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Distribution, composition, and age structure of black gum (Nyssa sylvatica) swamps in New Hampshire.
Crowley, Katherine1, Sperduto, Daniel1, Nichols, William1, Bechtel, Douglas2, 1 2
ABSTRACT- Black gum is a widespread tree species of eastern North America. In New England it is occasional and typically most abundant with red maple (Acer rubrum) in swamp settings. To examine variability in vegetation structure, composition, and age structure among black gum swamps in New Hampshire, we collected plot data and tree cores throughout the distribution of black gum in the state. Swamps generally occurred in small basins (< 20 acres) at low elevations (< 1000 feet); had shallow (average depth 0.9 meter), acidic (pH=4.4), moderately well decomposed peat; and were composed of species indicative of oligotrophic to weakly minerotrophic conditions. Canopy structure ranged from sparse woodland to closed-canopy forest. While size structure varied among stands, multiple size classes of black gum occurred in most plots, and the relationship between tree age and DBH was relatively strong. Together, these factors suggest that an uneven-aged stand structure may be typical of black gum swamps in New Hampshire. In addition, black gum may be the longest-lived broadleaf deciduous tree species in North America: we documented six sites with black gum trees older than 500 years of age, the oldest of which exceeded 679 years. Black gum's longevity, ability to sprout from a clonal root system, and tolerance of hurricanes and other disturbances appear to be important life history traits that help maintain uneven-aged, old-growth examples of black gum swamps in New Hampshire.
KEY WORDS: Nyssa sylvatica, black gum, old-growth, New Hampshire