Calibration of a species-specific spectral vegetation index for leaf Aaea index (LAI) monitoring: Example with MODIS Reflectance time-series on eucalyptus plantations

Le Maire Guerric, Marsden Claire, Nouvellon Yann, Stape Jose Luiz, Ponzoni Flávio Jorge. 2012. Calibration of a species-specific spectral vegetation index for leaf Aaea index (LAI) monitoring: Example with MODIS Reflectance time-series on eucalyptus plantations. Remote Sensing, 4 (2) : 3766-3780.

Quartile : Q2, Sujet : REMOTE SENSING

Résumé : The leaf area index (LAI) is a key characteristic of forest ecosystems. Estimations of LAI from satellite images generally rely on spectral vegetation indices (SVIs) or radiative transfer model (RTM) inversions. We have developed a new and precise method suitable for practical application, consisting of building a species-specific SVI that is best-suited to both sensor and vegetation characteristics. Such an SVI requires calibration on a large number of representative vegetation conditions. We developed a two-step approach: (1) estimation of LAI on a subset of satellite data through RTM inversion; and (2) the calibration of a vegetation index on these estimated LAI. We applied this methodology to Eucalyptus plantations which have highly variable LAI in time and space. Previous results showed that an RTM inversion of Moderate Resolution Imaging Spectroradiometer (MODIS) near-infrared and red reflectance allowed good retrieval performance (R2 = 0.80, RMSE = 0.41), but was computationally difficult. Here, the RTM results were used to calibrate a dedicated vegetation index (called "EucVI") which gave similar LAI retrieval results but in a simpler way. The R2 of the regression between measured and EucVI-simulated LAI values on a validation dataset was 0.68, and the RMSE was 0.49. The additional use of stand age and day of year in the SVI equation slightly increased the performance of the index (R2 = 0.77 and RMSE = 0.41). This simple index opens the way to an easily applicable retrieval of Eucalyptus LAI from MODIS data, which could be used in an operational way.

Mots-clés Agrovoc : Eucalyptus, plantations, indice de surface foliaire, méthodologie, télédétection, spectrométrie, réflectométrie, modélisation environnementale, mesure (activité), âge, variation saisonnière, spectroscopie infrarouge

Classification Agris : F40 - Écologie végétale
F62 - Physiologie végétale - Croissance et développement
U30 - Méthodes de recherche
K10 - Production forestière
U10 - Informatique, mathématiques et statistiques

Champ stratégique Cirad : Axe 1 (2005-2013) - Intensification écologique

Auteurs et affiliations

• Le Maire Guerric, CIRAD-PERSYST-UMR Eco&Sols (FRA) ORCID: 0000-0002-5227-958X
• Marsden Claire, IRC [Institut des régions chaudes] (FRA)
• Nouvellon Yann, CIRAD-PERSYST-UMR Eco&Sols (BRA) ORCID: 0000-0003-1920-3847
• Stape Jose Luiz, North Carolina State University (USA)
• Ponzoni Flávio Jorge, INPE (BRA)

Source : Cirad - Agritrop (https://agritrop.cirad.fr/567128/)

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