McMillan, Brett A. , Day, Frank P. .
The ‘pimple’ dunes of Virginia’s barrier islands.
'PIMPLES' are peculiarly circular dunes found on the barrier islands of the Virginia Coast Reserve LTER site. Although pimples are typically <1.5 m higher than the elevation of the surrounding marsh and only 10-40 m in diameter, they may support several distinct vegetation zones. The obvious primary driver of these patterns is the availability of fresh water as determined by elevation. The importance of interactions between free surfaces of land, water bodies, and ground water, is a key concept at the VCR. We are studying plant assemblages on pimples and the environmental factors influencing them. Of special interest is the importance of secondary factors like aspect, slope, or soil nutrients to the distribution of species within the constraints of access to the freshwater table. We have used multivariate analyses of floristic structure on pimples to describe in greater detail the importance of the interaction of water table and elevation in determining species distribution. Water level best explained distribution of most hydrophytes, whereas height above marsh explained presence of xerophytes. Nevertheless, some plants considered belonging to marsh or dune appeared more plastic in their habitat preferences. Other seemingly generalist species were found to prefer specific aspects, i.e., eastern vs. western exposure. This probably reflects the importance of exposure to salt spray or winds from the ocean. Analysis of soil nutrient, water quality, and water availability data has further elucidated factors that create microhabitat differences on these dunes and determined small scale variation in distributions of individual species.
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1 - Old Dominion University, Biological Sciences, Norfolk, Virginia, 23529, USA
Presentation Type: Oral Paper:Papers for Sections
Date: Tuesday, August 1st, 2006
Time: 10:45 AM