Surface mine reforestation research: Evaluation of tree response to low compaction reclamation techniques

In 1996, a multidisciplinary group of researchers at the University of Kentucky initiated a study on the Starfire surface mine in eastern Kentucky to evaluate the effects of soil compaction and two organic amendments on the survivability and growth of high value tree species. Three types of prepared rooting medium were examined: compacted spoil, lightly compacted spoil, and uncompacted spoil. The compacted spoil was prepared using normally accepted spoil handling techniques that resulted in a smooth graded surface. The lightly compacted spoil was loose-dumped and struck-off with one or two passes of a bulldozer. The uncompacted spoil was loose-dumped and not further disturbed. In addition, organic amendments (mulches) were evaluated within the three reclamation techniques. The organic amendments used were processed hardwood bark mulch and a combination of straw and horse manure mulch. The following six species of trees were planted: white oak (Quercus alba), white ash (Fraxinus americana), eastern white pine (Pinus strobus), northern red oak (Quercus rubra), black walnut (Juglans nigra), and yellow poplar (Liriodendron tulipifera). Five of the six species, the exception being white ash, showed increased survivability as compaction was minimized. Additionally, the loose-graded techniques led to enhanced growth in height for the seedlings. The addition of organic amendments also showed additional benefit but results varied by species and by treatment. Results definitively show that strike-off and loose-dump techniques improve seedling height and survival. The data also suggest that even a small amount of traffic (i.e., one or two passes per the strike-off method) may result in enough compaction to significantly reduce survival and growth in some species, such as yellow poplar and white pine. In the backfilling and grading process, spoil material should be placed and compacted according to standard engineering practices so that the required stability and approximate original contour is achieved. However, the top 1.2 to 1.8 meters (4 to 6 feet) of material should not be graded or only lightly graded so that it is as uncompacted as possible.