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Accueil du site → Master → Afrique du Sud → Estimating foliar and wood lignin concentrations, and leaf area index (LAI) of Eucalyptus clones in Zululand usig hyperspectral imagery

University of KwaZulu-Natal (2006)

Estimating foliar and wood lignin concentrations, and leaf area index (LAI) of Eucalyptus clones in Zululand usig hyperspectral imagery

Mthembu, Ingrid Bongiwe

Titre : Estimating foliar and wood lignin concentrations, and leaf area index (LAI) of Eucalyptus clones in Zululand usig hyperspectral imagery

Auteur : Mthembu, Ingrid Bongiwe.

Université de soutenance : University of KwaZulu-Natal

Grade : Master of Science (MS) 2006

Résumé
To produce high quality paper, lignin should be removed from the pulp. Quantification of lignin concentrations using standard wet chemistry is accurate but time consuming and costly, thus not appropriate for a large number of samples. The ability of hyperspectral remote sensing to predict foliar lignin concentrations could be utilized to estimate wood lignin concentrations if meaningful relationships between wood and foliar chemistry are established. LAI (leaf area index) is a useful parameter that is incorporated into physiological models in forest assessment. Measuring LAI over vast areas is labour intensive and expensive ; therefore, LAI has been correlated to vegetation indices using remote sensing. Broadband indices use average spectral information over broad bandwidths ; therefore details on the characteristics of the forest canopy are compromised and averaged. Moreover, the broadband indices are known to be highly affected by soil background at low vegetation cover. The aim of this study is to determine foliar and wood lignin concentrations of Eucalyptus clones using hyperspectral lignin indices, and to estimate LAI of Eucalyptus clones from narrowband vegetation indices in Zululand, South Africa Twelve Eucalyptus compartments of ages between 6 and 9 years were selected and 5 trees were randomly sampled from each compartment. A Hyperion image was acquired within ten days of field sampling, SI and LAI measurements. Leaf samples were analyzed in the laboratory using the Klason method as per Tappi standards (Tappi, 1996-1997). Wood samples were analyzed for lignin concentrations using a NIRS (Near Infrared Spectroscopy) instrument. The results showed that there is no general model for predicting wood lignin concentrations from foliar lignin concentrations in Eucalyptus clones of ages between 6 and 9 years. Regression analysis performed for individual compartments and on compartments grouped according to age and SI showed that the relationship between wood and foliar lignin concentration is site and age specific.

Mots clés : Wood — Chemistry—Properties — Eucalyptus — Near infrared reflectance spectroscopy. – Leaves – Composition — Remote sensing — Forest canopies — Remote sensing – Pulping — Foliar diagnosis

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