As a consequence of the regional topography and semi-arid climate of southern Africa, there is a general lack of continuous terrestrial palaeoenvironmental archives and, therefore, ambiguity prevails over how terrestrial ecosystems responded to past climate fluctuations in the region. Leaf wax stable carbon isotope (δ13Cwax) signatures of peat-forming plants are primarily controlled by the C fixation pathways employed during photosynthesis. Consequently, observed changes in peat δ13Cwax trends can best be explained by the changes in relative abundances between C3 and C4 plant inputs at the time of deposition. It is still not clear how the balance between competing southern African tropical woodlands / rainforests (C3) and grasslands (predominantly C4) were affected by changes in temperature, moisture and pCO2 in the past. Regional palynology studies have gone some way to elucidate changes in past plant assemblages. However, these records do not extend as far back as the last glacial maximum (LGM) and tend to suffer from temporal discontinuities, pollen dispersal range and dating uncertainties. In this study, we employed bulk and compound-specific isotope analyses of terrestrial plant lipids extracted from the Mfabeni Peatland, KwaZulu-Natal, South Africa. The 14C age of the basal peat is c. 47 kcal yr BP, making this setting one of the oldest continuous coastal peatlands on the African continent. This unique archive allowed us to directly reconstruct the changes in local plant type assemblages. We used bulk and compound-specific δ13C records to explore the changes in proportions of C3 and C4 plant input into the Mfabeni and to compare them with local palynology and peatland chronology records to infer the changes in the palaeoenvironment since the late Pleistocene. Our results suggest shifts between the two dominant competing plant types, in general correlation with the fossil pollen incidence and peat stratigraphy, through C4 plant dominant input being exhibited from c.44.5 to 39.0 kcal yr BP and the late Holocene, while c. 46.9 – 45.7, 38.0, 14.8 kcal yr BP and early Holocene periods demonstrated C3 dominant plant input. These trends advocate that the local Mfabeni plant population responded relatively rapidly to changes in local palaeoenvironment, mainly as a consequence of fluctuations in peatland hydrology. Furthermore, our data showed that there was a poor correlation between the changes in plant type assemblages and known regional and global climate events, which suggests that the local palaeohydrological forcings could have overprinted the regional climate influences on peatland plant communities in the Mfabeni since its inception.
- Leaf wax C stable isotopes
- terrestrial palaeoenvironment
- C3 vs C4 plant assemblages
- subtropical peatland
- late Pleistocene