Salt marsh soil carbon content, loss on ignition, dry bulk density, carbon stocks and carbon accumulation rates for Clayoquot Sound, British Columbia, Canada

The goal of this project was to provide the first estimates of blue carbon stocks and carbon accumulation rates in the high and low marsh zones of salt marshes from the Pacific Coast of Canada, within the Clayoquot Sound UNESCO Biosphere Reserve and Pacific Rim National Park Reserve on the Pacific Coast of Canada. Thirty-four sediment cores were collected from seven salt marshes during summer (June-September) 2016. Sediment cores were collected using a simple percussion coring technique in which a length of two-inch (57 mm) diameter, PVC vacuum tubing fitted with a plastic core catcher (AMS Inc.) was hammered into the ground until the depth of refusal. At the GBK location, a steel sledge corer (AMS Inc.) was used to extract four cores before mechanical problems required switching to the simpler percussion method.

The purpose of collecting these cores was to determine soil carbon and sediment properties necessary for calculating carbon stocks and accumulation rates in different marsh zones. At each core site, marsh zone (high vs low) was determined using vegetation types surrounding the core site. Coring spots were considered low marsh if the species Triglochin maritima, Salicornia spp., Fucus ssp. or Ditschilis spicata were present, and high marsh if it included Plantago maritima, Deschampsia caespitosa, Grindelia integrifolia, Potentilla anserina, Lysimachia maritima, or Eleocharis ssp. The majority percent cover of high or low marsh species was used to determine a "high" or "low" marsh designation. On all 34 cores, we measured core compaction, dry bulk density, % loss-on-ignition, and % organic carbon (using an elemental analyzer, on select number of samples). Compaction was measured as length of core penetration divided by the length of core recovered. From these measured parameters, we estimated % organic carbon (using a regression equation between % organic carbon and %LOI), soil carbon density, and carbon stocks measured to (a) the depth of the basal peat layer, (b) a depth of 20 cm, and (c) to the depth of the 30-year horizon (estimated in the 8 cores where 210Pb analysis was completed).