A Late-Holocene pollen record from the coastal Mkhuze swamp, KwaZulu-Natal, South Africa

Abstract

Pollen analysis was conducted on core materials that were deposited over the last 2000 cal years BP in Mkhuze wetland, KwaZulu-Natal. The objective was to reconstruct past vegetation and infer past changes in climate or possible human disturbances by enhancing both pollen and non-pollen proxy data in the summer rainfall region. Palynological results show a dominance of Poaceae (grasses >70%) that suggests a predominance of grassy vegetation in and around the swamp with some woodland and forest elements from the surroundings. Between 1700 and 1200 cal years BP, fungal spores, cryptogams, wetland plants, Podocarpus , and other forest pollen elements declined. Bushveld tree pollen of Spirostachys increased, indicating a decrease in moisture availability (humidity) and a change from forest to an open savanna vegetation. A peak of microscopic charcoal and Poaceae with a corresponding decrease in Spirostachys pollen around 800–500 cal years BP suggests an increase in wildfires under dry conditions that may have been caused by anthropogenic forest clearance for farming by the Iron Age people. The increase in microscopic charcoal, charred cuticles, a peak of Amaranthaceae pollen, and a corresponding decrease in trees and grasses in the last 280–200 cal years BP may be due to regional drought. The appearance of exotic Pinus pollen during the most recent period corresponds to the introduction of alien vegetation by European settlers. We compared changes in the pollen record of the Mkhuze freshwater swamp with a coeval section of a previously published longer pollen sequence in the nearby Lake St Lucia estuary to confirm if regional vegetation trends can also be observed in the section. Wider regional environmental trends were also assessed using other non-pollen proxies like isotopic data for comparison. Results align with δ 18 O, d 13 C and N 15 studies, although some, especially the latter, may not suggest parallel moisture conditions over the distances involved. This indicates that diverse environmental conditions prevailed in the region in the last c. 2000 years BP.