Use this URL to cite or link to this record in EThOS:
Title: The late Quaternary history of the rainforest-savanna boundary in SW Amazonia
Author: Metcalfe, P. R.
Awarding Body: University of Wales Swansea
Current Institution: Swansea University
Date of Award: 2005
Availability of Full Text:
Access from EThOS:
This research assesses how forest-savanna boundaries have shifted in response to past environmental changes, which is crucial to understanding the present-day vegetation mosaic and the origins of Amazon biodiversity as a whole. Individual plant leaf-wax compounds can be extracted from lake sediments and their isotopic values measured by compound-specific 13C analysis, permitting the evaluation of past changes in the abundance of C3 and C4 graminoids, and thereby clarify ambiguities in the pollen record. In this study, a multiproxy approach, using grass-cuticle assemblages and stable carbon-isotope analyses of total organic carbon, is being applied to a lake-sediment core from Laguna Chaplin (14o28’S, 61o04’W), situated in Noel Kempff Mercado National Park (which straddles a climatic transition zone between Amazonian moist evergreen forest, semi-deciduous forest, and savanna). The δ13C values of TOC ranged from 17% at the LGM to 26% in the late Holocene, suggesting an increased representation of C4 graminoids during glacial times. This finding is consistent with the corresponding glacial-age uncharred fossil cuticle coverages of Salviniaceae as well as pollen assemblages, which are dominated by grasses and palms (Mauritia/Mauritiella) with low levels of rainforest taxa, implying an expansion of seasonally-flooded savannas at the expense of seasonally-flooded forest. Compound-specific 13C analyses of leaf-wax n-alkanes and n-alkanoic acids show a dominance of algal and aquatic macrophytes biomarkers in the last glacial period lending additional support to this inference. The palaeoecological inferences previously made from pollen and bulk carbon-isotope data will be tested using these results, permitting overall conclusions to be drawn at much greater taxonomic resolution.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available