Coastal Foredune Belowground Biomass, Aboveground Biomass, and Species Cover

We collected data from cross-shore transects at seven sites; three categorized as unmanaged (i.e., Corolla Reserve, the northern dunes of the US Army Engineer Research and Development Center [ERDC] Field Research Facility [FRF North], and dunes in the southern reaches of that same site [FRF South]) and four categorized as managed (i.e., Southern Shores, Nags Head, Pine Island and Duck). Sediment vibracores (n = 15 managed, 10 unmanaged) were collected between September and December 2020 at the dune toe, dune face, crest and back along a single transect at each site. Cores were stored at 4 °C and processed within one week of collection to prevent root degradation. Cores were bisected longitudinally and the sediment from each half was segmented into 30 cm sections from the ground surface (i.e., 0–30 cm, 31–60 cm, 61–90 cm, 91–120 cm, 121–150 cm). To separate belowground biomass, core sections were wet sieved using stacked 3.36 mm, 1.0 mm and 0.5 mm mesh-size sieves. Living belowground biomass was characterized as the sample portions with roots, rhizomes and belowground stems that were still flexible and did not exhibit signs of decomposition. All other biotic material was classified as non-living biomass (e.g., decayed plant material, twigs, seeds, wrack). Within the living belowground biomass component, live roots were separated from other belowground structures (rhizomes, belowground-stems) and scanned using an Epson Perfection V800 Photo electric scanner calibrated for image analysis with WinRhizo™ Pro 2019a by Regent Instruments (Regent Instruments Inc, Quebec City, Quebec, Canada). Images were analyzed to quantify root surface area by diameter size class. Fine roots were defined as those with < 1 mm diameter. All living and non-living belowground biomass was oven-dried at 60 °C for 72 hours and weighed. 

Soil organic matter content was quantified by loss-on-ignition following manual removal of roots. Samples (1 g of sediment from each core section) were baked in a muffle furnace at 550 °C for 5 hours and reweighed to estimate soil organic matter content (%). Aliquots (300 mg) of each core segment were submitted to the Cornell Stable Isotope Laboratory for % carbon (C) and % nitrogen (N) analysis. Due to cost, only the top 90 cm of soils were sent for C and N analysis.

Vegetation surveys were conducted during Summer 2021. We established vegetation survey plots (0.25 m­­2 plot size) centered on each exact coring location. We estimated vegetation cover by species (within 0.25 m2 plot), cover of bare ground, dead plant cover. Adjacent to the coring plots, aboveground biomass (within a 0.1 x 1 m plot) was collected to complement belowground biomass sampling at all sites except Duck, where grasses had been manually planted and permission to harvest aboveground biomass was not granted to maintain the vegetation on the dune face. Aboveground biomass was oven-dried at 60 °C for 72 hours, weighed and scaled to g m-2.

More details can be found in the manuscript:

White AE, Cohn N, Davis EH, Hein CJ, Zinnert JC. Coastal dune management affects above and belowground biotic characteristics. Scientific Reports (in press).