A combined biogeochemical and palaeobotanical approach to study permafrost environments and past dynamics

When investigating past peatland processes and related carbon cycle dynamics, it is essential to identify and separate different peat environments: bogs, fens and permafrost, and their historical plant assemblages. Bog peat layers contain relatively well-preserved plant material for palaeoecological examination, whereas fen and permafrost peats are often highly humified, which in turn constrains reconstructions of past plant assemblages. Here, we analysed the chemical composition of arctic peat plateau plants to create a local reference training-set of plant biomarkers. We then combined palaeobotanical, biogeochemical and chronological analyses to one permafrost peat sequence collected from the East European Russian tundra (67 degrees 03N, 62 degrees 57E) to investigate past peatland dynamics and to evaluate the performance of the biomarker method in a highly decomposed permafrost environment. The results show that the chronologically constrained macrofossil analysis provided most of the essential information about the peatland succession. However, a more robust reconstruction of the past peatland dynamics was achieved by combining palaeobotanical and biogeochemical data sets. The similarity of the lipid biomarker distributions of the arctic and boreal peatland plants also implies that any established modern biomarker training-set of peatland plants could be applied universally to palaeoecological studies on peat sediments.