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sur le développement des zones arides et semi-arides

Titre : Revisiting the dendroclimatological potential of Afrocarpus falcatus, South Africa

Auteur : Baverstock, Jean Dorathea.

Université de soutenance : University of KwaZulu-Natal

Grade : Master Degree (Geography) 2021

Résumé
The long-lived evergreen conifer Afrocarpus falcatus has been shown to have dendrochronological potential, however, complex tree-ring structures have hampered further research on the species. Hall (1976) produced a classic South African tree-ring width-based rainfall record using an Afrocarpus falcatus museum specimen from the Karkloof Forest in KwaZulu-Natal, South Africa. Despite wide application of this palaeoclimate rainfall record, the dendroclimatological potential of this species has yet to be fully explored, nor has the associated climate environmental forcing been validated. The aim of this research was to investigate tree-growth climate relationships and to develop a modern analogue for Afrocarpus falcatus in the Karkloof Forests. Twenty trees were sampled from the Karkloof Forests, but due to ring-width eccentricity, only a limited number could be used to develop a ring-width and ring stable carbon isotope based mean chronology using classical methods. When tested against instrumental climate records, temperature, not rainfall, was found to be the most important variable driving tree growth. Ring δ13C series were shown to be unaffected by compression and ring-width eccentricity, requiring a much smaller sample size than the ring-width analysis. Where annual rings can be correctly identified, and an adequate number of samples crossdated, ring δ13C series of Afrocarpus falcatus can potentially provide a reliable proxy for temperature. Dendroclimatological studies of Afrocarpus falcatus therefore have the potential to make an important contribution in a region where reliable palaeoclimate records are limited.

Mots clés  : Afrocarpus falcatus ; dendroclimatology ; dendrochronology ; tree-ring width ; carbon isotopes ; South Africa

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