Experimental charring of degraded and healthy wood for understanding firewood acquisition in prehistoric societies

PIQUÉ I HUERTA RAQUEL; CIAMPAGNA M. L.; ORTIZ MORALES G.

Barcelona

Congreso; 24th Annual Meeting of the European Association of Archaeologists; 2018

The goal of this work is to explore the preservation after charring of traits produced by environmental and biological agents on living and dead wood. An experimental approach is developed in order to obtain a reference collection of alterations in Mediterranean wood. The experimental sample comprises seven taxa: Pinus halepensis, Acer campestre, Populus sp, Ulmus sp, Genista sp, Quercus ilex and Corylus avellana. Living and dead wood in different state of preservation were collected from three different places located in the Vallès Occidental region (North-east of Iberia). Four wood pieces of 1.5 cm length and 3 cm maximum diameter were obtained from each taxon, which were measured and weighed before carbonization. Thin slices of the three diagnostic histological sections(TS, LRS, LTS) were taken from one of the wood pieces and anatomical alterations due to environmental factors, xylophages and fungi, as opposed to healthy logs, was recorded before combustion. The remaining three different piece of wood of the same taxon were then charred at temperatures of 400, 500 and 600 º C respectively. Dimensions and weight were taken after charring to calculate shrinkage and traits produced during the carbonization at different temperatures (i.e. contraction cracks, vitrification) were recorded with the stereoscopic and optical microscope. Results show that xylophages galleries and tissue degradation by fungi and calluses observed in fresh material can berecognized after charring. These features differ from those morphological alterations produced by the charring process itself (vitrification, cracks or eyes). Finally, these criteria have been applied for studying the charcoal remains of the site of Les Maleses (Montcada i Reixac, Vallès Occidental, Spain), dated second half first millennium BC, in order to identify and quantify the presence of this alterations and obtain a better understanding of firewood acquisition.