Ecosystem Development on a Coastal Barrier Island Dune Chronosequence

Abstract

Soil and litter organic carbon, nitrogen, and phosphorus were measured across a dune chronosequence on Sapelo Island, Georgia, U.S.A., to characterize ecosystem development and nutrient cycling during primary succession. As successional theory predicts, litter biomass and soil organic matter increased with dune age. The proportion of nutrients contained in the litter also increased with dune age. No litter was present in the grass-dominated foredunes, whereas in the forested dunes litter accounted for 37%, 17%, and 0.11% of the ecosystem (soil plus litter) C, N, and P, respectively. Soil C and N pools increased from the foredunes to older dune classes. Surface soil (0–10 cm) plant-available N (NH 4, NO−3) increased from the foredunes to middunes, whereas soil P showed little change with dune age. Nitrogen was highly limiting across the chronosequence. Total soil N ranged from 0.006% (per gram of dry soil) in the foredunes to 0.087% in the middune. Soil N : P was less than 1.3 across all sites, also suggesting N limitation of plant productivity. Plant-available NO−3 and total N concentrations in soil and ecosystem (litter plus soil) pools were greater in the middunes, where the N-fixing shrub Morella cerifera was present, than in either the foredunes or forested dunes. Our results suggest that the development of dune nutrient cycles is controlled by both successional age and colonization by N-fixing species.