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Palaeoecological records provide a rich source of information to explore how plant distribution ranges respond to climate changes, but their use is complicated by the fact that, especially when based on pollen data, they are often spatially too inaccurate to reliably determine past range limits. To solve this problem, we focus on hazel (Corylus avellana), a tree species with large and heavy fruits (nuts), which provide firm evidence of the local occurrence of species in the past. We combine the fossil nut records of hazel from Fennoscandia, map its maximum distribution range during the Holocene thermal maximum (HTM) and compare the fossil record with the Holocene hazel range shift as simulated by the LPJ-GUESS dynamic vegetation model. The results show that the current northern range limit of hazel in central and eastern Fennoscandia is constrained by too short growing seasons and too long and cold winters and demonstrate that the species responded to the HTM warming of about 2.5°C (relative to the present) by shifting its range limit up to 63–64°N, reached a rough equilibrium with the HTM climatic conditions and retreated from there to about 60°N during the last 4000 years in response to the late-Holocene cooling. Thus, the projected future warming of about 2.5°C would reverse the long-term southward retraction of species’ northern range limit in Europe and is likely to lead to hazel being a common, regeneratively reproductive species up to 63–64°N. In addition to the accuracy of the projected warming, the likelihood of this scenario will depend on inter-specific competition with other tree taxa and the potential of hazel to migrate and its population to grow in balance with the warming. In general, the range dynamics from the HTM to the present suggest a tight climatic control over hazel’s range limit in Fennoscandia. [ABSTRACT FROM AUTHOR]

Little is known concerning climate changes in the Eastern Baltic region during the last interglacial-glacial cycle and in particular, climate changes during the Weichselian. In this study, a quantitative reconstruction of the mean January and July temperature for the Medininkai-117 site in Lithuania is presented. The reconstruction is based on pollen and plant macrofossils from this site, which reveal that the vegetation was characteristic of many northern Europe sites during the Eemian and Early Weichselian. Gradual evolution of the vegetation suggests that relatively uniform climate conditions existed during the Eemian. Our reconstructions support the view of a relatively stable Eemian, with short cooling phases of low amplitude. A strong increase in temperature was apparent during the beginning of the interglacial and decrease during the transition to the Weichselian. Reconstructed July temperatures of the Eemian interglacial were approximately 2°C higher than today (18.5°C; today: 16.2°C) and were similar to today for January (-5.2°C; today: -5.1°C). July temperatures during the Early Weichselian were only ~2°C lower than during the Eemian, whereas the January temperatures gradually decreased. Winter temperatures were relatively high (above -10°C) during the Early Weichselian. [ABSTRACT FROM AUTHOR]

Lakes Holzmaar and Meerfelder Maar are located in the Westeifel Volcanic Field less than 10 km apart. Both maar lakes are well known for their annually laminated (varved) sediments covering the past 15 000 years. Here, we focus on reconstructing the history of Holocene vegetation, human impact and climate using high-resolution pollen data. Detailed correlation between the two records using palynologically defined tie-points provides for the first time a test of the precision of the individual varve chronologies. The high-resolution pollen records of both Holzmaar and Meerfelder Maar show continuous natural successions of vegetation during the early and mid-Holocene controlled by the development of soil, climate, immigration and competitive expansion of thermophilous tree species. From 6500 varve yr BP onwards, human impact became an increasingly more important factor. Given the high chronological precision of both records, regional similarities, but also local differences of anthropogenically influenced vegetation changes, can be recognized. The reconstructed July temperature between 8500 and 5000 varve yr BP is around 1 °C higher than today, most likely in response to higher summer insolation related to orbital forcing. High variability of reconstructed July and January temperatures as well as annual precipitation around 5000 varve yr BP is a prominent climatic signal. This is consistent with other records in several areas of Europe which also identify this period as climatically highly variable. [ABSTRACT FROM AUTHOR]

Abstract: Dramatic changes in European vegetation occurred during the transition from the Eemian interglacial to Weichselian glacial climates, correlative with major changes in global ice core and marine records. Quantitative knowledge of climate change is important for understanding of the climate system and for climate modelling, for which reconstructions of this transitional period are of special interest. However, it has been difficult to quantify the climatic changes involved in the Eemian to Early Weichselian transition from terrestrial archives due to the lack of modern vegetation analogues. To circumvent this problem, we applied a suitable multivariate probabilistic approach to pollen and plant macrofossil assemblages to reconstruct temperature and precipitation for this transition in central Europe. Our reconstructions span the interval from the beginning of the Eemian (Marine Isotope Stage (MIS) 5e) to the Odderade interstadial (MIS 5a). They indicate a relatively stable Eemian, with increasing precipitation reducing the continentality of the climate with time. During the transition from the Eemian to the Herning stadial, mean July and January temperatures decreased by ∼4°C and by as much as ∼20°C, respectively. Temperatures remained high enough to support forests during the stadials, and we infer that the reconstructed decrease of precipitation below 500mm per year caused the extirpation of forests during these periods. Thus, we conclude that precipitation, although difficult to reconstruct, is of vital importance for explaining vegetation change during the Eemian and Eemian/Early Weichselian transition. [Copyright &y& Elsevier]

Vegetation and climate during the last ice age and the Last Glacial Maximum (LGM, ∼23,000–19,000 cal BP) were considerably different than during the current interglacial (Holocene). Cold climatic conditions and growing ice-sheets during the last glaciation radically reduced forest extent in Europe to a restricted number of so-called “refugia”, mostly located in the southern part of the continent. On the basis of paleobotanical analyses the Euganian Hills (Colli Euganei) in northeastern Italy have previously been proposed as one of the northernmost refugia of temperate trees (e.g. deciduous Quercus, Tilia, Ulmus, Fraxinus excelsior, Acer, Abies alba, Fagus sylvatica, Carpinus and Castanea ) in Europe. In this study we provide the first quantitative, vegetation independent summer air temperature reconstruction for Northern Italy spanning the time ∼31,000–17,000 cal yr BP, which covers the coldest periods of the last glacial, including the LGM and Heinrich stadials 1 to 3. Chironomids preserved in a lake sediment core from Lago della Costa (7m a.s.l.), a small lake at the south-eastern edge of the Euganean Hills, allowed quantitative reconstruction of Full and Late Glacial summer air temperatures using a combined Swiss-Norwegian temperature inference model based on chironomid assemblages from 274 lakes. Chironomid and pollen evidence from Lago della Costa derives from finely stratified autochthonous organic gyttja sediments, which excludes major sediment mixing or reworking. After reconstructing paleo-temperatures, we address the question whether climate conditions were warm enough to permit the local survival of temperate tree species during the LGM and whether local expansions and pollen-inferred contractions of temperate tree taxa coincided with chironomid-inferred climatic changes. Our results suggest that chironomids at Lago della Costa have responded to major climatic fluctuations such as temperature decreases during the LGM and Heinrich stadials. The vegetation of the Euganean Hills shows responses to these climatic oscillations although the effects of temperature changes were probably also strongly influenced by changes in humidity. Reconstructed July air temperatures at Lago della Costa never fell below 10–13 °C (error range of reconstruction ∼ ±1.5–1.6 °C), which is considerably above the limit considered necessary for forest growth (8–10 °C). Instead rather mild climatic conditions prevailed ∼31,000–17,000 cal yr BP with average summer temperatures between ∼12 and 16 °C, which most likely allowed survival of temperate tree taxa in the warmest (and moistest) microhabitats of the Euganean Hills during the LGM. Only assuming local survival is it possible to explain the repeated expansions and collapses of temperate trees at Lago della Costa which faithfully accompanied the climatic oscillations. [ABSTRACT FROM AUTHOR]