This study of the Kanna calcareous spring fen on Saaremaa, the largest island of Estonia, elucidates its history of fen development and vegetation diversity over the last 9,200 years. Pollen, spores, ...non-pollen palynomorphs, macrofossils, loss-on-ignition and humification index analyses were carried out to reconstruct fen succession, vegetation development, environmental changes and human impact. Hierarchical clustering, ordination analysis and linear regression were applied to examine the vegetation composition and richness patterns through time and to identify the potential environmental drivers underlying these patterns. Our results suggest reverse mire development from bog to fen, a rare occurrence and contrary to typical mire autogenic succession from groundwater fed to rainwater fed. Kanna developed as a small bog for the first 2,000 years from 9,200 to 7,200 cal yrs
bp
. Changes to the hydrological regime around 7,200 cal yrs
bp
, due to a warmer and drier climate and land uplift, caused a change from an ombrotrophic to a minerotrophic environment. Typical spring fen characteristics developed ca. 5,000 cal yrs
bp
and continued until ca. 400 cal yrs
bp
, when the fen was fed by calcareous mineral-rich groundwater and reached very high floristic diversity with various calciphilous and relict plant taxa. We conclude that general changes in the Kanna fen succession, vegetation community and diversity are associated with climatic changes. The present high diversity of the fen is a result of a long-term stable fen environment, which may have been even higher in the past. However, the pollen richness has decreased during the last 400 years, possibly due to human or natural factors.
The recent advancements of new quantitative tools compatible with plant macrofossil proxy data have revived its potential for paleoclimate research. Plant macrofossils are commonly used in so-called ...indicator-species approaches, using methodologies that are typically built on known observations linking modern plant distributions with climate. This allows complementary paleoclimate reconstructions using an approach that is not limited by the spatial availability of calibration samples obtained from surface sediments (e.g., pollen or chironomids).
We aim to evaluate the impact that various methodological choices have on the plant-macrofossil based reconstructions of January and July temperature patterns for the Lateglacial (14–11 ka BP) period. We use a variety of classic and novel quantitative climate reconstruction algorithms with plant macrofossil assemblages from 13 sites of the Baltic States. We use unfiltered plant data to evaluate the ability of each method to also handle the presence of plants that might have a weak sensitivity to temperature. Additionally, we test the influence of another methodological choice – the choice of modern calibration region – on the reconstructed climate.
Our findings indicate that, with no prior filtering of summer and winter-sensitive plants, temporal temperature variations can be reconstructed with methods that implement probability density functions. Although some disparities in reconstructions are seen between the tested algorithms, we note that the choice of calibration region bears a greater influence on the results. A calibration region that best represents the past environment should be chosen rather than one representing the same spatial extent as the fossil site(s). Moreover, for long-term reconstructions, a “dynamic calibration set” approach should be considered in future studies by using a range of calibration regions and mirroring the continuously changing broadscale environmental regime of the past.
•Seasonal temperature reconstructions vary across climate reconstruction algorithms.•Calibration region impact is greater in January temperature reconstructions than July.•Proper calibration region evaluation is crucial before reconstructions.•Calibration regions should be based on environmental instead of geographical fit.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
Pollen records from Lake Prossa, located in the Saadjärv Drumlin Field, indicate rather homogeneous pollen spectra in the pre-Allerød period and a thick sediment sequence suggesting high input of ...mineral matter and erosion. This period is characterized by pioneer vegetation with dwarf-shrubs. At the beginning of the Allerød, Salix, Artemisia and redeposited temperate and thermophilous taxa prevailed in pollen spectra, referring to shrub tundra conditions, followed later by Betula and Pinus(?) arrival. Silt with organic debris deposited. Vegetational set-back and tundra plant species with scattered birches and silty deposits containing abundantly Drepanocladus fragments characterize the Younger Dryas stadial. The sedimentation rate decreased markedly and was followed by a hiatus at the beginning of the Holocene. The AMS 14C dates, and microfossil and sedimentological data show that the ice front receded and stratified sediments started to deposit about 14 200–14 300 cal yr BP, permitting specification of poorly constrained ice recession chronology in central Estonia.
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DOBA, IZUM, KILJ, NUK, ODKLJ, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
Disturbances by fire are essential for the functioning of boreal/hemiboreal forests, but knowledge of long-term fire regime dynamics is limited. We analysed macrocharcoal morphologies and pollen of a ...sediment record from Lake Lielais Svētiņu (eastern Latvia), and in conjunction with fire traits analysis present the first record of Holocene variability in fire regime, fuel sources and fire types in boreal forests of the Baltic region. We found a phase of moderate to high fire activity during the cool and moist early (mean fire return interval; mFRI of ∼280 years; 11,700–7500 cal yr BP) and the late (mFRI of ∼190 years; 4500–0 cal yr BP) Holocene and low fire activity (mFRI of ∼630 years) during the Holocene Thermal Optimum (7500–4500 cal yr BP). Charcoal morphotypes and the pollen record show the predominance of frequent surface fires, occasionally transitioning to the crown during Pinus sylvestris-Betula boreal forests and less frequent surface fires during the dominance of temperate deciduous forests. In contrast to the prevailing opinion that fires in boreal forests are mostly low to moderate severity surface fires, we found evidence for common occurrence of stand-replacing crown fires in Picea abies canopy. Our results highlight that charcoal morphotypes analysis allows for distinguishing the fuel types and surface from crown fires, therefore significantly advancing our interpretation of fire regime. Future warmer temperatures and increase in the frequency of dry spells and abundant biomass accumulation can enhance the fire risk on the one hand, but will probably promote the expansion of broadleaf deciduous forests to higher latitudes, on the other hand. By highlighting the capability of broadleaf deciduous forests to act as fire-suppressing landscape elements, our results suggest that fire activity may not increase in the Baltic area under future climate change.
•Charcoal morphologies a promising tool to distinguish surface from crown fires.•Pinus-Betula dominant boreal forest linked to surface fires with occasional crown fires.•Picea abies dominant boreal forest associated with increased occurrence of crown fires.•Temperate deciduous forest connected with surface fires.•Deciduous forest can offset the effect of climate on fire regime.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
ABSTRACT
The latest data on holes in the spinous processes of the vertebrae of woolly mammoths, a rare pathology, are presented. This was identified at 19 sites of northern Eurasia. Such destructive ...changes are recorded ca. 34–12k 14C a bp, and only two sites dated to >50k and >41k 14C a bp. The main hypotheses about hole formation are: vertebral abnormalities; bone infections; genetic traits; and unfavourable geochemical environment. The pathology occurred in mammoths of all age groups, and could have arisen at the embryonic stage. There are two types: classic holes associated with osteolytic changes; and very rarely tumour‐like lesions. The most likely cause of the lesions is alimentary osteodystrophy caused by chronic mineral starvation. The aetiology of this disease is usually associated with a deficiency or excess of macro‐ and microelements in the geochemical landscape, and through forage and water this leads to a severe metabolic disorder. Analysis of palaeopathological data shows two waves of geochemical stress in animals, ca. 26–18k and ca. 16–12k 14C a bp. Therefore, the woolly mammoth extinction can be viewed as a non‐linear function, with two peaks of high mortality corresponding to the Last Glacial Maximum and the Lateglacial.
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FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
This paper discusses a complete record of vegetation history since the Bølling (GI-1e) warming (14,500calyrBP) up to the Holocene in Latvia. To date, this is the only complete record of such age in ...the eastern Baltic area and the northernmost area for which Bølling records are present. Combining pollen evidence, pollen accumulation rates (PAR) and plant macrofossil data, we assess the local and regional vegetation development, and we attempt to separate the true Lateglacial vegetation signal by removing the obviously redeposited thermophilous pollen; however, we remove not only their signal, we discuss the possibilities of separating the redeposition signal of the so-called “local Lateglacial trees”, pine and birch, by looking at their corrosion and degradation. The results show that the Bølling warming in the eastern Baltic area was a treeless tundra community consisting of the shrubs Betula nana, Dryas octopetala and Salix polaris. The Older Dryas cold spell is clearly recognised as a decline in the total concentration of plant macrofossils and PARs at between 14,200 and 13,500calyrBP. At 13,460calyrBP, the B. nana macrofossils disappear, and tree birch (Betula sect. Albae) appears, marking the start of tree birch forest. The presence of pine forest is confirmed by a variety of macrofossils, including bark, wood, needles and seeds, since 13,400calyrBP, at the same time at which pine stomata are found. The first identified pine stomata finds are associated with a Pinus PAR over 3000grainscm−2yr−1 and pine macrofossil finds with a Pinus PAR over 4000grainscm−2yr−1. During the warmest period of the GI-1a (Allerød) at 13,000–12,700calyrBP, a pine forest with deciduous trees (birch –Betula pendula and aspen –Populus tremula) developed in the study area. The Younger Dryas (GS-1) cooling strongly affected the floral composition in eastern Latvia. The PAR of the tree taxa declined abruptly from a maximum value at 12,700 to below 1000grainscm−2yr−1 at 12,600calyrBP. The response time for the pine forest to collapse was 100 years according to the PAR data. Pine macrofossils disappear simultaneously with the pollen signal at 12,600calyrBP, yet occasional Pinus stomata are recorded throughout the Younger Dryas (GS-1). The landscape was treeless shrub tundra again, with D. octopetala, S. polaris, B. nana and Juniperus present. Picea is introduced in the region within the cold Younger Dryas and is represented by stomata (12,400–12,200calyrBP), needles, seeds and wood (since 12,050calyrBP up to the Holocene). The Pleistocene/Holocene boundary at 11,650calyrBP is marked by changes both in vegetation composition and sediment type. The organic rich gyttja accumulated instead of silts and clays, and the start of the Holocene warm period permitted forest re-expansion in eastern Latvia.
► Unambiguous vegetation record since Bølling warming from NE Europe since 14,550calyrBP. ► Multiproxy evidence of regional and local vegetation responses to Lateglacial climate. ► New method applying corroded pollen and macrofossil data for Lateglacial vegetation signal. ► Evidence of rapid establishment of Lateglacial birch, pine, spruce and aspen forests. ► Climate sensitivity of terrestrial vs. aquatic evidence of NE European biota.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
Comparisons of climate model hindcasts with independent proxy data are essential for assessing model performance in non-analogue situations. However, standardized palaeoclimate data sets for ...assessing the spatial pattern of past climatic change across continents are lacking for some of the most dynamic episodes of Earth's recent past. Here we present a new chironomid-based palaeotemperature dataset designed to assess climate model hindcasts of regional summer temperature change in Europe during the late-glacial and early Holocene. Latitudinal and longitudinal patterns of inferred temperature change are in excellent agreement with simulations by the ECHAM-4 model, implying that atmospheric general circulation models like ECHAM-4 can successfully predict regionally diverging temperature trends in Europe, even when conditions differ significantly from present. However, ECHAM-4 infers larger amplitudes of change and higher temperatures during warm phases than our palaeotemperature estimates, suggesting that this and similar models may overestimate past and potentially also future summer temperature changes in Europe.
Spring onset is an important phenological observation
that is sensitive to modern climate change and can be traced back in
geological time. The Late Glacial (∼ 14 500–11 700 cal yr BP)
spring onset ...and growing season (growing degree days) dynamics in the
eastern Baltic region were reconstructed using the micro-phenological
approach based on the dwarf birch (Betula nana) subfossil leaf cuticles. The presented
study sites, Lake Lielais Svetinu (eastern Latvia) and Lake Kosilase
(central Estonia), are located ∼ 200 km apart in the region
affected by the south-eastern sector of the Scandinavian Ice Sheet. During
the Late Glacial period the region and its biota were influenced by the
retreating glacier and the different stages of the Baltic Ice Lake. The
plant macrofossil data confirm that the study sites were in different
vegetation zones (arctic-to-boreal) during the Late Glacial period. The
dynamics of the estimated length of the growing season and spring onset,
combined with the regional collection of plant macrofossil records, suggest
the importance of local settings to species migration. During the
Late Glacial warming period (Bølling–Allerød), a notable spring warming
and longer growing season was calculated based on micro-phenology, but the
treeline did not extend beyond central Estonia. The comparison of pollen-
and chironomid-inferred past temperature estimations with spring onset,
growing degree days, and plant macrofossil data shows coherent patterns
during the cooler Older Dryas and warmer Bølling–Allerød periods, while suggesting more complicated climate dynamics and possible warmer episodes during the Younger Dryas cold reversal.
The hemispheric-scale climatic fluctuations during the Holocene have probably influenced the large Siberian rivers. However, detailed studies of the West Siberian Plain postglacial environmental ...change are scarce and the records of millennial-scale palaeohydrology are nearly absent. This paper presents the Holocene palaeoecological reconstruction based on the sedimentary record of Lake Svetlenkoye, located near the confluence of major Siberian rivers Ob and Irtysh. Postglacial history of flooding, dynamics of regional and local vegetation, sedimentation regime, geochemical changes and lake water pH were reconstructed based on multi-proxy studies. We used palaeobotanical (plant macrofossils, pollen, diatoms), geochemical (organic matter, total organic carbon and nitrogen content, carbon/nitrogen ratio) and chronological (14C dates, spheroidal fly-ash particle counts) methods. The studied sediment section started to accumulate ~11,400 cal. yr BP. The initial shallow water body was flooded by Ob River waters ~8100–8000 cal. yr BP as confirmed by a remarkable increase in the sedimentation rate and the accumulation rate of the aquatic vegetation proxies. The period of flooding coincides with the high humidity periods reconstructed from regional palaeobotanical records. About 6800–6700 cal. yr BP, the study site became isolated from the Ob River floodplain and remained a small lake until present. The diatom-based lake water pH estimates suggest fluctuations in the pH values during the Holocene, the recent decrease since 1960s being the most notable. The vegetation record revealed constant postglacial presence of tree taxa – Betula, Pinus and Picea – although in different pollen ratios and accumulation rates through time. The paludification of the surroundings occurred since ca. 8500 cal. yr BP.
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