A late Quaternary pollen sequence from Mfabeni Peatland, South Africa: Reconstructing forest history in Maputaland

Abstract

This paper documents a continuous ∼ 44,000-yr pollen record derived from the Mfabeni Peatland on the Maputaland Coastal Plain. A detailed fossil pollen analysis indicates the existence of extensive Podocarpus-abundant coastal forests before ∼ 33,000 cal yr BP. The onset of wetter local conditions after this time is inferred from forest retreat and the development of swampy conditions. Conditions during the last glacial maximum (∼ 21,000 cal yr BP) are inferred to have been colder and drier than the present, as evidenced by forest retreat and replacement of swampy reed/sedge communities by dry grassland. Forest growth and expansion during the Holocene Altithermal (∼ 8000–6000 cal yr BP) indicates warm, relatively moist conditions. Previous records from Maputaland have suggested a northward migration of Podocarpus forest during the late Holocene. However, we interpret a mid-Holocene decline in Podocarpus at Mfabeni as evidence of deforestation. Forest clearance during the mid-Holocene is supported by the appearance of Morella serrata, suggesting a shift towards more open grassland/savanna, possibly due to burning. These signals of human impact are coupled with an increase in Acacia, indicative of the development of secondary forest and hence disturbance.

Climatic variability in Mfabeni peatlands (South Africa) since the late Pleistocene

“…Core SL6 %TOC (n = 198), bulk carbon (n = 198) and leaf wax (n = 35) isotope profiles in comparison with peatland development chronology by Grundling et al (2013), palynology record by Finch and Hill (2008) and local hydrology interpretation of the Mfabeni peatland. Core SL6 %TOC and bulk C isotopic data modified from Baker et al (2014).…”

“…It was formed by valley infilling within the KwaMbonanbi formation coastal dune depression (Smuts, 1992), as a result of sustained, but varying groundwater input from the Maputaland aquifer and aggregational blockage of a palaeochannel linking the southern part of the peatland basin with Lake St Lucia (Grundling et al, 2013). The iSimangaliso wetland park vegetation is broadly made up of Maputaland wooded grassland, coastal belt and sub-tropical freshwater wetland and northern coastal forests (Mucina et al, 2006), whereas the fen itself is dominated by herbaceous reed sedges and grasses (Finch and Hill, 2008).…”

“…To assist in delineating the late Pleistocene and Holocene palaeoenvironmental origins of the significant shifts in leaf wax and bulk C isotopic signature in the Mfabeni fen, we compare our sedimentary records with proximal stratigraphy (Grundling et al, 2013) and palynology studies (Finch and Hill, 2008). The palynology research was conducted on a single core extracted from the deepest part of the fen in close proximity to core SL6, while the stratigraphic investigation was based on several cores drilled along eight east-west transects, spaced between 800 and 1600 m apart from north to south (see Fig.…”

“…Under current CO 2 concentrations, the C 4 pathway was predicted to have a higher photosynthetic efficiency at growing season temperatures in excess of 27 °C, while the C 3 pathway was more efficient at temperatures below 22 °C . It has also been observed that C 4 tropical grasses display a higher water use efficiency (WUE) rate than their C 3 counterparts (Downes, 1969) which led to a general acceptance that C 4 plants Finch and Hill, 2008) and most proximal and deepest stratigraphic transect (M 8; Grundling et al, 2013) included for orientation. WRZ = winter rainfall zone; ARZ = all-year rainfall zone; SRZ = summer rainfall zone.…”

“…We show compound specific δ 13 C wax , bulk δ 13 C and total organic carbon (%TOC) records, integrated with information from proximal stratigraphic (Grundling et al, 2013) and palynological (Finch and Hill, 2008) studies undertaken in the peatland, to reconstruct peatland hydrology, sedimentation regimes and proportional inputs of C 3 /C 4 plants. We then compare our findings with other regional climate studies to infer the climate controlling these ecological variables, and by presenting the data sets in a Northern Hemisphere climatic framework (Fig.…”