The development pathways of two peatlands in South Africa over the last 6200 years: Implications for peat formation and palaeoclimatic research

Abstract

For the first time, plant macrofossil analysis supported by detailed stratigraphic studies was used to reconstruct peatland development in South Africa. Two peat cores (4.69 and 1.5 m) from two coastal peatlands in KwaZulu-Natal were analysed for carpological macrofossils, wood and macrocharcoal. The first one, Matitimani, is an unchannelled valley bottom peatland (site VB), and the second one, KwaMazambane, an interdune depression peatland (site ID) further up in the same catchment. Radiocarbon dating reveals the peatland initiation at site VB at about 6260 cal. yr BP. Rising sea level and humid climatic conditions during that time coincide with the formation of organic gyttja (dominantly aquatic seeds like Nymphaea sp.). In ca. 4950 cal. yr BP, a change to drier condition took place, revealed by the formation of radicell peat from Cyperaceae, and an increase of fire frequency (macrocharcoal). After ca. 1200 cal. yr BP, peat swamp forest emerged, with Ficus trichopoda, Syzygium cordatum and Voacanga thouarsii forming wood peat. Site ID dates back to ca. 920 cal. yr BP. Its initiation is assumingly related to reduced drainage capacities of the catchment subsequently to the peat formation in Matitimani valley. A steady change from gyttja forming communities (Nymphaea sp.–Eleocharis dulcis) to radicell peat-forming Cyperaceae communities took place. The long-term apparent rate of carbon accumulation (LORCA) is higher for site ID (89 gC m⁻² yr⁻¹) than for site VB (55 gC m⁻² yr⁻¹). Except for the peat swamp forest period, fire occurred frequently at both sites, however less in environments with frequent inundations.