Supervising wood exploitation can be very challenging due to the existence of many similar species and the reduced number of wood identification experts to meet the demand. There is evidence that valuable endangered wood species are being smuggled disguised as other species. Near infrared spectroscopy (NIRS) and chemometrics has been successfully used to discriminate between Amazonian wood species using high resolution instruments. In this study, a handheld spectrometer was evaluated for the discrimination of six visually similar tropical wood species using PLS-DA. Woods of mahogany (Swietenia macrophylla) and cedar (Cedrela odorata), both high value tropical timber species included in Appendixes II and III of the CITES, respectively; crabwood (Carapa guianensis); cedrinho (Erisma uncinatum); curupixá (Micropholis melinoniana); and jatobá (Hymenea coubaril). The data for model development and validation take into account both laboratory and field measurements. Outlier exclusion was performed based on Hotelling T2, residuals Q and errors in the estimated class values. The efficiency rates were higher than 90% for all species, showing that the handheld NIR combined with PLS-DA succeeded in discriminate between these species. These results stimulate the application of handheld NIR spectrometers in the supervision of wood exploitation, which can contribute to the species preservation.

The determinations of cellulose and lignin are important in wood analysis from both perspectives: chemistry composition, commercial and industrial application of woods. In this context, Raman image spectroscopy was applied in the determination of cellulose and lignin distribution in wood surfaces of Swietenia macrophylla King (Mahogany) and Eucalyptus hybrid (E. urophylla × E. camaldulensis). The relative concentration maps were obtained by applying a multivariate curve resolution procedure. The estimated Raman spectra for cellulose and lignin agrees with the ones available in the literature. The cellulose concentration maps showed similar variations for both studied species with an average value of nearly 85% as obtained by the reference method. The lignin concentration maps were somewhat different. The Eucalyptus hybrid presents a broader distribution (20 to 45%) while for Mahogany it is nearly constant, around 25%, with localized regions presenting contents of 45 to 65% of lignin. The reference method showed that the mean lignin content of both species is 27%. The cellulose and lignin concentration maps agree with the biological functions of the anatomic structures observed in the images.