Abstract

The American chestnut is functionally extinct in its former range from chestnut blight introduction. To reintroduce this foundation species, The American Chestnut Foundation is attempting to create blight-resistant American-Chinese chestnut hybrids. Much of the ecological research has used out-planted, nursery seedlings, with little known about seedling establishment, often the most challenging stage in a tree's life cycle. This study examined the survival, growth, and photosynthetic characteristics of American, Chinese, and F1 hybrid chestnut seeds planted in corresponding chestnut, and a silver maple (control) stand to determine establishment in conspecific and non-conspecific stands. If parent trees harbor distinct ectomycorrhizal communities, conspecific seedlings might benefit from connecting into these networks. Steady-state light response curves were measured to estimate photosynthetic parameters. Growth parameters (leaf, stem, root, shoot, and total mass; number of leaves and leaf area; stem basal diameter, and root:shoot ratio) of harvested seedlings were analyzed using two-way ANOVAs with seed-type and stand as factors. Where interactions were not significant, one-way ANOVAs were used to assess stand and seed-type effects. Maximum photosynthetic capacity was highest for seedlings in the American, lowest in the maple, and intermediate in the Chinese and hybrid stands, likely as a result of significantly higher light in the American stand. There were few and inconsistent significant interactions but stand and seedling-type had significant effects. In general, seedlings in the American stand had larger basal diameter, stem length, and shoot mass while the Chinese seedlings had larger basal diameter, stem length, shoot mass, despite germinating almost a month after the other seeds. ANOVA of ectomycorrhizal colonization found the American and Chinese stands had significantly higher inoculation frequency, while linear regression found that root and shoot mass increased with inoculation. Ectomycorrhizal inoculation varied by mature stand genotype, but with limited effects on conspecific seedling growth in monotypic plantation environments.

Keywords

American Chestnut, Castanea dentata, Chinese Chestnut, Castanea mollissima, Chestnut Blight, Cryphonectria parasitica

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