Pa. forestland not hurt by longwall mine subsidence

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HARRISBURG, Pa. – An independent, scientific study has found no patterns of stress to forestland from longwall mine subsidence in Washington and Greene counties in Pennsylvania.

No evidence found.

“Using remote sensing techniques and field investigations, our contractor found no patterns of forest canopy stress due to longwall mine subsidence,” said Pennsylvania DEP deputy secretary for mineral resources management Jeffrey Jarrett.

“Researchers found that the areas where trees were experiencing significant stress was due primarily to insect damage, with only localized subsidence-related stresses at isolated locations.

“The insect damage was detected among trees in undermined areas and in those areas that were not undermined.”

About the study.

The study examined nine large forested tracts, ranging from 430 to 890 acres, in Washington and Greene counties.

Three areas had been undermined within the past five years; three had been undermined 10 or more years ago; and three areas were control tracts that had not been affected by longwall mining.

The primary evaluations were conducted in late June and early July 2000 using remote sensing data obtained from an airborne scanner unit, which simultaneously records data in different spectral channels.

Successful technology.

This technology has been used successfully in other studies to detect areas of stress in crops and forestland.

Areas that were identified as stressed in the images were examined on the ground by a survey crew led by Donald Davis, a forest pathologist with Penn State University.

The crew also examined trees in areas where subsidence effects from longwall mining were known – near ground cracks or above panel boundaries.

What they found.

“Evaluations of the remote sensing images and field observations revealed 48 areas within the study area that experienced significant forest canopy stress, ranging from one to 10 acres in size, due mostly to insect infestation,” Jarrett said.

Field crews also observed that trees in the immediate vicinity of ground cracks or scarps, the sloped edge of a ditch, from subsidence, which were tilted or had their roots exposed, had little crown damage.

Future studies.

This study is the first of the three independent studies commissioned by DEP to document the effects of subsidence from longwall mining.

In February, DEP awarded a contract to study the effects of subsidence on streams, wetlands and riparian areas, which is scheduled to be completed this fall.

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