Reliability of wood identification using DART-TOFMS and the ForeST© database: A validation study

Abstract

The Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES) has listed over 100 species of trees whose trade is primarily in timber, and whose existence may be endangered due to either indiscriminate or illegal logging. Species determination of timber is essential for enforcing logging quotas and species protections laws, but it is a challenging endeavor. Here we present a technique that relies on mass spectra chemotypes for species assignment and demonstrate that it provides high reliability.The reliability of timber identification by mass spectrometry relies on multiple factors: 1) access to a robust wood spectra database (e.g., ForeST ©: Forensic Spectra of Trees) derived from a curated xylarium, 2) analysis of the correct wood tissue (i.e., heartwood vs sapwood), 3) reproducibility of the spectra, 4) repeatability of the analysis and 5) skill in interpreting the data. The goal of timber identification is to assign wood products to species, but in some cases the precision of the analysis will be to the genus or even family level. This may be due, for example, to shared chemotypes among closely related tree species. These higher taxa assignments do not represent an error (false positive or false negative), but rather reflect the complexity of wood chemistry in relation to phylogeny. Such higher taxa determinations are often sufficient for enforcement purposes, as many timber trees are protected at the genus or above.