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Stable isotopes in water (δ²H and δ18O) are important indicators of hydrological and ecological pattern and process. δ²H and δ18O of water are incorporated into geological and biological systems in a predictable manner and have been used extensively as tracers in hydrological, ecological and forensic studies. Physical processes result in spatial variation of δ²H, δ18O in water across the landscape (so-called "isoscapes") and provide the basis for hydrological, ecological, archaeological and forensic studies. Southern Africa is a globally important meeting point for ocean and climate systems, biological diversity and human societies, yet there is little information on the spatial variability of δ²H and δ18O in water across this important region. Here we present the first ground water and tap water isoscapes for southern Africa. We compare and contrast these two water resources, and consider how well global models of precipitation isotopes capture isotopic variation across South Africa. Ground water and tap water samples were collected from across South Africa, analysed for δ²H and δ18O, and used to generate interpolated δ²H, δ18O and deuterium-excess (d = δ²H - 8*δ18O) isoscapes. We found coherent spatial structure in δ²H, δ18O and d of ground water and tap water that could be predicted by a geostatistical model based on simple environmental parameters (elevation, mean annual precipitation, precipitation minus potential evaporation, distance to coast and modeled isotope ratio of precipitation). This spatial structure resulted in considerable differences in isotopic composition of water in many of the major wildlife reserves in South Africa, indicating a good potential for wildlife forensics in this region. δ²H and δ18O of ground water, and to a lesser extent tap water, reflected the δ²H and δ18O of long-term weighted annual precipitation at the two GNIP stations in South Africa. However, large discrepancies between modelled isotopic composition of precipitation and our ground water and tap water isoscapes, particularly at higher elevations, highlighted uncertainty in the accuracy of modelled precipitation isoscapes for this region. Increased spatial sampling of precipitation, especially for high elevation regions, and temporal sampling of ground and tap water would considerably aid isotopic studies in this region. [ABSTRACT FROM AUTHOR]

THE PRINCIPAL SOURCE OF CAPE TOWN'S future water needs is the Table Mountain Group aquifer. The floral characteristics of the region overlying this aquifer are unique with five endemic and one near-endemic families. Many of these endemics are restricted to areas such as wetlands and marshes that are supplied by aquifer water, making them vulnerable to groundwater abstraction. Here we report the results of a study undertaken at two sites in the Cape Point Nature Reserve using stable hydrogen isotopes to determine the water source of plants to establish dependence on a permanent water supply. The results from the Suurdam site suggest that Erica labialis has a more diverse rooting strategy than Erica multumbellifera, with two plants sourcing water close to the surface, whereas others extract water much deeper down. The results from the Anvil Hill site, however, suggest that the rare Mimetes hirtus uses water very close to the surface that has undergone extensive isotopic fractionation. These results indicate that this species is shallow-rooted and dependent on surface soil water for survival. As such, it would be vulnerable to an even slight lowering of the water table during the dry summer months, when the surface soil water would be replenished mainly from the permanently saturated zone of the wetland. These results have implications for other endemic plant families with the same water requirements. [ABSTRACT FROM AUTHOR]

The foragers of the southern African Middle Stone Age were among the first humans to adapt their environment and its resources to their needs. They heat-treated stone to alter its mechanical properties, transformed yellow colorants into red pigments and produced moldable adhesive substances from plants. Until now, only Podocarpus conifers have been identified as the botanical origin of Middle Stone Age adhesives. This is curious as these conifers do not produce sticky exudations that could be recognized as potential adhesives. To obtain an adhesive, tar must be made with a technical process based on fire. However, the nature of these technical processes has remained unknown, hampering our understanding of the meaning of this adhesive technology for the cultural evolution of early Homo sapiens. Here, we present the first evidence of a technique used for tar making in the Middle Stone Age. We created an experimental reference collection containing naturally available adhesives along manufactured tars from plants available in the Middle Stone Age and compared these to artifacts using gas chromatography-mass spectrometry and infrared spectroscopy. We found that, in the Howiesons Poort at Sibhudu Cave, tar was made by condensation, an efficient above-ground process. Even more surprisingly, the condensation method was not restricted to Podocarpus. The inhabitants of Sibhudu also produced tar from the leaves of other plants. These tars were then used, either without further transformation or were processed into ochre-based compound adhesives, suggesting that people needed different moldable substances with distinct mechanical properties. This has important implications for our understanding of Middle Stone Age H. sapiens, portraying them as skilled engineers who used and transformed their resources in a knowledgeable way., (Copyright © 2024 The Authors. Published by Elsevier Ltd.. All rights reserved.)

Studying the earliest archaeological adhesives has implications for our understanding of human cognition. In southern Africa, the oldest adhesives were made by Homo sapiens in the Middle Stone Age. Chemical studies have shown that these adhesives were made from a local conifer of the Podocarpaceae family. However, Podocarpus does not exude resin, nor any other substance that could have been recognized as having adhesive properties. Therefore, it remains unknown how these adhesives were made. This study investigates how Podocarpus adhesives can be made, comparing their mechanical properties with other naturally available adhesives. We found that Podocarpus tar can only be made by dry distillation of leaves, requiring innovative potential, skill, and knowledge. This contrasts with our finding that the Middle Stone Age environment was rich in substances that can be used as adhesives without such transformation. The apparent preference for Podocarpus tar may be explained by its mechanical properties. We found it to be superior to all other substances in terms of its adhesive properties. In addition, the condensation method that allows producing it can be recognized accidentally, as the processes take place above ground and can be triggered accidentally. Our findings have implications for establishing a link between technology and cognition in the Middle Stone Age.

Background: In arid systems with no surface water, deep boreholes in ephemeral river beds provide for humans and animals. With continually increasing infrastructure development for tourism in arid wildlife parks such as the Kgalagadi Transfrontier Park in southern Africa, we ask what effects increased abstraction may have on large trees. Large trees in arid savannas perform essential ecosystem services by providing food, shade, nesting sites and increased nutrients for many other plant and animal species and for this are regarded as keystone species., Methods: We determine seasonal fluctuations in the water table while also determining the water source for the dominant large tree species in the Auob and Nossob rivers in the Park. We also determine the extent to which these trees are physiologically stressed using leaf δ 13 C, xylem pressure potentials, specific leaf area and an estimate of canopy death. We do this both upstream and downstream of a low water use borehole in the Auob River and a high water use borehole in the Nossob River., Results: Our results show that the trees are indeed using deep groundwater in the wet season and that this is the same water used by people. In the dry season, trees in the Auob downstream of the active borehole become detached from the aquifer and use more isotopically enriched soil water. In the Nossob in the dry season, all trees use isotopically enriched soil water, and downstream of the active borehole use stomatal regulation to maintain leaf water potentials. These results suggest that trees in the more heavily utilised Nossob are under more water stress than those trees in the Auob but that trees in both rivers demonstrate physiological adaptation to the changes in available water with smaller heavier leaves, no significant canopy dieback and in the dry season in the Nossob stomatal regulation of leaf water potentials., Discussion: An increase in abstraction of groundwater particularly at the Nossob borehole may cause an additional draw down of the water table adding to the physiological stress demonstrated in our study. The managers of the Kgalagadi Transfrontier Park have a mandate that includes biodiversity conservation. To fulfil this mandate, upper and lower thresholds for groundwater abstraction that allow for an adequate ecological reserve have to be determined., Competing Interests: The authors declare there are no competing interests.

South Africa has in recent years gained increasing importance for our understanding of the evolution of 'modern human behaviour' during the Middle Stone Age (MSA). A key element in the suite of behaviours linked with modern humans is heat treatment of materials such as ochre for ritual purposes and stone prior to tool production. Until now, there has been no direct archaeological evidence for the exact procedure used in the heat treatment of silcrete. Through the analysis of heat-treated artefacts from the Howiesons Poort of Diepkloof Rock Shelter, we identified a hitherto unknown type of organic residue - a tempering-residue - that sheds light on the processes used for heat treatment in the MSA. This black film on the silcrete surface is an organic tar that contains microscopic fragments of charcoal and formed as a residue during the direct contact of the artefacts with hot embers of green wood. Our results suggest that heat treatment of silcrete was conducted directly using an open fire, similar to those likely used for cooking. These findings add to the discussion about the complexity of MSA behaviour and appear to contradict previous studies that had suggested that heat treatment of silcrete was a complex (i.e., requiring a large number of steps for its realization) and resource-consuming procedure., (Copyright © 2015 Elsevier Ltd. All rights reserved.)