A half dozen men from the U.S. Park Service rallied around a tree yesterday on a gash in the Arlington mud abouve Spout Run. They listened as Virginia highway officials argued that the tree should yield to the inevitable, oncoming pavement of Interstate 66.

"It's only a locust," a tree consultant to the state Department of Highways and Transportation said.

"But it is a tree," replied a park ranger in his best, stern Smokey the Bear tones.

In the end, the locust tree won.

Others were not so lucky, as highway and park service officials marched the 1,000-foot boundary that the parkland bordering George Washington Memorial Parkway will share with the interstate highway that is inching its way toward the Potomac River through mud and controversy.

Park rangers marked about 40 trees yesterday, mostly maple, beech and hickory, to be either felled or trimmed because they lie too close to where park and pavement will meet. A team of park service tree specialists moved warily, trunk by trunk, along the boundary listening to the highway officials' suggestions.

"We've not out here cutting any deal with them," Park Superintendent Don Castleberry said. "We're going to take everything back to the office and consider it." But Castleberry displayed little happiness when a tree was marked with a red "R" - meaning "remove".

"The whole thing (I-66) has been a controversy for years, and this is only a minor element," he said."But a decision to cut or trim a tree is important to me."

The park service team approved the cutting of a number of trees because construction of the retaining wall on the park side of the highway will damage their root systems. But they were clearly happier when a tree needed only a trimming.

"It's not the best," said park maintenance chief Hillard Ratliff. "The best is like they are. But it's better to leave them than cut them."

The future of the Spout Run forest, a mature stand of tulip poplar, beech sycamore, maple, hickory and dog-wood, has been a subject of controversy among opponents of the interstate. None was present yesterday, however, when the trees' fates were being decided.