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

    39 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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    moderate resolution imaging spectroradiometer
    leaf area index
    savanna
    MODIS
    savannas
    leaves
    Northern Territory
    biometry
    ground-based measurement
    photographs
    annual variation
    photograph
    dry season
    transect
    vegetation
    analysis

    Cite this

    Sea, William ; Choler, P ; Beringer, Jason ; Weinmann, Richard ; Hutley, Lindsay ; Leuning, Ray. / Documented improvement in leaf area index estimates from MODIS using hemispherical photos for Australian savannas. In: Agricultural and Forest Meteorology. 2011 ; Vol. 15, No. 11. pp. 1453-1461.
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    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 north{\^a}¿¿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 1{\^a}¿¿2 m2 m{\^a}¿¿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 m{\^a}¿¿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.",
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    Documented improvement in leaf area index estimates from MODIS using hemispherical photos for Australian savannas. / Sea, William; Choler, P; Beringer, Jason; Weinmann, Richard; Hutley, Lindsay; Leuning, Ray.

    In: Agricultural and Forest Meteorology, Vol. 15, No. 11, 2011, p. 1453-1461.

    Research output: Contribution to journalArticle

    TY - JOUR

    T1 - Documented improvement in leaf area index estimates from MODIS using hemispherical photos for Australian savannas

    AU - Sea, William

    AU - Choler, P

    AU - Beringer, Jason

    AU - Weinmann, Richard

    AU - Hutley, Lindsay

    AU - Leuning, Ray

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    N2 - 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.

    AB - 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.

    KW - LAI

    KW - Savannas

    KW - MODIS validation

    KW - Hemispherical photos

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    SN - 0168-1923

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    ER -