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

Research output: Contribution to journalArticle

E-pub ahead of print

DOI

  • Anthony R. Palmer
  • Onalenna Gwate
  • Zahn Munch
  • Lesley Gibson
  • Perpetua Okoye
  • Sukhmani K. Mantel
  • Andiswa Finca

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Original languageEnglish
JournalAfrican Journal of Range & Forage Science
Early online date17 Apr 2017
DOIs
StateE-pub ahead of print - 17 Apr 2017

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 Eucalyptusplantation. 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.

Keywords

  • fPAR, leaf area index, land cover, Pot River