International audienceWe present pollen-based reconstructions of the spatio-temporal dynamics of northern European regional vegetation abundance through the Holocene. We apply the Regional Estimates of VEgetation Abundance from Large Sites (REVEALS) model using fossil pollen records from eighteen sites within five modern biomes in the region. The eighteen sites are classified into four time-trajectory types on the basis of principal components analysis of both the REVEALS-based vegetation estimates (RVs) and the pollen percentage (PPs). The four trajectory types are more clearly separated for RVs than PPs. Further, the timing of major Holocene shifts, rates of compositional change, and diversity indices (turnover and evenness) differ between RVs and PPs. The differences are due to the reduction by REVEALS of biases in fossil pollen assemblages caused by different basin size, and inter-taxonomic differences in pollen productivity and dispersal properties. For example, in comparison to the PPs, the RVs show an earlier increase in Corylus and Ulmus in the early-Holocene and a more pronounced increase in grassland and deforested areas since the mid-Holocene. The results suggest that the influence of deforestation and agricultural activities on plant composition and abundance from Neolithic times was stronger than previously inferred from PPs. Relative to PPs, RVs show a more rapid compositional change, a largest decrease in turnover, and less variable evenness in most of northern Europe since 5200 cal yr BP. All these changes are primarily related to the strong impact of human activities on the vegetation. This study demonstrates that RV-based estimates of diversity indices, timing of shifts, and rates of change in reconstructed vegetation provide new insights into the timing and magnitude of major humandisturbance on Holocene regional vegetation, features that are critical in the assessment of humanimpact on vegetation, land-cover, biodiversity, and climate in the past
Abstract. Die Kenntnis der regionalen Paläohydrologie ist eine wesentliche Grundlage für das Verständnis aktueller Umweltfragen, wie zum Beispiel nach den Gründen von hydrologischen Veränderungen, dem Einfluss von Landnutzungsstrategien und der Wirksamkeit von Renaturierungsvorhaben in Feuchtgebieten. Auch die Interpretation von Modellierungsergebnissen zu den künftigen Einflüssen des Klima- und Landnutzungswandels auf das Gewässersystem kann durch die Einbeziehung (prä-) historischer Analogien verbessert werden. Für das glazial geprägte nordostdeutsche Tiefland wurde eine Übersicht der vorliegenden paläohydrologischen Befunde für den Zeitraum der letzten etwa 20.000 Jahre erarbeitet. Die Entwicklung der Flüsse wurde mit Blick auf die Tal-/Auengenese und das Ablagerungsmilieu, die Veränderung des Tal- und Gerinneverlaufs sowie den Paläoabfluss bzw. das Paläohochwasser betrachtet. Wesentliche genetische Unterschiede bestehen zwischen Alt- (Elster- und Saalekaltzeit) und Jungmoränengebieten (Weichselkaltzeit) sowie zwischen hoch und tief gelegenen Tälern. Letztere sind stark durch Wasserspiegelveränderungen in der Nord- und Ostsee beeinflusst worden. Die Entwicklung der Seen wurde hinsichtlich der Seebildung, die überwiegend eine Folge der spätpleistozänen bis frühholozänen Toteistieftau-Dynamik ist, und der Veränderungen im Ablagerungsmilieu analysiert. Weiterhin standen Seespiegelveränderungen im Fokus, wobei sich hoch variable lokale Befunde mit einigen Übereinstimmungen zeigten. Der Überblick zur Moorentwicklung konzentrierte sich auf hydrogenetische Moorentwicklungsphasen und auf die langfristige Entwicklung des Grundwasserspiegels. Enge Beziehungen zwischen der Entwicklung der Flüsse, Seen und Moore bestanden insbesondere im Spätholozän durch komplexe Vermoorungsprozesse in den großen Flusstälern. Bis in das Spätholozän wurde die regionale Hydrologie überwiegend durch klimatische, geomorphologische und nicht-anthropogene biologische Faktoren gesteuert. Seit dem Spätmittelalter wurde in der Region das Gewässernetz und der Wasserkreislauf im starken Maß durch anthropogene Interventionen beeinflusst (z.B. Aufstau von Flüssen und Seen, Bau von Kanälen und Deichen, Moorkultivierung). In den letzten etwa 50 Jahren haben dann sogar die kurzfristigen anthropogenen Eingriffe, z.B. in Form von Abflussregulierung, Hydromelioration und künstlicher Seebildung, die Wirksamkeit langfristiger klimatischer und geomorphologischer Prozesse übertroffen.
Chance discoveries of weapons, horse bones and human skeletal remains along the banks of the River Tollense led to a campaign of research which has identified them as the debris from a Bronze Age battle. The resources of war included horses, arrowheads and wooden clubs, and the dead had suffered blows indicating face-to-face combat. This surprisingly modern and decidedly vicious struggle took place over the swampy braided streams of the river in an area of settled, possibly coveted, territory. Washed along by the current, the bodies and weapons came to rest on a single alluvial surface.
Ice-wedge polygon mires feature a micro-relief of dry ridges, shallow wet depressions, deeper wet troughs and transitional sites, resulting in a local mosaic of vegetation. The correct recognition of these landscape elements in palaeoecological studies of peat sections requires insight about the suitability of proxies and their potential for palaeoecological reconstruction in order to reconstruct vegetation and wetness patterns as well as dynamics. This paper analyses a 105.5 cm long peat section with a base dating to about 4000 cal yr BP from an ice-wedge polygon mire near Kytalyk (NE Siberia). Pollen, macrofossils, testate amoebae, geochemistry and sediment properties were analysed in order to compare the suitability of these proxies to reconstruct past surface wetness. The proxies show similar wetness trends. Pollen and geochemistry data did not always permit wetness reconstruction, the former because many pollen types do not allow the identification of taxa at a low taxonomic resolution, the latter because later taphonomic processes modify chemical variables in deeper peat layers. Macrofossils provided the most detailed wetness reconstruction, because they could be identified to genera or species, for which the moisture requirements are accurately known from their present-day distribution in ice-wedge polygons. All proxies, except geochemistry, show an obvious change from wet to dry conditions at around 20 cm depth. However, as the proxies sometimes show contradictory results, a multi-proxy approach is preferable over a single proxy interpretation as it allows the reconstruction of environmental development in a broader palaeoecological context. Figure 2 Location of ice-wedge polygon Lhc11 near the Kytalyk research station along the Berelekh River: (A, B) the study area, indicated are the most important landforms; (C) satellite image of the study area (GeoEye image from 2010, 0.5 m resolution, by courtesy of K. van Huissteden, Vrije Universiteit, Faculty of Earth and Life Sciences, Amsterdam); and (D) ice-wedge polygon Lhc11. This figure is available in colour online at wileyonlinelibrary.com/journal/ppp 78 A. Teltewskoi et al.
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