Holocene reconstruction of vegetation and fire history at South Lake Futululu, northern KwaZulu-Natal.

Abstract

This study investigated a Holocene palaeoenvironmental record from South Lake Futululu, a blocked valley lake in the Mfolozi-Msunduze catchment, northern KwaZulu-Natal. A multi-proxy approach was applied, combining accelerator mass spectrometry (AMS) radiocarbon and optically stimulated luminescence (OSL) dating, with fossil pollen and charcoal analysis to investigate Holocene climate and vegetation change. The record commenced ca. 7600 yr BP with a dominance in pollen from local reed sedge wetland taxa with the presence of prominent grasses and low abundance of tree taxa. This early phase was followed by a pollen preservation hiatus from ca. 6600-5900 yr BP. The Mid Holocene (ca. 5900-4900 yr BP) saw an environmental transition with the appearance of key coastal forest taxa like Podocarpus, Celtis and Trema and swamp forest taxa like Barringtonia, Ficus, Morella and Syzygium, high in abundance, which lasted well into the Mid Holocene inferring wet conditions. This was followed by a coastal forest retreat during the latter part of the Mid Holocene transitioning to the Late Holocene (ca. 1200-300 yr BP). This period inferred an interesting linkage with the charcoal data indicating a clear shift from grassy (W/L: <0.5) to woody (W/L:>0.5) fuel type. The Late Holocene presents a clear indication of a retreat in forest taxa and a shift to coastal grassland thicket inferring dry conditions during last ca. 300 yr BP. The charcoal record provided insight into past fire regimes and fuel types, reflecting the interplay between changes in available fuel within the landscape, and shifts between natural fires and anthropogenic burning. The South Lake Futululu record falls under the understudied Mfolozi-Msunduze catchment hence extending the existing knowledge of palaeoenvironments in the subregion.