Imperiled Ecosystems in a Shifting Climate
2016 Atlantic White Cedar Symposium
May 24-26, 2016

Hotel 1620, 180 Water St., Plymouth, MA

Examining historic growth patterns of Atlantic white cedar in contrasting hydrological conditions within the Great Dismal Swamp

K. Kowalski

kristina.kowalski.10@cnu.edu

R. B. Atkinson

atkinson@cnu.edu

Department of Organismal and Environmental Biology, Christopher Newport University

Abstract
Chamaecyparis thyoides (L.) B.S.P., or Atlantic white cedar (AWC), is an obligate wetland tree that once dominated the Great Dismal Swamp (GDS), located on the eastern VA/ NC border. However, the species now exists in small, scattered stands. Today, the GDS contains over 315 km of ditches which have lowered the local water table in some areas. Previous research found AWC growing in well drained soils have greater radial growth than those in poorly drained soils. The purpose of this study is to assess radial growth of AWC in saturated and drained soils within the GDS. Two perpendicular samples were collected from 10 mature AWC in each site; increment cores in the saturated site, and cross section radii in the drained site. Ring widths were measured to the nearest 0.001 mm using a boom microscope; cross dating and analysis were performed using R Studio. Raw ring widths were transformed into cumulative basal area increments (CBAI) in order to investigate growth trends at both sites. Slopes of CBAI at the saturated site were greater (not significantly) than the drained site over the entire course of the study, however between 1966 and 1992 the drained site had greater slopes (p=0.02). An ANCOVA testing the entire course of the study found no significant influence of water levels or site on slope of the CBAI, however results suggest that site had a significant influence on CBAI when controlling for water level between 1966 and 1992 (p=0.05). Results suggest that site history, such as competition and ditching, may have been more influential than current water levels on tree growth.  The results from this study may be used to better understand growth trends of AWC in different management units throughout the GDS.

Key words: dendroecology, Great Dismal Swamp, basal area increments, ring width index.