Cobbs Creek forest is both healthy and dying

THERE IS a mystery deep in the Haddington Woods.

Behind the Cobbs Creek bocce courts on Vine Street near Daggett, there are two forests, standing side by side, as different as night and day.

One is the picture of good health - mature native trees towering toward the sun while a young generation of saplings flourishes beneath them.

The neighboring forest is dying, strangled by a thick jungle of invasive vines, shrubs and trees. Why?

"That's the $10,000 question," said Tom Witmer, director of natural resources for the city's Parks & Recreation Department. "We don't know the answer."

Witmer and Joan S. Blaustein, Parks & Rec's director of urban forestry, are spending the winter in Haddington Woods with project manager Curtis Helm, trying to find the answer and the antidote.

"We're cleaning up the degraded forest, restoring it, getting it moving on the trajectory of the good forest," Witmer said during yesterday's walk through both woods.

The healthy forest has mature oaks, maples, tulip poplars and other native trees, surrounded by saplings from their seeds.

"Here's an oak," Helm said, pointing to one of hundreds of saplings. "Anywhere else in Philadelphia, a deer would eat it. Not here." Another mystery.

But on the opposite side of a small creek, deer have decimated the saplings, and the degraded forest has few mature native trees because they've been crowded out by invasive Ailanthus that can grow to 70 feet high and Norway maple that can reach 90 feet.

Invasive vines like multiflora rose and porcelain-berry cover the surviving trees like a shroud.

Helm said contractors are cutting down invasive vegetation with a forestry mower - "like a lawn mower on steroids" - this winter, and killing the vines.

Before replanting next fall, they will install deer fences.

"The overabundance of deer wreak havoc on the forest you're trying to regenerate," Witmer said. "Deer eat seedlings and saplings so you can never get that new forest coming up underneath the canopy."

Blaustein said fencing off the vulnerable areas "will take deer out of the equation and we'll see what regenerates when you don't have deer pressure."

Michael DiBerardinis, deputy mayor for environmental and community resources, said "citizen scientists" will be the backbone of the reforestation.

"We'll train citizens to collect data in the park," he said. "They'll be out there doing diagnostic work, not just pulling invasives."

DiBerardinis envisions citizens from the Cobbs Creek neighborhood working with Parks & Rec foresters to revitalize Haddington Woods - and solve the mystery of its split personality.