Anatomical changes to the wood of Croton sonderianus (Euphorbiaceae) when charred at different temperatures

Abstract

Wood retains most of its anatomical characteristics when charred, but charring temperature determines the appearance of the resulting charcoal and this depends largely on the proportions and distribution of the constituent vessels, fibres and parenchyma, as well as moisture content. This study describes the structural changes in the charcoal of the wood of Croton sonderianus Muell. Arg. at two temperatures, 400 °C or 600 °C. This species is an important source of charcoal in the caatinga of the northeast part of Brazil. The samples were heated for ten minutes to reach treatment temperature, charred for two hours at either 400 °C or 600 °C and then left to cool to ambient temperature for 30 to 60 minutes. Our observations showed that most of the changes occurred when charcoal was produced at 600 °C, but the qualitative features necessary for identification were retained. At this temperature, cells lost their circular shape, became angular and occasionally amorphous, the middle lamella disappeared and the walls of adjacent cells coalesced, cell walls became thinner, and the prismatic crystals developed cracks and became porous. Our findings are compared with those for two previously studied Mimosa species which have an entirely different anatomy.