Graziani, D.J. and Day, F.P., 2015. Thresholds of change in decomposition rate along a dune/swale transect on a Virginia barrier island.
The objective of the current study was to examine fine spatial scale variation in aboveground decomposition rate over a barrier island dune/swale gradient in relation to the ground-water-free surface, soil nitrogen, and associated ecosystem states in order to identify thresholds of process or state change. The litterbag study was conducted on the Virginia Coast Reserve-Long Term Ecological Research Site in Virginia, United States. Mean aboveground decay rate (yr−1) ranged from 0.339 (upper dune) to 0.699 (marsh/lower dune transition). The upper dune, marsh, and lower dune (Morella thicket side) had the lowest aboveground decay rates. The marsh edge, marsh/lower dune transition and Morella thicket exhibited the highest decomposition rates. Our results did not suggest that soil N content was a good indicator of state change or system process rates, whereas, distance to ground water demonstrated a significant relationship with aboveground decay. Relatively small (approximately 0.2–0.4 m) increases or decreases in elevation affected decay rates and community state. Free-surface thresholds that cause state changes or shifts in ecosystem processes provide the capability to project changes prompted by sea-level rise or shifts in other free surfaces over entire landscapes. Our results suggest that the ground-water-free surface is a good candidate for making such projections.
