Distribution and Persistence of American Chestnut Sprouts, Castanea dentata (Marsh.) Borkh., in Northeastern Ohio Woodlands

Sprouts and stumps of American chestnut, Castanea dentata [Marsh.] Borkh., were mapped from data collected at three forested sites of varying size and historical background in Cuyahoga County of northeast Ohio to compare the species' present distribution with that of its historical distribution in the mentioned areas. Sprouts were absent from one site despite a dense population of remnant chestnut stumps. Distribution of sprouts within the two remaining sites was sparse except for localized high concentrations. In addition to the aggregated pattern, sprout distribution was somewhat shifted from chestnut stump distribution indicating that such stumps are not the direct sources of regenerative tissue, but were the likely seed sources for younger, active root systems presently generating sprouts. Data collected to assess sprout location in relation to canopy changes indicated a continued association of American chestnut with white oak, Quercus alba, and red oak, Quercus rubra. Variations in sprout distribution are related to past land use and the subsequent stage of development of each site. The absence of sprouts from the old growth forest is attributed to competitive exclusion by shade tolerant species—mainly sugar maple, Acer saccbarum, and American beech, Fagus grandifolia. Although comparisons of sprouting rates versus death rates over a three year period indicated a 30% increase in the number of chestnut stems giving the appearance of a growing population, succession toward beech-maple forests was evident at all three sites as is the case in many forested areas of this region. OHIO J. SCI. 95 (4): 281-288, 1995 INTRODUCTION At the beginning of this century, eastern deciduous forests displayed stands of American chestnut, Castanea dentata [Marsh.] Borkh., that ranged over 200 million acres from Maine to Georgia west to the Mississippi (Peattie 1950). The chestnut's tolerance of a wide range of soil conditions and temperature differences made it not only a climax species of the oak-chestnut forest in its primary range of the southern Appalachians and Northern Blue Ridge area, but it was a major constituent of the adjacent mixed mesophytic forest. Chestnut could also be found as a climax species in physiographic climax communities as well as in developmental communities within the western mesophytic forest and the beechmaple forest of the glaciated area just north (Braun 1950). Like a number of the deciduous species tolerant of colder temperatures (heech-Fagus grandifolia, red maple-Acer rubrum, sugar maple—Acer saccbarum, white oakQuercus alba) the expanse of chestnut had continually broadened northward for approximately 25,000 years with the retreat of the Wisconsin Glacier (Sears 1930). Within the area of Cuyahoga County, OH, recognized as a part of the beech-maple climax region, are remnants of oak-chestnut communities. Capable of growing on the young podzolic soils of glaciated territoiy, such communities may have been able to sustain themselves for as long as the topographic form upon which they thrived endured. Now these communities show evidence of transition toward the beech-maple climax species of the area (Braun 1950). Important to note is that this region's forested areas are of secondaiy growth following the 'Manuscript received 8 August 1994 and in revised form 12 September 1995 (#94-18). decline of agriculture and the onset of urbanization and industrialization. The character of the soil that would likely have maintained more of these oak-chestnut communities as self-sustaining physiographic forests has been altered toward more mesic conditions through grazing, plowing, and fire suppression. To compound the dynamics of forest succession in these oak-chestnut communities, the invasive fungus subsequently identified as Cryphonectria parasitica [Murr.] Barr (formerly Endothia parasitica [Murr.] And.) was inadvertently introduced to America via a shipment of lumber from the Orient (Peattie 1950). Since its introduction, perhaps as early as 1905 (Merkel 1905), the blight fungus quickly spread throughout the chestnut range, killing 3-5 billion chestnut trees (Nash 1988) faster than they could reproduce and leaving little chance for blight resistance to evolve. The character of the forests in which chestnut dominated have changed significantly as young oaks filled the voids or beech and maple took root in forests already showing transition toward more shade-tolerant species (Braun 1950). In later attempts to halt the spread of blight and retrieve valuable lumber, the Civilian Conservation Corps (CCC) and the Work Projects Administration (WPA) had many chestnuts felled, thereby further reducing potential genetic sources of blight resistance. Because few chestnuts reached sexual maturity in the presence of the blight, vegetative regeneration of tissue from living root crowns has been the only means of eluding extirpation from Ohio. There are a number of conservation efforts of the American chestnut. In addition to its obvious use as a food resource for wildlife and for its rot-resistant lumber, there are important insights to be gained. Scientifically, the fungal epidemic and the response of Castanea offer a continuing glimpse into a prolonged, adversarial, 282 AMERICAN CHESTNUT POPULATION IN OHIO VOL. 95 host-pathogen relationship. The diminution of a dominant species in such a short period of time makes clear the impact of human endeavors and the need to preserve this species and others through an interdisciplinary approach in an effort to secure biodiversity. Perhaps most apparent is the need for controls in the movement of organisms. Two promising directions of research are presently being pursued with the goal of returning the American chestnut to a useful canopy tree. One approach is through hybridization. The American Chestnut Foundation has been crossing Chinese chestnut (Castanea mollissima Bl.) and Japanese chestnut (Castanea crenata Sieb. & Zucc.) with American chestnut in an attempt to combine blight resistance, a characteristic of the Oriental species of Castanea, with the favorable lumber qualities of the American chestnut in the resulting hybrid. The second approach attempts to exploit a natural occurrence of less virulent strains of C. parasitica. Hypovirulent strains carry a virus-like double stranded RNA molecule referred to as HAV or hypovirulence associated virus (Shapiro et al. 1991) which invades the cytoplasm of other strains of the blight after anastomosis (Anagnostakis 1987). The presence of dsRNA in hypovirulent strains is associated with phenotypic distinctions from the original virulent types, such as reduced sporulation, reduced pigmentation, and superficial canker fermentation (Hebard 1982, Shapiro et al. 1991). Use of hypovirulent strains of C. parasitica have been tried as a biological control of chestnut blight in Connecticut orchards with some success (Anagnostakis 1990). Such efforts may eventually lead to the introduction of genetically altered chestnuts or weakened strains of the blight fungus into natural areas where American chestnuts previously existed. MATERIALS AND METHODS American chestnut sprout populations were observed in three forest sites in Cuyahoga County, OH. The sites are located within three reservations of the Cleveland Metroparks. These sites are the A. B. Williams Memorial Woods of North Chagrin Reservation, a ridge along a portion of Tinker's Creek in the Bedford Reservation, and an area just east of the Brecksville Nature Center in the Brecksville Reservation. Since the park's inception in 1917, the purchase of each reservation has afforded them protection from most disturbances. All study sites have a number of chestnut stumps. Sites at Bedford and Brecksville are secondary growth forests, while the A. B. Williams Memorial Woods display remnants of original forest altered only by climatic succession, not by farming or grazing (Williams 1949). A grid was established at each of the three sites. In North Chagrin, the grid encompassed 7,200 m; in Bedford, 18,800 m; and in Brecksville, 32,400 m (Figs. 1-3). The size of the grid was determined by natural or manmade boundaries. Each grid, by compass and meter gauge, was then divided into 20 m by 20 m quadrats. Each quadrat was traversed at 5 m intervals during late spring and throughout the summer in search of American chestnut stumps and sprouts. Sprouts were identified by phenotypic characteristics of their leaves described by Gleason and Cronquist Scale: Area: Stumps: Sprouts: Canopy: 1.3 cm = 20 m 18* 800 m • 33 •32 D beech maple • oak FIGURE 1. Distribution map of American chestnut stumps and sprouts over 18,800 m at the Bedford site. The distribution of sprouts is aggregated under oak canopy and exhibits segregation from chestnut stumps. OHIO JOURNAL OF SCIENCE P. A. SCHWADRON 283