POLLEN EVIDENCE AND SIMULATED LATE GLACIAL AND HOLOCENE CLIMATE OF LJUBLJANA MOOR, SLOVENIA

Pollen analyses from Bistra, southwestern Ljubljana Moor, Slovenia, and macrophysical climate models for Ljubljana Moor were compared in order to reconstruct the past environment, especially climatic changes in the last 14000 years and vegetation history during the Holocene.

Temperature and precipitation models suggest a substantial rise in January and July temperatures and a noticeable decrease in annual rainfall in the Late Glacial near Ljubljana Moor. These climatic changes may have had an important influence on the occurrence and development of mesophilic Holocene vegetation. In the beginning of the Holocene the cold-period Pinus-Betula stands, characteristic for the Late Glacial, were already to a large extent replaced by mixed-deciduous forests dominated by Fagus, as observed in the pollen record from Bistra. They became well established on the surrounding slopes, and after the appearance of Abies a predominant association of Abieti-Fagetum developed. In the pollen sequences from around 8000 until 6000 ¹⁴C years BP, a thinning of beech-fir forest and temporary expansion of Corylus and Alnus are observed. The climate models for the same period suggest that the described changes in forest composition could be attributed to an increase in summer temperatures. Warmer summers were presumably less favorable for Fagus, which became dominant again around 5000 ¹⁴C years BP, after summer temperatures started to drop significantly. The pollen record from Bistra also indicates that major changes in Holocene vegetation composition occurred towards the end of the Mid-Holocene. Changes in the surrounding vegetation such as an increase in herbs, especially Cyperaceae, presence of cereals, and a decrease in arboreal vegetation, are correlated with simulated cooler climatic conditions, but also reflect human impact on the landscape in the vicinity.

All in all, the pollen record from Bistra shows a good correlation with temperature models on the larger time scale. On the other hand, modeled rainfall indicates that precipitation did not have much effect on vegetation development around Ljubljana Moor after the Early Holocene. However, further comparative studies are needed to draw firmer conclusions.