Résumé
Near infrared spectroscopy (NIRS) is a promising tool for valorizing herbarium specimens as it allows the gathering information on plants without damaging valuable and historical samples. The CIRAD herbarium is currently testing various approaches. These research can be separated into three areas: Firstly, we are using the NIR spectrum as a trait, studying its covariation with some other more “classic” functional traits such as Specific Leaf Area and leaf thickness. We are working on a dataset of Combretum genus from West and Central Africa to assess relationships between functional traits and a rainfall gradient. We are also examining functional traits of a Sahelian species, Balanites aegyptiaca, in relation with water availability. Secondly, we are experimenting with NIRS as a tool for systematics discrimination. Assuming that intraspecific variations in the spectrum are smaller than interspecific variations, it may be possible to make identifications in herbarium within some genus, using appropriate calibration. A test was carried out on two Pistacia species and their hybrid, with some specimens dating back 150 years and others collected recently. Using these two datasets, we evaluate the ability of NIR models built on older collections to discriminate recent samples or, in opposite, the possibility of discriminating older samples with recent collections. Finally, we are experimenting NIRS for the prediction of leaf chemical composition. As prediction of fodder chemical value is already possible from the use of NIRS on grounded vegetal material, we are building a large calibration set to test the feasibility of applying the same method non-destructively on complete herbarium specimens. We present an overview of the research underway in our laboratory, spanning these three areas with practical case studies and initial results.