Performance and Phenotypic Variation of American Chestnut (Castanea dentata) Hybrids on Newly Reclaimed Mine Sites in Eastern Ohio, USA

Abstract

Surface mining for coal represents a significant form of anthropogenic disturbance on the landscape. Currently there are more than one million hectares of former mined land in the United States. New reclamation procedures are being examined to accelerate forest succession on former coal mine sites in eastern Appalachia. Our study was conducted on public lands that had been previously surface-mined for coal, reclaimed in 1978, and re-mined and reclaimed using new methods in 2007. We planted 535 American chestnut seeds in March 2008 at the study site in 107 blocks. Each block contained five seeds from five different genetic lines including Pure American, Pure Chinese, and three intergraded hybrid Chinese-American lines. We saw few significant differences in performance between pure American chestnuts and more advanced backcrossed generations of hybrid trees. However, Chinese chestnut and early-generation hybrids showed significantly better growth and survival measurements. The American Chestnut Foundation’s breeding program appears to have been successful at capturing a morphological fidelity between the latest hybrids and pure American trees. Trees with a greater percentage of Chinese parental material possess a suite of leaf characters that may make those hybrids better suited for the arid, high light conditions found on reclaimed mine sites (particularly thickness, length to width ratio, and pubescence). Development of goal-specific cultivars by the American Chestnut Foundation might aid in more successful restoration attempts but also may limit genetic diversity in those lines if intensive inbreeding or cultural cloning is utilized. Additionally, restoration at end-dump sites may need to pursue a phased system of introduction after initial extreme environmental conditions have been ameliorated by the use of early successional species in order to ensure the success of desirable species.