PARENT SESSION
Oral Session 8: Forest Ecology I: Dynamics and Succession.
Presiding: A Fiala and D Kashian
Monday, August 2, 8:00 AM to 11:30 AM, Meeting Room B 117.

Fifty years of vegetation change in the Connecticut College Arboretum relative to site conditions and historical disturbance.

Small, Christine^*,1, ¹ Connecticut College, New London, CT, cjsma@conncoll.edu

ABSTRACT- Forests of southern New England have undergone dramatic changes over the past 350 years due to historical and ongoing disturbances including farming, grazing, altered fire regimes, storm damage, and exotic pests. The Bolleswood Natural Area, a 65 ha long-term research site in the Connecticut College Arboretum, provides a unique opportunity to examine natural dynamics and successional patterns in the central hardwoods-hemlock forest region with minimal human influence and to investigate the relative contributions of disturbance and site factors to community composition. All vegetation strata were sampled in 89-0.01 ha quadrats at ten year intervals from 1952 and 2002. Seven major vegetation types were identified based on NMS ordination and UPGMA cluster analyses, including wetland, post-agricultural, and upland forest communities. Between 1952 and 1992, basal area of Tsuga canadensis-dominated communities more than doubled (19.7 to 42.1 m²/ha) with recovery following 1938 hurricane damage. Introduction of the hemlock woolly adelgid (1987) caused rapid basal area decline by 2002, particularly on exposed ledge sites (28.8%), and greatly reduced T. canadensis importance on ledges and protected ravines (65-70% relative importance (RIV) decline). Wetlands showed little compositional change since 1952, with continued dominance of Acer rubrum (RIV 63%, 1952 to 2002), but doubled in basal area (16.8 to 32.1 m²/ha), representing a transition from formerly open marshes to wooded wetlands. Over the 50-year period, basal area across the Natural Area increased dramatically (92.6%) and - and -diversity declined. Composition shifted toward more mesophytic species, particularly T. canadensis (prior to the adelgid) and A. rubrum, with reduced Quercus spp. regeneration, likely due to prolonged absence from fire and logging. Such long-term studies serve as an unmanaged control in largely managed landscapes, contributing significantly to our understanding of regional vegetation dynamics and disturbance response.

Key words: long-term ecological research, hemlock decline, land-use history, community classification