Holocene fire regime changes from multiple-site sedimentary charcoal analyses in the Lourdes basin (Pyrenees, France)

Abstract

International audienceOne lake and three peat bogs from the Lourdes glacial basin (France) were used for macrocharcoal analyses and fire frequency reconstruction over the entire Holocene (11700 years). The chronology was based upon thirty-three 14C AMS dates. Comparison of the distribution of both CHarcoal Accumulation Rate (CHAR) and fire return intervals showed that charcoal accumulation significantly differs between the lake and the peat bogs, but that frequency calculation overcomes the disparity between these site types. A composite frequency was built from the four individual records to assess regional versus local variability and fire regime controls by comparisons with regional fire activity, Holocene climatic oscillations and vegetation history. The millennial variability can be depicted as follows: relatively high frequency between 8000 and 5000 cal a BP (up to 5 fires/500 yrs), relatively low frequency between 5000 and 3000 cal a BP (down to 0 fires/500 yrs), and an increase between 3000 and 500 cal a BP (up to 4 fires/500 yrs). From 8000 to 5000 cal a BP, fire frequency displays strong synchrony between sites and appears to be mostly driven by increased summer temperature characterizing the Holocene Thermal Maximum (HTM). On the contrary, during the last 3000 years fire frequency was heterogeneous between sites and most probably human-driven. However, higher frequency at the millennial scale during the mid-Holocene strongly suggests that the perception of human-driven fire regime depends on the strength of natural controls

Biomass burning response to high-amplitude climate and vegetation changes in Southwestern France from the Last Glacial to the early Holocene

“…in the distribution of CHAR), with respect to climate and vegetation change. Usual methods include non-parametric tests such as MannWhitney (Rius et al 2011). In this case, the boundaries of the chronological periods to be tested against each other have to be arbitrarily pre-determined.…”

“…However, climate and fire are not linearly linked as other interacting drivers (e.g. vegetation and/or land use changes) may interfere at annual (Zumbrunnen et al 2011) to centennial and millennial scales Rius et al 2011). This combination of multiple factors also accounts for a non-spatially uniform response of fire regimes to global warming (Flannigan et al 2009).…”

“…Given the current fire season in the Pyrenees, i.e. an anthropogenic one linked to pasture management in winter and a natural one in summer (July and August, Rius et al 2011), a proxy for summer temperature was needed. We also discuss the role of vegetation type, structure and biomass availability using pollen analysis from Ech palaeolake and Lourdes (Reille and Andrieu 1995).…”

A case study of the role of climate, humans, and ecological setting in Holocene fire history of northwestern Europe

“…Fire history on long or short time scales is used as an indicator of climate change and/or human impact (e.g., Mooney et al, 2001;Black and Mooney, 2006;Power et al, 2008;Rius et al, 2011;Kasin et al, 2013;Vannière et al, 2011Vannière et al, , 2013Molinari et al, 2013) and is assumed to have been a major factor in shaping biodiversity through time at the landscape-, habitat-and species-level scales (e.g., Lindbladh et al, 2003Lindbladh et al, , 2008Ohlson et al, 2011;Colombaroli and Tinner, 2013;Jansen et al, 2013a,b). Moreover, global warming is expected to cause more fires as a result of an increase in drought, wind, and lightning in certain regions of the world (IPCC Report 2007, 2013.…”

Historia del fuego y la vegetación en una secuencia holocena del Pirineo central: la Basa de la Mora

“…En la vertiente norte del Pirineo central se han llevado a cabo estudios que reconstruyen los regímenes de incendios de manera local (Rius et al, 2009(Rius et al, , 2011(Rius et al, , 2012. Sin embargo, el único estudio existente hasta el momento de reconstrucción de dinámica de incendios regionales en el Pirineo meridional es el realizado por Bal et al (2011), que describe la dinámica del fuego durante los últimos 3300 años, no habiendo hasta el momento datos que cubran todo el Holoceno, y que por tanto permitan comparar periodos en los que la intervención humana en la génesis de incendios no sea un actor a tener en cuenta.…”