Influence of relative water content variation on the spectral behavior of Eucalyptus spp.
Conteúdo relativo de água afeta o comportamento espectral de folhas de Eucalyptus spp.
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Water availability is fundamental for the development of the plant and its scarcity limits forest growth, triggering specific responses in each species of Eucalyptus spp. In this study the influence of the relative water content (CRA) through dehydration on the spectral behavior, was measured on leaves of 11 genotypes of Eucalyptus spp. Sampled leaves were dried progressively and, after weighing, a hyperspectral reading was made. Water has a higher reflectance in the medium infrared (1300 nm at 2500 nm). The greatest variation occurred between the wavelengths of 1300 nm - 2500 nm. The regions near 1400 nm and 1900 nm showed greater sensitivity to water content variation. A classification of the leaves’ spectral data with major and minor CRA was done with Principal Components Analysis (PCA). After this analysis, the wavelengths 1450 nm, 1887 nm and 2101 nm were the most efficient in classifying the progress level of dehydration, which was confirmed by the Tukey test. Therefore, the CRA variation was inversely related to the spectral response of Eucalyptus spp., mostly in the medium infrared region. Thus, the smaller the amount of water in leaf, the higher the reflectance factor. Among the different genotypes studied E. benthamii resulted in a lower reflectance factor in the near and medium infrared.