Documented improvement in leaf area index estimates from MODIS using hemispherical photos for Australian savannas

William Sea, P Choler, Jason Beringer, Richard Weinmann, Lindsay Hutley, Ray Leuning

    Research output: Contribution to journalArticle

    42 Citations (Scopus)

    Abstract

    This paper compares estimates of Leaf Area Index (LAI) obtained from the MODIS (Moderate Resolution Imaging Spectroradiometer) collections 4.8 (MC4) and 5.0 (MC5) with ground-based measurements taken along a 900 km northâ¿¿south transect through savanna in the Northern Territory, Australia. There was excellent agreement for both the magnitude and timing in the annual variation in LAI from MC5 and biometric estimates at Howard Springs, near Darwin, whereas MC4 overestimated LAI by 1â¿¿2 m2 mâ¿¿2 for the first 200 days of the year. Estimates of LAI from MC5 were also compared with those obtained from the analysis of digital hemispherical photographs taken during the dry season (September 2008) based on algorithms that included random and clumped distribution of leaves. Linear regression of LAI from MC5 versus that using the clumping algorithm yielded a slope close to 1 (m = 0.98). The regression based on a random distribution of leaves yielded a slope significantly different from 1 (m = 1.37), with higher Mean Absolute Error (MAE) and bias compared to the clumped analysis. The intercept for either analysis was not significantly different from zero but inclusion of five additional sites that were visually bare or without green vegetation produced a statistically significant offset of +0.16 m2 mâ¿¿2 by MC5. Overall, our results show considerable improvement of MC5 over MC4 LAI and good agreement between MC5 and ground-based LAI estimates from hemispherical photos incorporating clumping of leaves.
    Original languageEnglish
    Pages (from-to)1453-1461
    Number of pages9
    JournalAgricultural and Forest Meteorology
    Volume15
    Issue number11
    DOIs
    Publication statusPublished - 2011

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