Pollen analysis of a peat profile from the Rieseberger Moor, Lower Saxony, Germany

The Rieseberger Moor is a fen, 145 hectares in size, situated about 20 km east of Brunswick (Braunschweig), Lower Saxony, Germany. Peat was dug in the fen - with changing intensity - since the mid-18th century until around AD 1955. According to Schneekloth & Schneider (1971) the remaining peat (fen and wood peat) is predominantly 1.5 to 2 m thick (maximum 2.7 m). Part of the fen - now a nature reserve (NSG BR 005) - is wooded (Betula, Salix, Alnus). For more information on the Rieseberger Moor see http://de.wikipedia.org/wiki/Rieseberger_Moor. Willi Selle was the first to publish pollen diagrams from this site (Selle 1935, profiles Rieseberger Torfmoor I and II). This report deals with a 2.2 m long profile from the wooded south-eastern part of the fen consisting of strongly decomposed fen peat taken A.D. 1965 and studied by pollen analysis in the same year. The peat below 1.45 m contained silt and clay, samples 1.48 and 1.58 m even fine sand. These samples had to be treated with HF (hydrofluoric acid) in addition to the treatment with hot caustic potash solution. The coring ended in sandy material. The new pollen data reflect the early part of the known postglacial development of the vegetation of this area: the change from a birch dominated forest to a pine forest and the later spreading of Corylus and of the thermophilous deciduous tree genera Quercus, Ulmus, Tilia and Fraxinus followed by the expansion of Alnus. The new data are in agreement with Selle's results, except for Alnus, which in Selle's pollen diagram II shows high values (up to 42% of the arboreal pollen sum) even in samples deposited before Corylus and Quercus started to spread. On contrary the new pollen diagram shows that alder pollen - although present in all samples - is frequent in the three youngest pollen spectra only. A period with dominating Alnus as seen in the uppermost part of Selle's pollen diagrams is missing. The latter is most likely the result of peat cutting at the later coring site, whereas the early, unusually high alder values of Selle's pollen study are probably caused by contamination of the pollen samples with younger peat. Selle took peat samples usually with a "Torfbohrer" (= Hiller sampler). This side-filling type of sampler with an inner chamber and an outer loose jacket offers - if not handled with appropriate care - ample opportunities to contaminate older peat with carried off younger material. Pollen grains of Fagus (2 % of the arboreal pollen sum) were found in two samples only, namely in the uppermost samples of the new profile (0.18 m) and of Selle's profile I (0.25 m). If this pollen is autochthonous, with other words: if this surface-near peat was not disturbed by human activities, the Fagus pollen indicates an Early Subboreal age of this part of the profile. The accumulation of the Rieseberg peat started during the Preboreal. Increased values of Corylus, Quercus and Ulmus indicate that sample 0.78 m of the new profile is the oldest Boreal sample. The high Alnus values prove the Atlantic age of the younger peat. Whether Early Subboreal peat exists at the site is questionable, but evidently none of the three profiles reaches to Late Subboreal time, when Fagus spread in the region. Did peat-growth end during the Subboreal? Did younger peat exist, but got lost by peat cutting or has younger peat simply not yet been found in the Rieseberg fen? These questions cannot be answered with this study. The temporary decline of the curve of Pinus for the benefit of Betula during the Preboreal, unusual for this period, is contemporaneous with the deposition of sand (Rieseberger Moor II, 1.33 - 1,41 m; samples 1.48 and 1.58 m of the new profile) and must be considered a local phenomenon. Literature: Schneekloth, Heinrich & Schneider, Siegfried (1971). Die Moore in Niedersachsen. 2. Teil. Bereich des Blattes Braunschweig der Geologischen Karte der Bundesrepublik Deutschland (1:200000). - Schriften der wirtschaftswissenschaftlichen Gesellschaft zum Studium Niedersachsens e.V. Reihe A I., Band 96, Heft 2, 83 Seiten, Göttingen. Selle, Willi (1935) Das Torfmoor bei Rieseberg. - Jahresbericht des Vereins für Naturwissenschaft zu Braunschweig, 23, 46-58, Braunschweig.

Pollen and macrofossils profiles and age determination from the Pittsburg Basin in the lowlands of south-central Illinois

Pollen and macrofossil evidence for the nature of the vegetation during glacial and interglacial periods in the regions south of the Wisconsinan ice margin is still very scarce. Modern opinions concerning these problems are therefore predominantly derived from geological evidence only or are extrapolated from pollen studies of late Wisconsinan deposits. Now for the first time pollen and macrofossil analyses are available from south-central Illinois covering the Holocene, the entire Wisconsinan, and most probably also Sangamonian and late Illinoian time. The cores studied came from three lakes, which originated as kettle holes in glacial drift of Illinoian age near Vandalia, Fayette County. The Wisconsinan ice sheet approached the sites from the the north to within about 60 km distance only. One of the profiles (Pittsburg Basin) probably reaches back to the late Illinoian (zone 1), which was characterized by forests with much Picea. Zone 2, most likely of Sangamonian age, represents a period of species-rich deciduous forests, which must have been similar to the ones that thrive today south and southeast of the prairie peninsula. During the entire Wisconsinan (14C dates ranging from 38,000 to 21,000 BP) thermophilous deciduous trees like Quercus, Carya, and Ulmus occurred in the region, although temporarily accompanied by tree genera with a more northerly modern distribution, such as Picea, which entered and then left south-central Illinois during the Woodfordian. Thus it is evident that arctic climatic conditions did not prevail in the lowlands of south-central Illinois (about 38°30' lat) during the Wisconsinan, even at the time of the maximum glaciation, the Woodfordian. The Wisconsinan was, however, not a period of continuous forest. The pollen assemblages of zone 3 (Altonian) indicate prairie with stands of trees, and in zone 4 the relatively abundant Artemisia pollen indicates the existence of open vegetation and stands of deciduous trees, Picea, and Pinus. True tundra may have existed north of the sites, but if so its pollen rain apparently is marked by pollen from nearby stands of trees. After the disappearance of Pinus and Picea at about 14,000 BP (estimated!), there developed a mosaic of prairies and stands of Quercus, Carya, and other deciduous tree genera (zone 5). This type of vegetation persisted until it was destroyed by cultivation during the 19th and 20th century. Major vegetational changes are not indicated in the pollen diagram for the late Wisconsinan and the Holocene. The dating of zones 1 and 2 is problematical because the sediments are beyond the14C range and because of the lack of stratigraphic evidence. The zones dated as Illinoian and Sangamonian could also represent just a Wisconsinan stadial and interstadial. This possibility, however, seems to be contradicted by the late glacial and interglacial character of the forest vegetation of that time.