Growth Form and Life Histories of American Chestnut and Allegheny and Ozark Chinquapin at Various North American Sites

Abstract

PAILLET, F. L. (U.S. Geological Survey, MS 403, Box 25046, Federal Center, Denver, CO 80225-0046). Growth form and life histories of American chestnut and Allegheny and Ozark chinquapin at various North American sites. Bull. Torrey Bot. Club 120: 257-268. 1993.-The distribution, size, growth form, and stem histories of American chestnut (Castanea dentata (Marsh.) Borkh.) and chinquapin (Castanea pumila (L.) Miller) were studied at three sites in eastern North America to compare reproduction by sprouting and effects of chestnut blight on clone survival. The three sites included one in Massachusetts with chestnut only, one in Arkansas with chinquapin only, and one in Virginia with about equal populations of chestnut and chinquapin. Spatial distribution of living Castanea clones is similar at all three sites, with clones occurring in irregular clusters with densities ranging from less than one to more than 200 clones per hectare. Large stems of chestnut and chinquapin killed shortly after the first appearance of blight were mapped at the Massachusetts and Arkansas sites. Extensive areas with old logs and stumps but with few or no living sprout clones appear to indicate failure of these species to reproduce in established stands in pre-blight times. Examination of root collar structure, manner of sprout initiation, and stem form for both Castanea species shows a continuum of growth habits that range from the regular generation of sprouts from laterally extensive and persistent root collars typical of Allegheny chinquapin in Virginia to the periodic regeneration and replacement of both stems and root collars typical of chestnut in Massachusetts. The single distinct difference between sprout regeneration in chestnut and chinquapin is that chestnut sprouts appear to always generate new root collars whereas chinquapin root collars remain alive almost indefinitely. Occasional destruction of chestnut stems by blight does not seem to significantly influence clone survival despite minimal blight resistance in chestnut. However, chinquapin appears to have more natural resistance to blight than chestnut. This prolongs the lifetime of active cankers and increases the long term impact of blight by providing sources for the infection of basal shoots stimulated by the infection. Such a process may explain the large number of dead chinquapin sprout clones found in Arkansas, and a smaller but significant number of dead chinquapin clones found in Virginia.