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

Abstract

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°03′N, 62°57′E) 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.

Inconsistent Response of Arctic Permafrost Peatland Carbon Accumulation to Warm Climate Phases

“…During the MCA, permafrost thawing and subsequent desiccation were recorded in our study sites (Zhang et al, 2018). In some parts of our sites, post-Little Ice Age (LIA) warming since 1850 CE has caused permafrost thawing and triggered Sphagnum establishment, while a stronger recent warming has started to desiccate the peat surface (Zhang et al, 2018 (Repo et al, 2009;Ronkainen et al, 2015).…”

“…In contrast to Seida, peat plateau vegetation at Indico is dominated by lichens and mosses, with less abundant shrubs. On both peat plateaus there are areas of bare peat approximately 4 m across (Repo et al, ; Ronkainen et al, ).…”

Warming of subarctic tundra increases emissions of all three important greenhouse gases – carbon dioxide, methane, and nitrous oxide

“…With its location close to the tree line in an area currently experiencing permafrost warming and thaw (Oberman & Mazhitova, 2001;Romanovsky et al, 2010), the site provides an ideal setting for assessing climate change impacts. Due to their location on top of the elevated peat plateau, these bare peat surfaces are exposed to wind abrasion and the top peat layer has eroded away, revealing decomposed fen peat as the surface layer (Ronkainen et al, 2015). The landscape in our study region comprises upland tundra with mineral soil overlain by a shallow organic layer (thickness 2-9 cm), as well as large peat plateau complexes with up to 4-m-thick peat deposits (Hugelius et al, 2012).…”

“…Set within the peat plateau are a number of naturally bare peat surfaces, in some cases partially covered by a thin moss layer and scattered lichens, but without vascular plants. Due to their location on top of the elevated peat plateau, these bare peat surfaces are exposed to wind abrasion and the top peat layer has eroded away, revealing decomposed fen peat as the surface layer (Ronkainen et al, 2015). Our warming experiment took place 2.5 km northwest of the location of GHG flux studies by Marushchak et al (2011Marushchak et al ( , 2013Marushchak et al ( , 2016.…”

“…We included the dominant tundra surfaces in our study region, representative for a typical subarctic landscape: upland tundra with mineral soil as well as peat plateaus, permafrost peatlands with vast peat deposits that were uplifted above the surrounding tundra landscape by frost heave (Zoltai, 1972;French, 2007). As a third surface type, we selected unvegetated patches of bare peat that occur on top of the peat plateau as a result of wind abrasion (Sepp€ al€ a, 2003;Ronkainen et al, 2015). Those bare peat surfaces have previously been identified as arctic N 2 O hot spots (Repo et al, 2009).…”