FORTY YEARS OF FOREST SUCCESSION IN CENTRAL NEW ENGLAND

The first 40 yr of forest succession on permanent plots at the Harvard Forest in central New England followed the initial floristic composition model of forest succession. After the 1938 hurricane removed the previous white pine (Pinus strobus) canopy, species regenerated within 4-6 yr by sprouts, buried seed, and wind-blown seed, with no method of regeneration uniformly contrib- uting more to species success than another. Hemlock (Tsuga canadensis) was the only species suc- cessfully regenerating after 1948. Pin cherry (Prunus pennsylvanica) was the early dominant in size and numbers (5000 stems/ha). At year 10, pin cherry, red maple (Acer rubrum), white ash (Fraxinus americana), and red oak (Quercus rubra) were dominant. Species diversity had reached a maximum. By year 40, red oak and paper birch (Betula papyrifera) showed strong canopy dominance, making up only 7.5 and 4.9W, respectively, of total density but 37.5 and 12.5%, respectively, of the size- dominant stems. Red maple and white pine were also codominant in 1978. Some evidence for an intermediate stage dominated by red maple and gray birch (B. populifolia) was found. On one pre- viously hardwood plot, the same species were present, and similar trends in species composition and dominance were followed, but there was more surviving hemlock advance regeneration and a lower density of some shade-intolerant early dominant species. The canopy structure was loosely multilay- ered, and at any given point in succession, species tended to be found in characteristic layers, although these relative positions could change with time.