American Chestnut Establishment Techniques on Reclaimed Appalachian Surface Mined Lands

Successful afforestation of lands surface-mined for coal in Appalachia presents the opportunity to also restore American chestnut (Castanea dentata) within its native range, now that it has been bred for chestnut blight (Cryphonectria parasitica) resistance. Chestnut, before the blight, was an important component of the mixed mesophytic forest in eastern North America, which is now being impacted by ongoing mining (Wickham et al. 2007, Sayler 2008). Over 0.6 million ha of land in this region have been surface mined for coal (United States Office of Surface Mining 2010). The American Chestnut Foundation (ACF) has been breeding American chestnut with Chinese chestnut (Castanea mollissima) since the early 1980s using a backcross breeding technique to achieve a blight-resistant hybrid with the form and ecological functions of American chestnut (Hebard 2001, Diskin et al. 2006, Jacobs 2007). Properly reclaimed mined land, having little competing forest vegetation, provides space for planting potentially blight-resistant crosses. Research and practice have shown that native trees can be re-established successfully on coal surface mines when appropriate reclamation procedures are applied (Burger et al. 2005).

Three key aspects to establishing chestnuts on mined land are: 1) finding the most successful hybrid backcross generations of chestnuts; 2) developing the most effective method of planting them; and 3) establishing herbaceous plants for erosion control that are compatible with chestnut establishment. We initiated 2 experiments to determine more effective methods for establishing chestnuts on reclaimed mines. The herbaceous seeding trial, begun in 2008, tested the effects of herbaceous species and backcross generation selection on survival and growth over 2 growing seasons. The planting method trial, begun in 2009, tested the effects of tree planting method and backcross generation selection on survival and height during the 2009 growing season.

We planted 6 breeding generations of chestnut [2 lines of American and 1 each of Chinese and backcross (B1-F3, B2-F3 and B3-F2)], provided by the ACF, in mid-March 2008 with 3 hydroseed groundcover treatments at 3 locations in southwest Virginia. Sites were constructed with varying spoil materials to serve as growth media (weathered and unweathered sandstone, siltstone, and shale), and these materials were all loosely graded. Each of 3 blocks contained 3 treatment plots, each roughly 0.4 ha in size. We seeded each treatment plot with either: 1) a conventional mix, containing cereal rye (Secale cereale), orchardgrass (Dactylis glomerata), perennial ryegrass (Lolium perenne), Korean clover (Kummerowia stipulacea), birdsfoot trefoil (Lotus corniculatus), white clover (Trifolium repens), redtop (Agrostis gigantea), and weeping lovegrass (Eragrostis curvula); 2) a less competitive mix, containing annual ryegrass (Lolium multiflorum), perennial ryegrass, timothy (Phleum pretense), birdsfoot trefoil, white clover, and weeping lovegrass; or 3) annual ryegrass alone. The conventional mix was designed to create >90% ground cover within the first few months of a growing season after seeding. The less competitive mix was designed to create a moderate level of initial ground cover ("tree compatible") while eventually covering the soil surfaces fully, and the annual ryegrass treatment was intended to create the lowest level of ground cover by planted species while allowing recruitment of native plant volunteers. We applied fertilizer at an approximate rate of 22 kg/ha nitrogen (N), 68 kg/ha phosphorus (P), and 18 kg/ha potassium (K) as part of the hydroseeding mix across all treatment plots. We planted the chestnuts as seeds in 1 L holes filled with a mix of potting soil, native forest topsoil, and on-site mine soil. To protect seedlings from herbivores, we installed tree tubes (Tubex, South Wales, UK), 38 cm tall and 10-15 cm in diameter, around each nut. The nuts were left to germinate and grow without further management.

Table 1.

Cumulative groundcover, with percent ground coverage in parentheses, and genotype effects on survival and total height after 2 growing seasons for the herbaceous seeding trial. Mean separation (Tukey HSD, α = 0.10) is indicated by different letters vertically beside values within categories.

In addition to the herbaceous seeding trial, we...