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Impact of drought on Eucalyptus wood chemistry by near infra red hyperspectral imaging

Chaix G., Pires Franco M., Chambi Legoas R., Gorretta N., Pasquini C., Vidal C., Roger J.M.. 2019. Pesquisa Florestal Brasileira, 39 : p. 175-175. IUFRO World Congress 2019 "Forest Research and Cooperation for Sustainable Development". 25, 2019-09-29/2019-10-05, Curitiba (Brésil).

The aim is to study tree development submitted to different water and mineral constraints. The objective is to correlate spatial distribution of wood chemistry with wood density secondary growth. We sampled wood discs from 54 trees in rainfall exclusion design with Eucalyptus grandis at Esalq-USP. ltatinga Station.brazil. We felled the 5 years old trees growing under different water availability. For each disk. we acquired an image with a near infrared (nir) hyperspectral camera (hs1, specim. pixel size 625 x 625µml. The challenge here was to transfer our previous nir calibrations for total extractives built with a benchtop spectrometer (vector. bruker) to a hsi camera by using standard sample set measured ,>n the two devices. An efficient model were built for the his camera with a prediction error of 10.3% compared to the prediction error of 11.60% for our previous calibration with benchtop spectrometer. Then, based on spectra from his image. we predicted extractive contents and built images. These allow us to compare their spatial distributions according to the growth conditions. In the absence or absence or fertilization, trees with higher water stress showed a higher heterogeneous distribution. from pith to bark, for the total extractive contents and a higher average mean value. In perspective. these data will allow us to study and reline the knowledge on cambium activity according to climatic variations by crossing variability of the chemical properties, x-ray micro-density and anatomy of wood, and diameter growth rate measured by electronic dendrometers.

Mots-clés : eucalyptus grandis; technologie du bois; propriété physicochimique; stress abiotique; nutrition des plantes; spectroscopie infrarouge; spectroscopie aux rayons x; dendrométrie; brésil; densité du bois

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