Linking near-infrared spectroscopy of 25 tropical Gabonese hardwoods to tree ecological temperament

Abstract

To use wood species appropriately and optimally, it is imperative to know their chemical composition. The application of near-infrared spectroscopy (NIRS) provided a valuable approach to correlate wood pro- perties with tree ecological traits and their adaptive responses. The study aim was to verify that different chemical compositions exist for a wide range of species grouped into distinct ecological temperaments. Thus, 25 tropical Gabonese hardwoods, mainly secondary species, were studied and divided into three ecological tempe- raments: pioneer, hemi-heliophilous, and shade-tolerant. The spectra studied were obtained using a Spectrum Two N spectro- meter (PerkinElmer) on the transverse faces of 368 unground samples of heartwood by reflectance in the range 1000 to 2500 nm. These were then subjected to pre-proces- sing (standard normal variable and second derivative), followed by principal compo- nent analysis and partial least squares discriminant analysis. The discrimination model used showed high performance in cross-validation and prediction at 93.2% and 88.3%, respectively. The results indicated differences in NIRS signatures between the three ecological temperaments. The hemi-heliophilous and shade-tolerant spe- cies had similar NIRS signatures but diffe- rent concentrations of chemical compounds (derived from NIRS spectra analysis). The pioneers had a different profile from the other two ecological temperaments. No significant difference in cellulose content was found between the three ecological temperaments. Hemicelluloses and lignin concentrations were higher in the shade species. The pioneer species had significant levels of extractives