High resolution reconstruction of modern charcoal production kilns: An integrated approach combining dendrochronology, micromorphology and anthracology in the French Pyrenees

Abstract

Numerous charcoal kiln remains can still be found throughout the world, evidencing wood harvesting related to former industries. These remains represent effective sources and tools for studying (i) pre-industrial pressures on forest resources and (ii) past strategies related to woodland management. However, radiocarbon dating (AMS), which is the main tool to reconstruct the chronology of past charcoal manufacturing activity, doesn't provide sufficiently accurate dating, especially for the post-1650 period, due to the broad probability range of the dates resulting from wiggles in the calibration curve. In order to overcome the radiocarbon dating limitation and therefore refine the chronology of modern charcoal manufacturing, this paper proposes to apply an integrated approach combining archaeology, micromorphology, anthracology and dendrochronology. To characterise the archaeological record of a target charcoal kiln terrace from the "Forêt de Bernadouze", located in a historical iron production valley of the Northern Pyrenees, we combined classical stratigraphic analysis with a micromorphological study. The results highlight the multiperiod nature of the terrace, i.e. a palimpsest of multiple charcoal production episodes, revealing two major phases marked by an abandonment period between them. Subsequently, we constructed a beech charcoal-ring (n=49) chronology cross-dated with the new "Forêt de Bernadouze" reference chronology from freshly felled, living beech trees (n=24) to obtain the annual resolution of charcoal ring formation. Based on the new reconstructed master chronology covering the 1879-2016 period, we were able to calibrate the charcoal-ring chronology for the 1881-1941 period. Consequently, we (i) dated the charcoal production activity performed on the target terrace during the 1924-1942 period and (ii) identified a shift in the rate of use of the terrace, from one-off to high-intensive use. This study also provides new insights regarding (i) the particular nature of the archaeological record and (ii) the operating and timing of past charcoal-making practices in connection with silvicultural treatments.

Did the charcoal-based iron industry really drive the forest cover decline in the Northern Pyrenees?

“…Since 2010, this area has comprised the Human-Environment Observatory of Haut-Vicdessos devoted to the interdisciplinary study of mountain mountain socio-ecosystems. The Bernadouze forest in Suc, which is an Instrumented Site in Global Ecology, provides a focus area where several in-depth studies have already been implemented (Py-Saragaglia et al, 2019;Saulnier et al, 2020;Fouédjeu et al, 2021b;2021a). Current vegetation around Bernadouze peat bog is almost exclusively composed of beech (Fagus sylvatica L.).…”

“…11). In 1892, the focus area was managed in a coppice selection system, with 20-50 year-old beech trees, and was then gradually converted into high forest (Fouédjeu et al, 2021a).…”

The socio-ecological legacies of centuries-old charcoal making practices in a mountain forest of the northern Pyrenees

“…To clarify which hypothesis is correct, we need to know if the anthracological records reflect the successive charring of monospecific wood piles with either fir or beech, or a mixture of two dominant species in the same wood pile. An argument in favor of successive monospecific charring is that CL records generally contain residues of several, rather than a single carbonization (Gebhardt, 2007;Dupin et al, 2019;Fouédjeu et al, 2021). The vertical and lateral displacement of remaining charcoal pieces may mix charcoal from the alternating charring of monospecific wood piles.…”

“…Possible coppice rotation would range from 6 to 30 years, with a dominance of wood harvested between 6 and 15 years. The over-representation of 1-5 years-old charcoal may result from fragmentation accentuated by (i) the scraping and cleaning of the terrace by charcoal burners before each carbonization, (ii) taphonomic processes in soils, and (iii) the archaeological sampling and sieving (Chrzavzez, 2013;Blondel et al, 2018;Fouédjeu et al, 2021).…”

“…However, the only way to develop an understanding of local practices and, more broadly, to learn how people worked before modern times, is to study CK remains. In this perspective, wood scientists are developing dendrometric and dendrochronological tools to accurately reconstruct the entire technical operational sequence of charcoal production, from wood selection and removal to silviculture management and the charring process (Ludemann and Nelle, 2002;Strachan et al, 2013;Raab et al, 2015;Dupin, 2018;Paradis-Grenouillet et al, 2018a;2018b;Fouédjeu et al, 2021).…”