Poor fen succession over ombrotrophic peat related to late Holocene increased surface wetness in subarctic Quebec, Canada

Abstract

Northern peatlands act as archives of environmental change through their sensitivity to water balance fluctuations, while being significant contributors to global greenhouse gas dynamics. Subarctic fens in north-eastern Canada are characterized by a dominance of pools and flarks. We aimed to reconstruct the late Holocene hydrological conditions of these fens to establish the timing of the initiation of pool and flark formation and possible links with climate. Testate amoebae and plant macrofossils from five cores, sampled in three fens, were analysed to infer water tables with chronologies based on 14 C and 210 Pb dating. All sites showed the presence of relatively dry, ombrotrophic conditions with abundant Picea from 5000 cal a BP, followed by a first shift to wet, poor fen conditions with pool and flark development around 3000 cal a BP and a subsequent wet shift after $800 cal a BP. These trends coincide with previously observed Neoglacial and Little Ice Age cooler and wetter conditions and therefore climate may well have been a dominant factor in the initiation and development of pools and flarks over the late Holocene. The effect of anticipated climate change on subarctic peatlands remains unclear, although wetter conditions might enhance pool expansion to the detriment of terrestrial components.

Integration of palaeohydrological proxies into a peatland model: a new tool for palaeoecological studies

“…On shorter timescales, however, some periods show clear discrepancies between the curves, for example, around 6000 cal BP at MOS and between ca 2000 and 1000 cal BP at both sites. During these periods, testate amoebae may be responding to other signals, perhaps linked to the fen–bog transition at MOS around 6000 cal BP and to some changes in the regional climatic conditions between 2000 and 1000 cal BP, as identified in other studies (Lamarre et al , ; van Bellen et al , ), or the model may be misrepresenting climate impacts on water‐table dynamics.…”

Europe on fire three thousand years ago: Arson or climate?

“…Temperatures in Québec, Canada, peaked ~3.2 ka while maximum temperatures in Labrador are recorded ~4 ka before declining during the late Holocene [ Viau and Gajewski , ]. Evidence supporting a shift toward wetter conditions were inferred at ~3 ka in Northern Québec [ van Bellen et al ., ; Van Bellen et al ., ] and Labrador [ Viau and Gajewski , ], and ~3.5 kyr in Southern Québec after a dry period between 4.8 and 3.4 ka, together with decreasing temperatures during the past 4.5 kyr [ Muller et al ., ]. Precipitation peaked ~1.5–2.0 ka in Labrador and Québec, while decreasing during the past 5.5 kyr in central Canada [ Viau and Gajewski , ].…”

Evaluating long‐term regional climate variability in the maritime region of the St. Lawrence North Shore (eastern Canada) using a multi‐site comparison of peat‐based paleohydrological records

“…Over the last decade, peatland paleohydrological research has been expanding in the boreal and subarctic regions of northeastern Canada (Loisel and Garneau, 2010;van Bellen et al, 2011van Bellen et al, , 2013Bunbury et al, 2012;Lamarre et al, 2012). These studies have linked long-term trends in BSW with documented climate changes, such as the Neoglacial and the Little Ice Age (LIA) cooling.…”