From natural to cultural mires during the last 15 ka years: An integrated approach comparing 14C ages on basal peat layers with geomorphological, palaeoecological and archaeological data (Eastern Massif Central, France)

Abstract

This paper studies mire initiation modalities from the Late-Glacial to the Holocene by comparing radiocarbon ages on basal peat layers (112 sites from the Eastern French Massif Central e EFMC) with long-term land cover changes. We developed a semi-quantitative method based on the degree of openness and on Anthropogenic Impact Factors (AIF scores) from palaeoecological data (mire and lake records). Archaeological information was also considered to evaluate human impact. We compared regional mire development trends with datasets from Northern Europe, Siberia, Alaska and Canada, and with global CH 4 emission. Heterogenous cases of mire initiation were highlighted during the last 15 ka years in the EMFC. From 15 to 11.7 ka cal. BP, some mires and histic horizons occurred, although further research is needed to better understand these peat accumulation phases. Related to the Early Holocene warming, a mire generation established by terrestrialization, in the southern EFMC where geomorphology favoured fens. Bogs also formed by paludification in the whole area between 10 and 7 ka cal. BP. Then, various cases of mire initiation were found from 4.4 to 2.4 ka cal. BP. The high number of mires established since 2.4 ka cal. BP could be related to major anthropogenic changes, indirectly favouring fens (in former ponds for instance) or small bogs (at the back of roads, walls or in abandoned drainage systems). This last generation was typical of Western European mountains and implied that moderate human impact may also produce socio-ecosystems with high ecological value.

Peatland initiation in Central European Russia during the Holocene: Effect of climate conditions and fires

“…It is evident that high fire frequencies could facilitate paludification and reduce forest production (Crawford, 2013; Simard et al, 2007, 2009). Charcoal layers located directly above mineral soil were observed in several peat sequences in regions of Europe and North America (Camill et al, 2009; Caseldine and Hatton, 1993; Dendievel et al, 2020; Dyakonov et al, 2017; Pajula, 2000). Alternatively, in many cases peat inception coincided with periods that had long fire-free intervals (Lafleur et al 2015; Schaffhauser et al, 2017) as fire increases the soil temperature and microbial activity, expands the aerated soil zone and suppresses Sphagnum growth (Payette et al, 2013).…”

“…During the last several decades numerous studies analysed carbon accumulation rates in peatlands during the Holocene in regions of Northern America and Eurasia; however, the main drivers of peat initiation as well as the age of peatland inception have not been thoroughly investigated and remain an important challenge (Camill et al, 2009; Charman et al, 2013, 2015; Kirpotin et al, 2007; Loisel et al, 2014; Lunt et al, 2019; Yu, 2012). Recently published basal radiocarbon dates from peatlands in the Northern Hemisphere indicate that most northern peatlands rapidly expanded between 12,000 and 8000 cal yr BP (Dendievel et al, 2020; Korhola et al, 2010; MacDonald et al, 2006; Morris at al., 2018; Yu, 2012; Zhao et al, 2014). Morris et al (2018) analysed an extensive database of peatland basal ages and regional climatic conditions during peatland initiation using numerical experiments with general circulation models, and showed that the initiation of peatlands in the regions formerly covered by ice sheets was primarily driven by climatic warming.…”

The Late Quaternary flora, vegetation and landscape of the Massif Central (France) under climatic and anthropogenic constrains

“…In this context lots of geomorphological, palynological, diatomological, macrofossil, as well as palaeoecological studies were performed since the late 1990s by the research group of Hervé Cubizolle at the University of Saint-Etienne (France), thanks to the interdisciplinary environmental PIREN-Program ("Programme Interdisciplinaire de Recherches sur l'Environnement") of the French National Research Centre (CNRS), which since 2001 became the "Zone Atelier Loire". This research was also supported by the Regional Directorate of Cultural Affairs (DRAC), the AGES program ("Ancient Geomorphological Evo-lutionS of the Loire"), and the "Etablissement Public Loire" (Argant and Cubizolle, 2005;Cubizolle, 2005;Cubizolle et al, 2005Cubizolle et al, , 2012Cubizolle et al, , 2013Cubizolle et al, , 2014Cubizolle et al, , 2015Cubizolle et al, , 2016Serieyssol et al, 2011Serieyssol et al, , 2012Dendievel et al, 2015Dendievel et al, , 2019Dendievel et al, , 2020Fassion et al, 2015;Dendievel, 2017). In addition, substantial palaeoecological studies concerned the formerly neglected areas, such as the Morvan Mountains (Jouffroy-Bapicot, 2010; Jouffroy- Bapicot et al, 2008Bapicot et al, , 2013.…”