PLANT RESPONSE TO NITROGEN FERTILIZATION ACROSS A VIRGINIA COAST
RESERVE DUNE CHRONOSEQUENCE.
Experimental and control plots (1 m2) were established on
three different age dunes (24, 36, and 120 yr old) on Hog Island,
part of the Virginia Coast Reserve LTER site. Nitrogen (15 g m-2
yr-1) was added to the treatment plots in the form of urea. At
the end of the 1991 growing season, plant biomass was harvested
from the plots and weighed. Biomass decreased from young to old
dune (174 g m-2 to 108 g m-2 in controls), but
root/shoot ratios increased in the controls (0.35 to 0.50). Biomass
increased in response to fertilization on all three sites; however, the
response was muted on the oldest dune (547 g m-2 to 338 g
m-2 from young to old). Root/shoot ratios decreased in
response to fertilization, but were the same across sites (0.21). The
damping of the response to N additions from younger to older
dunes may reflect the higher natural levels of N in the older
dune soils or other limiting factors such as soil moisture.