HOLOCENE HYDROCLIMATE AND VEGETATIONAL DYNAMICS IN THE LAKE IZABAL BASIN, EASTERN GUATEMALA: INSIGHTS FROM POLLEN AND CHARCOAL ANALYSES

The Holocene has been characterized by multiple changes in precipitation on annual to millennial time scales, which have modulated the structure and composition of vegetation. The palynological record from Lake Izabal in eastern Guatemala offers an opportunity to study the temporal relationship between climate and vegetation during the Holocene. The goal was to identify the patterns of environmental variability based on pollen and charcoal concentrations to reconstruct vegetation variability and paleo-fire dynamics. Modern occurrences of genera associated with the taxa found in the sedimentary record were used to model the environmental distribution of floras, which was in turn used to quantitatively estimate past temperature and precipitation. Charcoal distribution was used to assess regional and local fires in time. Though forest taxa exhibited a differential variability on different time scales, an overall decreasing trend through time was inferred. Herbaceous and anthropic taxa on the other hand increased progressively up to the present. The reconstructed regional vegetation trends correlated with the Holocene insolation patterns of the Northern Hemisphere at millennial timescales. Conversely, the observed centennial timescale variability compared more with regional phenomena, such as changes in the spatial configuration of the North Atlantic Subtropical High (NASH) and other regional and local factors. Quantitative estimations suggest that vegetation patterns during the late Holocene may have been amplified and modulated by anthropic activities and other local factors. While precipitation seasonality was substantially variable across early, mid, and late Holocene, the overall mean annual precipitation seemingly increased through time. Thus, the sedimentary record indicates a variable precipitation seasonality through the Holocene that follows the solar insolation pattern on millennial timescales, while other factors, such as anthropic impacts and microclimate of the Lake Izabal Basin apparently defined the vegetation cover on centennial to lower timescales.