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No description available.

No description available.

In most of Africa archaeological charcoal samples are often used to establish chronology through radiocarbon dating, but are rarely used to address why people may have selected specific wood taxa for particular purposes. This thesis is an enquiry into the palaeo-ethnobotanical and palaeoecological implications of charcoal assemblages dated to the late Holocene from the Great Zimbabwe and Chigaramboni sites, Zimbabwe. The research provided a more detailed picture of socio-economic utilization of wood, such as the use of woods for iron smelting, construction and domestic hearths. Previous excavations at Great Zimbabwe and Chigaramboni have produced large samples of charcoal at specific activity sites and at a few different depths thus giving a minor perspective of time. There was a wider selection of wood at Great Zimbabwe as compared to Chigaramboni. Charcoal samples analyzed in this thesis are a product of purposeful human action and they represent a subsample of the local vegetation and related human activities contemporaneous with the period of sites’ use. A substantial effort has been invested in the development of a modern vegetation reference collection database. This will go a long way in assisting future researchers in the region and is an extremely valuable and essential primary contribution to the development of wood charcoal studies in the region. Thirty different tree species were burnt at Great Zimbabwe and indicate the multipurpose nature of the settlement. In contrast only 14 species were exploited at Chigaramboni which is an iron and metallurgical processing site. The latter fuel woods were also used at Great Zimbabwe. Based on the cracks and fissures in the charcoal it is postulated that the firewood used in metallurgy were collected whilst they were wet. Since Spirostachys africana and Colophospermum mopane do not occur in the area today it is suggested that there was long distance movement of wood, particularly those with excellent construction qualities. It is quite possible that the inhabitants of Great Zimbabwe, or their trading partners, opted to travel long distances in order to collect those particular logs. The fuel woods used at the two sites occur in the region today so it is likely that the Miombo woodlands of Great Zimbabwe and Chigaramboni have not changed notably from the time of occupation by their original inhabitants to date. Based on the mesophytic species identified, such as Acacia robusta, Acacia sieberiana, Acacia xanthophloea, Acacia polyacantha, Acacia burkei, Faurea saligna, Schotia brachypetala, Kigelia africana and Parinari curatellifolia, it is concluded that the inhabitants of ancient Great Zimbabwe and Chigaramboni archaeo-metallurgical site experienced a mesic environment. New excavations of different occupation levels would be required to determine vegetation and climate fluctuations during the past but at present there is a moratorium on such disturbance of the historical sites.

The evolution of the Metazoa is among the greatest success stories in Earth history. From modest origins, probably in the Cryogenian (~720 - 635 Ma), metazoans had acquired hard parts, and a vast range of life strategies and body plans by the middle Cambrian (around 520 Ma). This leaves a long delay between the origin of the Metazoa and their rise to ecological dominance. A popular explanatory hypothesis for this delay is that atmospheric oxygen levels, low in the Proterozoic (< 0.001 % PAL), began to rise towards modern levels towards the end of the Neoproterozoic. Among the earliest known putative metazoans are Namacalathus, Namapoikia and Cloudina, calcified marine invertebrates abundant in the latest Ediacaran (~ 548-541 Ma) Nama Group, Namibia. Although they were pioneers of metazoan biomineralisation, little is known of their affinities or palaeocology. The Nama Group, a well-characterised, relatively undeformed mixed carbonate and siliciclastic succession, provides a rare opportunity to investigate the palaeoecology of these important organisms in their environmental context. New geochemical data from the Nama Group confirm the heterogeneity of Ediacaran redox conditions. These contextualise in situ fossil assemblages which reveal diverse ecological strategies among the calcified metazoans of the Nama Group, and offer constraints on their affinities. Based on its large size (< 1 m), modular body plan and internal structure of interlinked tubules, Namapoikia was a long-lived specialist and possible Poriferan. I show that Namapoikia colonised both lithified and living microbial substrates in oxic, mid-ramp reef crypts. By contrast, size and occurrence data show that Namacalathus was an environmental generalist, forming large, thick aggregations in persistently oxic, mid-ramp reef environments but opportunistically exploiting the transiently oxic, inner ramp setting. Bilaterally symmetrical, asexual budding and a microlamellar skeletal ultrastructure suggest that Namacalathus may have been an early lophophorate, and had flexible growth depending on environmental setting, showing a cup diameter of 2 – 35 mm, and size distributions varying with substrate type, redox and water depth. In oxic mid-ramp reefs, Cloudina constructed large (> 20 m) reefs showing mutual attachment and consistent orientation in life position, making it the earliest known reef-building metazoan and suggesting that it was a passive suspension feeder. I further present food webs based on fossil assemblages from Ediacaran to Cambrian Stage 4 carbonate successions and evaluate their usefulness in tracking metazoan trophic diversification in the early Cambrian. Ediacaran redox conditions were a major control on the ecologies of the earliest metazoans. A requirement for oxygen made persistently oxic conditions a prerequisite for complex and long-lived ecologies, while highly flexible life strategies were used to exploit changeable environments. Ediacaran metazoans represent a phylogenetic and ecological foreshadowing of the complexity of the Phanerozoic, but it was not until much later that the Metazoa would attain their evolutionary potential.

Jurassic marine ecosystems (ca. 201-145 million years ago) were dominated by three different lineages of reptiles - plesiosaurians, ichthyosaurs and thalattosuchian crocodylomorphs. Stratigraphic and fossil evidence indicates that these animals, like their modern counterparts, were able to coexist in the same environment for over ~50 million years from the Early Jurassic (~180 million years ago) to the Early Cretaceous (~130 million years ago). Marine reptile ecosystems were often very diverse, and included animals from different lineages, of disparate body-size and inferred ecology living alongside each other in the same environment. This unusual diversity suggests that marine reptiles formed complex ecosystems, and may have occupied analogous ecological roles today held by large fish, sharks, crocodiles, sirenians, and cetaceans. However, these comparisons are essentially qualitative, as they are based on the recurring convergent morphologies of skulls, mandibles and dentitions in aquatic tetrapods. Yet, they have never been quantitatively tested. Furthermore, although we have a comprehensive understanding of the anatomy, systematics, phylogenetic relationships, physiology and feeding ecology of these extinct animals, little is still known about the structure and evolution of their ecosystems. Thus, we do not understand what enabled marine reptiles to form complex assemblages, how their fauna changed through time, and more importantly how climatic and environmental changes shaped their long-term evolution. Answering these questions is essential because understanding past marine ecosystems may inform on whether and how modern ones can adjust to changes in the ocean temperature, chemistry and sea-level. In order to establish the reliability of these comparisons, in this project, I consider the evolution of the diverse marine reptile fossil assemblage of the Jurassic Sub-Boreal Seaway (JSBS) of the UK. The fossil record of the JSBS is an ideal case-study for many reasons. Firstly, it is a well-documented, high-diversity ecosystem, represented by hundreds of well-preserved specimens collected from the world-famous Oxford Clay Formations (OCF Callovian-early Oxfordian, late Middle to early Late Jurassic) and Kimmeridge Clay Formation (KCF - Kimmeridgian to Tithonian, Late Jurassic). These specimens have been intensively collected since the XIX century, and are available in museum collections. Secondly, the fossil record of the JSBS covers a continuous interval of ~18 million years (middle Callovian-early Tithonian ~166-148 million years ago) of marine reptile evolution, in a single seaway, during a time of well-documented environmental changes. These changes in sea-level, temperature and chemistry happened in concert with drastic changes in the composition between the OCF and KCF marine reptile faunas across the Middle-Late Jurassic boundary. Unfortunately, to date, the attempts to understand whether there is a correlation between these events have been hampered by the scarcity of fossils material from the intermediate layers of the Oxfordian 'Corallian Gap'. After a brief introduction (Chapter I), this project articulates in two parts. In the first descriptive section (Chapters II, III and IV), I set the bases for the second part by reviewing the fossil record of ichthyosaurs, plesiosaur and thalattosuchians of the JSBS. Particular emphasis was put on the systematics of thalattosuchian crocodylomorphs, and the fossil assemblage of the 'Corallian Gap'. The second part of this thesis is an analytical section (Chapters V and VI), in which, using a suite of numerical techniques, I investigate the ecology, evolution and feeding ecology of marine reptiles through time. A summary of the main conclusions and future directions are presented in Chapter VII. Chapter II is a description of a new genus and species, Ieldraan melkshamensis, a metriorhynchid thalattosuchian from the Callovian of England. The stratigraphic occurrence of this new taxon demonstrates that all the macrophagous lineages of Late Jurassic metriorhynchids originated in the Middle Jurassic, earlier than previously supposed. This also has important implications for the evolution of macropredatory features (particularly the dentition) in this group. In Chapters III and IV, I review the scarce fossil record of the Oxfordian 'Corallian Gap', the least studied stage of the considered ~18 million-year interval. The results show that despite the scarcity and poor preservation of materials compared to the underlying and overlying fossil-rich OCF and KCF, a large variety of marine reptiles lived in the JSBS during the 'Corallian Gap' (middle-late Oxfordian). The study confirms a drop in marine reptile diversity in the Oxfordian, exemplified by the demise of several OCF taxa, but partially counterbalanced by the contemporaneous radiation of some KCF lineages. This review confirms that a faunal turnover severely affected the composition of the JSBS across the Middle-Late Jurassic boundary, and I hypothesise that these faunal changes may have been driven by environmental perturbations during the Oxfordian. In Chapter V, I use the most common marine reptile fossils - teeth - and the revised stratigraphic occurrences of the JSBS (from the previous Chapters), to investigate the evolution of marine reptile groups, through time. Using a multivariate approach I established a quantitative system to assign species to dietary guilds based on dentition features that together with the availability of teeth, allowed examination of diversity and disparity patterns at unprecedented time, and systematic resolutions. The results show that different taxonomic/dietary groups did not overlap, suggesting partitioning of resources based on diet/feeding strategy. The analyses show a decline of shallow-water specialists, the diversification of macrophagous species, deep-diving taxa, and increasing body-size in concert with a deepening of sea-level across the Middle-Late Jurassic boundary. These trends are not accompanied by drops in disparity, but by a selective decline/increase of specific ecological guilds, that mimic the transition from shallow/nearshore to deeper/offshore habitats in modern cetacean coastal assemblages. In Chapter VI, I use a variety of multivariate techniques to present a quantitative assessment of the feeding behaviour of marine reptiles. The aim of this study is investigating the morphological and functional variation of ichthyosaur, plesiosaur and thalattosuchian lower jaws. This is done using a variety of multivariate techniques, and a biomechanical comparative approach. The analyses confirm previous qualitative observations that the ecosystems in the OCF and KCF were markedly distinct in faunal composition and structure. Phylogenetically closely related taxa preferentially cluster together, with minimal overlaps amongst groups in the morphospace. Focus examinations of key morphofunctional complexes reveals that marine reptile subclades are characterised by different combinations that are consistent with their inferred feeding ecologies (based on tooth morphology). Overall, the present quantitative results validate previous qualitative hypothetical feeding ecologies, and reveal multiple instances of morphofunctional convergent evolution. Overall my results also show that, like in modern ocean ecosystems, complex mechanisms of niche and habitat partitioning may have facilitated the coexistence of diverse marine reptile assemblages over tens of millions of years of evolutionary time.

The climate of the Earth is expected to warm due to increasing atmospheric concentrations of greenhouse gases, particularly carbon dioxide (CO 2). The impact of this change on terrestrial ecosystems is uncertain, yet these ecosystems contain three times more carbon (C) than the atmosphere and could considerably augment anthropogenic CO2 emissions. This thesis aimed to quantify the terrestrial C stored in an area of Pennine moorland and predict its response to changes in climate and management. The area of soil and vegetation types was determined using existing maps of the study site and a geographical information system. Vegetation C was assessed using results from published productivity studies, and soil C was evaluated from a programme of field sampling. Most C was contained in peat soils and comparison of the results with the UK's national C inventory identified inaccuracies in the national values. The impact of sheep grazing and moorland burning on C storage was investigated by utilising long-term experiments at the site. Areas where sheep had been excluded for forty years were compared to grazed areas and burning was investigated using a randomised block experiment. Grazing had little impact on terrestrial C storage, but regular burning significantly reduced C sequestration in peats. The response of the C store to climate change was investigated by i) determining the impact of past climate on C storage and ii) developing a predictive model by measuring the underlying processes of C input and output in the ecosystem. Both approaches illustrated the sensitivity of the ecosystems C balance to climate, suggesting that global warming will reduce C accumulation at the site and, therefore, augment atmospheric CO 2 concentrations. The novel use of near infrared reflectance spectroscopy to characterise peat samples was also demonstrated, indicating opportunities for application of this technique in palaeoecological studies of peats.

No description available.

There is a polarised debate amongst Neotropical archaeologists and ecologists over the extent of Pre-Columbian (pre-AD 1492) anthropogenic environmental impacts in Amazonia. While some maintain the old paradigm of pre-Columbian Amazonia as a “pristine wilderness”, which was sparsely populated by humans, others point to the discovery of an increasing number of archaeological sites across the Amazon basin as evidence for large, complex societies, supported by intensive agriculture and management of forest and aquatic resources. Under this model, pre- Columbian people had profound impacts on biogeochemical cycles through largescale deforestation and biomass burning, and left an indelible legacy on Amazonian ecosystems by altering edaphics, geomorphology, hydrology, and the distribution of plant taxa. However, so far this debate has continued amongst a paucity of palaeoecological data, meaning that we have little evidence to indicate the scale of impact, and often no palaeoenvironmental context in which to place these societies. Other aspects of pre-Columbian cultures, such as their chronology, land use practices and subsistence strategies, are also poorly understood. In this thesis, palaeoecological methods are applied to improve our understanding of the scale, nature, and legacy of land use associated with pre- Columbian geometric earthwork cultures in north-east Bolivia. The methodology employs analysis of fossil pollen and macroscopic charcoal from lake core sediments. In total 110 pollen and 628 charcoal samples were analysed from four lakes: Laguna Isireri (14°49’18”S, 65°40’57”W), Laguna Orícore (13°20’44”S, 63°31’31”W), Laguna Granja (13°15’44”S, 63°42’37”W) and Laguna La Luna (13°21’20”S, 63°35’2”W). Chronologies were built for these cores from 12 AMS 14C dates. Results are presented in four chapters (thesis chapters 2-5), in the form of academic papers. Chapter 2 describes a new laboratory technique co-developed with Whitney et al., which improves the recovery of cultigen pollen grains from sediments from large, Neotropical lake basins. This technique was applied in the laboratory preparations of sediments analysed for Chapters 3-5. Chapter 3 employs palaeoecological reconstructions from differently sized lakes (L. Granja and L. Orícore) in the same earthwork region, to obtain both a regional- and a local-scale history of environmental change/human impact around the archaeological site. Key findings of this paper are: 1) earthworks were built in an originally open savannah landscape, which existed under drier-than-present climatic conditions in the mid-to-late-Holocene; 2) forest expanded into this region from ~ 2000 (cal yrs) BP and was supressed locally around the settlement to maintain an open landscape; therefore, 3) earthwork construction across southern Amazonia, may not have required extensive deforestation, and pre-Columbian impacts on biogeochemical cycling may have been much less than some authors have suggested. Chapter 4 looks more closely at the local scale record provided by L. Granja. These data are integrated with phytolith data analysed by co-author J. Watling and existing archaeological data, to discuss the chronology of settlement on the site, the agricultural/land use strategies employed by its inhabitants, and the spatial scale and distribution of impacts locally around the site. Key findings are that: 1) first occupation of the site is much earlier than previously dated from archaeological contexts, beginning ~2500 BP; 2) maize was the staple crop grown on site; 3) land use involved more extensive and intensive burning of the landscape than compared to modern slash-and-burn agriculture; 4) site decline occurred ~ 500 BP, and may have been related to the Columbian Encounter of AD1492; 5) the close integration of local scale palaeoecological records with archaeology, is highly useful in discerning aspects of chronology and spatial variability of land use. Chapter 5 presents a 6000 year record of palaeoenvironmental change and land use on a pre-Columbian forest island site. Key findings are that: 1) As in Chapter 3, inhabitants exploited an originally open landscape and practiced forest suppression to maintain that open landscape; 2) the earliest recorded evidence for maize agriculture in the region is found at 2100 BP; 3) the economically useful species Theobroma cacao, which is abundant on the site today, is not detectable in the pollen record; 4) clear-cutting was not practiced on the site and previous population estimates, based on labour for deforestation, must be reconsidered. The work in this thesis reveals a new model of human-environment interactions, demonstrating that pre-Columbian earthwork cultures in southern Amazonia occupied and adapted to a region of dynamic, climatically controlled forest-savannah transition during the mid-to-late-Holocene. Obtaining a palaeoenvironmental context for archaeological landscapes, is shown to be a vital pre-requisite to inferring past environmental impacts. Furthermore, we demonstrate the valuable contribution that palaeoecology can make to a better understanding of the chronology and land use practices of pre-Columbian cultures.

A debate that has received much attention in recent years is the nature and scale of pre-Columbian impact in the Amazon lowlands. While the notion that Amazonia is a “pristine wilderness" has long been debunked, several papers have proposed that human impact in western regions was more sporadic and on a smaller scale than impacts in central and eastern regions, and that western Amazonia supported sparse pre-Columbian populations. The discovery of over 400 geometrically-patterned earthworks (geoglyphs) in the western Brazilian Amazon, which until recently lay under in-tact tropical forest, has raised important questions about the kind of societies that built them and the impact that they had on the terra firme upland landscapes. This study represents the very first investigations into human-environment interactions in the geoglyph region. By analysing phytoliths, charcoal and stable carbon isotopes from a series of soil profiles in the vicinities of two well-dated and excavated geoglyph sites, this study aims to discern the nature of the environment before, during and after the construction and use of the sites, and the spatial and temporal scales of landscape transformations that were effected by the geoglyph cultures. The data call for a re-appraisal of what is meant by “scales" of human impact in Amazonia, and propose that an understanding of the diversity of human-environment interactions must be considered through studies that closely combine regionally-sensitive archaeological and palaeoecological data.