Many forested landscapes around the world are severely altered during mining for their rich mineral and energy reserves. Herein we provide an overview of the challenges inherent in efforts to restore mined landscapes to functioning forest ecosystems and present a synthesis of recent progress using examples from North America, Europe and Australia. We end with recommendations for further elaboration of the Forestry Reclamation Approach emphasizing: (1) Landform reconstruction modelled on natural systems and creation of topographic heterogeneity at a variety of scales; (2) Use and placement of overburden, capping materials and organic amendments to facilitate soil development processes and create a suitable rooting medium for trees; (3) Alignment of landform, topography, overburden, soil and tree species to create a diversity of target ecosystem types; (4) Combining optimization of stock type and planting techniques with early planting of a diversity of tree species; (5) Encouraging natural regeneration as much as possible; (6) Utilizing direct placement of forest floor material combined with seeding of native species to rapidly re-establish native forest understory vegetation; (7) Selective ongoing management to encourage development along the desired successional trajectory.

Typical reclamation practices in the central Appalachian coal region often use compacted spoils as a topsoil replacement, and these soils are revegetated with aggressive grasses and legumes. This restoration approach results in an herbaceous-dominated landscape with limited natural succession by native flora. An alternative restoration method is to save topsoil prior to mining, stockpile it during mining, and then replace it on uncompacted spoils to ''inoculate'' the site with native plant species. In an effort to test this approach, vegetation assessments were performed at a relatively undisturbed forested site in Clay County, Kentucky, U.S.A. Eight 15 3 15-m plots were established, and soils from individual plots were used in seed bank studies both in the greenhouse and on loose-dumped mine spoils. Bulk soil samples were removed from the plots and subjected to cold stratification for 13 weeks, after which seeds were allowed to germinate under greenhouse conditions for 1 year. Additional topsoil (approximately 1.5 m 3 from the upper 0-20 cm) was removed from the plots and replaced on fresh spoil in eight 2 3 5-m plots. Controls consisted of uncompacted spoil material substrate only. A total of 105 species emerged in the greenhouse from the seed bank. On the relocated topsoil, 69 species were recorded of which 39 were also observed in pre-mine vegetation surveys. Ten of the 17 most important pre-mine forested site species emerged from the relocated topsoil treatments on the mine site. Our results indicate that application of topsoil could enhance plant diversity and native species reestablishment on surfacemined lands.

Six research plots were established on a surface mine for the purpose of evaluating the forest productivity potential and hydrological and water quality characteristics of three different loose-graded spoil types. The three spoil types were: (1) predominately brown, weathered sandstone (BROWN); (2) predominately gray, un-weathered sandstone (GRAY); and (3) mixed weathered and un-weathered sandstones and shale material (MIXED). The average area of the six plots was approximately 3,658 m 2 . The physical and chemical soil characteristics that gave the BROWN spoil type a predictably higher productivity potential and natural regeneration than the GRAY and MIXED spoil were its finer soil texture, higher CEC and P concentration, and a pH that was more suitable for native hardwood trees. Four species of tree seedlings were planted into the spoils. Growth and survival of the planted trees were evaluated for three years. As an indicator of natural succession potential, percentage ground cover of volunteer vegetation on the three spoil types was also evaluated. By the third year (2007) after planting, the BROWN spoil type had a significantly higher average tree volume index than the MIXED spoil and MIXED was significantly higher than GRAY. Ground cover from natural regeneration was found to be 66.4% on the BROWN spoil (61 different species), 5.8% on the MIXED spoil (35 different species), and less than 2.0% on the GRAY spoil (12 different species). Results showed that the loose-graded spoil in this experiment was characterized by low discharge volumes, small peak discharges, and long durations of discharge and had hydrologic characteristics of a forested watershed, even at this early stage of development. Generally, concentrations of Ca, Mg, and SO 4 2-decreased over time in GRAY and MIXED and increased in BROWN. The pH of the water discharge from all three spoil types has increased from about 7.5 to 8.5. Although the average electrical conductivity (EC) in water discharged from the BROWN spoil remained relatively level during the study period, the GRAY and MIXED appears to be on a downward trajectory from about 1500 µS cm -1 to about 500 µS cm -1 . The latter value of EC has been reported as the apparent threshold at which the benthic invertebrate community returns to drastically disturbed headwater streams of eastern Kentucky and adjacent coal-producing Appalachian 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.

Reforestation research on mined lands has shown that loosely graded topsoil, weathered sandstone and/or other non-toxic topsoil substitutes are suitable growing media for establishing native forests in Appalachia. Reclamation practitioners however, have expressed confusion as to what constitutes the best available material other than topsoil. Six research plots were established on a surface mine for the purpose of evaluating the influence of three different loosegraded spoil types on tree performance. The three spoil types are: (1) predominately brown weathered sandstone; (2) predominately gray un-weathered sandstone; and (3) mixed weathered and un-weathered sandstones, and shale material (mine-run spoil). The total area of each plot is approximately 4,050 square meters (one acre). Four species of tree seedlings were planted into the spoils. Growth and survival of the planted trees were evaluated for two years. As an indicator of natural succession potential, percent ground cover of volunteer vegetation on the three spoil types was also evaluated. Preliminary observations indicated that by the second year (2006) after planting, the gray plots had an overall higher average survival (96%) than the mixed (84.5%) and brown plots (83%). The brown sandstone plots however, showed significantly more growth in height and diameter than the gray and mixed plots. Ground cover from natural regeneration was found to be 42.3 percent on the brown plots (40 different species), 2.6 percent on the mixed plots (21 different species), and less than 1 percent on the gray plots (6 different species).