Lake Sediment-Based Reconstructions of Late-Holocene Lowland Environments of Dominican Republic and Barbuda, Northern Caribbean

Academic) Questions remain regarding the impacts of late-Holocene human activities and environmental change on landscapes of the Caribbean islands. This dissertation examined the long-term environmental history of two sites in the northern Caribbean primarily through the analysis of proxy data sources contained in sediment cores. At Laguna Alejandro, a coastal lagoon in the southwestern Dominican Republic, we interpreted, from sediment lithology and stable oxygen isotope data, at least ten storm events over the past 1,000 years, producing the first long record of storm activity from the island. During the Little Ice Age (1400−1800 CE), we interpreted an increased frequency of hurricane landfalls at the study site with longer ecosystem recovery times and decreased fire activity versus during earlier, more moist periods of the late-Holocene. At Freshwater Pond, an inland pond on Barbuda, we interpreted vegetation disturbance from presence of disturbance pollen taxa and biomass burning near the pond from abundance of macroscopic (>125 μm) charcoal from sediments representing ~150 BCE–1250 CE, with consistency of burning and human history on the island informed by the archaeological record suggesting fire activity was primarily due to Pre-Columbian inhabitants. Microscopic charcoal analysis indicated that extra-local burning, primarily island-wide, continued until ~1610 CE then declined, possibly reflecting a change in land-use practices by Europeans who entered the region in 1492 CE and established a permanent settlement on the island in the 1660s. My study on modern pollen from surface soils and sediments, the first from lowland seasonally-dry vegetation of the Greater Antilles, informed our ideas on vegetation-pollen representation in different plant communities, including tropical dry forest, thorn forest, mangrove, mudflat, and lagoon. My modern pollen results also aided in the interpretation of stratigraphic pollen in the study of nearby L. Alejandro’s sediments and revealed changes in floristic composition at the study site through time. Pollen of maize (Zea mays) and Prosopis juliflora in sediments representing ~1760 CE document human subsistence agriculture and disturbance to tropical dry forest in the watershed. Lake Sediment-Based Reconstructions of Late-Holocene Lowland Environments of Dominican Republic and Barbuda, Northern Caribbean Allison Renee Le Blanc Abstract (General Audience)General Audience) Past (or paleo-) environments of the Caribbean islands are understudied. This dissertation examined the long-term environmental history of two sites in the northern Caribbean primarily through proxy data sources contained in lake sediment cores, namely pollen and spores, charcoal particles, and sediment physical and chemical characteristics. Analysis of multiple proxies allowed the reconstruction of watershed vegetation and fire history, wetland development, and possible human impacts on the environment. At Laguna Alejandro, a coastal lagoon in the Dominican Republic (DR), we interpreted at least ten tropical storm events over the past 1,000 years, producing the first long record of hurricanes for the island. During the Little Ice Age (LIA, 1400−1800 CE), we interpreted an increased frequency of hurricane landfalls at the study site and longer ecosystem recovery times and decreased fire activity versus during earlier, more moist periods, possibly linked to more arid conditions and associated declines in biomass. At Freshwater Pond, an inland pond on Barbuda, we interpreted vegetation disturbance from presence of pollen of disturbance taxa and biomass burning near the pond from abundance of large charcoal fragments in sediments representing ~150 BCE–1250 CE. The consistency of burning and human history on the island, informed by the archaeological record, suggests fire activity was largely controlled by Pre-Columbian inhabitants. Smaller charcoal fragments suggest island-wide burning continued until ~1610 CE then declined, possibly reflecting a change in land-use practices by Europeans who entered the region in 1492 CE and established a permanent settlement on the island in the 1660s as well as declines in biomass tied to LIA. The analysis of pollen and spores collected from surface soils and sediments (modern pollen) in lowland seasonally-dry vegetation types in the Dominican Republic, revealed how different vegetation types (tropical dry forest, thorn forest, mangrove, mudflat, and lagoon) were represented in the pollen rain, including identifying pollen provenance and overand underrepresented taxa. The study also aided in the interpretation of sediment core pollen from Laguna Alejandro, documenting changes in the composition of the vegetation through time and revealing subsistence agricultural activities and disturbance to tropical dry forest.