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

Abstract

The main drivers of fire regimes in southern Europe are climate, vegetation and land-use changes that interact at different spatio-temporal scales. These complex interplays between ''natural'' and anthropogenic forcings hinder the identification of fire-climate linkages on the long time scale. In this paper, we focused on the Last GlacialHolocene transition, which is the last time Europe experienced rapid warming of similar magnitude and rate of change as predicted for the future, and with minimal human impact (no agricultural activities). We derived fire activity from two neighbouring lacustrine macrocharcoal records, Ech paleolake and Lake Lourdes, located 3 km apart. To understand the effect of external forcings, we reconstructed summer T°changes and vegetation dynamics from two independent proxies. We then compared both paleofire records with chironomid-inferred summer air temperature reconstruction from Ech paleolake. We discuss the role of vegetation type, structure and biomass availability using pollen analysis from Ech paleolake and Lourdes. Fire activity is strongly modulated by summer T°o scillations as shown by the highly contrasted responses between the Oldest Dryas/Interstadial and Younger Dryas/ Holocene transitions. However, vegetation type and biomass availability act as limiting factors: the slight increase in fire activity at the onset of the Interstadial is triggered by a 7°C summer T°increase but remains limited by low availability of woody biomass in a steppe environment. On the contrary, the onset of the Holocene is characterised by a 2°C summer T°increase and an unprecedented increase in fire activity, conditioned by the establishment of dense deciduous forests.

Climate-driven past fires in central Sicily

“…To the contrary, microscopic charcoal and pollen of evergreen oaks were negatively correlated at other lacustrine sites of central-eastern Mediterranean ). Rius et al (2013) highlighted the link between fire regimes and vegetation in the Holocene summer-drought climate (Pyrenean area). They also established that deciduous woodlands promoted higher fire activity.…”

Late Holocene history of woodland dynamics and wood use in an ancient mining area of the Pyrenees (Ariège, France)

“…Only vitrified charcoals (undeterminable Angiospermae twigs) from the level V of Lacore 1, dating from the Early Holocene, certainly originate from natural fires. At the regional scale, this period is characterised by increasing drought and summer temperature combined with increasing woodland biomass favouring a higher fire activity (Rius et al, 2014). Locally, charcoal analysis suggests that the vegetation cover was scarcely populated by trees and probably dominated by deciduous shrubs.…”

The Late-Glacial and Holocene Marboré Lake sequence (2612 m a.s.l., Central Pyrenees, Spain): Testing high altitude sites sensitivity to millennial scale vegetation and climate variability

“…Holocene (e.g. Pla and Catalan, 2005;Miras et al, 2007;Pèlachs et al, 2011;Pérez-Obiol et al, 2012;Pérez-Sanz et al, 2013;Pérez-Díaz et al, 2015;Garcés-Pastor et al, 2016 and few of them include the Late Glacial-Holocene transition (LGH) (Montserrat-Martí, 1992;González-Sampériz et al, 2006Gil-Romera et al, 2014;Rius et al, 2014) a key interval to provide contrasting boundary conditions for terrestrial ecosystems, particularly at high altitudes (Brisset et al, 2015). After alpine glacier retreat, new environmental conditions developed on freshly ice-free valleys, profoundly modifying mountain landscapes (e.g.…”