Aboveground plant biomass change along a coastal barrier island dune chronosequence over a six-year period

Plant communities on barrier island dunes can undergo succession but they are also subject to abrupt state changes. At the Virginia Coast Reserve (VCR) Long Term Ecological Research (LTER) site, state changes are hypothesized to be principally controlled by changes in the position of free surfaces (land, sea, and fresh groundwater). The objectives of the current study were to quantify aboveground plant biomass (total and by species) along a chronosequence of dunes on Hog Island (part of the VCR-LTER site) over a six year period and to look for patterns that may relate to the position of the free surfaces (particularly groundwater). Harvest samples of aboveground vegetation were obtained in early August in 1993, 1996 and 1999. Generally, aboveground biomass decreased on all dunes over the six-year period. However, the magnitude of the decrease was least on the oldest dune, where Schizachyrium increased. The results suggest that typical succession. with biomass increasing progressively. is not occurring on Hog Island dunes. Correlation analysis indicates that the position of the groundwater free surface may play a major role in determining aboveground biomass levels. Other factors possibly involved are salt and sand deposition by storms. herbivory and changes in biomass allocation aboveground versus belowground.