Dry season mapping of savanna forage quality, using the hyperspectral Carnegie Airborne Observatory sensor

Nichola M. Knox*, Andrew K. Skidmore, Herbert H. T. Prins, Gregory P. Asner, Harald M. A. van der Werff, Willem F. de Boer, Cornelis van der Waal, Hendrik J. de Knegt, Edward M. Kohi, Rob Slotow, Rina C. Grant

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

85 Citations (Scopus)


Forage quality within an African savanna depends upon limiting nutrients (nitrogen and phosphorus) and nutrients that constrain the intake rates (non-digestible fibre) of herbivores. These forage quality nutrients are particularly crucial in the dry season when concentrations of limiting nutrients decline and non-digestible fibres increase. Using artificial neural networks we test the ability of a new imaging spectrometer (CAO Alpha sensor), both alone and in combination with ancillary data, to map quantities of grass forage nutrients in the early dry season within an African savanna. Respectively 65%, 57% and 41%, of the variance in fibre, phosphorus and nitrogen concentrations were explained. We found that all grass forage nutrients show response to fire and soil. Principal component analysis, not only reduced image dimensionality, but was a useful method for removing cross-track illumination effects in the CAO imagery. To further improve the mapping of forage nutrients in the dry season we suggest that spectra within the shortwave infrared (SWIR) region, or additional relevant ancillary data, are required.

Original languageEnglish
Pages (from-to)1478-1488
Number of pages11
JournalRemote Sensing of Environment
Issue number6
Publication statusPublished - 2011
Externally publishedYes


  • Kruger National Park
  • Savannah
  • Carnegie Airborne Observatory
  • Forage quality
  • ANN
  • Hyperspectral


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