Determining fPAR and leaf area index of several land cover classes in the Pot River and Tsitsa River catchments of the Eastern Cape, South Africa

Anthony R. Palmer, Andiswa Finca, Sukhmani K. Mantel, Onalenna Gwate, Zahn Munch, Lesley A. Gibson

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    Abstract

    Determining the quantum (both annual maxima and minima) and the temporal variation in the leaf area index (LAI), and the fraction of photosynthetically active radiation (fPAR), are three fundamental biophysical characteristics of the plant canopy that should parameterise ecophysiological models of water use (evapotranspiration) and carbon sequestration. Although Earth observation provides values and time series for both these parameters, in-field validation of these values is necessary. Following a very wet summer season, we conducted field surveys of several land cover classes within two quaternary catchments in the Eastern Cape province, South Africa, to determine maximum values of LAI and fPAR that occur within each of these land cover classes. To assist in up-scaling these point measures to the landscape, we present a regression relationship between Landsat 8 NDVI and LAI measured using an Accupar Ceptometer (r2 = 0.92). Peak wet season LAI varied from extremely high (>7.0) under the canopy of invasive black wattle (Acacia mearnsii) trees to ~2.0 under the canopy of a Eucalyptus plantation. Ungrazed native grassland displayed an intermediate LAI value of 3.84. The black wattle stand absorbed 97% of the available PAR, whereas the mature Eucalyptus plantation only absorbed 66% of PAR.
    Original languageEnglish
    Pages (from-to)33-37
    Number of pages5
    JournalAfrican Journal of Range and Forage Science
    Volume34
    Issue number1
    Early online date17 Apr 2017
    DOIs
    Publication statusPublished - 2017

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    Keywords

    • fPAR
    • leaf area index
    • land cover
    • Pot River
    • agroforestry
    • ecosystem ecology
    • remote sensing

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