TREE GROWTH ON RIPPED, COMPACTED, AND SLIGHTLY COMPACTED GRAY SANDSTONE TOPSOIL SUBSTITUTE ON A SURFACE COAL MINE IN WEST VIRGINIA 1

Steep topography and thin native soils characterize the coal mining regions of southern West Virginia. State and federal regulations require replacement of native topsoil during reclamation for re-establishment of a vegetative cover. Due to hazards and expense associated with collecting this thin layer of soil before mining, regulators have allowed mine operators to use substitute topsoil materials, including weathered (brown) and unweathered (gray) geologic materials for growth media. For pasture and hayland post-mining land uses, substitute materials provide suitable physical and chemical properties for establishment and growth of forages with fertilization and liming. When reforestation is the post-mining land use, regulations in West Virginia require a 1.2 m layer of native topsoil and brown weathered sandstone, but unweathered materials may be used if native topsoil quantities are insufficient. This study examined tree growth on areas where brown and gray sandstone materials were applied to the surface as growth media at the Samples Mine in West Virginia. In a study already published at this site, we found significant differences in tree growth on brown and gray sandstone plots. For this study, we selected two additional gray sandstone plots for comparison to the original brown and gray plots. The two original sites were brown sandstone compacted and gray sandstone compacted, and we added nearby plots of gray sandstone slightly compacted and gray sandstone compacted and then ripped. Average pH ranged from 7.3 to 7.9 on the gray plots compared to 5.4 on the brown plot. Tree growth on brown sandstone was more than triple that of tree growth on all of the gray sandstone plots. Mean tree volume index on the brown compacted plot was 3108 cm 3 while mean tree volume index was significantly lower on the gray compacted plot (909 cm³), the gray slightly compacted plot (407 cm 3 ), and the gray ripped plot (885 cm³). Eight years after reclamation, the gray sandstone plots, whether slightly compacted, compacted, or ripped, showed poor tree growth compared to brown sandstone. Gray sandstone has proven to be an inferior topsoil substitute for reforestation on this site.