Replacement of native oak and hickory tree species by the introduced American chestnut (Castanea dentata) in southwestern Wisconsin

Abstract

American chestnut was introduced at West Salem, Wisconsin, about 1880 and had begun to replace native tree species in adjacent oak-hickory woodland before 1930. Chestnut is now an important canopy species over about 20 ha of forested ridge extending north and south of the original plantation. A smaller area of less than 5 ha is dominated by chestnut in both the canopy and understory. Chestnut seedlings and small saplings are more numerous along woodland edges and in recently disturbed soil, they are rare in the interior of ungrazed pasture and entirely absent from intensively grazed areas adjacent to chestnut-dominated woodland. Random sampling of recently established seedlings indicates that from 1 to 5 seedlings/(year ∙ ha) became established in undisturbed woodland between 1986 and 1988. The general pattern of chestnut distribution indicates the importance of woodland edges in chestnut propagation and the effects of livestock grazing in excluding chestnut. Replacement of native species by chestnut appears to have occurred in two steps: isolated groups of trees became established at favorable locations, after which many additional chestnut stems became established in the understory. The recent discovery and treatment of blight indicates that the West Salem site may not be available for study of blight-free chestnut in the future.