Thirty-six years of change in an eastern hemlock-white pine stand in western Massachusetts

The vegetation of an eastern hemlock (Tsuga canadensis)-white pine (Pinus strobus) stand at Arcadia Wildlife Sanctuary, Easthampton, Massachusetts, was studied in 1963, in 1975, and again in 1998—99. Hemlock remained dominant from 1963 through 1999 despite extensive mortality of smaller stems. White pine and two minor canopy species, red maple (Acer rubrum) and black cherry (Prunus serotina), also declined. Changes in stem size structure of tree populations within the stand may have reflected in part increasing stand maturity, resulting in fewer and larger trees. In addition, low recruitment into the canopy and numerous tree deaths between 1963 and 1975 occurred at a time of widespread regional drought. Tree seedlings, nearly absent from the site in 1963, were well established by 1975, approximately five years after rainfall amounts returned to normal levels, but extensive mortality of canopy trees continued through 1998, particularly hemlock and black cherry. Tree deaths during this latter period coincided with defoliation by gypsy moths (Lymantria dispar) and wind throw during severe ice storms in the winter of 1996—1997. Hemlock wooly adelgids (Adelges tsugae) were not observed at the site until after the 1998 sampling; thus this study may serve as a baseline for assessing adelgid damage in the future.