Dr. Kostas Panagiotopoulos

Topography of Lake Prespa. Lake catchment (blue line) and core locations (Co1215, this study) are shown (SRTM Data: Jarvis et al., 2008; Panagiotopoulos et al., 2014).

The pollen spectra allow for the zoning of the record in three major phases of vegetation de- velopment corresponding to Marine Isotope Stages 5 to 1. The forested phases of MIS 5 and MIS 1 are dominated by thermophilous and drought-sensitive trees (e.g. Quercus, Carpinus, Fagus) suggesting higher temperatures and moisture availability during their growing season. Increased lake productivity, hypolimnion anoxia and calcite precipitation are recorded in these intervals. Continuous presence of Mediterranean frost-sensitive species (e.g. Pistacia, Phillyrea) during the Holocene implies rising temperatures in late winter and spring. Sporadic occurrence of maquis pollen in MIS 5 suggest that temperature was probably limiting their expansion. Increasing fuel availability and summer aridity most likely account for a higher microscopic charred particle concentration during the Holocene (in particular after c. 5.5 ka). However, intensifying anthropogenic activity has probably overridden climate forcing over the last c. 2 ka. Within MIS 5 and MIS 1, brief periods (centennial to millennial) of open landscape are also documented and are ascribed to colder and drier climate conditions persisting at Prespa. During MIS 3, the relatively open landscape is characterized by several deciduous trees besides Pinus. An open steppe landscape with scattered tree stands comprising mostly Pinus prevailed in MIS 4 and MIS 2. High Artemisia and Chenopodiaceae abundances point to rather cold and arid conditions at Prespa. This appears to be in agreement with low lake productivity, enhanced mixing and increased ice-cover documented for this time. However, occurrences of deciduous tree pollen throughout the Last Glacial provide evidence for the survival of several tree species in sheltered locations at Prespa or its vicinity.

This study underscores the sensitivity of the Lake Prespa region to climate forcing over the Last Glacial and the Holocene. The vegetation history of the region was examined focusing on ecological processes such as immigration, competition, succession, population growth and stability. Ongoing investigations may offer further insights into the paleoenvironment and paleoclimate at Prespa. The Prespa pollen underline the potential of the region to serve as refugium over longer time scales. In spite of systematic conservation efforts over the last decades, the question of whether Prespa’s ecosystems will withstand increasing anthropogenic pressures remains open.