Testing the usefulness of pine stomata as a proxy in lake sediment cores from low-latitude environments

Paleoecological research, using lake cores to reconstruct past climatic and anthropogenic changes, is a burgeoning field in the circum-Caribbean. The Dominican Republic’s Las Lagunas region is being studied for this purpose using many proxies. One possible proxy for study there is pine stomata. Concentrations of pine stomata in lake sediments have been used in high-latitude and alpine locations to reconstruct tree-line movement and stand invasion, but have never been used in low-latitude environments. In this thesis I present results of analyses of Pinus occidentalis Swartz (Hispaniolan pine or West Indian pine) stomata concentrations in lake-sediment cores from two lakes in the Las Lagunas region, Laguna Castilla and Laguna de Salvador. Stomata concentrations, along with prior pollen counts, provide a detailed, site-specific view of historic pine distribution near the lakes. Previous higher-latitude studies provide background and context for this project, which aims to establish pine stomata as a useful proxy in low-latitude environments. Stomata concentrations in Castilla and Salvador, though never high, improved the interpretability of previous pine pollen counts. Pollen and stomata tended to co-vary down the Salvador core, and more weakly in the Castilla core where stomata concentrations were lower. Overall, pine stomata proved a useful proxy at Las Lagunas that can be used in future paleoecological studies of other low-latitude environments. In addition to the Las Lagunas temporal study, this thesis examines spatial patterns of stomata deposition in mid-latitude Crystal Lake, Knoxville, Tennessee, from the edge of the lake to its middle. Typically, sediment cores are taken centrally in lakes, so this study examines whether stomata are distributed evenly enough across lakes to be well represented in central cores. The Crystal Lake study provided useful insights into the deposition and redeposition paths followed by stomata after they enter water bodies. Concentrations of stomata decreased on a dry weight basis, traversing away from shore, with a slight increase where a typical core site location would be, at the lake’s center. Based on these results, central coring sites might often fall short of yielding representative concentrations of the stomata entering lakes