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Abstract
This dissertation develops novel high-resolution paleoclimate and paleoenvironmental reconstructions for Chirripo National Park of Costa Rica in Central America, using sub-fossil chironomid remains, macroscopic charcoal and the geochemical signals extracted from sediment cores recovered from glacial lakes located in the park. Comparison is made between the late Holocene hydroclimate and paleoenvironmental conditions at mid- and high-elevation sites in Costa Rica and the surrounding regions, to facilitate an assessment of the relationship between possible driver(s) of hydroclimate variability and paleoenvironmental change in this region between ~640 and 1230 CE. Lastly, highly resolved charcoal and geochemical data are analyzed to identify how fire events have influenced nutrient flux and vegetation dynamics within the Chirripo paramo during the late Holocene. The results generated in this dissertation indicate that the glacial highlands in central Costa Rica experienced a relatively warm and wet climate between ~5290 and 2780 cal yr BP, with evidence of an abrupt climate change event found at ~5200 cal yr BP. The intervals between ~8770 and5290 cal yr BP and between ~2780 cal yr BP and the present were generally characterized by cold and dry conditions, with the most frequent wildfires occurring during approximately the past 3300 years. The chironomid-inferred thermal variations, which are tightly coupled with fire history, vegetation dynamics and nutrient fluxes in the glacial highlands of Chirripo National Park, can provide useful reference for the park staff to manage the paramo ecosystem in light of projected climate change. The timing and the expression of hydroclimate change observed in southern Central America during the Terminal Classic Drought (TCD: ~770-1100 CE) and the early Medieval Climate Anomaly (MCA: ~950-1250 CE) supports the hypothesis that depressed sea surface temperatures in the tropical North Atlantic, in conjunction with a stronger North Atlantic Subtropical High and a southward shifted Intertropical Convergence Zone (ITCZ), were responsible for the dry conditions observed between ~750 and 1100 CE in this region.