Holozäne Vegetationsentwicklung im hinteren Klostertal (Vorarlberg, Österreich) und Hinweise zur prähistorischen Landwirtschaft auf Grund palynologischer Untersuchungen

Holocene vegetation development in the Hinteren Klostertal (Vorarlberg, Austria) and evidence for prehistoric agriculture based on palynological investigations. The subalpine peat bog located above the village of Stuben at the Arlberg pass road (Vorarlberg, Austria, 1630 m a.s.l.) consists of Late-glacial and Holocene peat beds of the last 12 300 years. Samples of a cross-section of the peat bog were analysed palynologically. They give information to the local and regional flora and vegetation history of the western Arlberg pass and the adjacent Klostertal area, including first human impact on the natural environment. The palynological diagram shows the Holocene immigration and spread of the actual dominant forest tree species Scots/ mountain pine (Pinus sylvestris / P. mugo), Norway spruce (Picea abies), European larch (Larix decidua), silver fir (Abies alba), of some deciduous trees of the oak(Quercus spec.) and beech (Fagus sylvatica) mixed forest, and green alder (Alnus viridis). The actual dominant Norway spruce migrated from the Tyrolian Alps westwards along the Inn valley, crossed the Arlberg pass and reached the inner Klostertal area during the Older Atlantic around 7800 cal yr BP (= calibrated years before present, i.e. before AD 1950). The green alder immigrated together with Norway spruce from East to West in the subalpine belt. During the Subboreal (ca. 5700–2650 cal yr BP) and Older Subatlantic (ca. 2650–1000 cal yr BP), Norway spruce and common/grey alder (Alnus glutinosa / incana) showed signs of recession due to first human clearings, whereas green alder shows a mass spread at the tree limit from the Eastern Alps to the Northwestern Prealps. In addition, first pollen of cereals (Triticum-type), hemp (Cannabis-type) and of indicators of meadows and alpine pastures (Poaceae, Plantago lanceolata, and other herbs) are recorded at the transition from the Neolithic to the Bronze Age (ca. 2200 BC). During Roman Times the sweet chestnut (Castanea sativa) was introduced, and a lowering of the tree limit with an increasing spread of green alder due to alpine clearings were recorded, whereas pollen indicators of pastures and ruderal plants (Plantago lanceolata, P. media, Urtica, Artemisia) show higher frequencies.