BELOWGROUND BIOMASS PATTERNS ON A COASTAL BARRIER-ISLAND IN VIRGINIA

Root distribution by depth, size class and community type was evaluate d along a chronosequence on Hog Island, part of the Virginia Coast Res erve Long Term Ecological Research site. Total nitrogen and phosphorus concentrations in roots were also determined. The communities include d an Ammophila breviligulata dune, two Myrica cerifera stands and two Spartina patens communities. Most biomass was within the top 20 cm of soil representing 75% to 93% of total biomass. Distributions of root m ass among size classes varied among sites. On Spartina sites, most tot al biomass (70% to 84%) was in the <2 mm size class. The 2-5 mm size c lass (59%) dominated the dune site and the >5 mm size class (51% to 78 %) dominated the Myrica sites. Total biomass increased with site age r anging from 372 g/m2 in the dune site to 4228 g/m2 in the older Myrica site. Nitrogen and phosphorus concentrations were low. In a nutrient limited ecosystem, conservative nutrient cycling may be enhanced by sl ow decay and high nutrient immobilization rates associated with poor q uality litter. Additionally, structural attributes of rooting systems such as dense fine root mats or clonal physiognomies may reduce nutrie nt losses through soil leaching.