Modern soil phytolith assemblages used as proxies for paleoscape reconstruction on the South Coast of South Africa

Abstract

South Africa continues to receive substantial attention from scholars researching modern human origins. The importance of this region lies in the many caves and rock shelters containing well preserved evidence of human activity, cultural material complexity and a growing number of early modern human fossils dating to the Middle Stone Age (MSA). South Africa also hosts the world's smallest floral kingdom, now called the Greater Cape Floristic Region (GCFR), with high species richness and endemism. In paleoanthropological research, improving our capacity to reconstruct past climatic and environmental conditions can help us to shed light on survival strategies of hunter-gatherers. To do this, one must use actualistic studies of modern assemblages from extant habitats to develop analogies for the past and improve paleoenvironmental reconstructions. Here, we present a phytolith study of modern surface soil samples from different GCFR vegetation types of the south coast of South Africa. In this study, the phytolith concentration and morphological distribution are related to the physicochemical properties of soils, the environmental conditions and the characterization of the vegetation for the different study areas. Our results show that phytolith concentration relates mostly to vegetation types and the dominant vegetation rather than to the type of soils. More abundant phytoliths from Restionaceae and woody/shrubby vegetation are also noted from fynbos vegetation and grass phytoliths are a recurrent component in all the vegetation types in spite of being a minor component in the modern vegetation. The grass silica short cells from these plants, however, suggest a mix of C3 and C4 grasses in most of the vegetation types with a major presence of the rondels ascribed to C3 grasses. The exceptions are riparian, coastal thicket and coastal forest vegetation, which are characterized by the dominance of C4 grass phytoliths.