Wildfires stunt pygmy pines’ growth, yet they thrive on it

Wildfires stunt pygmy pines’ growth, yet they thrive on it

27 November 2010

published by www.pressofatlanticcity.com

USA —  LITTLE EGG HARBOR TOWNSHIP – The pygmy pine trees that grow along the border of Burlington and Ocean counties are a biological oddity. They stand only a few feet tall, their trunks mangled and contorted, despite decades of growth.

A range of hypotheses has been floated over the years to explain their dwarfism, but the dominant theory stems from the trees’ relationship with fire. They not only tolerate fire, but these trees form one of the most flammable sections of the country.

An estimated 12,400 acres of pygmy forest is found in southern New Jersey, the largest habitat of its kind on Earth. Researchers say it developed that way because of how common it was for fire to sweep across the dry, raised area – absent of natural fire breaks, such as rivers and lakes – where wind blows easily over the surrounding flat land and pushes it east.

Modern experience, historical records and layers of ash in the soil show that fires have long been common in the Pinelands and remain a force for rejuvenation.

Walter Bien, director of Drexel University’s Laboratory of Pinelands Research, has been examining a deep layer of clay beneath an area surrounding the Warren Grove Gunnery Range in northern Bass River Township, Burlington County, that he believes holds minerals used by the roots above.

He thinks the way the trees slowly feed off this deeper pool of nutrients – a mix of the phosphorous and nitrogen the plants need – helps them recover from sudden and violent wildfires and survive in the long term.

They remain shortened from the bonsai-like way the fire periodically cuts them back. They hold a store of carbohydrates in their base, and when trimmed by fire, they pull from that store of energy to sprout again.

It takes time for that store to replenish, however, so they sacrifice height for the ability to endure.

“The whole system is really, really in tune with fire,” Bien said.

A pygmy forest

Andrew Windisch, a researcher with the state Department of Environmental Protection, spent a recent morning in the Stafford Forge Wildlife Management Area, where a hilltop offered a distant view of the canopy dominated by green pine needles and red oak leaves.

“A lot of people look down their noses at the Pinelands. It doesn’t get the respect of a rainforest, but it’s still important to worldwide biodiversity,” he said.

Windisch’s short-term mission is to knock back some of the oversized trees in the East Pine Plains, one of the two main locations of New Jersey’s dwarf pines. The other is the West Pine Plains on the Woodland Township-Barnegat Township border along Route 72.

He wants to restore the area to what he believes it originally looked like, with low bush and shrub cover that look up to pygmy pines as the tallest plants, not the dense forest it is today.

With the modern suppression of forest fires, the pines surrounding Warren Grove have grown large, taking advantage of a lull in what was historically common.

That has been to the detriment of other species that require an uncrowded canopy to thrive. Conrad’s Broom-crowberry is one modest but also rare plant species that grows close to the ground.

Windisch and volunteers have been trimming back trees and lighting their own controlled fires in an attempt to restore the pygmy forest that earned its name the “pine plains” when settlers first arrived because of its relative flatness.

The benefits of wildfire

Meanwhile, Bien has been examining the rare plants, mammals, reptiles and insects that live around the military base, such as the Pine Barren gentian, the southern bog lemming, the northern pine snake and a variety of moths and butterflies.

The cold-blooded northern pine snakes are fond of warming themselves in the areas left open to the sun’s rays through the military’s constant fire management in that area. The purple-flowering gentian also prefers open areas.

The mammals there, such as the white-footed mouse, have learned to survive frequent fires as well, by burrowing underground while the flames pass overhead. Even in enormous blazes, the heat does not carry far below the surface.

“Very few animals actually died in that fire,” said Bien, referring to a 2007 wildfire sparked by a wayward flare from an F-16 fighter jet. “The thermal inertia doesn’t go down, so things that could burrow survived.”

When wildfire was allowed to run unchecked, the pine seeds would scatter on the ground and have little competition from the bushes and trees that were consumed by the blaze.

The ash acts as a natural fertilizer, and what does not germinate is food for the surrounding wildlife.

Indeed, the day after wildfire devastated 26 square miles of East Pine Plains, the upland environment bustled to life: Native animals scoured the millions of pine seeds released when flames melted the sap trapping them in their cones.

That’s the scene Bien saw when he visited the area after the 2007 fire: It was not a wasteland, it was just the latest setting for rebirth.

“The thing I always leave people with,” he said, “is the idea that disturbance isn’t necessarily a negative word.”

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