Browsing by Author "Finch, Jemma M."

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A 40,000-year record of vegetation and fire history from the Tate Vondo region, Northeastern Southpansberg, South Africa.
(2014) Baboolal, Deeva Lata.; Finch, Jemma M.
Records from the Quaternary period are used to confirm possible inferred climatic changes, reveal the responses of species to these changes, and serve as an archive against which modern environmental dynamics can be assessed. Fueled by a need to understand current climatic changes, the call for palaeoclimatic research in the southern African subregion has become more compelling. In southern Africa, such research has been largely restricted to springs and swamps as the subregion lacks natural lakes, with some exception of a few coastal lakes such as Lake Sibaya and Lake Eteza. Due to the arid and semi-arid landscapes which prevail in southern Africa, there is a paucity of suitable sedimentary deposits in the region. The highly organic peat deposit of Mutale Wetland, situated in the Tate Vondo region of the northeastern Soutpansberg presents an ideal opportunity for conducting palaeoenvironmental research. The Mutale Wetland contains relatively old sediments dating back to >30,000 cal years BP, placing this record within the late Quaternary period. Palaeoenvironmental techniques including radiocarbon, pollen and charcoal analyses were applied to produce a palaeoenvironmental reconstruction for Tate Vondo. A 302 cm sedimentary core was extracted from the Mutale Wetland. Detailed analyses show that prior to ca. 34,000 cal yr BP, conditions were fairly warm and dry. This is inferred from a dominance of open grassland vegetation. An expansion of Podocarpus forests together with an increase in fynbos elements suggest a shift to cool, subhumid conditions during the LGM. Cooler conditions persisted until ca. 12,000 cal yr BP. Thereafter, a climatic amelioration was experienced. The appearance of low charcoal concentrations throughout the late Pleistocene suggests that fire was infrequent. Between ca. 4000 – 1500 cal yr BP, conditions became warmer and drier, inferred from the development of arid savanna vegetation. The sharp increase in charcoal after ca. 4000 cal yr BP, broadly coinciding with the arrival of the first agriculturalists in the area, has implications for the history of human occupation in the Soutpansberg rather than shifts in climate. The succession from savanna to fynbos vegetation together with expanded forests implies a return to cool and moist conditions from ca. 1500 – 400 cal yr BP. Arid savanna persists from ca. 400 to the present, implying warmer and drier conditions towards the present day. Furthermore, from ca. 400 cal yr BP, the pollen and charcoal record indicate that the majority of recent changes in vegetation have been driven by anthropogenic activity. This record has contributed to an improved understanding of late Quaternary changes in climate, vegetation history and human impact in the northeastern Soutpansberg.
Application of intertidal salt-marsh foraminifera to reconstruct late Holocene sea-level change at Kariega Estuary, South Africa.
(2013) Strachan, Kate Leigh.; Hill, Trevor Raymond.; Finch, Jemma M.
Unclear predictions surrounding climate change, associated sea-level rise and potential impacts upon coastal environments have placed an emphasis on the importance of sea-level change. Past sea-level fluctuations have been measured using biological and geomorphological forms of evidence. One such biological proxy is salt-marsh foraminifera, which have been used as a high-resolution indicator of past sea-level change, based on the assumption that surface foraminiferal assemblages are similar in composition to buried fossil foraminifera. In South Africa, there is ongoing research seeking to produce high-resolution records of sealevel change, however foraminifera remain an underutilized source of proxy evidence. This research applies salt-marsh foraminifera as precise indicators of relative sea-level change at Kariega Estuary on the Eastern Cape coastline of South Africa. Distributions of modern foraminiferal assemblages were investigated, revealing vertical zonation across the intertidal zone. The foraminiferal and marsh vegetation zones were in part similar and overlapped to a certain extent, identifying three zones; high, low and tidal flats. This suggested foraminiferal distribution is a direct function of elevation relative to tidal fluctuation. A 94 cm core consisting of peat, sand and clay sediments was extracted from the salt marsh. A chronological framework for the core was based on five AMS radiocarbon age determinations of both bulk sediment and shell fragment samples placing the record within the last 1500 years Before Present (BP). The basal shell age was a clear outlier to all bulk sediment ages, possibly as a result of shell recrystallisation. The bulk sediment age determinations suggested two possible age reversals, potentially linked to sedimentary hiatus or contamination. These inconsistencies in the chronology were best viewed as separate age models. The core was analysed at a high resolution, whereby fossil foraminifera were extracted every 2 cm’s down the core. A transfer function was applied to calculate the former elevation at which each core sample once existed, to produce a relative sea-level reconstruction. The reconstruction was related to the age models to produce two possible sea-level curve scenarios. Reconstructed curves from both scenarios depict a 0.5 m (±0.16 m) sealevel highstand at 1500 cal years BP followed by a lowstand of -0.6 m (±0.03 m). Scenario One reached its lowest recorded sea-level between 600 cal years BP and 500 cal years BP and then fluctuated below present day levels. Scenario Two reached its lowest recorded sea-level around 1200 cal years BP, followed by low amplitude fluctuations and a relatively stable period from 100 cal years BP till the present day. The 1500 cal years BP highstand recorded for both scenarios correlates well with existing palaeoenvironmental literature from the southern African coastline. Chronological limitations associated with the remainder of the record hinder inter-comparison with previous studies. The outcomes of this research suggest that intertidal saltmarsh foraminifera demonstrate enormous potential for the high-resolution reconstruction of relative sealevel change in the South African context.
Assessing the dendrochronological and dendroclimatological potential of Acacia nilotica (L.) in northern KwaZulu-Natal.
(2014) Bhugeloo, Astika.; Finch, Jemma M.
In the face of evidence of predicted climate change, there is a lack of information available on past climatic variability, particularly in southern Africa. Focus on the recent past is critical to understanding the natural variability underlying anthropogenic climate change. High resolution climatic records, such as tree ring series, are crucial to studying past climatic changes. Dendrochronology in the southern hemisphere has not been widely explored due to the perceived lack of annual growth rings in tropical and subtropical tree species. In this study, Acacia nilotica (L.) was assessed for its dendrochronological and dendroclimatological potential using 31 stem discs collected from the Bonamanzi Game Reserve, situated in northern KwaZulu-Natal, South Africa. Annual growth rings characterized by terminal parenchyma bands occurred on all samples, however, a number of growth ring anomalies, including missing, false and indistinct growth rings, were commonly encountered. Cross-dating was attempted on all individuals and a 99-yr regional chronology for northern KwaZulu-Natal, ranging between the years 1914‒2013 was developed. The regional chronology indicates variable periods of increased and decreased growth of A. nilotica throughout the 99 year period, with no coherent growth pattern evident between trees. Correlation analysis was performed with locally averaged climate data, high resolution gridded datasets, the Southern Oscillation Index and the El Niño3.4 index. The weak mean sensitivity indicated by the master chronology suggests that A. nilotica is not strongly influenced by environmental variables. This may call into question the reliability of the cross-dating results and master chronology presented, and limit the further application of climate correlation analysis. This research has demonstrated some potential to develop a century long annual tree ring chronology using A. nilotica for northern KwaZulu-Natal. A network of tree ring series from southern Africa would extend the spatial and temporal scale of high resolution palaeoclimatic records for the subregion, further increasing our understanding of contemporary climate variability. This study has explored the dendrochronological and dendroclimatological potential of A. nilotica thereby contributing to southern African tree ring research.
Assessing the distribution of sedimentary heavy metals in the Msunduzi River Catchment, KwaZulu-Natal, South Africa.
(2015) Shozi, Mendy Zibuyile.; Finch, Jemma M.; Pillay, Letitia.
Heavy metal pollution of freshwater environments is a global and local crisis due to the toxic nature of metals. Elevated concentrations of heavy metals in sediments, in comparison to sediment quality guidelines (SQGs), are an indication of anthropogenic input into the environment. Concentrations of cadmium (Cd), chromium (Cr), copper (Cu), lead (Pb), nickel (Ni) and zinc (Zn) were investigated in the water and sediments of Msunduzi River and two of its tributaries, the Bayne’s Spruit and Slangspruit, in KwaZulu-Natal, South Africa. Macro-elements, aluminium (Al), iron (Fe) and manganese (Mn) were also investigated and compared to the distribution and partitioning pattern of the trace metal concentrations. Total metal concentrations in the water samples were below the detection limit of the Inductively Coupled Plasma–Optical Emission Spectrometry (ICP-OES) for most metals. In surface sediments, total metal concentrations were >Effects Range-Low (ERL) of the SQG. The Community Bureau of Reference (BCR) sequential extraction protocol was used to determine speciation of metals in the sediments and implications for potential bioavailability and overall metal toxicity. Results indicated that potentially mobile sediment fraction concentrations were >ERL for most of the metals. Fe-Mn oxyhydroxides, organic matter content and redox potential had an effect on the geochemical partitioning and possible remobilisation or precipitation of the metals in all three rivers. Negative redox values were indicative of reducing conditions that remobilised metals from the sediments. In the sediment core, the trace metals had the same deposition pattern and were correlated to organic matter content at depth. Normalisation with Al, at 95% confidence interval indicated that the sediment in the Msunduzi River Catchment is enriched with anthropogenic heavy metal input. In terms of particle size distribution in the sediment core, the sediment was mainly made up of fine sediment (≤500 μm). The sediment is a potential source of long-term heavy metal pollution in the catchment.
Holocene environmental changes derived from a montane pollen sequence in the KwaZulu-Natal midlands, South Africa.
(2013) Geer, Anél.; Hill, Trevor Raymond.; Finch, Jemma M.
There is a limited understanding of the climatic history of summer rainfall regions of South Africa, especially the east coast, even though palaeo-research has become a popular technique used in southern Africa to determine past environmental and climatic changes. Sites such as wetlands and peatlands are ideal for palaeo-environmental research as they are of high organic content and enable pollen preservation. Dartmoor Vlei, situated at Mt. Gilboa, KwaZulu-Natal, is surrounded by Midlands Mistbelt grassland and in close proximity of the Karkloof Forest archipelago, rendering the site ideal for investigating grassland/forest dynamics. A minimally disturbed, 240 cm, organic rich sediment core was obtained from Dartmoor Vlei for analyses. A multi-proxy approach, viz. radiocarbon, charcoal, geochemical (carbon and nitrogen stable isotopes) and palynological analyses, was adopted to determine past environmental changes. Six samples were used for AMS radiocarbon dating, which indicates sediments date back ca. 12,200 cal yr BP at 144 cm. Environmental conditions at Dartmoor Vlei during the early Holocene are characterised by warmer, dry conditions, and arboreal pollen taxa are found in high concentrations between ca. 12,300 and 9000 cal yr BP. The mid-Holocene marks a period where systematic changes begin to occur at Dartmoor Vlei, as wetter conditions in accordance with the Holocene Altithermal are evident ca. 8000 cal yr BP. A period of locally drier conditions at ca. 6000 cal yr BP is followed by a decrease in arboreal taxa such as Podocarpus, Brassicaceae, Anacardiaceae and Celtis at ca. 5800 cal yr BP. The occurance of Zea mays in the record at ca. 1600 cal yr BP, the increase in fire intensity and frequency, and subsequent decrease in some arboreal taxa is a robust indication of anthropogenic activity in the KwaZulu-Natal Midlands region, attributed to Iron Age settlers. Arboreal and grassland pollen signals indicate the existence of a mosaic of montane and sub-alpine grassland and montane forests in the region of Dartmoor Vlei throughout the Holocene, and at present.
Holocene reconstruction of vegetation and fire history at South Lake Futululu, northern KwaZulu-Natal.
(2022) Reddy, Salona Sathaiaseelen; Finch, Jemma M.
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.
Intertidal salt-marsh foraminifera as sea-level indicators : lessons from the South African coastline.
(2016) Strachan, Kate Leigh.; Hill, Trevor Raymond.; Finch, Jemma M.
Microfossils of the group foraminifera are widely used as robust, high-precision sea-level proxy indicators associated with salt marshes. These microfossils exhibit vertical zones related to elevation across the intertidal zone, and are well preserved within salt marsh sediments, leaving a permanent record of sealevel change. This research explores the application of intertidal salt-marsh foraminifera as sea-level indicators along the southern African coastline. It further describes the development of a regional transfer function and assesses its performance in reconstructing sea-level change. Three permanently open estuarine environments were selected for this study, Kariega and Keiskamma along the eastern coastline, and Knysna along the southern coastline. Foraminiferal sea-level records depend on the accurate characterisation of modern foraminiferaenvironment relationships and salt-marsh zonation representative of a study site. Contemporary foraminiferal assemblages were surveyed across the intertidal zone, and corresponding vegetation and environmental data (pH, salinity, soil properties and elevation) were collected. Multivariate ordination was used to examine the correlation between living foraminiferal assemblages and environmental parameters. It was established that elevation was the key environmental variable governing the distribution of salt-marsh foraminifera at the Keiskamma and Knysna estuaries. Salinity had a significant but opposite influence to elevation at the Keiskamma Estuary. At Knysna Estuary, pH was the secondary driver of foraminiferal composition. The contemporary intertidal environments at Keiskamma and Knysna estuaries were described in relation to the zonation of foraminifera across each salt marsh. Cluster analysis was performed to separate foraminifera into salt-marsh zones. Whilst the composition and vertical ranges of assemblage zones vary between sites, we suggest that South African salt marshes can be classified according to four broad subdivisions. The mudflats have the most diverse assemblages, consisting predominately of calcareous species. Ammonia spp., dominates the lower marsh zone followed by Miliammina fusca, which dominates the middle- to lower marsh vegetated zone. The high marsh zone is characterized by the high abundance of Trochammina inflata. Modern training datasets from the selected study sites were used to investigate the suitability of local versus regional datasets for reconstructing recent sea-level trends. The results suggest that a regional transfer function using weighted averaging models is suitable for the analysis of fossil material, producing sea-level reconstructions with an error of ±0.22 m. As a validation exercise the regional transfer function was applied to a sediment core from Kariega, and compare with tidal gauge data. Sea-level records from far field sites offer important constraints on the timing and amplitude of global sea-level changes and improve our understanding of the driving mechanisms behind the late Holocene sea-level change. The regional transfer function has the potential to link short-term instrumental records with longer-term relative sea-level reconstructions, advancing research into past sea-level fluctuations along the South African coastline, and provide a baseline understanding of the nature and causes of sea-level variation. Intertidal salt-marsh foraminifera provide South African sea-level studies with an indicator that is reliable and can be used at multiple sites, allowing for comparisons between studies.
The late quaternary palaeoenvironments of a subalpine wetland in Cathedral Peak, KwaZulu-Natal Drakensberg.
(2011) Lodder, Jared.; Hill, Trevor Raymond.; Finch, Jemma M.
In contrast to the wealth of palaeoenvironmental research stemming from the eastern Afromontane archipelago, the southern Afromontane component, which comprises largely of the Drakensberg, remains understudied. The Drakensberg constitute an area of significant biodiversity, cultural and economic importance. Suitable sites for palaeoenvironmental research are rare in South Africa due to general arid climatic conditions over much of the country. The KwaZulu-Natal Drakensberg offers a unique opportunity for palaeoenvironmental research through its increased rainfall and higher altitudes, which enable the development of wetlands that have the potential for polliniferous accumulation to occur. Catchment Six in Cathedral Peak is one such wetland that has provided an opportunity to research palaeoenvironmental conditions of the southern Afromontane archipelago component. A 371 cm sediment core was extracted from a subalpine wetland in Catchment Six and analysed using multiple proxies including; pollen, charcoal and geochemistry (carbon and nitrogen stable isotopes). A chronological framework for the core was established based on accelerated mass spectrometry radiocarbon dating of eight bulk sediment samples. A basal date of 15,100 ± 445 cal yr BP was determined at a depth of 298 cm. Poor pollen preservation of the basal portion of the core limited palaeoenvironmental inference for the late Pleistocene section of the record. The multiproxy record provides high chronological resolution for the early to late Holocene. Multi-proxy data indicate that the Holocene period in the Drakensberg was characterised by variable climatic conditions. Charcoal data indicate periods of increased regional fires in the last ca. 400 cal yr BP. Palaeoenvironmental inferences from the Catchment Six record are broadly in agreement with regional climatic indications based on existing literature.
Late quaternary palaeoenvironments of the Mfabeni Peatland, Northern KwaZulu-Natal.
(2005) Finch, Jemma M.; Hill, Trevor Raymond.; Ellery, William Nolan.
To assist in developing a more precise understanding of past climatic changes in southern Africa, further pollen analytical research is required. In the past, pollen sites in the subregion have been restricted to swampy areas such as permanent springs and peat deposits. While such sites are often rare as a consequence of the aridity of the country, rich polliniferous deposits can be found in the peatlands surrounding coastal lakes in the Maputaland Coastal Plain. The Mfabeni peatland, situated on the eastern shores of St. Lucia, contains relatively old sediments dating back to >45000 years bp at a depth of 7.80m. A multi-proxy approach, comprising radiocarbon, stable carbon isotope (513C) and palynological analysis, was applied in the investigation of Late Quaternary climatic conditions and vegetation changes along the Maputaland Coastal Plain. A single 10 m sediment core, dating back to >45000 years bp, was extracted from the Mfabeni Peatland. A detailed fossil pollen analysis of Mfabeni sediments indicated the existence of extensive Podocarpus-abundant coastal forests before ca. 44500 years bp. The onset of wetter local conditions after this time is inferred from forest retreat and the development of swampy conditions, which prevailed until ca. 25000 Cal years BP. Conditions during the Last Glacial Maximum (LGM; 18000 years BP) are inferred to have been generally colder and drier, as evidenced by forest retreat and replacement of swampy reed/sedge communities by dry grassland. A significant depletion in 813C values at ca. 18200 Cal years BP indicates the dominance of C3 vegetation during the LGM, reflecting considerably colder conditions. This is in agreement with palaeoenvironmental indications from elsewhere in the Transvaalian Ecozone, although conditions at Mfabeni were more moderated in their manifestation, which can be attributed to the proximity of this site to the ocean. Cool, relatively moist conditions are inferred for the Holocene Altithermal (ca. 8000-6000 years BP), as evidenced by forest growth and expansion during this time. Warm, dry conditions are inferred for the Late Holocene, with the establishment of grassland/savanna type vegetation in the area after ca. 2000 Cal years BP.
Ostracods as bioindicators to reconstruct past environmental conditions at Lake St Lucia, South Africa.
(2017) Spershott, Kirsty.; Finch, Jemma M.; Frenzel, Peter.
Lake St Lucia, situated along the east coast of South Africa, is a highly dynamic system subject to both tidal and freshwater influences with changing environmental conditions. These fluctuating salinity regimes effect the biological communities within the lake, and thus the resilience of the system. Hypersaline conditions have been recorded within St Lucia as a result of severe and prolonged drought events with mass mortalities ensuing. St Lucia is a highly managed system and has recently received a great deal of attention through monitoring programmes, however, few of these encompass long-term changes spanning more than multi-decadal timescales. This underpins the lack in understanding of natural baseline conditions. As salinity is largely variable and the driving factor behind ecosystem functioning, it remains pertinent to gain a long-term understanding of the system. Ostracods, microscopic bivalved crustaceans, have been noted for their sensitivity environmental factors, salinity in particular. These biological indicators can thus offer important insights into past environmental conditions, yet have been under-utilised in the South African context. Here we present a detailed record of palaeosalinity for the Holocene through fossil ostracod analysis of sediment cores retrieved from Lake St Lucia. A 16 m sediment core was extracted from both North Lake and False Bay, and a 12 m sediment core was extracted from Catalina Bay using a piston corer. Core chronology was based on a total of 29 Accelerator Mass Spectrometry radiocarbon age determinations across the three cores. Preservation potential is greatest in the basal region of the cores, with Catalina Bay yielding the highest species diversity and abundance. Fossil records indicate that North Lake illustrates a dominance in brackish-marine ostracod taxa, whilst False Bay depicts a fresher system overall, due to its sheltered landward positioning, and Catalina Bay has a higher marine influence, likely due to its proximity near the estuary mouth. A transfer function was applied to ostracod data to reconstruct palaeosalinity over the Holocene. Results indicate elevated salinities over the early Holocene (~9500-7250 cal yr BP), and ostracod assemblages vastly differing in richness and abundance from those evident in the late Holocene. The early Holocene saw St Lucia as a deep water system with significant marine influence through various tidal inlets, and hence records reflect a high marine dominance. Ostracods appear to thrive in times of increased marine influence as higher water volumes would have been conducive to continual flow and mixing between basins, facilitating ostracod movement. As Lake St Lucia transitioned from a deep water system to the shallow estuarine system evident today, environmental conditions appear less favourable to ostracods found in North Lake and Catalina Bay. A shallower system is more at risk of desiccation and sediment reworking via wind turbulence, both of which will also hinder fossil success and preservation. Fossil records reflect the transition from marine influenced assemblages to estuarine ostracod assemblages occurred around 7000-6000 cal yr BP, the early to mid Holocene. Today, decreased marine influences are heightened by anthropogenic interventions and modifications, and has consequently put extra pressure on an already stressed ecosystem. Hypersaline events, recently noted in St Lucia literature, are not evident in the ostracod record, likely the results of time averaging through sediment mixing. However, a low species diversity experienced in North Lake and Catalina Bay over the late Holocene is indicative of unstable environmental conditions. As there is significant focus on St Lucia’s management, and in particular its mouth and the relinking to the sea, this study will aid in the decision-making process by providing insight on environmental conditions at a multi-millennial scale.
A palaeoreconstruction of late holocene fire history and vegetation dynamics from a savanna ecosystem at Mapungubwe National Park, Limpopo Valley, South Africa.
(2016) Ngoloyi, Nonkululeko Mantombi Nomalanga.; Hill, Trevor Raymond.; Finch, Jemma M.
Palaeoenvironmental studies facilitate the understanding of palaeoclimatic trends that have been difficult to understand within the African context. Multi-proxy climatic reconstructions are spatially and temporally limited in southern Africa due to the shortage of continuous, chronological and high-resolution sequences and the scarcity of suitable terrestrial archives such as wetlands, peatlands and lakes; alternative archives such as swamps, isolated pans and springs have been used in savanna ecosystems. Due to the ecological importance of savannas, there is a need to understand long-term ecosystem processes in these environments, particularly in southern African savannas where there is a lack of records representing the late Holocene, Mapungubwe National Park (MNP) located in the lower Limpopo Valley represents one such site. Situated within the savanna biome and characterised by Colophospermum mopane Bushveld; the UNESCO World Heritage Site (inscribed in 2003) is of biodiversity, cultural and archaeological signsificance. A palaeoreconstruction of MNP was conducted using a multi-proxy fossil based approach. Pollen, charcoal analysis and radiocarbon dating were applied to determine past vegetation change and fire history. Two sites were analysed to infer palaeoenvironmental dynamics at MNP, Croc Pan (CP) and Leokwe Rock Pool (LRP). The AMS radiocarbon dating indicated that the sediments represented young sediments falling within the very late Holocene epoch, with the CP and LRP sequences dating back to ca.1700 cal. AD and ca. 1900 cal. AD, respectively. However; chronological uncertainties were acknowledged due to the limitations of dating young records. Analyses show that the ca. 1700-1865 cal. AD period in the MNP record was broadly contemporaneous with the Little Ice Age (LIA; ca. 1500-1800 AD); declines in arid woodland savanna taxa and Cyperaceae indicated cool, dry conditions; approaching ca. 1800 cal. AD warm wet conditions persisted. The charcoal signal indicated a high frequency of regional fire activity. Between ca. 1865-1945 cal. AD, the charcoal record continued to reflect a regional fire signal; declines in aquatics, riparian and warm savanna taxa at the beginning of this period implied reduced moisture availability however, peaks in Cyperaceae suggested incidents of increased local moisture and changes in local hydrological conditions. The reduction in Cyperaceae and pteridophytes between ca. 1945-1960 cal. AD reflected drying conditions whilst reduced microscopic and macroscopic charcoal suggested inconsistent local and regional fire activity. Between ca. 1960-1985 cal. AD, a transition from warm, dry conditions indicated by increases in Euphorbiaceae undiff. and warm savanna woodland elements to warm, wetter local conditions marked by sharp peak in Cyperaceae was observed. The influx of macroscopic charcoal during this period is suggestive of more frequent local fire activity. Evidence of warm woodland vegetation such as Combretaceae undiff., Capparaceae undiff. and Fabaceae undiff. accompanied by the inconsistent occurrence of Cyperaceae allude to warm temperature and variable moisture conditions from 1985 to present. The regular increase of macroscopic charcoal is suggestive of an increased frequency of local fires, coincidently, this period of the record overlaps with the known fire regime for MNP. The increase in macroscopic charcoal towards the end of the Mapungubwe record can also be associated with human activity. The pollen records for MNP reflects that the region has generally been characterised by warmer temperatures and drier conditions during the late Holocene; the vegetation dynamics of MNP have not been directly influenced by fire activity as the record generally indicates regional fire activity. These results show similar trends to other savanna ecosystems in the Limpopo Valley, excluding sites with grassland traits. Pollen and charcoal signals from the MNP records have improved the understanding of tree-grass coexistence and the impact of fire on the dynamics of the savanna ecosystem in the Limpopo Valley. This record has therefore contributed to a greater understanding of late Holocene vegetation change and the fire history of the greater Limpopo Valley.
Revisiting the dendroclimatological potential of Afrocarpus falcatus, South Africa.
(2021) Baverstock, Jean Dorathea.; Hill, Trevor Raymond.; Finch, Jemma M.; Woodborne, Stephan M.
Abstract available in pdf.
Sediment dynamics and provenance of hydrologic and vegetation signals of the Mzimvubu Catchment, Eastern Cape, South Africa.
(2020) Frankland, Tarryn.; Finch, Jemma M.; Schefuβ, Enno.
Southern Africa has a high vulnerability to future climate change, therefore realiable and comprehensive information on local hydrological, vegetation and sediment processes are crucial for future mitigation and management practices. Marine sediments can provide valuable, continuous and long-term data about climatic, vegetation and sediment dynamics of the adjacent continent. To accurately interpret these records, the question of terrestrial organic and inorganic material provenance and their contribution to marine archives is essential. Provenance studies however, have mostly been conducted along the western shoreline, very few studies exist along the eastern shoreline. This study presents an investigation of inorganic and organic signals transported within the Mzimvubu Catchment, Eastern Cape.To investigate proxy provenance, plantleaf-wax derived long-chain n-alkanes, pollen grains and element compositions of 32 River Bed Sediment (RBS) and Suspended Particulate Matter (SPM) samples of the five major tributaries were compared over three different seasons. The δ13C composition of river sediment yielded depleted values indicating input from predominantly C3vegetation. δD of RBS changed with increasing altitude and distance from the ocean and rainfall amount. Enriched δ13C values, depleted δD values, reduced norm31 and low CPI values indicate input from arborealvegetation with elevated sediment erosion rates originating from the northern tributaries. Depleted δ13C values, enriched δDvalues, elevated norm31 and high CPI values indicate reduced sediment erosion rates and input from adjacent grasslands in the southern tributaries. XRF Fe/K, Ti/Al and Al/Si ratios revealed areas of high erosion of fine grained particles due to anthropogenic pressures and aeolian dust input from south easterly trade winds in the northern tributaries, compared to the fluvial input of coarse grained particles in the southern tributaries and river mouth. Proxy signals were influenced by various environmental,physiological and taphonomic processes. These findings present the first comprehensive multiproxy overview of vegetation, sediment and hydrologic provenance based on palynomorph abundance, n-alkane isotopic distributions and elemental compound dynamics within the Mzimvubu Catchment, which can aid the interpretation of marine cores extracted from the Indian Ocean for future palaeoclimatological and palaeoenvironmental research.