Aboveground biomass and net primary production along a Virginia barrier island dune chronosequence

Aboveground biomass was measured along a chronosequence of dunes on Hog Island, a Virginia Coast Reserve LTER site. The dominant species were Ammophila breviligulata and Spartina patens. Aboveground biomass was harvested monthly from 10 quadrats on 6, 24, 36 and 120-yr-old dunes from April to November 1993. Total aboveground biomass decreased along the chronosequence and ranged from 205 g m(-2) on the 6-year-old dune to 152 g m(-2) on the 120-yr-old dune in October 1993. Spartina patens biomass exceeded A. breviligulata biomass on the 6, 24 and 36 yr-old-dunes. Spartina patens biomass decreased along the chronosequence; in July it ranged from 72 g m(-2) on the 6-yr-old dune to 5 g m(-2) on the 120-yr-old dune. Ammophila breviligulata biomass increased from 17 g m(-2) on the 6-yr-old dune to 39 g m(-2) on the 120-yr-old dune. Ammophila breviligulata had greater biomass than S. patens on only the 120-yr-old dune. Net aboveground primary productivity did not vary along the chronosequence. Aboveground net primary production (ANPP) from the sum of species peaks was 259 g m(-2) yr(-1) for the 6-yr-old dune, 226 g m(-2) yr(-1) for the 24-yr-old dune, 256 g m(-2) yr(-1) for the 36-yr-old dune and 274 g m(-2)yr(-1) for the 120-yr-old dune. There was no opportunity to study dunes of the same or comparable ages on other barrier islands, so these inferences apply only to the four dunes studied on Hog Island.