Exploring the link between clouds, radiation, and canopy productivity of tropical savannas

Kasturi Devi Kanniah, Jason Beringer, Lindsay Hutley

    Research output: Contribution to journalArticleResearchpeer-review

    Abstract

    The control of clouds on the canopy gross primary productivity (GPP) was examined at Howard Springs, a tropical savanna site in the Northern Territory, Australia. It was demonstrated in this study that cloudiness can increase the initial canopy quantum efficiency (?), midday light use efficiency (LUE) and water use efficiency (WUE), but decrease GPP in savannas. Thick clouds (clearness index of 0-0.3 in the wet season produced much more diffuse fraction of Photosynthetically Active Radiation (fDPAR. >. 80%), which caused increases in ? by 24% and 62% compared to thin clouds (fDPAR between 30% and 80%) and clear sky (fDPAR. <. 30%) conditions respectively. The influence of environmental conditions shows that under similar vapour pressure deficit, temperature and soil water content classes, ? values were significantly higher under thick clouds compared to thin clouds or clear skies. This indicates the importance of diffuse radiation in enhancing LUE even within similar environmental conditions. However, the enhanced LUE under cloudy skies is insufficient to increase GPP due to the dramatic decline in total radiation. Therefore, it can be concluded that the quantity of solar radiation is more critical than the quality of radiation in savannas. However, savanna ecosystems appear to be well adapted to the environment where a 63% decrease in PAR only reduced GPP by 26%. These findings highlight the importance of clouds as a critical factor in determining savanna productivity that has implications for savannas carbon cycle. 
    Original languageEnglish
    Pages (from-to)304-313
    Number of pages10
    JournalAgricultural and Forest Meteorology
    Volume182-183
    DOIs
    Publication statusPublished - 2013

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    savanna
    savannas
    canopy
    productivity
    light use efficiency
    primary productivity
    clear sky
    photosynthetically active radiation
    environmental conditions
    environmental factors
    Northern Territory
    vapor pressure
    water use efficiency
    carbon cycle
    cloud cover
    wet season
    radiation
    soil water content
    solar radiation
    soil water

    Cite this

    @article{15bd90ad9d5a4f4fb1fcd441b8316e0a,
    title = "Exploring the link between clouds, radiation, and canopy productivity of tropical savannas",
    abstract = "The control of clouds on the canopy gross primary productivity (GPP) was examined at Howard Springs, a tropical savanna site in the Northern Territory, Australia. It was demonstrated in this study that cloudiness can increase the initial canopy quantum efficiency (?), midday light use efficiency (LUE) and water use efficiency (WUE), but decrease GPP in savannas. Thick clouds (clearness index of 0-0.3 in the wet season produced much more diffuse fraction of Photosynthetically Active Radiation (fDPAR. >. 80{\%}), which caused increases in ? by 24{\%} and 62{\%} compared to thin clouds (fDPAR between 30{\%} and 80{\%}) and clear sky (fDPAR. <. 30{\%}) conditions respectively. The influence of environmental conditions shows that under similar vapour pressure deficit, temperature and soil water content classes, ? values were significantly higher under thick clouds compared to thin clouds or clear skies. This indicates the importance of diffuse radiation in enhancing LUE even within similar environmental conditions. However, the enhanced LUE under cloudy skies is insufficient to increase GPP due to the dramatic decline in total radiation. Therefore, it can be concluded that the quantity of solar radiation is more critical than the quality of radiation in savannas. However, savanna ecosystems appear to be well adapted to the environment where a 63{\%} decrease in PAR only reduced GPP by 26{\%}. These findings highlight the importance of clouds as a critical factor in determining savanna productivity that has implications for savannas carbon cycle. ",
    keywords = "carbon cycle, clear sky, cloud cover, environmental conditions, forest canopy, light use efficiency, net primary production, photosynthetically active radiation, radiative transfer, savanna, soil water, tropical region, vapor pressure, water content, water use efficiency, Australia, Howard Springs, Northern Territory",
    author = "Kanniah, {Kasturi Devi} and Jason Beringer and Lindsay Hutley",
    year = "2013",
    doi = "10.1016/j.agrformet.2013.06.010",
    language = "English",
    volume = "182-183",
    pages = "304--313",
    journal = "Agricultural and Forest Meteorology",
    issn = "0168-1923",
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    }

    Exploring the link between clouds, radiation, and canopy productivity of tropical savannas. / Kanniah, Kasturi Devi; Beringer, Jason; Hutley, Lindsay.

    In: Agricultural and Forest Meteorology, Vol. 182-183, 2013, p. 304-313.

    Research output: Contribution to journalArticleResearchpeer-review

    TY - JOUR

    T1 - Exploring the link between clouds, radiation, and canopy productivity of tropical savannas

    AU - Kanniah, Kasturi Devi

    AU - Beringer, Jason

    AU - Hutley, Lindsay

    PY - 2013

    Y1 - 2013

    N2 - The control of clouds on the canopy gross primary productivity (GPP) was examined at Howard Springs, a tropical savanna site in the Northern Territory, Australia. It was demonstrated in this study that cloudiness can increase the initial canopy quantum efficiency (?), midday light use efficiency (LUE) and water use efficiency (WUE), but decrease GPP in savannas. Thick clouds (clearness index of 0-0.3 in the wet season produced much more diffuse fraction of Photosynthetically Active Radiation (fDPAR. >. 80%), which caused increases in ? by 24% and 62% compared to thin clouds (fDPAR between 30% and 80%) and clear sky (fDPAR. <. 30%) conditions respectively. The influence of environmental conditions shows that under similar vapour pressure deficit, temperature and soil water content classes, ? values were significantly higher under thick clouds compared to thin clouds or clear skies. This indicates the importance of diffuse radiation in enhancing LUE even within similar environmental conditions. However, the enhanced LUE under cloudy skies is insufficient to increase GPP due to the dramatic decline in total radiation. Therefore, it can be concluded that the quantity of solar radiation is more critical than the quality of radiation in savannas. However, savanna ecosystems appear to be well adapted to the environment where a 63% decrease in PAR only reduced GPP by 26%. These findings highlight the importance of clouds as a critical factor in determining savanna productivity that has implications for savannas carbon cycle. 

    AB - The control of clouds on the canopy gross primary productivity (GPP) was examined at Howard Springs, a tropical savanna site in the Northern Territory, Australia. It was demonstrated in this study that cloudiness can increase the initial canopy quantum efficiency (?), midday light use efficiency (LUE) and water use efficiency (WUE), but decrease GPP in savannas. Thick clouds (clearness index of 0-0.3 in the wet season produced much more diffuse fraction of Photosynthetically Active Radiation (fDPAR. >. 80%), which caused increases in ? by 24% and 62% compared to thin clouds (fDPAR between 30% and 80%) and clear sky (fDPAR. <. 30%) conditions respectively. The influence of environmental conditions shows that under similar vapour pressure deficit, temperature and soil water content classes, ? values were significantly higher under thick clouds compared to thin clouds or clear skies. This indicates the importance of diffuse radiation in enhancing LUE even within similar environmental conditions. However, the enhanced LUE under cloudy skies is insufficient to increase GPP due to the dramatic decline in total radiation. Therefore, it can be concluded that the quantity of solar radiation is more critical than the quality of radiation in savannas. However, savanna ecosystems appear to be well adapted to the environment where a 63% decrease in PAR only reduced GPP by 26%. These findings highlight the importance of clouds as a critical factor in determining savanna productivity that has implications for savannas carbon cycle. 

    KW - carbon cycle

    KW - clear sky

    KW - cloud cover

    KW - environmental conditions

    KW - forest canopy

    KW - light use efficiency

    KW - net primary production

    KW - photosynthetically active radiation

    KW - radiative transfer

    KW - savanna

    KW - soil water

    KW - tropical region

    KW - vapor pressure

    KW - water content

    KW - water use efficiency

    KW - Australia

    KW - Howard Springs

    KW - Northern Territory

    U2 - 10.1016/j.agrformet.2013.06.010

    DO - 10.1016/j.agrformet.2013.06.010

    M3 - Article

    VL - 182-183

    SP - 304

    EP - 313

    JO - Agricultural and Forest Meteorology

    JF - Agricultural and Forest Meteorology

    SN - 0168-1923

    ER -