Calibration of a Species-Specific Spectral Vegetation Index for Leaf Area Index LAI Monitoring: Example with MODIS Reflectance Time-Series on Eucalyptus PlantationsReportar como inadecuado




Calibration of a Species-Specific Spectral Vegetation Index for Leaf Area Index LAI Monitoring: Example with MODIS Reflectance Time-Series on Eucalyptus Plantations - Descarga este documento en PDF. Documentación en PDF para descargar gratis. Disponible también para leer online.

1 Eco&Sols - Ecologie fonctionnelle et biogéochimie des sols et des agro-écosystèmes 2 UMR Eco&Sols 3 Departamento de Ciências Atmosféricas 4 Department of Forestry and Environmental Sciences 5 Remote Sensing Department

Abstract : 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 R-2 = 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 R-2 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 R-2 = 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.

Keywords : remote sensing eucalypt EucVI MOD13Q1 radiative transfer model PROSAIL thematic mapper forest canopy model red derivation biomass ndvi





Autor: Guerric Le Maire - Claire Marsden - Yann Nouvellon - José-Luiz Stape - Flavio Jorge Ponzoni -

Fuente: https://hal.archives-ouvertes.fr/



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