RESPONSE OF IMPROVED AMERICAN CHESTNUTS TO PLANTING PRACTICES ON RECLAIMED SURFACE MINED LAND

摘要

Hybrids of chestnut that are botanically indistinguishable from American chestnut {Castanea dentatd) and have the blight-resistance of Chinese chestnut {Castanea mollissima) are being developed by the American Chestnut Foundation. Reclamation of mined land in the Appalachians can aid the introduction of these hybrids because of the coincidence of the Appalachian coalfield with the central range of the American chestnut and because of the large areas of land opened up by mining that are available for afforestation. There are questions about whether mined lands can be a suitable habitat for the American chestnut, how the survival of various backcross generations from the breeding program will compare in the field, and the best planting practices to aid establishment. Two experiments were begun to test the performance of several breeding generations of chestnut on reclaimed surface mined land, chestnut compatibility with three ground cover types, and the effect of establishment method. Six breeding generations of chestnuts were direct seeded in 2008 within three different groundcover seeding mixtures: a conventional mine-reclamation mix of tree-competitive legumes and grasses, a tree-compatible mix of less-competitive legumes and grasses, and annual ryegrass only. The 2008 experiment was replicated on three different sites. These trees were planted as nuts in a mix of potting soil, native forest soil and mine soil, and within a tree tube shelter. After two years of growth, the annual ryegrass treatment allowed greater survival (71%) than the conventional tree-competitive seeding mix (50%). In 2009, five breeding generations were planted on four sites, with half planted as unprotected, bare-root seedlings and the other half direct seeded with shelters. After one season, survival of the bare-root seedlings (83%) was higher than that of the direct seeded trees (76%) and the first-year total height of the bare-root seedlings (470 mm) was also greater than that of the planted nuts (347 mm). Survival and growth varied among the various hybrid breeding generations, but none demonstrated consistently superior performance. Labor, time per tree for planting, and supply costs were much greater for the direct-seeded trees than for those planted as bare-root seedlings. Overall, early chestnut survival on a variety of reclaimed mined land is comparable to that of other Appalachian hardwood species. These results suggest that if blight resistance can be effectively conveyed through breeding, reclaimed mined land has potential for use in restoration of the American chestnut as a component of reestablished multi-species forests across central Appalachia.