Fine-Root Biomass Distribution and Production Along a Barrier Island Chronosequence

Abstract

-Fine roots are important in community development on barrier islands. Fine roots can influence nutrient losses from the soil environment along with regulating water loss based on their distribution and concentration. A sequential coring method was used to determine live fine-root biomass along a barrier island dune and swale chronosequence on the Virginia Coast Reserve-Long Term Ecological Research Site. Fine-root production and the effects of nitrogen fertilization were also examined using an in-growth core method along the chronosequence. Variation in biomass was associated with topographic position and the interaction with nitrogen and water availability along the chronosequence. The swales had significantly larger accumulations (16 to 180 g/m2) of live fine-root biomass (LFRB) than the dunes (4 to 13 g/m2). Higher LFRB was probably due to higher nitrogen levels and moister conditions in the swales. LFRB changed very little across the dune chronosequence but LFRB in the swales generally decreased from the 6-yr to the 120-yr site. However, the 6yr swale had significantly lower biomass than the other swales. LFRB was concentrated in the upper 10-20 cm of soil in dune and swale sites across the chronosequence, with swales having proportionally more (70%) in the upper 10 cm of soil than dunes (29%). Root nitrogen concentration in LFRB was higher in the older dunes and swales. Root phosphorus concentrations increased from the 6-yr to the 120-yr dune but were not different in the swales. Fineroot production increased significantly with N-fertilization in the dune communities, 1.5 times to 2.5 times the reference sites. Nitrogen fertilization also increased nitrogen concentrations in live fine roots.