Grassland development under glacial and interglacial conditions in southern Africa: review of pollen, phytolith and isotope evidence

Abstract

Pollen evidence suggests that grasslands were well established in southern Africa by the Late Tertiary. Evidence for grassland composition in the region during the Quaternary includes published accounts of isotopes, grass phytoliths and pollen of both grasses and woody plants from a wide range of different environments. Isotope data were derived from speleothems (stalagmites), fossil bones, and fossil tooth enamel and plant material in fossil hyrax dung. The different data types suggest that, with perhaps the exception of the dry southern Kalahari region, temperate grassland consisted of a relatively increased C 3- to C 4-grass ratios during the Last Glacial Maximum (LGM). Cold winter temperature extremes in the southern high latitude and altitude regions and a persistent winter rainfall pattern over the Cape region during the LGM probably limited the distribution of C 4 grasses and canceled out any advantages gained from lowered CO 2 concentrations in the atmosphere. In contrast, in the tropics where marked seasonal temperature fluctuations were lacking, C 4-grass growth was favored.