Influence of spoil type on afforestation success and natural vegetative recolonization on a surface coal mine in Appalachia, United States

Surface mining has altered a vast land area in the Appalachian Region, threatening highly biodiverse native forest, contributing to habitat fragmentation, and generating severely disturbed sites that are unsuitable for succession to native ecosystems. Although there are many factors that influence species colonization and establishment on these sites, selection of topsoil substitutes suitable for native species is of particular concern. A series of experimental plots was installed in 2005 on a reclaimed mine site in eastern Kentucky, United States, to examine the suitability of three spoil types (unweathered GRAY sandstone, weathered BROWN sandstone, and MIXED sandstone/shale) as topsoil substitutes. Bareroot 1:0 seedlings of four native hardwood species (Fraxinus pennsylvanica, Quercus rubra, Q. alba, and Liriodendron tulipifera) were planted in the spoil. Seed required for ground cover was not applied so that natural colonization could be evaluated. Two years after installation, researchers concluded that tree growth was highest on BROWN; in addition, species richness and ground cover of volunteer vegetation were higher on BROWN. In 2013, tree volume was over 50 times higher in BROWN than GRAY. In addition to planted hardwoods, naturally colonizing vegetation provided nearly 100% cover on BROWN compared to 20% on MIXED and less than 10% on GRAY plots. Species richness of volunteer vegetation continued to be higher on BROWN (41) than GRAY (30) or MIXED (30), with native species comprising 65-70% of total species richness on all plots. Findings suggest that when topsoil substitutes are used, weathered spoils are more favorable to reforestation than unweathered spoil.