Sixty years of management and natural disturbance in a New England forested landscape

Abstract

Changes in species composition of overstory trees (percent of basal area) and size class were monitored over 60 years on 441 cruise plots located on the Bartlett Experimental Forest, a 1052 ha experimental forest in the White Mountains of New Hampshire. The plots were analyzed by elevation class, landtype (deciduous and coniferous), and year (1931–32, 1939–40, and 1991–92) within managed and unmanaged stands. The primary changes in species composition over the 60-year period were due to natural succession, which resulted in marked increases (doubling) of the eastern hemlock ( Tsuga canadensis (L.) Carr.) component, and consistent decreases in paper birch ( Betula papyrifera Marsh.), yellow birch ( B. alleghaniensis Britton) (at medium or low elevations), and aspen ( Populus spp.). Timber management resulted in small decreases in the beech ( Fagus grandifolia Ehrh.) and red spruce ( Picea rubens Sarg.) component and slight increases in sugar maple ( Acer saccharum Marsh.). Natural disturbances (beech-bark disease and hurricane damage) had only minor effects on species occurrence. No consistent evidence of red spruce ( Picea rubens Sarg.) decline was detected. Eastern hemlock, a climatically sensitive species in northern New England with a limited elevational range, increased dramatically at moderate to low elevations, but showed little tendency to invade the highest elevation class; apparently, the warming trend reported elsewhere in New Hampshire is not occurring, or the species are not responding in terms of changes in elevational distribution. The results emphasize the resilience of New England forests and their resistance to exogenous disturbance.