Australian vegetated coastal ecosystems as global hotspots for climate change mitigation

Data on C stocks and sequestration rates in Australian tidal marshes, mangrove forests and seagrass meadows were compiled from published data. In addition, unpublished studies from the CSIRO Marine and Coastal Carbon Biogeochemistry Cluster project and other studies by the co-authors were included. Data from 1,553 study sites (593 from tidal marshes, 323 from mangrove forests and 637 from seagrass meadows) on soil C stocks (1,103 cores in total), soil C sequestration rates (352 cores in total) and standing C stocks in aboveground biomass (98 measurements in total) were used in this study. Detailed methods are provided in the manuscript linked to this dataset.\nLineage: Soil cores were sampled using different coring mechanisms. The cores were sliced at regular intervals, each slice/sample was weighed before and after oven drying to constant weight at 60-70°C (i.e. dry weight, DW).\nThe Champagne test' was used to determine whether soil samples contained inorganic carbon. The soil core sub-samples containing carbonates were acidified with 1 M HCl, centrifuged (3500 RPM; 5 minutes) and the supernatant with acid residues was removed, then washed in deionized water, centrifuged again and the supernatant removed and dried before C elemental analyses. Where carbonates were absent, bulk soil samples were milled and encapsulated without acid pre-treatment before C analyses. The C content was obtained using a dry combustion elemental analyser or mass spectrometer. \nData on soil accumulation rates from 315 cores derived by means of 210Pb and 14C was compiled. Concentration profiles of 210Pb were determined by alpha spectrometry using Passivated Implanted Planar Silicon (PIPS) detectors after acid digestion of the samples. Selected samples from each core were analysed for 226Ra by ultra-low background liquid scintillation counting (LSC, Quantulus 1220) or gamma spectrometry. Gamma spectrometry measurements were conducted in some cores using semi-planar intrinsic germanium high purity coaxial detectors. Sediment accumulation rates were obtained by applying the Constant Rate of Supply (CRS) or the Constant Flux:Constant Sedimentation models (CF:CS). \nSamples of bulk soil, plant debris and shells along the cores were radiocarbon dated following standard procedures. The 14C dates from seagrass cores were calibrated using the marine13 calibration curve considering a local Delta R ranging from 3 to 71 years as a function of study site. The corrected ages were used to prod