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Spring-fed fen deposits (peat-tufa sequences) from northern Poland were investigated for Holocene environmental reconstruction (climate and hydrology) using multi-proxy analysis (lithofacies, molluscs, pollen, plant macrofossils, geochemistry, and stable oxygen- and carbon-isotopes). The main aims of these studies were: (1) comparison of several similar sites with the same type of groundwater supply and sedimentation on a widespread space scale, (2) detailed reconstruction of their long-term development, assessing their sensitivity to climate change, (3) verification of the synchronicity of the record of different proxies in distant sites in the context of Holocene climate changes in relation to specific well-known global and/or regional climate events (so-called Bond events), and (4) discussion on permafrost degradation as a driver of spring-fed fens development. Based on our palaeogeographical data, we have distinguished an asynchronicity of the beginning of the development of spring-fed fens in the eastern and western parts of the studied region that is associated with different times of ascending groundwater supply unblocking after complete permafrost degradation. Therein, asynchronicity of permafrost degradation was brought about by multiple climatic, geological and structural conditions. Our results also indicate significant differences in the trends of succession (ecological and lithological) caused by the geographical location of the studied sites. Asynchronicity of the occurrence of wet and dry phases, as well as significant differences in their duration were noted. This depended upon the influence of oceanic (western part) or continental climates (eastern part). Warm and humid oceanic climate promoted the domination and longer duration of wet phases (especially in the Eo- and early Mesoholocene), while the harsh continental climate promoted the more frequent occurrence of dry phases, with short episodes of increased humidity. From the middle Mesoholocene, this marked regional diversification becomes less pronounced. Results also allowed for the recognition of several palaeoclimatic events on a regional scale. Four main cold episodes (Bond events 8–5): during LG/H transition (11.5 ky cal BP), Eo- (∼10.25 ky cal BP, ∼9.4 ky cal BP) and at the beginning of the Mesoholocene (∼8.2 ky cal BP) are well-documented by multiple proxies at all study sites. Other cold episodes (Bond events 4–0) are slightly less documented and are not clear for interpretation. The results of our study demonstrate the importance of spring-fed fen deposits for detailed palaeoenvironmental reconstruction on a regional scale.

An analysis was performed on samples from a series of well-preserved tree trunks and in situ stumps of Allerod/Younger Dryas age found in Koźmin and Kwiatkow, Kolska Basin, Central Poland. Five different types of wood preparation methods were investigated in three Polish radiocarbon laboratories (Gliwice, Poznan and Krakow) in order to find the most stable, repeatable and reliable procedure. Their effect was tested on the stable carbon isotope ratio (δ13C) and 14C age. Additionally, FTIR spectroscopy was used as a simple technique for obtaining rapid information on the structure of wood constituents and chemical changes taking place in wood due to various chemical treatments. The results of AMS measurements did not show statistically significant differences in radiocarbon ages of samples prepared according to the tested methods. On the other hand, δ13C measurements showed that the smallest scattering results gave α-cellulose obtained by the method BABA + Bleaching (with NaClO2 and HCl) + strong base. Moreover, the mean δ13C values for holo-cellulose samples are higher than those for α-cellulose samples. Studies evidenced that the methods of preparation leading to holo- or α-cellulose gave the same FTIR spectra, while the standard method of the chemical pretreatment of samples for 14C measurements (ABA) preceded by mercerization is insufficient for removing compounds containing aromatic rings.

Pollen, non-pollen palynomorphs (NPPs), diatoms, and geochemistry of lake sediments with partially preserved annual lamination were used to reconstruct post-glacial environmental changes of northern Poland in the Baltic region. The main stages in the lake's evolution indicate the following: (1) eutrophic conditions in the final stage of the Lateglacial, (2) very low trophy and strongly changeable water levels in the early Holocene, (3) slowly rising trophy through the mid- and late Holocene enabling persistence of the oligotrophic state of the lake up to c. AD 1450, (4) strong cultural eutrophication of the lake in the recent period (c. 150 years), and (5) maximum Ca content in the early Holocene followed by a gradual decline to minimum values in recent time. Distinct, concurrent shifts in limnological proxies and tree pollen accumulation rates (PARs) enabled the identification of several potential Holocene cool climatic events of different magnitudes and durations. Strong reduction in Tetraedron minimum and declines in tree PARs illustrate limitation of physiological processes in plants, which could result from shorter growing seasons and lower summer temperatures and insolation. Higher precipitation of Fe and Mn indicates more intensive weathering in the catchment, while peaks in Fe/Mn ratio and concurrent drops in Ca content suggest at least seasonal anoxia, which could result from a longer duration of ice cover and shorter periods of mixing. The data seem to display striking conformity of the main cooling events with the “Bond cycles” (Bond et al., 1997, 2001), but also indicate a more variable pattern that may reflect traces of a more complex cyclicity of climatic shifts.

14 C inversion abstract The main aim of this paper is to present the pitfalls connected with the construction of reliable chro- nologies for anthropogenically disturbed peatlands over the last two millennia based on 210 Pb and 14 C dating, i.e. the period of the strongest human impact on these ecosystems. The following hypotheses have been formulated: i) parts of peatlands suspected to be affected by peat extraction may possess traces of mechanical disturbances undetectable using different analyses based on biota proxy; ii) failure to consider information included in radionuclide date inversions may contribute to the establishment of misleading chronologies. To test these hypotheses, different scenarios of chronology based on high

A palaeolimnological study of Lake Khall was undertaken to reconstruct impacts from five thousand years of climate change and human activity in the Ol'khon region of Lake Baikal. Taiga biome dominated regional landscapes, although significant compositional turnover occurred due to the expansion of eurythermic and drought resistant Scots pine. Climate during the mid-Holocene was wetter than the present, and Lake Khall was fresh, with abundant molluscs. By 4.4 cal ka BP, sedimentary geochemistry indicated a gradual change in lake water chemistry with an increase in lake salinity up to the present day, most likely controlled by groundwater influences. Vegetation turnover rate was highest between 2.75 and 2.48 cal ka BP, with the onset of drier, more continental climate, which resulted in an influx of aeolian particles to the lake. This abrupt shift was coincident with ice rafted debris event (IRD-2) in North Atlantic sediments and an attenuation of the East Asian summer monsoon. A second arid period occurred shortly afterwards (2.12–1.87 cal ka BP) which resulted in the decline in ostracod numbers, especially Candona sp. A rather more quiescent, warmer period followed, between 1.9 and 0.7 cal ka BP, with very little change in vegetation composition, and low amounts of detrital transfer from catchment to the lake. Peak reconstructed temperatures (and low amounts of annual precipitation) were concurrent with the Medieval Climate Anomaly. Between 0.77 and 0.45 cal ka BP, climate in the Ol'khon region became colder and wetter, although Lake Khall did not become fresher. Cold, wet conditions are seen at other sites around Lake Baikal, and therefore represent a regional response to the period concurrent with the Little Ice Age and IRD-0. After AD 1845 the region warms, and Pediastrum appears in the lake in high abundances for the first time. This increase is ascribed to nutrient enrichment in the lake, linked to the rapid increase in regional pastoral farming.

The laboratory for 14 C AMS sample preparation in the Gliwice Radiocarbon Laboratory has gradually evolved since its start in 1999 to cater for an increase in volume and variety of radiocarbon dating samples. To date, nearly 2000 graphite targets have been produced from materials such as plant macrofossils, charcoal, peat, bones, shells and wood. The equipment comprises a station for chemical preparation and high vacuum lines for production, purification and graphitization of sample carbon dioxide. The present capacity allows preparation of up to 400 targets annually for the needs of scientific projects and external orders for radiocarbon dating continuously received by the GADAM Centre of Excellence. The laboratory’s sample preparation protocols and recent improvements are described and its performance during the 10 years of activity is discussed in terms of parameters obtained from reference materials prepared in this laboratory and demonstrated with a few science applications.

New results of carbon isotopic composition from tree rings have been analyzed. Δ14C and δ13C data, representing the isotopic composition of carbon in “clean air”, were obtained from annual rings of a pine tree (Pinus sylvestris) taken in the Niepolomice area, 25 km east Krakow, Poland. All samples were processed to extract α-cellulose, and the radiocarbon concentration in each annual ring was measured using AMS at the University of Nagoya. Stable isotopic composition of carbon was determined using isotope ratio mass spectrometry. The dataset covers the growth period between 1960 and 2003. The average difference between radiocarbon concentrations in Niepolomice and the North Hemisphere zone 1 (NH zone 1) for the period between 1960 and 1999 is 3.5 ± 1.6‰. These data are compared with previously presented results from the city of Krakow, where a local decrease in 14C concentration was observed due to local CO2 emission from fossil fuel use. The differences in observed 14C concentrations were used to estimate a magnitude of the local Suess effect in Krakow. Based on mass balance equations for CO2 14C concentrations, it was possible to calculate the CO2 concentration associated with fossil fuel emission (Cfoss) into the atmosphere. The highest values of Cfoss were recorded in the years 1986 (11.9 ± 1.4 ppm V) and 1983 (8.1 ± 1.3 ppm V), while the lowest value of 0.6 ± 1.8 ppm V was recorded in 2001.

Boreal ecosystems are highly vulnerable to climate change, and severe ecological impacts in the near future are virtually certain to occur. We undertook a multiproxy study on an alpine lake (ESM-1) at the modern tree-line in boreal, southern Siberia. Steppe and tundra biomes were extensive in eastern Sayan landscapes during the early Holocene. Boreal forest quickly expanded by 9.1 ka BP, and dominated the landscape until c 0.7 ka BP, when the greatest period of compositional turnover occurred. At this time, alpine meadow landscape expanded and Picea obovata colonised new habitats along river valleys and lake shorelines, because of prevailing cool, moist conditions. During the early Holocene, chironomid assemblages were dominated by cold stenotherms. Diatoms for much of the Holocene were dominated by alkaliphilous, fragilarioid taxa, up until 0.2 ka BP, when epiphytic species expanded, indicative of increased habitat availability. C/N mass ratios ranged between 9.5 and 13.5 (11.1–15.8 C/N atomic ratios), indicative of algal communities dominating organic matter contributions to bottom sediments with small, persistent contributions from vascular plants. However, δ13C values increased steadily from −34.9‰ during the early Holocene (9.3 ka BP) to −24.8‰ by 0.6 ka BP. This large shift in magnitude may be due to a number of factors, including increasing within-lake productivity, increasing disequilibrium between the isotopic balance of the lake with the atmosphere as the lake became isotopically ‘mature’, and declining soil respiration linked to small, but distinct retreat in forest biomes. The influence of climatic variables on landscape vegetation was assessed using redundancy analysis (RDA), a linear, direct ordination technique. Changes in July insolation at 60 °N significantly explained over one-fifth of the variation in species composition, while changes in estimates of northern hemisphere temperature and ice-rafted debris events in the North Atlantic were also significant, but considerably less important. The potential importance of climate and biome development (tundra, steppe, cold deciduous forest and taiga) on different trophic levels (i.e. chironomid and diatom communities) in lake ESM-1 was also assessed using RDA. Climate predictors had a more significant influence on Holocene chironomid assemblages, especially July insolation at 60 °N, estimates of regional precipitation and estimates of northern hemisphere temperature, while only the development of the taiga biome had a significant impact on these primary consumers. Diatom communities also had a small, but significant influence on Holocene chironomid populations, perhaps linked to variation in faunal feeding strategies. In contrast, climatic and biome predictors explained similar amounts of variation in the Holocene diatom assemblage (approximately 20% each), while chironomids themselves as predictors explained just under 7% of diatom variation. Lake acidity was inferred using a diatom inference model. Results suggest that after deglaciation, the lake did not undergo a process of gradual acidification, most likely due to the presence of continuous permafrost and low levels of precipitation, preventing base cations and dissolved organic carbon entering the lake (except for the period between 1.7 and 0.7 ka BP). We conclude that lakes in continental, boreal regions undergo different models of lake ontogeny than oceanic boreal regions. Unlike other regions discussed, climate is a more important driver of ecosystem change than catchment changes. We also demonstrate that the start of the period coincident with the onset of the Little Ice Age resulted in important thresholds crossed in catchment vegetation and aquatic communities.

New results of radiocarbon concentration in tree rings from the City of Valladolid (Spain) covering a growth period of 22 year have been measured using an AMS. Samples were taken using a hollow drill from a living tree, and α-cellulose was extracted from each of annual rings (early and late wood separately). The set of data shows lower radiocarbon concentration than that reported for “clean air” at the reference station, indicating a remarkable input of “dead” CO 2 of fossil fuel origin. Using data of carbon dioxide and 14 C concentrations from Schauinsland, the corresponding summer and winter values of the fossil component ( c f ) in carbon dioxide were calculated for the City of Valladolid. By fitting exponential and linear functions to the experimental data, the exchange time was calculated, and the expected future 14 C concentration in the atmosphere was estimated.