tuesday he took a quick and telegenic trip to Maryland's scenic Delmarva peninsula. Today he plans to appear on Theodore Roosevelt Island, a pastoral spot in the middle of the Potomac, and sign a US environmental report.

Thursday he is scheduled to descend on Kentucky's Mammoth Cave National Park, and address a meeting of hikers and campers. Cave rangers find the prospect of a President in their midst somewhat startling.

''This has been rumored for some time,'' says one, ''but it didn't become official until last weekend.''

This burst of activity is not, however, a quick reaction to the controversy stirred by the reappearance of Anne Burford. Mrs. Burford, former head of EPA, was appointed July 3 to head a US advisory commission on oceans and atmosphere.

The trips are part of a long-planned campaign to position Mr. Reagan as an environmental moderate, say government and environmental group sources. The White House aim is not to win over the Sierra Club and other critics, but to convince most of America that the President's position on the environment is in the mainstream.

''This was all planned some time ago,'' says one US environmental

agency official. ''They've just been trying to fit it into the President's schedule.''

Reagan's environmental offensive actually began almost a month ago, at the June 20 dedication of a new National Geographic building in downtown Washington. Speaking on that occasion, the President said his administration had brought ''energy and vision'' to protecting the environment. He charged that his environmental critics unnecessarily ''politicized'' the issue and were prone to ''blind and ignorant attacks'' on business and farmers.

The White House campaign was to smoothly swing into a July 3 luncheon with moderate environmental leaders - but the Burford affair intervened. In a classic case of poor political timing: Her reappointment was announced just before the lunch, turning it into a confrontational meeting rather than a conciliatory one.

But Reagan aides hope this week's trips will make voters forget Burford's new job, and enable the President to take the environmental high ground away from groups such as the Sierra Club. Backdrops should produce marvelous presidential photographs, while the excursions pointedly avoid places where such sensitive topics as hazardous waste or acid rain might be raised.

Environmentalists, meanwhile, have been stung by the President's characterization of them as extremists. They have hit back with heavy rhetoric.

The White House is in the midst of a ''hastily prepared whitewash campaign,'' responds Sierra Club legislative director David Gardiner.

Environmentalists are concerned that they indeed are being outflanked by President Reagan. Reagan's appointment of William Ruckelshaus to head EPA and his naming William Clark as Interior secretary have proved politically successful moves, environmental group officials admit.

Thus some environmentalists are privately gleeful at having Burford to kick around again. ''This is the stupidest thing the administration could have done, '' gloats one who asked not to be named.