Genetics and Silvicultural Treatments Influence the Growth and Shoot Winter Injury of American Chestnut in Vermont

Abstract

The backcross breeding of American chestnut (Castanea dentata [Marsh.] Borkh.) with Chinese chestnut (Castanea mollissima Blume) may provide an effective method to increase resistance against chestnut blight and help restore American chestnut throughout its historic range. However, the comparative adaptation (e.g., cold hardiness and growth) of American and Chinese chestnut source material in the north has been largely overlooked. We assessed first-year growth and shoot winter injury of 13 genetic sources of American chestnut and 2 sources each of Chinese chestnut and red oak (Quercus rubra L., a native competitor) under three silvicultural treatments (open, partial, and closed canopy overstories) in Vermont, USA. Seedlings grown under open canopies that provided greater access to light exhibited greater growth than seedlings grown under partial and closed canopies. However, open canopies also resulted in lower winter temperatures that increased winter injury. Chinese chestnut seedlings had significantly greater growth but experienced greater winter injury than American chestnuts, whereas red oaks generally grew the least and experienced intermediate levels of winter injury. There were also differences in growth and winter injury among American chestnut sources: seedlings from warm and moderate temperature zones (based on meteorological data recorded near source origins) grew more in height and diameter but experienced greater winter injury than seedlings from colder climates.