Resurrecting the Lost Flames of American Chestnut
Loss of native foundation tree species to introduced pests profoundly alters the structure and function of many forest ecosystems. Recent advances to resurrect or prevent the loss of species by developing resistant hybrids hold promise, but uncertainty remains about the potential impacts of introducing a novel genotype on ecological processes, such as fire. A classic example of a non-native, pathogen-caused loss of a foundation species is American chestnut (Castanea dentata), a species now functionally extinct from the eastern US but undergoing experimental trials to resurrect the species with a putatively disease-resistant genotype. We compared the litter flammability among American chestnut, Chinese chestnut (C. mollisima), and a population of first intercross, third-generation backcrossed hybrid (BC3F2) using laboratory burning experiments. Litter flammability of American chestnut was consistently greater than Chinese chestnut, whereas the hybrid had an intermediate flammability or more closely resembled Chinese chestnut flammability by some measures. Greater flammability in American chestnut was associated with a longer leaf structure with greater curling when dry. American chestnut had flammability properties consistent with other pyrophytic species present in contemporary fire-prone ecosystems. The loss of American chestnut may have altered litter flammability of some eastern US forest ecosystems, a result more commonly associated with compositional changes in conjunction with fire exclusion and other disturbances. Resurrecting American chestnut with a hybrid genotype may mitigate this change in areas where less flammable species have replaced American chestnut. Resurrection of lost foundation species through introduction of resistant genotypes may represent a resounding ecological success story, but unanticipated changes to ecological processes, such as fire, should be considered.
Keywordsfire ecology disease resistance global change litter flammability mesophication restoration resurrection ecology
Laboratory burning and moisture trials were assisted by L. Rios, A. Cowen, K. Dedrick, T. Bradley, and J. Avitia. Field collections of samples and leaf scans were conducted by S. Greenler. Discussions with J. Kreye and D. Orwig were helpful in advancing our thoughts on the topic. Two anonymous reviewers also provided helpful suggestions and comments to an earlier draft. Financial support for this research was provided by the USDA National Institute of Food and Agriculture, McIntire-Stennis Cooperative Forestry Research Program at Humboldt State University (Project #CALZ-157) and Purdue University (IND011557MS), the National Fire Plan, and Hardwood Tree Improvement and Regeneration Center.
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