Appalachian Trail maintenance a labor of love for volunteers.

In the welcome quiet of the woods as he walks along parts of the famous Georgia-to-Maine Appalachian Trail, Harold Croxton, a retired accountant from Coopersburg, Pa., finds ''a chance to do a little thinking of your own, a chance to meditate.'' Sometimes good ideas ''tap you on the shoulder,'' he says.

And after a day's hike he likes to camp near a stream, cook a meal, and lie down to rest. ''You listen to the cicadas and tree frogs,'' he says. One night he heard six owls at one time, some nearby and some in the distance.

Now he and several thousand other hikers who love the Appalachian Trail are beginning to manage some of the federally owned land alongside the trail in what federal officials call a first-of-its-kind partnership of volunteer citizens managing federal lands.

If the experiment is successful, it eventually may be applied to some of the other 12 national long distance trails in the US, says Bob Karotko, trails director for the National Park Service.

''We're depending more and more on volunteers,'' he says.

Volunteers have maintained much of the 2,100-mile Appalachian Trail since it was completed in the late 1930s. But this work is limited primarily to the trail itself. It includes erosion control, building bridges, and erection of shelters next to the trail.

But under an agreement signed earlier this year between the US Department of the Interior and the Appalachian Trail Conference (ATC), a volunteer organization, volunteers are assuming much broader responsibilities.

Starting with some 250 miles of trail, in Virginia and other states from Pennsylvania to Maine, volunteers are beginning to manage the federally owned trail corridor (typically about 1,000 feet wide) while continuing to do most of the maintenance on the several-yards-wide portion people hike on.

The new responsibilites include erecting gates to close old backroads leading across the corridor; checking to see if anyone is stealing timber off the federal land, and attending local zoning meetings relating to development near the trail.

''It's a lot of work, we're finding out,'' says Larry Van Meter, executive director of the 18,000-member ATC.

Why do the volunteers willing to take on the extra work?

The answer goes back to the late Benton MacKaye, a prominent forester, who proposed the trail in l921, says Van -Meter. MacKaye called the trail the ''body'' of the project and the volunteer spirit to maintain it the ''soul.

Harold Croxton explains further: ''I know when I hike the trail I really enjoy it. Turnabout's fair play, isn't it?'' He works on a 20-mile section of the trail with other active members of the Allentown (Pa.) Hiking Club. ''It's better than sitting at home.''

Croxton recently spent eight hours on a hot Sunday painting trail blazes for hikers.

For the past two years, mathematics Prof. Charles Parry of Blacksburg, Va., along with other volunteers in the area, has been helping establish three miles of relocated Appalachian Trail over a scenic mountain crest near Roanoke, Va. It has been hard work, he says, but ''I like to do something productive and meaningful. There's a bit of pride involved.''

Congress has authorized $95 million to buy the remaining sections of trail route still in private hands. About $65 million of that has been spent, and the balance will more than cover the additional 325 miles still to be purchased, says Charles Rinaldi of the National Park Service. In a few cases the power of eminent domain has been used to buy out reluctant landowners, he said.

In a few places, through developed areas, the trail corridor gets down to about 50 feet in width, but usually it is about 1,000 feet, he says. ''The biggest intrusion (on the tranquillity hikers seek) is noise'' from motor vehicles and machinery, he explains.

At least on paper, the US has about 20,000 miles of federally designated long-distance trails, according to Karotko. The federal government is buying land only for the Appalachian Trail, he said, but volunteers are developing many miles of land in various states.

The Boston-based Appalachian Mountain Club, with a grant from the Richard King Mellon Foundation, is helping volunteer groups organize to develop and maintain trails in Florida, New Mexico, California, Washington, and Pennsylvania.