A 5000-yr record of Afromontane vegetation dynamics from the Drakensberg Escarpment, South Africa

Abstract

Afromontane environments are sensitive to climatic and environmental change as a consequence of their inherent altitudinal and latitudinal gradients. Palaeoecological investigations have been used in these areas to track ecosystem response to climatic and anthropogenic drivers, and have gained prominence in recent years in the context of the need to understand faunal and floral response to future climate uncertainty. This paper focusses on long-term vegetation history in the Drakensberg Escarpment of South Africa, an area with a long history of human habitation, that is internationally recognised for its conservation importance. Ecologists have hypothesised that human-induced burning during the late Quaternary may have been responsible for the expansion of Afromontane grasslands at the expense of forests, which currently exist as refugial patches within fire-protected valleys. Here we test this argument using empirical palaeoecological evidence derived from a subalpine wetland in the Cathedral Peak area of the Drakensberg Escarpment. An age model derived from eight AMS radiocarbon ages, and supported by a pollen time-marker, is used to provide chronological control. Fossil pollen, and carbon and nitrogen isotope analyses, are combined to reconstruct past vegetation dynamics. Results indicate a lack of major compositional vegetation change over the past 5000 years, suggesting long-term vegetation and climatic stability throughout the record. The pollen data show that grasslands have dominated the region, while forests expanded during the late Holocene, thereby refuting the notion of recent forest reduction in the Drakensberg.