Sincronologia e sincorologia dei boschi di faggio (Fagetalia sylvaticae) nell'Europa centrale

Abstract

From Preboreal to Late Atlantic times the landscape of Central Europe was covered by dense primeval woodlands, with the final stages of the natural succession differing from site to site, according to the climatic and soil conditions. There is evidence today, that the potential natural state of vegetation exists under the prevailing environmental conditions. In the same way, the Late- and Postglacial vegetation types and stages are supposed to have had floristical differences, or at least regional differences in the dominance or composition of their characteristic species. According to that, the periodic development phases of broad-leaved woodland with the successive immigration of the respective trees till the middle of the Atlantic period (until about 6000 yr. B.P.; POTT 1988) reflect the ecological balance under different climatic and edaphic conditions and are exclusively due to natural factors. In conifer-woods of Boreal and Pre-Atlantic fires, insects and diseases were the most important natural factors influencing vegetation in the past, and they also affected the virgin forests.So, during the long-lasting Postglacial process of woodland development - even before the Neolithic landnam periods - the changes in the appearance and the composition of plant communities resulted from habitat patterns and were modified by edaphic or biological factors. The vegetation of the EMW (oak-mixed Atlantic forests) varied in space and time with Quercus, Ulmus, Tilia, Fraxinus and Alnus as predominant species. The broad-leaved forests of the Atlantic period are often reflected in pollen diagrams derived from the Pleistocene loess and sand accumulations for example of the Northwest German lowlands. The abundance of Tilia, Quercus and Ulmus on loess soils and their restricted occurrence with dominance of Alnus on sandy soils with high ground-water levels is very significant (BAKELS 1978, 1982; POTT 1982).