Ein frühweichselzeitliches Profil aus der Niederterrasse der mittleren Lahn (Weimar-Niederweimar, Hessen) - geologische, pollenanalytische und makrorestanalytische Untersuchungen

Die Niederterrasse der mittleren Lahn ist in mindestens drei Aufschotterungsphasen zu gliedern, die dem Weichsel-Frühglazial, dem Weichsel-Pleniglazial und dem ausgehenden Weichsel-Spätglazial (Jüngere Dryas) zuzuordnen sind. Die Paläo-Rinnen im unteren Schotterkörper haben nach den palynologischen und karpologischen Untersuchungen ein brörupzeitliches Alter, wobei aber nicht die gesamte Vegetationsabfolge überliefert ist. Als Bindeglied zwischen dem nördlichen Mitteleuropa und dem Alpenvorland kommt den brörupzeitlichen Profilen aus dem Lahntal von Weimar-Niederweimar eine überregionale Bedeutung bei der Beurteilung des Paläoklimas zu. Pflanzensippen mit subozeanischer Verbreitungstendenz belegen, dass das Klima während des Brörup-Interstadials nicht extrem kontinental getönt war. Die Mittelgebirgszone bildete offenbar die nördliche Verbreitungsgrenze wärmeliebender Laubgehölze (Eiche, Ulme), wobei die Lange der Vegetationsperiode sowie die Niederschlagsverhältnisse mögliche Ursachen für eine Begrenzung der Ausbreitung nach Norden gewesen sein könnten.researc

A three thousand year succession of plant communities on a valley bottom in the Vosges Mountains, NE France, reconstructed from fossil pollen, plant macrofossils, and modern phytosociological communities

Pollen and macrofossils were studied in a core from a fen at the foot of a slope in the Vosges Mountains, NE France. The present-day vegetation of little disturbed Abies, Fagus, and Picea forest and wetlands has been described in detail in terms of phytosociological communities using the Braun-Blanquet approach. Past ecological conditions are reconstructed in five steps: (1) The modern vegetation types are described as combinations of phytosociological species groups. (2) Micro- and macrofossils are assigned to these groups. (3) These in combination determine the past vegetation types at the site; there were simultaneously several such types in some biozones. (4) The sequence of past vegetation types is interpreted as successional pathways. (5) Past ecological conditions are inferred from these pathways. Results are: (1) The types of local forest and fen were the same around 1000 b.c. as today. (2) Rising groundwater around 650 b.c. caused a natural wet meadow to develop at the site. (3) Trees were felled near the site in the first century b.c. (Late Iron Age), facilitating the immigration of Picea. (4) Groundwater level rose during early Medieval times because of a wetter climate and alder carr replaced the dry-soil forest close to the site. (5) During High Medieval Times (10th-13th century) the nearby raised bog expanded over the site. (6) Forestry starting around a.d. 1750 caused nutrient-rich water to reach the site, resulting in abrupt vegetation change. (7) The creation of a forest road around a.d. 1855 (historical information) caused further nutrient enrichment of the site. The validity of the method used depends on the assumption that past and present vegetation types are virtually identical, which is true in our study area and study period, according to all the indications that we hav