Changes of wood anatomical characters of selected species of Araucaria- during artificial charring - implications for palaeontology

Abstract

Charcoal is widely accepted as evidence of the occurrence of palaeo-wildfi re. Although fossil charcoal remains have been used in many studies, investigation into the anatomical changes occurring during charring are few. Th e present study analyses changes in selected anatomical characters during artifi cial charring of modern wood of three species of the genus Araucaria (i.e. Araucaria angustifolia, Araucaria bidwillii and Araucaria columnaris). Wood samples of the studied species were charred under controlled conditions at varying temperatures. Measurements of anatomical features of uncharred wood and artifi cial charcoal were statistically analysed. Th e anatomical changes were statistically correlated with charring temperatures and most of the parameters showed marked decreases with increasing charring temperature. Compared to the intrinsic variability in anatomical features, both within and between growth rings of an individual plant, the changes induced by temperature account only for a comparatively small percentage of the observed variability. Regarding Araucaria charcoal, it seems possible that at least general taxonomic and palaeoenvironmental implications can be drawn from such material. However, it is not clear so far whether these results and interpretations based on only three taxa, can be generalized for the entire family and anatomically similar fossil taxa or not.

A contribution to the identification of charcoal origin in Brazil III: microscopic identification of 10 Cerrado species

“…Ruptures were either present or absent regardless of ray width, which was already mentioned for various species in different climatic conditions (e.g. McGinnes et al 1971;Kim and Hanna 2006;Braadbaart and Poole 2008;Dias Leme et al 2010;Théry-Parisot and Henry 2012;Gonçalves et al , 2014Souza et al 2015;Afonso et al 2015;Gasson et al 2017;Osterkamp et al 2018). It is important to mention that the presence of ruptures might compromise the analysis if the professional is not well trained.…”

Charcoal anatomy and NIR spectra of Spirostachys africana, Terminalia sp. and Colophospermum mopane in different carbonization process

“…Also, thickness of fiber cell wall can also affect the ray width. The literature reports modifications as well as no statistical variations in charcoal, depending on the species [16,22,34]. The divergences can be attributed to chemical changes in wood during carbonization.…”

“…Ruptures in charcoal can be the result of regions with concentration of tension related to the high impermeability of heartwood [6]. They were observed in rays in some Mozambican species [37], in Eucalyptus species [38], Brazilian Cerrado species [39] and also in Araucaria species [34].…”

Charred conifer remains from the Late Oligocene – Early Miocene of Northern Hesse (Germany)

“…However, due to the very fragmentary preservation of the charcoal from Frielendorf, and the likelihood that some aspects and especially dimensions of the cells changed during charring (e.g. Cutter et al 1980, Osterkamp et al 2018, this type of charcoal (observed in 2 specimens from Frielendorf) can only be identified as indet. conifer.…”