Vegetation in South America has been impacted by multiple Pleistocene glacial events, climatic changes, volcanic eruptions, fire and human settlement on different temporal and spatial scales. Vegetation dynamics have been inferred from previous pollen studies, but some areas remain vastly understudied, despite the presence of suitable palaeoecological sites. Impenetrable volcanic tephra layers often restrict the ages of these sediments, limiting the age of palaeoecological studies. Combining palaeoecology with phylogenetics increases our understanding of the timing and spatial changes of vegetation movement. Two lake sediment sequences in central Argentina were analysed for pollen, and the phylogenetic history of two trees (the threatened Araucaria araucana and disjunctly distributed Lomatia hirsuta) were studied to better understand the postglacial movement of these species. Pollen indicated that vegetation has been relatively stable for the last 5,000 cal. yr BP in the region, with major changes (such as the introduction of Pinus sylvestris, and opening of the forest canopy) occurring only with the arrival of European settlers around 150 years ago. Populations of Araucaria araucana expanded after the Last Glacial Maximum, but also survived in situ at the edge of the Northern Patagonian glaciers. Preliminary analysis of ancient DNA from Araucaria araucana shows the species' range has not changed in 2,500 cal. yr BP. Lomatia hirsuta is disjunctly distributed due to long-distance dispersal, although research in this thesis was not able to refine the timing of this population split. This research successfully reconstructed the vegetation history from two lakes during the late Holocene, and highlights the complexity of vegetation response to natural and anthropogenic forcings.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:675928 |
| Date | January 2014 |
| Creators | Johnson, Kate |
| Publisher | Queen's University Belfast |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
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