River flooding as a driver of polygon dynamics: modern vegetation data and a millennial peat record from the Anabar River lowlands (Arctic Siberia)

Abstract

Abstract. The spatial and temporal variability of a low-centred polygon on the eastern floodplain area of the lower Anabar River (72.070° N, 113.921° E; northern Yakutia, Siberia) has been investigated using a multi-method approach. The present-day vegetation in each square metre was analysed, revealing a community of Larix, shrubby Betula, and Salix on the polygon rim, a dominance of Carex and Andromeda polifolia in the rim-to-pond transition zone, and a predominantly monospecific Scorpidium scorpioides coverage within the pond. The total organic carbon (TOC) content, TOC / TN (total nitrogen) ratio, grain size, vascular plant macrofossils, moss remains, diatoms, and pollen were analysed for two vertical sections and a sediment core from a transect across the polygon. Radiocarbon dating indicates that the formation of the polygon started at least 1500 yr ago; the general positions of the pond and rim have not changed since that time. Two types of pond vegetation were identified, indicating two contrasting development stages of the polygon. The first was a well-established moss association, dominated by submerged or floating Scorpidium scorpioides and/or Drepanocladus spp. and overgrown by epiphytic diatoms such as Tabellaria flocculosa and Eunotia taxa. This stage coincides temporally with a period in which the polygon was only drained by lateral subsurface water flow, as indicated by mixed grain sizes. A different moss association occurred during times of repeated river flooding (indicated by homogeneous medium-grained sand that probably accumulated during the annual spring snowmelt), characterized by an abundance of Meesia triquetra and a dominance of benthic diatoms (e.g. Navicula vulpina), indicative of a relatively high pH and a high tolerance of disturbance. A comparison of the local polygon vegetation (inferred from moss and macrofossil spectra) with the regional vegetation (inferred from pollen spectra) indicated that the moss association with Scorpidium scorpioides became established during relatively favourable climatic conditions, while the association dominated by Meesia triquetra occurred during periods of harsh climatic conditions. Our study revealed a strong riverine influence (in addition to climatic influences) on polygon development and the type of peat accumulated.

A robust vegetation-based elevation transfer method for reconstructing Arctic polygon mire palaeo-microtopography

“…The clear differentiation of the five plant communities in terms of GSH, frost surface height, litter and vegetation cover (Figs. 6,7,8), and the high number of significant indicator species confirm the pattern already identified in other studies of Arctic ice-wedge polygons (De Klerk et al, 2009Minke et al, 2007Minke et al, , 2009Boike et al, 2013;Zibulski et al, 2013Zibulski et al, , 2016Wolter et al, 2016). The applied relevé size of 1 m 2 corresponds to the recommended sampling size for peatlands of 1-5 m 2 (Glavac, 1996;Westhoff and Van der Maarel, 1973).…”

“…For all encountered plant species the potential for fossilization and fossil identification was estimated, using experiences from earlier studies (De Klerk et al, 2009, 2011Teltewskoi et al, 2016;Zibulski et al, 2013) and determination literature (Table 1). Potential fossils were subdivided into potential (i) pollen/spores types, given that Arctic pollen deposition mainly reflects short-distance vegetation patterns (De Klerk et al, 2009, (ii) belowground macrofossils, (iii) vegetative aboveground/near surface macrofossils and (iv) generative aboveground macrofossils.…”

“…of the height of microrelief elements is crucial in these studies. This relief/wetness is generally reconstructed using plant fossils, which are attributed to wetness classes or to a relative position on a conceptual dry-wet gradient (Ellis and Rochefort, 2004;De Klerk et al, 2011;Zibulski et al, 2013;Fritz et al, 2016;Teltewskoi et al, 2016). Better understanding of polygon dynamics and former carbon and greenhouse gas fluxes requires, however, more detailed and better quantified palaeomicrotopographical information.…”

Late Holocene ice-wedge polygon dynamics in northeastern Siberian coastal lowlands

“…The functioning and dynamics of polygonal ecosystems have increasingly been studied in recent years (e.g., de Klerk, Theuerkauf, and Joosten 2017;Fritz et al 2016;Jorgenson, Shur, and Pullman 2006;Zibulski et al 2013). A first comprehensive species inventory of tundra-wetland ponds combined with a detailed survey of physical and chemical water parameters was carried out from 1971 to 1973 near Barrow, Alaska (Hobbie 1980;Hobbie et al 1999); it was repeated forty years later by Lougheed et al (2011).…”

Disturbance-effects on treeline larch-stands in the lower Kolyma River area (NE Siberia)

“…At P, the most extreme site, all size classes grow clumped at all scales. Clustering at this site can most probably be attributed to terrain, with larch recruitment limited to dry polygon rims (Zibulski et al 2013;Frost and Epstein 2014). At such sites, seedlings are also in competition with a dense herbaceous layer (Bell et al 2000).…”