Swiss vegetation history during the last 18 000 years

Abstract

summaryThis paper gives a detailed outline of Swiss vegetation history during the last 18 000 years. For each pollen zone, a map is given showing vegetation development from the late Würmian to the present. A concise historical review of the Swiss pollen analytical research during the last 60 years is presented is followed by some discussion of the central European glacial refugia. Based on a selection of over 100 pollen‐analytically investigated sites, the development of Swiss vegetation since the late Würmian can be presented as follows: Oldest Dryas. After the Wurm maximum the ice network melted back quickly to small mountain glaciers. At some localities, several types of an Artemisia‐Chenopodiaceae‐Jitniperus‐Ephedra‐Helianthemim Poaceae steppe/tundra have been recorded, representing an apparent uniformity over the whole Swiss area. Böiling Interstadial. This first, late Würmian, warm phase is characterized by the occurrence of Betula, Hippophaë, Juniperus, Ephedra and Salix. Older Dryas, Little evidence for this period has yet been found in Switzerland. Alleröd Interstadial. This marked warm phase led to a typical late Wiirmian reforestation, with both Betula and Pinus up to about 1200–1600 m above sea level. Younger Dryas. In the whole alpine area there is good evidence for this last, late Würmian climate deterioration, which led to renewed glacier activity and to an alpine timber‐line depression of 200–300 m. Preboreal. For the central Alps and the Prealps a wide occurrence of Pinus sylvestris/mugo, P. cembra, Larix and Betula has been recorded, whereas in southern Switzerland the first mixed oak forest developed. Boreal. Corytus and mixed oak forest spread in some cases rapidly over a wide area, chiefly in the Prealps, the Plateau, the Jura and in southern Switzerland. In the high mountains Pinus sylvestris/mugo, P. cembra and Larix still dominated. Older Atlantic. In both the Plateau and the Prealps, Corylus and mixed oak forest dominated, whereas in the continental Alps Pinus sylvestris/mugo, P. cembra and Betula grew with some elements of mixed oak forest. In the Orisons the immigration of Picea from east to west has been identified; in the eastern Prealps Abies spread. Younger Atlantic. This period is characterized by a first maximum of the timber‐line extension to an altitude of about 2300 m. The spread ot Fagus from west to east is seen. On both the montane and subalpine belt, first Abies and later Picea dominated. Picea immigration to the west continued. Subboreal. Until 3000 yr B. P. forest achieved its optimum development with a distribution up lo 2000 m above sea level. In both the Plateau and the Jura the major spread of Fagus took place in this period. Picea now reached southwestern Jura and even the Lake Geneva region. Subatlantic. This period is characterized by man's influence on the vegetation. According to the evidence of both pollen analysis and archaeology, the first anthropogenic influences on Swiss vegetation took place between 6000 and 4500 yr B.P. In the anthropogenic timber‐line belt secondary forests of Belula, Alnus and Pinus formed. On the southern alpine border, the Romans introduced Castanea, whereas on the Plateau Picea, Abies and Pinus have been planted.