ABOVEGROUND BIOMASS AND NET PRIMARY PRODUCTION ALONG A BARRIER
ISLAND DUNE CHRONOSEQUENCE.
Aboveground biomass was examined along a chronosequence of
dune communities on Hog Island, a Virginia Coast Reserve LTER
site. The dominant species are Ammophila breviligulata and
Spartina patens. Aboveground biomass was harvested monthly from
ten quadrats on dunes 6, 24, 36, and 120 years old. Sampling was
conducted from April to November 1993. Biomass values were
greater for younger dunes. Spartina patens biomass was greater
than Ammophila breviligulata for the 6, 24, and 36 year old dune
ridges. It also showed a pattern of decreasing biomass with
increasing dune age; in July it ranged from 72 g/m2 to 5 g/m2.
The same month showed less variation in Ammophila breviligulata;
it increased from 17g/m2 to 39g/m2 across increasing dune age.
Ammophila breviligulata had greater biomass for only the 120 year
old dune. There appeared to be a midsummer decline in biomass due
to drought conditions. This variation in production of
aboveground biomass across dune age may be controlled by
moisture, microclimatic conditions and soil nitrogen levels.