Lateglacial and early holocene environments and human occupation in Brandenburg, Eastern Germany

The paper reports on the results of the pollen, plant macrofossil and geochemical analyses and the AMS 14C-based chronology of the «Rüdersdorf» outcrop situated east of Berlin in Brandenburg (Germany). The postglacial landscape changed from an open one to generally forested by ca. 14 cal. kyr BP. Woody plants (mainly birch and pine) contributed up to 85% to the pollen assemblages ca. 13.4–12.5 cal. kyr BP. The subsequent Younger Dryas ( YD) interval is characterized by a decrease in arboreal pollen (AP) to 75% but led neither to substantial deforestation nor spread of tundra vegetation. This supports the concept that the YD cooling was mainly limited to the winter months, while summers remained comparably warm and allowed much broader (than initially believed) spread of cold-tolerant boreal trees. Further support for this theory comes from the fact that the relatively low AP values persisted until ca. 10.6 cal. kyr BP, when the «hazel phase» of the regional vegetation succession began. The postglacial hunter-gatherer occupation is archaeologically confirmed in Brandenburg since ca. 13 cal. kyr BP, i.e. much later than in the western part of Germany and ca. 1000 years after the major amelioration in the Rüdersdorf environmental record

Lateglacial And Early Holocene Environments And Human Occupation In Brandenburg, Eastern Germany

The paper reports on the results of the pollen, plant macrofossil and geochemical analyses and the AMS 14C-based chronology of the «Rüdersdorf» outcrop situated east of Berlin in Brandenburg (Germany). The postglacial landscape changed from an open one to generally forested by ca. 14 cal. kyr BP. Woody plants (mainly birch and pine) contributed up to 85% to the pollen assemblages ca. 13.4–12.5 cal. kyr BP. The subsequent Younger Dryas ( YD) interval is characterized by a decrease in arboreal pollen (AP) to 75% but led neither to substantial deforestation nor spread of tundra vegetation. This supports the concept that the YD cooling was mainly limited to the winter months, while summers remained comparably warm and allowed much broader (than initially believed) spread of cold-tolerant boreal trees. Further support for this theory comes from the fact that the relatively low AP values persisted until ca. 10.6 cal. kyr BP, when the «hazel phase» of the regional vegetation succession began. The postglacial hunter-gatherer occupation is archaeologically confirmed in Brandenburg since ca. 13 cal. kyr BP, i.e. much later than in the western part of Germany and ca. 1000 years after the major amelioration in the Rüdersdorf environmental record

River flooding as a driver of polygon dynamics: modern vegetation data and a millennial peat record from Anabar River lowlands (Arctic Siberia)

The spatial and temporal variability of a low-centred polygon on the eastern floodplain area of the lower Anabar River (72.070° N, 113.921° E; northern Yakutia, Siberia) has been investigated using a multi-method approach. The present-day vegetation in each square metre was analysed, revealing a community of Larix, shrubby Betula, and Salix on the polygon rim, a dominance of Carex and Andromeda polifolia in the rim-to-pond transition zone, and a predominantly monospecific Scorpidium scorpioides coverage within the pond. The total organic carbon (TOC) content, TOC / TN (total nitrogen) ratio, grain size, vascular plant macrofossils, moss remains, diatoms, and pollen were analysed for two vertical sections and a sediment core from a transect across the polygon. Radiocarbon dating indicates that the formation of the polygon started at least 1500 yr ago; the general positions of the pond and rim have not changed since that time. Two types of pond vegetation were identified, indicating two contrasting development stages of the polygon. The first was a well-established moss association, dominated by submerged or floating Scorpidium scorpioides and/or Drepanocladus spp. and overgrown by epiphytic diatoms such as Tabellaria flocculosa and Eunotia taxa. This stage coincides temporally with a period in which the polygon was only drained by lateral subsurface water flow, as indicated by mixed grain sizes. A different moss association occurred during times of repeated river flooding (indicated by homogeneous medium-grained sand that probably accumulated during the annual spring snowmelt), characterized by an abundance of Meesia triquetra and a dominance of benthic diatoms (e.g. Navicula vulpina), indicative of a relatively high pH and a high tolerance of disturbance. A comparison of the local polygon vegetation (inferred from moss and macrofossil spectra) with the regional vegetation (inferred from pollen spectra) indicated that the moss association with Scorpidium scorpioides became established during relatively favourable climatic conditions, while the association dominated by Meesia triquetra occurred during periods of harsh climatic conditions. Our study revealed a strong riverine influence (in addition to climatic influences) on polygon development and the type of peat accumulated

Stable isotope (δ¹³C, d15N), and n-alkane patterns of bryophytes along hydrological gradients of low-centred polygon of the Siberian Arctic

Mosses are a major component of the arctic vegetation, particularly of wetlands. We present C/N ratio, d13C and d15N data of 400 moss samples belonging to 10 species that were collected along hydrological gradients within polygonal mires located on the southern Taymyr Peninsula and the Lena River delta in northern Siberia. Additionally, n alkane patterns of six of these taxa were investigated. The aim of the study is to see whether the inter- and intra-specific differences in biochemical and isotopic signatures are indicative of habitat with particular respect to water-level. Overall, we find high variability in all investigated parameters. The C/N ratios range between 15.4 and 70.4 (median: 42.9) and show large variations at intra-specific level. However, species preferring a dry habitat (xero-mesophilic mosses) show higher C/N ratios than those preferring a wet habitat (meso-hygrophilic mosses). We assume that this mainly originates from the association of mosses from wet habitats with microorganisms which supply them with nitrogen. Furthermore, because of the stability provided by water, they do not need to invest in a sturdy stem-structure and accordingly have lower C contents in their biomass. The d13C values range between -37.0 and 22.5 per mil (median = -27.8 per mil). The d15N values range between -6.59 and +1.69 per mil (median = 2.17 per mil). We find differences in d13C and d15N signatures between both habitat types and, for some species of the meso-hygrophilic group, a significant relation between the individual habitat water-level and isotopic signature was inferred as a function of microbial symbiosis. The n alkane distribution also shows differences primarily between xero-mesophilic and meso-hygrophilic mosses, i.e. having a dominance of n-alkanes with long (n-C29, n-C31) and intermediate chain lengths (n-C25), respectively. Overall, our results reveal that biochemical and isotopic signals of certain moss taxa from polygonal wetlands are characteristic of their habitat and can thus be used in (palaeo-) environmental studies

Physico-chemical parameters of sediment core PG1972-1 (09-Tik-03) from a Tundra Lake, Northeastern Siberia

Thermokarst lakes in the Siberian Arctic contain sediment archives that can be used for paleoenvironmental inference. Until now, however, there has been no study from the inner Lena River Delta with a focus on diatoms. The objective of this study was to investigate how the diatom community in a thermokarst lake responded to past limnogeological changes and what specific factors drove variations in the diatom assemblage. We analysed fossil diatom species, organic content, grain-size distribution and elemental composition in a sediment core retrieved in 2009 from a shallow thermokarst lake in the Arga Complex, western Lena River Delta. The core contains a 3,000-year record of sediment accumulation. Shifts in the predominantly benthic and epiphytic diatom species composition parallel changes in sediment characteristics. Paleoenvironmental and limnogeological development, inferred from multiple biological and sedimentological variables, are discussed in the context of four diatom zones, and indicate a strong relation between changes in the diatom assemblage and thermokarst processes. We conclude that limnogeological and thermokarst processes such as lake drainage, rather than direct climate forcing, were the main factors that altered the aquatic ecosystem by influencing, for example, habitat availability, hydrochemistry, and water level