Using Before-After-Control-Impact-Pairs to Monitor the Effect of Longwall Mining on Mature Forest Stands in Southeastern Ohio

—Longwall mining involves complete removal of coal from underground seams which results in varying degrees of surface subsidence. In Belmont County, OH, The Ohio Valley Coal Co. is planning to mine the Pittsburgh No. 8 coal seam that lies 300 600 feet below the surface of an old growth forest, Dysart Woods. The mining, and associated subsidence, is opposed by several groups on the grounds that it may harm the old growth forest. This study was designed to investigate the potential impacts of longwall mining and other environmental stresses by intensively monitoring two forest ecosystems before, during and after mining. One stand (test stand) is in an area that was undermined at a depth of 400 500 feet below the surface during the winter of 2001-2002. The other is in an area that was not undermined. Otherwise the two stands are relatively similar. Several standards were used to indicate the health and vigor of the trees and stands, including tree growth rates, vigor ratings, and mortality rates. The two sites represent maturing stands of 5 acres or larger that possessed many of the attributes of old-growth forests. They both contained a mixture of species that are best described as “mesophytic hardwoods” including oaks, yellow-poplar, white ash, black cherry and a component of shade tolerant species such as American beech and sugar maple. The general approach was to collect pre-mining data for both stands from 1999 through most of 2001. The test site was mined under in late 2001, and then data were collected during all of 2002 to provide post-mining data. The ecological performance (tree growth, vigor, and mortality) was measured to determine if any divergence occurred between the two sites. The trees responded to the drought in 1999 with a generally reduced radial growth at both sites. In fact the two sites behaved in a similar manner over the course of the study except for the unusually high rate of growth for the test stand in 2001. But the tree response was not associated with mining, since the growth, vigor and mortality of trees at the test site did not change appreciably relative to the control site in 2002, the post-mining year. Introduction Coal removal by the longwall method is a type of deep mining process that extracts all the coal in a particular geologic layer (seam) resulting in subsidence at the surface and fracturing of rock layers above the mine. Concerns have been expressed by several groups that longwall mining could result in damage to forests, because of the hydrologic alterations caused by subsidence. Of particular concern is Dysart Woods, an old growth remnant of mesophytic hardwoods in Belmont County, OH. This study is designed to investigate the potential impacts of longwall mining on forests by intensively monitoring two forest ecosystems before, during and after mining. The methodology we used can be described as before-after-control-impact-pairs (BACIP). This approach is one of several similar methods termed “quasi-experiments” described by Zenner (2003) as being appropriate for elucidating ecological patterns and processes. In preparation for this study, two maturing hardwood stands with an oak component and other site and stand characteristics that were similar to old growth remnant forests in southeastern Ohio were located. One stand (test stand) is in an area that was mined under at a depth of 400500 feet below the surface during the winter of 2001-2002. The other is in an area that was not mined under. Although the slope aspects of the two stands were somewhat different, the stands †Professor (RRH) and Assistant Professor (JSR); Division of Forestry, West Virginia University, PO Box 6125 Morgantown, WV 26506-6125. RRH is corresponding author: (304)293-2941 ex 2424 or rhicks3@wvu.edu