MSc., Faculty of Science, University of the Witwatersrand, 2011 / Little is known about the longevity of grassland suffrutex plants and the relationship between longevity and plant morphological structures and seedling growth strategies. The aim of this study was to determine the longevity of four grassland suffrutex plant species, namely Berkheya insignis, Callilepis laureola, Protea insignis and Tephrosia kraussiana. Seed viability, seedling growth, morphology, habitat and population structure and demography were also assessed and related to plant age. The rhizomes, seeds (if available) and canopies of B. insignis, C. laureola, P. simplex and T. kraussiana were removed from a site near Port Edward in the Pondoland region, KwaZulu-Natal, South Africa in April 2008. Seeds were available for P. simplex and T. kraussiana only. Seed germination and viability were tested in the field and laboratory using germination trials and tetrazolium tests. Greenhouse and field grown seedlings were used to monitor seedling growth and to record seedling morphology. The aerial and rhizome morphologies of adult plants excavated from the field were also recorded. The largest of these rhizomes were aged using radiocarbon dating. Attempts were made to develop morphological surrogates for plant age as no method currently exists. Plant density, demographies, number of inflorescences and various environmental variables of wild populations of B. insignis, C. laureola, P. simplex and T. kraussiana were sampled from the Red Desert Nature Reserve and the Umtamvuna Nature Reserve. Species morphologies varied, however important similarities suggest convergent evolution. These included a single vertical main stem rhizome with multiple side branches, early rhizome development in seedlings, and high root: shoot ratios. Seed viability was high in the laboratory but low seedling emergence was observed in the field. Seedling growth was rapid for T. kraussiana and slow for P. simplex. The population stage structure for all four species comprised primarily adults with few or no juveniles. Wild population plant height and main stem diameter followed normal distributions. Number of stems, basal area, canopy area and the number of floral structures had distributions favouring the smaller size classes. Soil P, N, K and organic carbon were important soil nutrients in a PCA analysis of the habitats of the four species. Radiocarbon dating yielded the following ages: B. insignis: 49-51 years, C. laureola: 49-50 years, P. simplex: 49-51 years and T. kraussiana: 51 years. There was a significant relationship between rhizome mass and canopy area, basal area, height, number of stems and main stem diameter. Since rhizome mass had a positive relationship with age- a relationship between age and aerial structures is likely. Therefore, creating surrogates for age may be possible. Overall, these species have moderate longevity, are poor seed producers with possibly slow population growth and are closely associated with soil nutrients. Therefore, these and other suffrutex species are particularly vulnerable to habitat destruction and climate change. The results of this study indicate that there needs to be a greater focus on below ground growth during ecological assessments in order to better understand the ecology of our diverse grassland biome plants.

Theories of socio-cultural change regarding the transition from the Chalcolithic to the Bronze Age in Cyprus have since the nascence of prehistoric archaeology on the island been the subject of lively debate between archaeologists who argue for internal versus external evolution processes. Yet, despite all efforts, a coherent model explaining the evident material culture differences between the two epochs remains elusive, an indication that the current polarization of theories masks inherent complexities of the archaeological record. Moving beyond the internal/external dichotomy, the present thesis argues for one such explanatory model and approaches this notable transition from three distinct and less explored aspects, namely chronology, pottery analysis and topography. Starting with chronology, the thesis assesses previous chronological schemata, examines issues of methodology, performs an in-depth data quality analysis, and, on the basis of the creative dialogue between absolute and relative dating data, proposes a novel chronology for the island. This chronology transcends linearity by adopting cultural period overlaps and differential regional adoption of technologies. Moving to spatial matters, the study disentangles space-time systematics for sites dating from the Middle Chalcolithic to the Philia Phase. In effect, it establishes a ceramic typology for the Chalcolithic that is applicable to the entire island; clarifies and records in a custom-made recording system, dubbed CARMA (Cyprus ARchaeological MAterials Relational Database System), the research history and material assemblages of each site; situates sites in the physical landscape of Cyprus and performs socio-spatial analyses, where the results of pottery analysis are interwoven with the spatial relationships between sites. The last analysis provides positive evidence for cultural uniformity in the Middle Chalcolithic, for the emergence of regional cultures in the Late Chalcolithic and the abandonment of settlements at the beginning of the Philia Phase, and for the co-existence of spatially distinct cultures during the Philia Phase. Lastly, the results of the chronology and spatial studies inform the data synthesis in the final section, where a different narrative of socio-cultural change is developed. This argues for the emergence of divergences already in the Late Chalcolithic, for the co-existence and uneven bi-directional interaction of indigenous and foreign populations during the Philia Phase, and for the development of regionalism in the Early Bronze Age as a result of variable adoption of technologies, entanglement and resistance to cultural identity assimilation.

Northern peatlands are an important carbon store, with carbon dynamics and hydrology intrinsically linked. The riparian zone is the interface between the terrestrial and aquatic systems, situated adjacent to the stream and characterised by periodic flooding, near surface water tables and unique soil and plant species composition. Due to its unique biogeochemical environment, the riparian zone has the potential to modify significantly the production, mobilisation and transport of carbon via the land-atmosphere and aquatic pathways. Two contrasting headwater catchments, an ombrotrophic peatland (Auchencorth Moss, SE Scotland) and a forested, till dominated catchment (Västrabäcken, N Sweden), were investigated. In each carbon concentrations in soil and stream water and hydrological parameters were measured in transects connecting the wider catchment, riparian zone and stream. The overarching aim was to investigate the role of the riparian zone on the hydrological and bio-geochemical functioning of peatland and forested catchments, focusing on carbon export via the aquatic pathway. Specific objectives were to: a) examine the importance of soils, water table and vegetation composition on riparian biogeochemical cycling, b) investigate riparian-stream hydrological connectivity and the transport of carbon across the soil-water interface and c) assess riparian processes in relation to the net ecosystem carbon balance (NECB) across northern latitude ecosystems. Porewater total carbon (TC) concentrations (sum of dissolved organic and inorganic carbon (DOC, DIC), CO2 and CH4) were on average higher in Auchencorth Moss (78.8-140 mg C L-1) than the Västrabäcken (27.7-63.2 mg C L-1) catchment. In both catchments, higher TC concentrations were observed in the riparian zone compared to the wider catchment. The dominant control for differentiating between catchment and riparian biogeochemical processes was the higher average riparian water table with each carbon species displaying a positive relationship with water table height. A range of other factors, including soil temperature and the carbon content of catchment and riparian soils, also contributed to the complexity of riparian carbon biogeochemical cycles. Catchment specific phenomena, including the presence of aerenchymous vegetation and stream sediment deposition onto the riparian zone, modified riparian carbon dynamics in the Auchencorth Moss catchment. Isotopically, porewater DOC, CO2 and CH4 had a 14C content >100 %modern, indicating that the modern plant derived DOC is being transported down the soil profile, providing the source for CO2 and CH4 production at depth. In both catchments the riparian zone represented an important and dynamic source of carbon to stream waters. Total annual CO2 export from the riparian zone of the Västrabäcken catchment to the stream channel over the hydrological year was 2.7 g CO2-C m2 yr-1 with export predominantly from between 40 and 55 cm depth within the soil. Two monthly peaks in CO2 export occurred over the hydrological year related to either storm events or the spring snow melt period which accounted for 19 % of annual export, highlighting the temporal variability in soil-stream linkages, especially during high flow periods. In the generally wetter peatland catchment, riparian-stream linkages were driven by antecedent conditions and variation in riparian water table, with changes in water input, rather than changes in CO2 source concentrations, controlling stream water composition. The negative CO2 concentration-discharge relationship in the stream suggested that event water dominated, with small but important inputs from high concentration soil water during individual events. The importance of event water in transporting carbon was confirmed through the isotope result. CO2, CH4 and DOC exported via the aquatic pathway predominantly contained modern, plant derived carbon from the near surface soil horizons but with a small contribution (5-28 %) from deeper geological sources leading to aged evasion CH4 (310-537 years BP) and CO2 (36 years BP to modern). In both catchments the riparian zone was more important, relative to the wider catchment, in controlling the export of carbon via the aquatic pathway. At Auchencorth Moss, the riparian zone, plus an area of the catchment extending ~20 m from the stream, were hotspots for land-atmosphere fluxes of CH4, with mean flux of 1.08-7.70 mg m2 hr-1 in comparison to the catchment overall (0.05 mg m2 hr-1). In both catchments, combining detailed catchment hydrological models with high temporal resolution carbon concentration measurements, especially in riparian zone soils, has the potential to improve estimates of downstream and evaded carbon export in headwater catchments. Riparian zones should therefore be included more in studies investigating hydrological and biogeochemical processes in northern latitude headwater catchments. The processes within riparian zones suggest that despite the relatively small area that riparian zones represent, in relation to the wider catchment, they may play an important role in the NECB of peatland and forested catchments under future management and climate change scenarios.

Arroyos are steep-walled, entrenched, typically ephemeral streams commonly found in dryland river systems that form when streams incise into previously deposited alluvial fill. Arroyos in the southwestern U.S. have been studied extensively following the historic period of arroyo cutting in the late 1800s and early 1900s A.D. The upper Escalante River in south-central Utah similarly began incising in 1909, and records evidence for past cut and fill cycles in well-exposed walls along the now continuous arroyo. Establishing robust geochronologies of past arroyo cycles in these fluvial settings has been difficult. Recent improvements in accelerator mass spectrometry (AMS) radiocarbon (14C) and optically stimulated luminescence (OSL) dating provide an opportunity to link more highly resolved fluvial records to existing paleoclimate records. This allows hypotheses regarding the causes of arroyo cycles to be tested, and for the role of climate versus intrabasinal characteristics to be examined. One major objective of this research was to examine the applicability of OSL and AMS 14C dating in the upper Escalante, as both methods have proved problematic in similar settings. In total, 37 ages were obtained, 21 OSL and 16 14C ages. The Holocene fluvial history of the upper Escalante River was reconstructed using these age results and stratigraphic relationships. The chronostratigraphic record developed in this study suggests that at least six arroyo cycles have occurred in the upper Escalante since the middle Holocene, with incision occurring ~4.4 – 4.2 ka, ~2.6 – 2.4 ka, ~1.8 – 1.5 ka, ~1.0 – 0.9 ka, ~0.5 - 0.4 ka, and during the historic period of arroyo entrenchment. While semi-synchronous arroyo cutting (indicative of a climate signal) appears to have occurred in the Paria and Escalante drainages over the last 1 ka, correlations between proximal drainages are less clear prior to 1 ka, although this may be due in part to preservation effects. Overall, linkages to specific climate regimes and correlations to regional drainages are difficult to identify, suggesting that internal geomorphic thresholds are important in determining when arroyo entrenchment occurs in individual catchments.

The Arctic and North Atlantic underwent significant climactic changes since the Last Glacial Maximum (25,000 years before present (1950 AD); ka BP), but offsets in the timing of events between the two regions are poorly constrained due to age model uncertainties that arise from changing radiocarbon reservoir ages. Here, we use a relatively high-resolution, multi-proxy stable isotope and sedimentologic dataset from Eastern Fram Strait (ODP Leg 162 Site 986) marine sediments to constrain the timing of Svalbard/Barents Sea Ice Sheet decay and infer deglacial reservoir ages over the last 30 ka. We use magnetic susceptibility, inorganic and organic carbon, foraminiferal assemblage counts, planktonic foraminiferal isotopes, and iceberg-rafted debris proxies to infer glaciomarine and paleoclimactic processes in Eastern Fram Strait. Significant negative Neogloboquadrina pachyderma (sinistral) δ18O episodes from background levels at 18.8 ka (-3.0 /) and 20.4 ka (-0.8 /) (on a radiocarbon-based age model) are shown to indicate meltwater discharge events from the Svalbard/Barents Sea Ice Sheet during the early glacial termination (21-14.7 ka). To allow for direct comparison between the timing of Eastern Fram Strait meltwater events and North Atlantic climate changes, the ODP Site 986 age model is correlated to the well-dated Greenland Ice Sheet Project 2 (GISP2) ice core δ18O record. The refined age model suggests that 16.0 and 18.1 ka are more realistic estimates for the meltwater events, inferring surface ocean reservoir age shifts of 1750 ± 1050 years in Eastern Fram Strait during the early glacial termination. Trends in reservoir ages throughout the last deglaciation mirror Nordic Sea deep ocean circulation changes and previously reported trends in the sub-polar North Atlantic; however, reservoir ages appear to be greater in Eastern Fram Strait. We hypothesize that processes affecting the distribution of reservoir ages in the North Atlantic and Arctic (e.g. sea ice cover, meltwater input, and ocean circulation) may have resulted in larger reservoir ages in polar regimes than in sub-polar ones during the last deglaciation, analogous to contemporary distributions. In contrast to previous radiocarbon age model-based studies in the Nordic Seas that predict a significant meltwater event at ~19 ka, these findings show that rapid Svalbard/Barents Sea Ice Sheet decay began at 16 ka and suggest that uncertainty on the order of thousands of years may exist in previous paleoclimate studies with radiocarbon-based age models from the deglacial Nordic Seas and Arctic.

名古屋大学年代測定総合研究センターシンポジウム報告

名古屋大学年代測定総合研究センターシンポジウム報告

名古屋大学年代測定総合研究センターシンポジウム報告

名古屋大学年代測定総合研究センターシンポジウム報告

Accelerator mass spectrometry (AMS) is by far the predominant technology deployed for radiocarbon tracer studies. Applications are widespread from archaeology to biological, environmental, and pharmaceutical sciences. In spite of its excellent performance, AMS is expensive and complicated to operate. Consequently, alternative detection techniques for 14C are of great interest, with the vision of a compact, user-friendly, and inexpensive analytical method. Here, we report on the use of intracavity optogalvanic spectroscopy (ICOGS) for measurements of the 14C/12C ratio. This new detection technique was developed by Murnick et al. (2008). In the infrared (IR) region, CO2 molecules have strong absorption coefficients. The IR-absorption lines are narrow in line width and shifted for different carbon isotopes. These properties can potentially be exploited to detect 14CO2, 13CO2, or 12CO2 molecules unambiguously. In ICOGS, the sample is in the form of CO2 gas, eliminating the graphitization step that h is required in most AMS labs. The status of the ICOGS setup in Uppsala is presented. The system is operational but not yet fully developed. Data are presented for initial results that illustrate the dependence of the optogalvanic signal on various parameters, such as background and plasma-induced changes in the sample gas composition.