A biogeographical study of the American chestnut: An evaluation of intentional introgression and a spatial analysis of chestnut habitat in Maryland

The American chestnut (Castanea dentata) was once a widespread foundation species in the eastern forests of the United States; the importation of the chestnut blight (Cryphonectria parasitica ) effectively wiped it out as a canopy tree in the early 1900's, but many sprouts remain. The American Chestnut Foundation has been breeding American and Chinese chestnuts together since 1989 in an effort to produce a resistant tree for restoration. They have also worked with the Appalachian Trail Conservancy MEGA-Transect to have citizen science volunteers collect data on sprout distribution. The purpose of this thesis was to do two studies to contribute to the biogeographical knowledge base regarding the tree. First, a morphological analysis of backcrossed trees was performed to determine whether the progeny were significantly more similar to American than Chinese chestnut. Results indicated that they were indeed mostly indistinguishable from the American chestnut. Second, a spatial analysis was executed on the distribution of sprouts along the Appalachian Trail in Maryland, to determine what environmental and geographical variables are most predictive of high chestnut sprout density. Solar radiation and elevation were the most significant predictors, although the percent of variance explained by them was very low. Both of these studies were completed in collaboration with The American Chestnut Foundation.