Prof. Lincoln Raitt

Permanent URI for this collection

https://hdl.handle.net/10566/1540

Prof. Lincoln Raitt

Position: Emeritus Professor
Department: Biodiversity and Conservation Biology Programme
Faculty: Faculty of Natural Science
Qualifications: BSc (UNISA), Hons BSc, MSc, PhD (Stell)
Tel: 021 959 2306
Fax: 021 959 2312
Email: lraitt@uwc.ac.za

Browse

Browsing by Subject "Lichens"

Now showing 1 - 1 of 1
  • Thumbnail Image
    Item
    Will climate warming exceed lethal photosynthetic temperature thresholds of lichens in a southern African arid region?
    (Wiley, 2013) Maphangwa, Khumbudzo Walter; Musil, Charles F.; Raitt, Lincoln; Zedda, Luciana
    Predicted elevated temperatures and a shift from a winter to summer rainfall pattern associated with global warming could result in the exposure of hydrated lichens during summer to more numerous temperature extremes that exceed their thermal thresholds. This hypothesis was tested by measuring lethal temperature thresholds under laboratory and natural conditions for four epilithic lichen species (Xanthoparmelia austro-africana, X. hyporhytida, Xanthoparmelia sp., Xanthomaculina hottentotta) occurring on quartz gravel substrates at a hot arid inland site two epigeous lichen species (Teloschistes capensis, Ramalina sp.) occurring on gypsum-rich topsoil at a warm humid coastal site. Extrapolated lethal temperatures for photosynthetic quantum yield under laboratory conditions were up to 4°C higher for lichens from a dry inland site than those from a humid coastal site. Lethal temperatures extrapolated for photosynthetic quantum yield at a saturating photosynthetic photon flux density of ≥11,000 µmol photons m-2s-1 under natural conditions were up to 6°C higher for lichens from the dry inland site than the more humid coastal site. It is concluded that only under atypical conditions of lichen exposure in a hydrated state to temperature extremes at high midday solar irradiances during summer could lethal photosynthetic thresholds in sensitive lichen species be potentially exceeded, but whether the increased frequency of such conditions with climate warming would lead to increased likelihood of lichen mortality is debatable.