Page 112 - Microbial methane cycling in a warming world From biosphere to atmosphere Michiel H in t Zandt

Chapter 5. Early Holocene carbon storage and microbial activity in North Sea peats
The main peat components (monocot epidermis, brown mosses, Sphagnum spp.) of both cores were quantified based on the quadrat and leaf Count (QLC) method (Barber et al. 1994; Barber, Chambers and Maddy 2003) using 15 averaged quadrat (1 x 1 cm) counts under low power (X10) magnification using a 10 x 10 square grid graticule. The main peat components were expressed as percentages (%). The complete samples were scanned for quantification of the less abundant macrofossils, in case of the Max Gundelach core, and seeds, fruits, leaves and fragments of mosses were picked out, counted and expressed as concentrations per unit of volume. Rare taxa are reported as presence. Preservation of the peat deposits was estimated qualitatively during analysis based on the preservation of the macro fossils: poorly preserved (+), intermediately preserved (++) and well preserved (+++). The diagram was constructed with Tilia Version 1.7.16 (Grimm 2004).
Radiocarbon-dating
For radiocarbon-dating purposes, the top and bottom 1 cm of the peat layers were sieved and searched for autochthonous terrestrial plant macrofossils or, in the absence of such fossils, charcoal (Hijma and Cohen 2010). If a 1-cm-thick section did not contain enough macrofossils, material from the subsequent cm was added. The selected macrofossils were sent to the Centre for Isotope Research (Groningen, the Netherlands) for AMS-radiocarbon dating. All radiocarbon ages were calibrated using OxCal 4.3 software (Bronk Ramsey 2009) with the INTCAL13-curve (Reimer et al. 2013).
Results
Lithographic features of the sampling sites
The localized nature of this landscape is apparent in the lithographic differences observed between and within sites (Fig. 2). The peat deposits in this area lie upon Pleistocene sands and are capped by either shallow marine clay or sands. Pleistocene sands lie 2-4 m below the sea floor (mbsf) in the southern North Sea and 1-3 mbsf in the Doggerbank region and are capped by 80-120 cm and 10-30 cm basal-peat layers in the southern North Sea and Doggerbank regions, respectively (Table S1). The basal-peat developed due to rising groundwater as a result
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