Doctoral Dissertations

Date of Award

5-2011

Degree Type

Dissertation

Degree Name

Doctor of Philosophy

Major

Geography

Major Professor

Sally P. Horn

Committee Members

Henri Grissino-Mayer, Liem Tran, David Finkelstein

Abstract

Stratigraphic analyses of lacustrine sediments provide powerful tools for reconstructing past environments. The records that result from these analyses are key to understanding present-day climate mechanisms and how the natural environment may respond to anthropogenic climate change in the future. This doctoral dissertation research investigates climate and environmental history at Laguna Saladilla (19° [degrees] 39' N, 71° [degrees] 42' W; ca. 2 masl), a large (220 ha) lake along the north coast of Hispaniola. I reconstructed changes in vegetation and environmental conditions over the mid to late Holocene based on pollen, microscopic charcoal, and diatoms in an 8.51 m sediment core recovered from the lake in 2001. Fieldwork in December 2009 included the use of ground penetrating radar to identify subaqueous deltas that indicate past positions of the Masacre river, which flows into the lake from the Cordillera Central. Laguna Saladilla was deeper and more saline from the base of the sediment profile approximately 8030 cal yr BP to about 3500 cal yr BP. Mangrove (Rhizophora) pollen percentages were highest around 7650 cal yr BP, when mollusk shells in the core suggest marine conditions. The lake became progressively brackish ca. 3500 cal yr BP, followed by a transition ca. 2500 cal yr BP to its current freshwater state. This shift in water chemistry was likely due in part to a change in the position of the Masacre river. Diatoms show that lake levels decreased as evaporation/precipitation ratios increased. Amaranthaceae and other herbs dominated the pollen record under the drier conditions of the last 2500 cal yr BP; pollen of fire-adapted taxa, particularly Pinus, increased in the last 800 years. Patterns of microscopic charcoal influx at Laguna Saladilla over the Holocene are similar to patterns at Lake Miragoane, Haiti and Laguna Tortuguero, Puerto Rico. The changes in fire frequency or extent indicated by these Caribbean charcoal records may be driven by increased winter insolation at ca. 5000 cal yr BP that led to earlier winter drying. Comparing the charcoal record to archeological data and other paleoenvironmental records facilitated the disentangling of changes in climate from anthropogenic impacts.

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