Pollen record from Kleiner Mochowsee, Germany

A Holocene pollen diagram from Kleiner Mochowsee (northern Niederlausitz, East Germany) shows pine as an important constituent of the woodland south of the Schwielochsee. Oak woodland was widespread since the Atlantic. Betula lost its importance at the end of the Preboreal. Fagus is represented continuously in the pollen record since the Atlantic, Carpinus since the Subboreal. However, the two latter tree species remain without great importance throughout the whole pollen record. The poor sandy soils are furthermore reflected by the low values of Corylus during the Boreal, comparable to other records from Berlin and its surrounding area. The 'classical' elm decline could be shown for the Niederlausitz, radiocarbon dates assume a contemporaneous age for this event with other records from northern Germany. Only small-scaled human impact is indicated in prehistoric times, during the migration period it seems to have ceased completely. Later, in the Medieval, deforestation and tillage can be shown. Secale was cultivated since the early Medieval; an accompanying weed flora appeared at the same time. Cultivation of Fagopyrum and Linum usitatissimum could be shown for the late Medieval times.

Pollen record and dating of a sediment profile from Ahlequellmoor in Germany

A pollen diagram from the Ahlequellmoor in the Solling area shows the history of vegetation and settlement over the last 7,800 years. In the early Atlantic period mixed deciduous forest with mainly Tilia together with Ulmus and Quercus grew in the area. In the late Atlantic period Quercus became most abundant. Fagus spread in the Sub-boreal period at about 2700 B.C. Since ca. 900 B.C. the Solling was covered by beech forests with some oak. In prehistoric times woodland grazing is indicated. Only in Medieval times are two settlements in the vicinity of the Ahlequellmoor reflected in the pollen diagram. The earlier one is dated to about A.D. 750-1020, and may be connected with the former Monastery of Hethis, which is thought to have existed close to the fen from A.D. 815 to 822. The second Medieval settlement dates to the 11th-12th century. The large-scale woodland destruction of late Medieval and modern times is not clearly visible. The silvicultural measures of the last 200 years are reflected by increasing values of spruce and grassland taxa.

Pollen assemblages of modern soil samples from the Old Botanical Garden of the University of Göttingen

The importance of pollen analytical data for the reconstruction of the natural conditions and their changes caused by human impact in prehistorical and historical times is beyond all doubt. Pollen analysis can, however, be hampered by poor pollen preservation and low pollen concentrations. As an example pollen assemblages from excavation areas near Pompeii (see doi:10.1594/PANGAEA.777531) and from the Old Botanical Garden of the University of Göttingen are discussed. A pollen diagram (see doi:10.1594/PANGAEA.820590) from the site Höllerer See in Austria (N of the city of Salzburg) demonstrates the intensive agricultural influence on the vegetation of the area during Roman and Medieval times. Human influence was much weaker during the Iron and the Bronze ages. There is no indication of human impact on the vegetation during the Migration period.

Accumulation rate and stable oxygen isotope ratios of the ice cores from the North Greenland Traverse

We present for the first time all 12 d18O records obtained from ice cores drilled in the framework of the North Greenland Traverse (NGT) between 1993 and 1995 in northern Greenland. The cores cover an area of 680 km × 317 km, 10 % of the Greenland ice sheet. Depending on core length (100-175 m) and accumulation rate (90-200 kg/m**2/a) the single records reflect an isotope-temperature history over the last 500-1100 years. Lowest d18O mean values occur north of the summit and east of the main divide as a consequence of Greenland's topography. In general, ice cores drilled on the main ice divide show different results than those drilled east of the main ice divide that might be influenced by secondary regional moisture sources. A stack of all NGT records and the NGRIP record is presented with improved signal-to-noise ratio. Compared to single records, this stack represents the mean d18O signal for northern Greenland that is interpreted as proxy for temperature. Our northern Greenland d18O stack indicates distinctly enriched d18O values during medieval times, about AD 1420 ± 20 and from AD 1870 onwards. The period between AD 1420 and AD 1850 has depleted d18O values compared to the average for the entire millennium and represents the Little Ice Age. The d18O values of the 20th century are comparable to the medieval period but are lower than that about AD 1420.

Pollen profile from sediment core Höllerer See

(expanded by Eberhard Grüger, Göttingen) The site "Höllerer See" is a lake in the northern foreland of the Alps, about 30 km north of the city of Salzburg/Austria, situated in the south-western part of Oberösterreich/Austria. A 2 m long piston core from this locality, consisting entirely of calcareous gyttja, was studied by pollen analysis. The three lowermost samples (1.98, 1.95 and 1.92 m) were deposited during the Preboreal when Pinus and Betula were still the dominating forest trees. High pollen values of thermophilous woody species (mainly Corylus and Quercus, but also Ulmus, Tilia, Fraxinus) prove the Boreal age of the next younger sample (1.91 m). The following two pollen spectra attest that Alnus (1.89 m) and - later (1.88 m) - Fagus had become important members of the local (Alnus) and the regional (Fagus) vegetation. From this level up to the top of the profile these two tree taxa contribute - together with Betula - always 50 to 80 % to the arboreal pollen sum. The upper 1.89 m of sediment of the Höllerer See core evidently date from the Subboreal and the Subatlantic. As Preboreal sediment was stated at the base of the profile it must be concluded that most of the Boreal and the Atlantic is - for whatever reason - not represented by sediment in this core. As no radiocarbon dates are available age estimates of the distinguished pollen zones can be achieved only by correlating major changes of the former vegetation with historical events which probably influenced the then contemporary vegetation. The pollen grains of the Triticum and Hordeum type found in samples of zone 2.1 might indicate the growing of cereals in the region during the Late Bronze Age. The first pollen grains of Secale date from the boundary Hallstatt/Latène Age (zone 2.2). The cereal curves become continuous in Bavarian times (Bajuwarenzeit, Middle Ages, zone 3.3). The Plantago laceolata curve, continuous since 1.7 m depth (zone 2.1), points to animal breeding since the Early Subatlantic (Hallstattzeit). This curve reaches its absolute maximum in Roman time (zone 3.1). Roman time forest clearance caused a drastic decrease of tree pollen curves (start of zone 3.1). Values of anthropogenic indicators as high as in zone 3.1 are found again - after a distinct decrease in zone 3.2 - not till the Bavarians settled in the region (6th century). Maximal Fagus values and the simultaneous total lack of anthropogenic indicators mark the Migration Period (zone 3.2). The Younger Subatlantic (zone 4) is characterized by a decrease of deciduous forests due to medieval forest clearance. At the same time the conifers Pinus and Picea gained in importance. The lake was probably used for retting hemp in Medieval times. The distinction of the pollen grains of Cannabis and Humulus might not be certain in all cases. It is known that hemp as well as hop was cultivated in the study area. Markers were added to the samples at the beginning of pollen preparation (13500 Lycopodium spores, sample volume 0.5 cm**3) and counted together with the pollen grains. Therefore pollen concentrations can be calculated: Concentration = C * F / V (with C = number of grains of a particular pollen type, V = volume of the untreated pollen sample, F = marker added/marker counted). F ranges from 39 to 1688. Factors that large are not suited to produce reliably interpretable pollen concentrations. Consequently no use was made of the pollen concentrations in this thesis, although a concentration diagram is added.

(Table 1) Age determination of sediment core SO147_106KL

Here we present a high-resolution marine sediment record from the El Niño region off the coast of Peru spanning the last 20,000 years. Sea surface temperature, photosynthetic pigments, and a lithic proxy for El Niño flood events on the continent are used as paleo-El Niño-Southern Oscillation proxy data. The onset of stronger El Niño activity in Peru started around 17,000 calibrated years before the present, which is later than modeling experiments show but contemporaneous with the Heinrich event 1. Maximum El Niño activity occurred during the early and late Holocene, especially during the second and third millennium B.P. The recurrence period of very strong El Niño events is 60-80 years. El Niño events were weak before and during the beginning of the Younger Dryas, during the middle of the Holocene, and during medieval times. The strength of El Niño flood events during the last millennium has positive and negative relationships to global and Northern Hemisphere temperature reconstructions.