When a tree toppled in a Mt. Lebanon woodland earlier this summer, it sparked debate over the very nature of, well, nature.

"We want to be a Tree City, USA, and we want beautiful trees, but we don't have enough in our budget to take care of them," said Lori Pearce, who has lived with her family near Bird Park since 1992.

In June, Mrs. Pearce was walking in Bird Park, one of the largest of Mt. Lebanon's 15 parks, with her three children, Henry, 10, Claudia, 8, and Lucy, 6.

Her friend, Teresa Kozlewchar, of Bethel Park, and twins, Eleni and Mark, 8, joined them.

With little warning, she said, a locust tree more than 100 feet in height came crashing down, leaving behind about 5 feet of trunk as it snapped.

"We were backpedaling, trying to get away. We probably had about four seconds and the tree kind of shifted, hitting other trees in the canopy," Mrs. Pearce said.

Although the trunk fell near where they stood, they avoided major injury.

"We were hurt, but not seriously. The tree left scratches; we could immediately see what looked like brush burns and scratches on our necks, on my hands.

"My 8-year-old took the worst of it, and she can't remember much. She must have thrown her arms up; she had bruises on the insides of them."

In the days that followed, part of the fallen locust that crossed the footpath was chopped up and removed by the municipal public works department. The rest was left where it fell, as per the policy of the Mt. Lebanon Nature Conservancy, which acts as consultant to public works.

Mrs. Pearce said that while she is grateful no one was badly hurt, she feels more should be done to cull sick and weakened trees. Fallen trees and brush, she said, should be removed because they pose a hazard.

"I've been told that the Nature Conservancy wants nature to be nature, so if a tree is damaged or dead, it should fall on its own.

"I, for one, have spent a lot of time in the woods in my life and I had always assumed there had to be a catastrophe like a lightning strike or high wind to topple a tree.

"There was no wind that day; it was gorgeous," she said.

The Conservancy doesn't maintain the parks, but it acts as an adviser, said Tom Kelley, director of public works. "Regarding the situation in Bird Park in particular, I have talked with Lori."

Beyond Mt. Lebanon's adherence to Conservancy policy, he added, there just isn't the money or manpower to check all the trees in all the parks on a regular basis. His department is also responsible for more than 10,000 street-level trees throughout the municipality.

In addition, there is an ordinance that allows public works to assess and act on "hazardous" tree conditions on private property.

"If someone calls up and says there is a hazard, a limb has fallen, we'll get out there. We will interrupt our regular work schedule," Mr. Kelley said. "But if it's just a standard tree trim, that's something that is scheduled."

His department has a crew of three. Mt. Lebanon removes up to 200 street-level trees each year that are diseased or damaged, he said.

Mt. Lebanon picked up an increase of about $25,000 to its proposed budget for forestry this year, pushing it to $238,070. This covers removal and maintenance of diseased and dying trees, basic tree trimming, replacement planting and some contractual services that include specialized trimming and pruning.

Mrs. Pearce, who said she recently called public works to assess a reportedly diseased maple near her front sidewalk, was informed it would be at least six months before it could be removed.

Removal of dying trees routinely is scheduled for the fall and winter months, said Mr. Kelley.

As for the problem with fallen trees in the parks, he said, Bird Park is a "passive park," like Twin Hills and Robb Hollow: "There really aren't any playground features in those parks.

"A lot of people use those parks and we hear from them, believe me, from regular people who find things they consider dangerous.

"Then we check them out."

What they can't do, he said, is routinely examine trees for signs of decay.

Even if we could, some [healthy-looking] trees fall, anyway, he said, noting a large, seemingly healthy oak blocked part of Orchard Drive a few years back.

The national Arbor Day Foundation has a designation of Tree City USA for towns that meet four standards of commitment to green space; Mt. Lebanon was awarded this status two years ago.

Mrs. Pearce said she is not impressed and still considers the park an unsafe place.

"There is a sleep over in Bird Park my son always goes to; they have it through the Mt. Lebanon recreation department," she said.

"I guarantee you, he is not going this year."