Nature rules here. Insects are allowed to kill great stands of lodgepole pine and lightning is allowed to burn forests without man's tinkering. As it always has been.

Still, this old park, set aside as the first national park in the world more than a century ago, is feeling immense unnatural pressures from within and without as its major tourist season nears a close this Labor Day weekend.

Most of that strain is a result of the energy crisis. The American public--having read about the world oil glut, growing accustomed to quadrupled gasoline prices--is on the road again. The Winnebagos, the Cadillacs, the Trans Ams and the Hondas jam the parking lot at Old Faithful Inn, a license plate from almost every state. After two stay-at-home summers, the people, the autos and the tour buses are back, draining aging facilities, taxing budget-trimmed work forces.

But the American government, with Interior Secretary James G. Watt in the forefront, sees the energy crisis differently. Watt will visit Yellowstone next Saturday, flying over the wilderness areas and five national forests that surround the park in a natural buffer zone. In these federal lands oil exploration is epidemic and derricks are creeping toward the edge of the park.

It is this paradox--tourists gorging Yellowstone because for them the oil crisis is over, oil rigs surrounding the park because for government officials it is not--that will tax the political acumen of Park Superintendent John Townsley when his boss visits.

Jim Sweaney's Cessna banks sharply through the dense smoke of the Two Oceans forest fire in isolated southeast Yellowstone, dipping low over orange flames that lick up the sides of the park's trademark lodgepole pine. It is a bad fire year just as, beyond the park's boundaries, it is a good oil year.

Off in the far distance, the profile of the majestic Grand Tetons stands obscured by the brown haze. Below, the billowing smoke mars the beauty of the 7,773-foot-high crystalline Yellowstone Lake.

For 11 years, Sweaney was a smoke jumper who parachuted in on fires like this. Now he is a park ranger who monitors the fires until they burn themselves out without human help. It is, he says, nature's way of regenerating itself. Nature's way rules here. Beyond Yellowstone's boundaries, man rules--and he is looking for oil, overruling nature.

By visiting Yellowstone, Watt is looking for a telegenic backdrop for his controversial parks policy. He has called the condition of the park shameful--rundown, unsafe, poorly maintained. To correct the problem, he wants to crack the sacrosanct Land and Water Conservation Fund, taking money the law now sets aside for new park purchases and using it for upkeep of existing parks instead.

To the consternation of many environmentalists, Townsley, in front of the television camera, will back Watt on that issue. He will be less helpful on others.

"It's something of an illusion--a nice one--to think we are going to acquire great new parks now," Townsley says. "Long before President Reagan was elected, the Park Service knew it needed a resting, a settling-in time to take care of what we already have."

Joan Anselmo, Yellowstone's spokeswoman, says the park's seasonal employes have been cut 20 percent in four years. The permanent work force, including rangers, is down 50 percent in the past 20 years. Reagan administration cuts and youth summer work programs will hurt even more next year.

Inflation has cut so savagely into Yellowstone's budget that Townsley has had to eliminate jobs to pay the skyrocketing fuel bills for taking tourists' garbage out of the park. In Yellowstone, garbage removal is more than a litter problem. It is a priority program for control and preservation of the famous Yellowstone bears. Other costs have skyrocketed, too.

Four years ago drinking water was so impure thousands of tourists became ill at one campsite. That problem was corrected at a cost of $20 million, but the annual cost of the park's sewer system has risen from $12,000 to $300,000, partly as a result, while the overall park budget has remained the same.

Because of this, the park has cut back on such basic services as night patrol of Yellowstone's 350-mile road system and boat patrols on treacherous Yellowstone Lake where three persons drowned last year.

Still, as Labor Day passes and the peak tourist season with it, Townsley thinks it is going too far to call Yellowstone's condition "shameful."

"The rhetoric sometimes gets out of hand and it all becomes a battle of one-liners," Townsley says of the controversy surrounding Watt. "Some of our people have trouble with some of the things that are said."

And Watt will find that his policies outside the park have Townsley in a different camp altogether. Nothing makes the superintendent more nervous than nearby energy exploration--efforts to tap thermal fields on the Idaho boundary of the park, threatening the geysers, and particularly the active oil exploration near the Wyoming borders.

Oil exploration is moving north up the side of the Continental Divide from Colorado to southern Wyoming. And a huge new controversy is brewing over oil leases in the Washakie Wilderness Area and Shoshone National Forest on the park's east boundary.

Townsley predicts the Washakie will create greater controversy than northern Montana's Bob Marshall Wilderness Area, now embroiled in lawsuits after Congress blocked Watt's hopes to drill there. Both the Marshall, which joins Glacier National Park, and Washakie are prime habitats of the endangered grizzly bear. The mean but shy grizzly flees from all development.

If nature's balance is altered outside the park, Townsley believes, the balance will be changed inside, too. Grizzlies, for example, have been known to travel as much as 800 miles in a week, crossing all the artificial boundaries. It is unrealistic to think that, contained in the park, the grizzlies can thrive, Townsley said. Still, Townsley fears the development and population growth accompanying the oil boom even more.

Drilling in Washakie, Townsley recently wrote to the head of the Shoshone National Forest, "would destroy the wilderness values in this wild, remote and indescribably scenic area adjoining Yellowstone National Park.

"It is the park's view that oil and gas leasing and development . . . will be detrimental to Yellowstone National Park."

That is not the view of Townsley's boss. But Townsley, a diplomatic and distinguished careerist, becomes almost passionate when he looks into a future with Yellowstone surrounded by oil boom towns.

It is that possibility, even more than budget cuts and inflation, that would make Yellowstone a "shameful" example for the American people, Townsley says. He watched the same sort of population growth change the nature of California's Yosemite National Park, where his father was a ranger.

"We need to make a commitment to minimum development, not maximum, of this part of the West," Townsley said. He reads the headlines that say oil is pumping $10 billion into the economy of the Rocky Mountain West and he knows that he is fighting a different kind of nature--man's nature.

Still, this kind of controversy will follow Watt as he moves through the park and makes the week-long swing through country that generally supports his policies and the megabucks they will bring in.

It is appropriate that Watt's helicopter will land him near the famous geyser that has erupted most faithfully for ages before man first visited Yellowstone.

Watt, in his eighth month as guardian of the nation's lands and parks, has caused almost as many eruptions almost as faithfully as the hourly fountain that helped draw a near record 2.4 million visitors to the nation's oldest park this year.

It is unlikely that either the natural or the political eruptions will halt with Watt's arrival.

In the park, 2,000 young summer workers also will greet Watt. They come from all over the country--wearing name badges like "Tillie, from Massachusetts"--waiting on tables and cleaning rooms in grand old hotels. Through the doors to the Old Faithful Inn's kitchen--safely out of the view of the tourists--the youngsters have pinned up a collection of anti-Watt cartoons.

A sample shows Watt, white-gowned and leading a crusade with a sign: "Jesus is returning." Behind Watt is an angry bear and behind the bear a stern-faced deer, marching in step. The bear carries a sign that says: "And He isn't happy." The deer's sign adds: "With James Watt."

A Sierra Club petition asking President Reagan to fire Watt swept through the hotel's young employes this summer, missing few signatures.

For the most part, outside the park Watt is viewed as a godsend by angry westerners who feel tied down by the federal government. In Billings, Mont., he will keynote a $500 Republican fund-raising party early this week. But even in Billings a $2 chili dinner is planned the same night as a protest. They are calling it a "chilly" dinner.

So goes it for James Watt as he travels through his native West trying to sell his philosophy of mixing man's nature with nature's nature.

In the way back from Two Oceans, Sweaney's Cesna briefly circles a new fire--a small puff in the forest framed in a view from the tightly turning airplane. By radio Sweaney directs two rangers walking into the small fire.

"If it's man-made, we'll snuff it," he says. "If it's a lightning fire, we'll let it go." Outward from the puff, the forest expands everywhere, but in different tones of old fire scars ranging in age from two-year-old brown to century-old light green. In two hundred years, Sweaney said, all of Yellowstone's lodgepole pines would burn and regenerate themselves naturally if left alone.

Then the Cessna heads home along the Idaho border of the park. Another new puff wisps out of the green, a half mile inside the park boundary from the Gallatin National Forest. Sweaney talks a long while on the radio, giving coordinates, debating. Then he calls in the smoke jumpers. The wind can pick up these fires, move them into the crowns of the trees and whisk them quickly across man's borders.

Across the green in Gallatin National Forest, nature's ways are the same. Man's are not.