NITROGEN AVAILABILITY AND N MINERALIZATION RATES ALONG A
COMMUNITY CHRONOSEQUENCE ON HOG ISLAND, VIRGINIA COAST RESERVE.
Available soil nitrogen and N-mineralization rates on a
dynamic nutrient-poor island are important in understanding the
succession of coastal island systems. On a 6, 24, 36 and 120
year-old chronosequence on Hog Island, the nitrogen availability
in the dunes increased with age. But in the associated swales
the nitrogen concentrations were higher with the dominance of
Myrica cerifera, a nitrogen fixing species. In general, the
swales had higher soil nitrogen levels (0.016-0.052 g m2) than
dunes (0.015-0.038 g m2) and the concentrations of ammonium-N
were higher than the nitrate+nitrite-N. Application of urea to
the dunes resulted in a 10-13 fold increase in nitrogen with
highest accumulation in the oldest dune. Net N-mineralization was
highest in the younger dune (0.053 mg kg-1 day-1),
and with fertilization this rate increased 15-fold. Fertilization had
only a minimal effect on mineralization in the oldest dune.
These results indicated that the younger dunes were N limited and
the limitation was minimized with age. Higher nitrogen levels in
the older dunes might be due to an input of N-rich litter from
the adjacent Myrica dominated swales.