Effects of Nitrogen Availability on Plant Biomass Along a Barrier Island Dune Chronosequence

ABSTRACT
Many researchers stress the importance of nutrient limitation on barrier island plant communities. The accreting north end of Hog Island, part of the Virginia Coast Reserve-Long Term Ecological Research site, provided an opportunity to quantify amounts of plant biomass along a natural dune chronosequence (24, 36, 120+ yr-old dunes) and biomass response to experimental additions of nitrogen. In a one-year study, nitrogen addition increased plant biomass, with greater allocation to shoots than roots. In response to nitrogen fertilization, soil nitrogen increases were greatest on the oldest site while biomass increases were smallest. Naturally occurring NO2- + NO3- availability increased with age across the chronosequence. Aboveground biomass was inversely proportional to nitrogen availability and decreased from younger dunes to the oldest. Nitrogen does not appear to be the major limiting factor along the chronosequence. Groundwater hydrographs suggest the oldest dune may be moisture limited.