Researchers studying waterlogged archaeological wood observed strong delignification of the secondary cell walls in both ash and oak samples, while the compound middle lamellae appeared structurally intact but with lower UV absorbance than normal wood. They concluded that oak heartwood was generally better preserved than ash wood based on the observation that the 4500-year-old oak samples appeared better preserved than the 5200-year-old ash samples.
Which one of the following would be most useful to know in evaluating the researchers’ conclusion regarding the relative preservation of oak and ash heartwood?
Answer: