干旱区生态环境知识资源中心

A recently recognized sequence of buried palaeosols within a colluvial hollow on the farm Voordrag, along the upper Mkuze River valley in northern Natal, provides evidence of climatically induced vegetation change during a period of cooling, the Late Pleistocene Hypothermal (LPH), between approximately 35 000 and 14 500 BP.

Cool, humid conditions between approximately 35 000 and 34 500 BP gave way to a colder, more arid environment during the period between approximately 20 000 and 18 700 BP, when shrubby karroid and ericoid fynbos species increased in the grasslands of the area. This is interpreted in terms of elevational lowering of vegetation belts in the region by up to 1 000 m during the coldest phase of the LPH. The co-existence of both dry karroid and ericoid fynbos vegetation suggests a more even seasonal rainfall distribution in the region which presently receives mainly summer rains. Isotopic evidence from palaeosol organic matter suggests, however, that the composition of the local aquatic and semi-aquatic plants at the site was predominantly of C4 type from approximately 35 000 to 14 500 BP, when temperatures were at their lowest. The climatic amelioration after 18 700 BP (the Last Glacial Maximum) saw a return to more humid conditions.