Patterns in vegetation and sedimentation during the Weichselian Late-glacial in north-eastern Germany

Aim To identify and interpret spatial patterns of vegetation and sedimentation during the Weichselian Late‐glacial. Location North‐eastern Germany and the adjacent fringe of north‐western Poland. Methods An inspection and comparison of palynological data from c. 150 sites. Results Open Vegetation phase I (Oldest Dryas = earlier part of the Meiendorf, 12,900–12,450 ¹⁴C bp ) and the Hippophaë phase (Bølling = later part of the Meiendorf; 12,450–12,000 bp ) were rather homogeneous palynologically in the study area. Open Vegetation phase II (Older Dryas; 12,000–11,900 bp ) is strongly recorded in the northern part of the study area with relatively thick sediments (suggesting severe soil erosion), but it can hardly be traced 200 km further to the south. This is attributed to sea buckthorn (Hippophaë) shrubs persisting longer in the south due to higher temperatures, to Betula forests expanding earlier under the influence of a more humid climate or to a generally denser vegetation independent of the behaviour of Hippophaë and Betula. During the late‐glacial Betula/Pinus forest phase (Allerød; 11,900–11,000 bp ), pine (Pinus) forests dominated in the southern regions, whereas birch (Betula) forests prevailed in the north. Open Vegetation phase III (Younger Dryas; 11,000–10,000 bp ) was characterized by heathlands in the northern regions with scattered birches and with sedimentation dominated by in‐washed silicates. In the south, pine parklands occurred with sedimentation dominated by local primary production which had markedly decreased after the previous warmer vegetation phase. Main conclusions The differences in vegetation and sedimentation during the open vegetation phases are attributed to a colder climate in the north than in the south, probably related to a climatic gradient between the ice‐free continental central Europe and the decaying Scandinavian ice sheet. The vegetation patterns during the late‐glacial Betula/Pinus forest phase are attributed to edaphic differences between the predominantly till plains in the northern part of the study area and the prevailing sandy outwash plains and Urstromtäler of the southern regions.     

Holocene persistence of wooded steppe in the Great Hungarian Plain

Aim We used a combination of new and previously published palaeoecological data to test three hypotheses: (1) that wooded steppe persisted in the Great Hungarian Plain throughout the Holocene; (2) that wooded steppe and steppe were most extensive between c. 9900 and 8300 cal. yr bp (the ‘Boreal steppe’ period); and (3) that Southern Continental, Pontic and Eastern Sub‐Mediterranean steppe species reached the region during the early Holocene via the ‘Lower Danube Corridor’. Location Sarló‐hát oxbow lake, Hungary and the Eastern European wooded steppe zone. Methods Holocene sediments deposited in the Sarló‐hát oxbow lake were subjected to pollen and microcharcoal analyses. Twelve radiocarbon age estimates were obtained to determine sediment chronology. In addition, previously published palaeoecological data from the Great Hungarian Plain were compiled, analysed and compared with previous studies in other regions of steppe and wooded steppe in eastern Europe. Results Palynological data from two sediment cores extending to c. 11,400 cal. yr bp indicate the persistent dominance of the landscape by temperate deciduous wooded steppe throughout the Holocene, although with varying canopy composition. Warm‐continental steppe grasslands and saline tall‐grass meadows developed on edaphically constrained areas, which remained steppe‐dominated throughout the Holocene. The extent of steppe grasslands did not increase between 9900 and 8300 cal. yr bp . After c. 3100 cal. yr bp , anthropogenic activities led to the development of cultural steppe. Thermophilous steppe species of the Southern Continental, Pontic and Sub‐Mediterranean floristic elements probably reached the Great Hungarian Plain principally via the Lower Danube Corridor during the late glacial interstadial and Holocene. Eurythermic members of these elements, however, probably survived the Last Glacial Maximum in favourable microsites, extending their ranges during the Holocene from these local sources. Main conclusions Our results confirm the Holocene persistence of wooded steppe in the Great Hungarian Plain, disprove the ‘Boreal steppe’ theory, and suggest an Early Holocene period of greater vegetation openness between 11,400 and 9900 cal. yr bp . Evidence for the post‐glacial immigration of south‐eastern steppe elements into the Carpathian Basin is equivocal: the last glacial/interglacial presence of several southern steppe species suggests that the Hungarian Plain hosted suitable habitats for them during warm and cold phases alike.     

Living on the good soil: relationships between soils,vegetation and human settlement during the late Allerød period in Denmark

The immigration of woody plants, especially Betula (tree birch), is examined in relation to geomorphological regions in a compilation of Late-glacial plant macrofossil records from Denmark. The immigration of trees led to a large ecological transformation of the landscape and had a major effect on the flora and fauna available to Palaeolithic people. We show that soil type was a controlling factor in the development of vegetation during the Allerød and Younger Dryas periods. Following the first immigration of trees during the Allerød period, woods became established in the eastern part of Denmark, where ice advances from the Baltic had deposited calcareous and clayey sediments. The western and northern parts of Denmark that are characterised by more sandy and non-calcareous sediments remained treeless throughout the whole Late-glacial period. Finds from the Bromme Culture are concentrated in the region which was wooded, suggesting that the regional variable environment allowed local adaptations using the diverse resources available.     

Interpretation of the last‐glacial vegetation of eastern‐central Europe using modern analogues from southern Siberia

Aim Interpretation of fossil pollen assemblages may benefit greatly from comparisons with modern palynological and vegetation analogues. To interpret the full‐ and late‐glacial vegetation in eastern‐central Europe we compared fossil pollen assemblages from this region with modern pollen assemblages from various vegetation types in southern Siberia, which presumably include the closest modern analogues of the last‐glacial vegetation of central Europe. Location Czech and Slovak Republics (fossil pollen assemblages); Western Sayan Mountains, southern Siberia (modern pollen assemblages). Methods Eighty‐eight modern pollen spectra were sampled in 14 vegetation types of Siberian forest, tundra and steppe, and compared with the last‐glacial pollen spectra from seven central European localities using principal components analysis. Results Both full‐ and late‐glacial pollen spectra from the valleys of the Western Carpathians (altitudes 350–610 m) are similar to modern pollen spectra from southern Siberian taiga, hemiboreal forest and dwarf‐birch tundra. The full‐glacial and early late‐glacial pollen spectra from lowland river valleys in the Bohemian Massif (altitudes 185–190 m) also indicate the presence of patches of hemiboreal forest or taiga. Other late‐glacial pollen spectra from the Bohemian Massif suggest an open landscape with steppe or tundra or a mosaic of both, possibly with small patches of hemiboreal forest. Main conclusions Our results are consistent with the hypothesis that during the full glacial and late glacial, the mountain valleys of the north‐western Carpathians supported taiga or hemiboreal forest dominated by Larix, Pinus cembra, Pinus sylvestris and Picea, along with some steppic or tundra formations. Forests tended to be increasingly open or patchy towards the west (Moravian lowlands), gradually passing into the generally treeless landscape of Bohemia, with possible woodland patches in locally favourable sites.     

Habitats of relict terrestrial snails in southern Siberia: lessons for the reconstruction of palaeoenvironments of full‐glacial Europe

Aim Shells of fossil molluscs are important for palaeoecological reconstructions. However, the habitat requirements of snail species typical of central European full‐glacial loess sediments are poorly known because most of them became very rare or extinct in Europe. The recent discovery of an almost complete extant assemblage of such species in mountainous regions of central Asia enables more precise characterization of their habitats, which may significantly improve reconstructions of Pleistocene environments. Location Altai Mountains, Russia. Methods Terrestrial snail assemblages, vegetation composition and selected environmental variables were recorded at 118 sites along a gradient of climatic continentality in the Russian Altai. Habitat characteristics of sites where species typical of the full‐glacial period occurred were described using a classification tree. Results Seven of the eight species that are typical of central European full‐glacial loess sediments were found in the study area. They were confined to cool areas with January mean temperatures below ?17 °C, but occurred mainly in sheltered habitats with a warmer microclimate, such as scrub or open woodland. Pupilla loessica and Vallonia tenuilabris had the broadest habitat range, occurring from woodland to dry steppe. Unexpectedly, Columella columella, Pupilla alpicola, Vertigo genesii, V. parcedentata and V. pseudosubstriata were found mainly in wooded fens and shrubby tundra rather than in open steppe. Most of these seven species were recorded in base‐rich wooded fens. Very dry open steppe habitats usually supported no snails. Main conclusions Habitat ranges of the studied snails in the Altai indicate that the full‐glacial landscapes of central European lowlands that harboured these species were not completely dominated by open and dry loess steppe. Most probably they contained a significant component of shrubby vegetation, patches of wet habitats, and probably also areas of woodland at sites with a favourable mesoclimate.     

Botanical macro-remains and insects from the Eemian and Weichselian site of Oerel (northwest Germany) and their evidence for the history of climate

The late Pleistocene site of Oerel which represents the Eemian and the Weichselian interstadials Brörup, Odderade, Oerel and Glinde as well as parts of the stadials Herning and Rederstall was investigated for botanical remains such as fruits, seeds, wood, leaves and mosses, as well as insect remains. A large number of taxa were identified. They show the different environmental conditions, in particular several changes of water level leading to the formation of lakes and diverse forms of mires up to raised bogs. The trophic conditions, too, changed several times. The macrofossil record supports the pollen evidence of dense forests during the two early Weichselian interstadials and tundra vegetation during the later ones. Several indicator species show comparably warm summers but very cold winters during the Brörup and Odderade while the climate during Oerel and Glinde was generally cool. Climatic reconstructions using the MCR method were performed on the basis of the beetle finds.     

Did tree‐Betula,Pinus and Picea survive the last glaciation along the west coast of Norway? A review of the evidence,in light of Kullman (2002)

Aim We discuss the hypotheses proposed by Kullman [Geo‐Öko 21 (2000) 141; Nordic Journal of Botany 21 (2001) 39; Journal of Biogeography 29 (2002) 1117] on the basis of radiocarbon‐dated megafossils of late‐glacial age from the central Swedish mountains that boreal trees survived the glaciation along the south‐west coast of Norway and subsequently migrated eastward early in the late‐glacial to early deglaciated parts of the central Swedish Scandes mountains. Methods We assess these hypotheses on the basis of glacial geological evidence and four lines of palaeoecological evidence, namely macrofossil records of the tree species, vegetation and climate reconstructions from plant evidence, independent climate reconstructions from other proxies for the late‐glacial environment of south‐west Norway, and the patterns of post‐glacial spread of the tree species. Location South and west Norway, central Swedish Scandes mountains (Jämtland). Results and conclusions South‐west Norway and the adjacent continental shelf were under ice at the last‐glacial maximum (LGM). The late‐glacial vegetation of south‐west Norway was treeless and summer temperatures were below the thermal limits for Betula pubescens Ehrh., Pinus sylvestris L. and Picea abies (L.) Karst. Instead of spreading immediately after the onset of Holocene warming, as might have been expected if local populations were surviving, B. pubescens showed a lag of local arrival of 600 to > 1000 years, Pinus lagged by 1500 to > 2000 years, and Picea only reached southern Norway c. 1500 years ago and has not colonized most of south‐west Norway west of the watershed. Glacial geological evidence shows the presence of an ice sheet in the Scandes at the LGM and in the Younger Dryas, which was cold‐based near or at the area where the late‐glacial‐dated megafossils were recovered by Kullman. We conclude that the samples dated by Kullman (2002) should be evaluated carefully for possible sources of contamination. All the available evidence shows that the biogeographical hypotheses, based on these radiocarbon dates taken at face value, of late‐glacial tree survival at the Norwegian coast and subsequent eastwards spread to the mountains, are unsupportable.     

Scattered late‐glacial and early Holocene tree populations as dispersal nuclei for forest development in north‐eastern European Russia

Aim Concepts about patterns and rates of post‐glacial tree population migration are changing as a result of the increasing amount of palaeobotanical information being provided by macroscopic plant remains. Here we combine macrofossil, pollen and stomata records from five sites in north‐eastern European Russia and summarize the results for the late‐glacial–early Holocene transition. The late‐glacial–early Holocene transition encompasses the first indications of trees (tree‐type Betula, Picea abies, Abies sibirica and Larix sibirica) and subsequent forest development. Considerable time‐lags between the first macrobotanical and/or stomata finds of spruce (Picea abies) and the establishment of a closed forest are reconsidered. Location Pechora basin, north‐eastern European Russia. Methods We used plant macrofossil, stomata, pollen and radiocarbon analyses to reconstruct late‐glacial and early Holocene tree establishment and forest development. The data were derived from lake sediment and peat archives. Results Palaeobotanical data reveal an early Holocene presence (11,500–10,000 cal. yr bp ) of arboreal taxa at all five sites. One site presently located in the northernmost taiga zone, shows the presence of spruce and reproducing tree birch during the late‐glacial. Given the current view of post‐glacial population dynamics and migration rates, it seems likely that the source area of these early tree populations in north‐eastern European Russia was not located in southern Europe but that these populations had local origins. Results thus support the emerging view that the first post‐glacial population expansions in non‐glaciated regions at high latitudes do not reflect migration from the south but were a result of an increase in the size and density of small persisting outlying tree populations. Main conclusions Results suggest that the area east of the margin of the Scandinavian ice sheet to the Ural Mountains had isolated patches of trees during the late‐glacial and early Holocene and that these small populations acted as initial nuclei for population expansion and forest development in the early Holocene.     

Last glacial maximum biomes reconstructed from pollen and plant macrofossil data from northern Eurasia

Pollen and plant macrofossil data from northern Eurasia were used to reconstruct the vegetation of the last glacial maximum (LGM: 18,000 ± 2000 ¹⁴C yr bp ) using an objective quantitative method for interpreting pollen data in terms of the biomes they represent ( Prentice et al., 1996 ). The results confirm previous qualitative vegetation reconstructions at the LGM but provide a more comprehensive analysis of the data. Tundra dominated a large area of northern Eurasia (north of 57°N) to the west, south and east of the Scandinavian ice sheet at the LGM. Steppe‐like vegetation was reconstructed in the latitudinal band from western Ukraine, where temperate deciduous forests grow today, to western Siberia, where taiga and cold deciduous forests grow today. The reconstruction shows that steppe graded into tundra in Siberia, which is not the case today. Taiga grew on the northern coast of the Sea of Azov, about 1500 km south of its present limit in European Russia. In contrast, taiga was reconstructed only slightly south of its southern limit today in south‐western Siberia. Broadleaved trees were confined to small refuges, e.g. on the eastern coast of the Black Sea, where cool mixed forest was reconstructed from the LGM data. Cool conifer forests in western Georgia were reconstructed as growing more than 1000 m lower than they grow today. The few scattered sites with LGM data from the Tien‐Shan Mountains and from northern Mongolia yielded biome reconstructions of steppe and taiga, which are the biomes growing there today.     

Proxy comparison in ancient peat sediments: pollen,macrofossil and plant DNA

We compared DNA, pollen and macrofossil data obtained from Weichselian interstadial (age more than 40 kyr) and Holocene (maximum age 8400 cal yr BP) peat sediments from northern Europe and used them to reconstruct contemporary floristic compositions at two sites. The majority of the samples provided plant DNA sequences of good quality with success amplification rates depending on age. DNA and sequencing analysis provided five plant taxa from the older site and nine taxa from the younger site, corresponding to 7% and 15% of the total number of taxa identified by the three proxies together. At both sites, pollen analysis detected the largest (54) and DNA the lowest (10) number of taxa, but five of the DNA taxa were not detected by pollen and macrofossils. The finding of a larger overlap between DNA and pollen than between DNA and macrofossils proxies seems to go against our previous suggestion based on lacustrine sediments that DNA originates principally from plant tissues and less from pollen. At both sites, we also detected Quercus spp. DNA, but few pollen grains were found in the record, and these are normally interpreted as long-distance dispersal. We confirm that in palaeoecological investigations, sedimentary DNA analysis is less comprehensive than classical morphological analysis, but is a complementary and important tool to obtain a more complete picture of past flora.     

Tree taxa immigration to the eastern Baltic region,southeastern sector of Scandinavian glaciation during the Late-glacial period (14,500–11,700 cal. b.p.)

The eastern Baltic region is situated in the southeastern part of the area which was covered by the last Scandinavian glaciation. Four well-dated sediment profiles from sites distributed along a ~330-km north–south transect were analysed for their macrofossil contents. The immigration of tree taxa during the Late-glacial (LG) period, which was the time of environmental change from tundra to woodland in previously glaciated areas, can be determined from these data. The pioneer vegetation in the study area was treeless dwarf shrub tundra with various dominant taxa. The so-called Allerød hemispheric warming permitted the Post-glacial immigration of trees into the southern part of the eastern Baltic region; however, these most probably disappeared during the following cold period, the Younger Dryas/GS-1. The local presence of Betula sect. Albae, Pinus sylvestris, Populus tremula and Picea abies during the LG period in the southern part of the region was confirmed. The northern part of the area presumably remained treeless for the entire LG period. Therefore, until the beginning of the Holocene, the tree line in the eastern Baltic region did not reach beyond 58°N.     

Late-glacial and Holocene palaeovegetation zonal reconstruction for central and north-central North America

Aim The purpose of this study is to develop palaeovegetation zonation models for central and north‐central North America, based on late‐Quaternary and Holocene pollen stratigraphic data (n = 246 sites). A secondary purpose was to evaluate an hypothesis ( Strong & Hills, 2003 ) to explain the disjunct distribution of species in western Alberta. Location Hudson Bay‐Lake Michigan to the Rocky Mountains region, north of 36° N to the Arctic Ocean (c. 70° N). Methods Pollen profiles spanning 40 years of palaeoecological research in North America were extracted from published and unpublished archival sources. Individual profiles were subdivided into 1000‐year increments based on the assumption of a constant sedimentation rate between stratigraphic dates (e.g. surface sediments, radiocarbon ¹⁴C dates, tephra layers). The pollen composition among profiles was standardized to 54 commonly recognized taxa, with percentage composition within each stratigraphic sample prorated to 100% prior to analysis. Near‐surface sediments from these profiles were included as analogues of modern vegetation. Cluster analysis was used as a guide to the classification of 2356 temporal stratigraphic samples, which resulted in the recognition of 16 pollen groups. These groups were summarized in terms of their pollen composition, mapped, and used in combination with terrain information and an ecological knowledge of the study area to construct six physiognomically‐based palaeovegetation zonation models at 2000‐year intervals from 14,000 to 4000 yr bp (radiocarbon years before present). Results The 14,000 yr bp model placed Boreal and Cordilleran Forests proximal to the southern glacial front, whereas Arctic tundra dominated the Yukon Territory–Alaska ice‐free zone. Pollen and macrofossil evidence suggests that this Boreal Forest zone contained a mixture of coniferous and deciduous tree species. Grassland was postulated immediately south of the forest zone, with its northern extreme near 49° N latitude in the Alberta–Montana border area. Separation of the Laurentide and Cordilleran glacial fronts about 12,000 yr bp initiated the northward advance of Boreal Forests into western Canada. By the end of the Hypsithermal at about 6000 yr bp , Boreal Forests occurred near the Arctic Ocean, and Grassland and Aspen Parkland zones may have extended to 54° N and 59° N latitude in Alberta, respectively. Between 6000 and 4000 yr bp , a 5° and 1° latitudinal southward shift of the northern Boreal Forest and Grassland/Aspen Parkland boundaries occurred, respectively, near their contemporary positions with corresponding expansions of the Subarctic and Arctic zones. Modern Canadian Cordilleran Forests along the eastern slopes of the Rocky Mountains were interpreted as originating from the north‐central Montana–south‐western Alberta area. Jack pine (Pinus banksiana Lamb.), a common Boreal Forest species, appears to have entered central Canada via the north side of Lake Superior after 11,000 yr bp . Main conclusions Modern vegetation in central Canada evolved from biomes located in the northern USA during the late‐Quaternary. The Boreal Forest biome contained the same arboreal taxa as the modern vegetation, except it lacked jack pine. The proposed regional palaeovegetation models support the hypothesis of Strong & Hills (2003) , but new independent palaeoecological data will be needed for a proper evaluation.     

Vegetation reconstruction on the basis of pollen in Late Pleistocene hyena coprolites from San Teodoro Cave (Sicily, Italy)

Vegetation reconstruction based on pollen from coprolites of extinct spotted hyena (Crocuta crocuta spelaea, Goldfuss 1832) recovered from excavations carried out in 1998 at San Teodoro Cave (Sicily, Italy) supports previous indications of pre-Late Glacial conditions. Eight of the twelve coprolites analysed contained well-preserved pollen grains. There is a general similarity between the pollen contents from the coprolites but they show variability. They suggest a main vegetation type dominated by steppic taxa (Poaceae, Artemisia, Ephedra, Chenopodiaceae and Asteraceae) but also including arboreal taxa (Pinus and Cupressaceae). Low percentages of pollen of mesophilous woody taxa (Quercus, Betula, Abies, Alnus, Pistacia, among others) are noticeable, suggesting the existence of nearby refugia for temperate and Mediterranean vegetation. A reconstruction of the landscape, using the coprolite pollen record and other pollen records from Sicily and south Italy, shows the predominance, during the pre-Late Glacial, of a wooded steppe biome, with elements representing a variety of local environmental conditions.     

Vegetation history from archaeological charcoals in central Australia: The late Quaternary record from Puritjarra rock shelter

Archaeological charcoals from Puritjarra rock shelter provide the first direct information about the vegetation of central Australia during the late Pleistocene and early Holocene. During the late Pleistocene there appears to have been a more open vegetation than today with fewer trees and shrubs, though with many of the taxa that are important in the modern central Australian flora. The persistence of species such as Acacia macdonnelliensis, Callitris glaucophylla and Eucalyptus opaca throughout the time of the last glacial maximum and the presence of appreciable quantities of wood charcoal in the archaeological deposits at this time indicate that the region was not a tree-less steppe even during full glacial aridity. From 13,000 B.P. onwards, acacias are strongly represented in the charcoal assemblage both quantitatively and in terms of the number of species present. Acacia aneura is for the first time a major component of the assemblage indicating that it had by this time become a significant element of the local vegetation. These changes coincide with evidence elsewhere in the Australian arid zone for the onset of wetter conditions in the early Holocene.     

Pollen-based biome reconstruction for southern Europe and Africa 18,000 yr bp

Pollen data from 18,000 ¹⁴C yr bp were compiled in order to reconstruct biome distributions at the last glacial maximum in southern Europe and Africa. Biome reconstructions were made using the objective biomization method applied to pollen counts using a complete list of dryland taxa wherever possible. Consistent and major differences from present‐day biomes are shown. Forest and xerophytic woods/scrub were replaced by steppe, both in the Mediterranean region and in southern Africa, except in south‐western Cape Province where fynbos (xerophytic scrub) persisted. Sites in the tropical highlands, characterized today by evergreen forest, were dominated by steppe and/or xerophytic vegetation (cf. today’s Ericaceous belt and Afroalpine grassland) at the last glacial maximum. Available data from the tropical lowlands are sparse but suggest that the modern tropical rain forest was largely replaced by tropical seasonal forest while the modern seasonal or dry forests were encroached on by savanna or steppe. Montane forest elements descended to lower elevations than today.     

Late-glacial chironomid-based temperature reconstructions for Lago Piccolo di Avigliana in the southwestern Alps (Italy)

Chironomid headcapsules were used to reconstruct late glacial and early-Holocene summer temperatures at Lago Piccolo di Avigliana (LPA). Two training sets (northern Sweden, North America) were used to infer temperatures. The reconstructed patterns of temperature change agreed well with the GRIP and NGRIP δ¹⁸O records. Inferred temperatures were high during the Bølling (ca 19 °C), slowly decreased to ca 17.5 °C during the Allerød, reached lowest temperatures (ca 16 °C) during the Younger Dryas, and increased to ca. 18.5 °C during the Preboreal. The amplitudes of change at climate transitions (i.e. Oldest Dryas/Bølling: 3 °C, Allerød/Younger Dryas: 1.5 °C, and Younger Dryas/Preboreal: 2.5 °C) were smaller than in the northern Alps but similar to those recorded at another site in northeastern Italy. Our results suggest that (1) Allerød temperatures were higher in the southern Alps and (2) higher during the Preboreal (1 °C) than during the Allerød. These differences might provide an explanation for the different responses of terrestrial-vegetation to late glacial and early-Holocene climatic changes in the two regions. Other sites on both sides of the Alps should be studied to confirm these two hypotheses.     

Late-glacial vegetational ecotones and climatic patterns in Western Norway

The mapping of Weichselian late-glacial interstadial (13-11 ka B.P.) and Younger Dryas stadial (11-10 ka B.P.) pollen percentages for selected taxa demonstrates vegetational and hence climatic differentiation in Western Norway during these times. In the south, early interstadial Salix dominance was replaced by Betula woodland development. During Younger Dryas time, Betula pollen declined to values consistent with a modern vegetational analogue of the vegetation at the upper forest limit. In the inner fjord areas north of Stavanger, the interstadial vegetation contained scattered birch trees, the density depending on local topography and soils. During the Younger Dryas, vegetation resembling the modern mid- and low-alpine vegetation developed. On the outer coast, the interstadial vegetation was probably treeless, and dominated by Salix spp., including S. herbacea, and herbs. The vegetation became even more open during the Younger Dryas, resembling that of the modern mid- and high-alpine zones. The spatial ecotones delimiting the three areas of different vegetation development during both the interstadial and the Younger Dryas can be placed north of Stavanger, separating the southern region, and between the outer coast and inner fjord areas to the north. The Younger Dryas drop in temperature in all areas was up to about 5°C, enough to pass ecotonal thresholds in time in all areas.     

A deep dig––hindsight on Holocene vegetation composition from ancient environmental DNA

Want a glimpse at past vegetation? Studying pollen and other plant remains, which are preserved for example in lake sediments or mires for thousands of years, allows us to document regional occurrences of plant species over radiocarbon‐dated time series. Such vegetation reconstructions derived from optical analyses of fossil samples are inherently incomplete because they only comprise taxa that contribute sufficient amounts of pollen, spores, macrofossil or other evidences. To complement optical analyses for paleoecological inference, molecular markers applied to ancient DNA (aDNA) may help in disclosing information hitherto inaccessible to biologists. Parducci et al. (2013) targeted aDNA from sediment cores of two lakes in the Scandes Mountains with generic primers in a meta‐barcoding approach. When compared to palynological records from the same cores, respective taxon lists show remarkable differences in their compositions, but also in quantitative representation and in taxonomic resolution similar to a previous study (Jørgensen et al. 2012). While not free of assumptions that need critical and robust testing, notably the question of possible contamination, this study provides thrilling prospects to improve our knowledge about past vegetation composition, but also other organismic groups, stored as a biological treasure in the ground.     

Elevational variation in regional vegetation responses to late‐glacial climate changes in the Carpathians

Aim We used fossil records to explore patterns of change in vegetation composition, turnover and diversity along an elevational gradient during the late‐glacial to early Holocene, and to locate the elevations most sensitive to past climate changes. Location Romania. Methods Changes in the late‐glacial vegetation communities were inferred from seven published pollen records distributed within the main vegetation belts of the Romanian Carpathians, at elevations from 275 to 1840 m. Principal components analysis, detrended canonical correspondence analysis (DCCA) and rarefaction analysis were undertaken on these data. Results DCCA indicates that compositional change is strongest (SD 1.2, c. 70%) at the late‐glacial/Holocene transition (c. 11,500 cal. yr bp ), but significant shifts also occur at c. 14,700, c. 13,800 and c. 12,700 cal. yr bp (SD 0.4–0.8, 25–50%). Palynological turnover is greater for mid‐elevation records (730–1100 m) than at low and high elevations. Intervals of greater palynological richness occur between c. 13,800 and 12,500 cal. yr bp and after 11,500 cal. yr bp , and intervals of lower richness occur before c. 14,000 cal. yr bp and between c. 12,900 and 11,500 cal. yr bp . Main conclusions Variations in species composition during repeated climate changes of the late‐glacial suggest that community composition at a given time was not only a result of the environmental conditions of that period, but also the legacy of previous cumulative recruitment and extirpation events. Turnover estimates suggest that mid‐elevations have been the most sensitive to climate change during the late‐glacial and early Holocene. Palynological richness estimates show a less clear elevational pattern and no evidence for a greater sensitivity of this measure of biodiversity at high elevations to past climate change. However, results may have been affected by taxa with high pollen productivity and distance dispersability. Our finding concurs with other palaeoecological and local‐scale modelling studies in suggesting that small populations have survived in favourable microhabitats embedded within larger unsuitable areas during the late‐glacial, features not captured by broad‐scale model predictions.     

Steppes, savannahs, forests and phytodiversity reservoirs during the Pleistocene in the Iberian Peninsula

A palaeobotanical analysis of the Pleistocene floras and vegetation in the Iberian Peninsula shows the existence of patched landscapes with Pinus woodlands, deciduous and mixed forests, parklands (savannah-like), shrublands, steppes and grasslands. Extinctions of Arctotertiary woody taxa are recorded during the Early and Middle Pleistocene, but glacial refugia facilitated the survival of a number of temperate, Mediterranean and Ibero-North African woody angiosperms. The responses of Iberian vegetation to climatic changes during the Pleistocene have been spatially and temporarily complex, including rapid changes of vegetation in parallel to orbital and suborbital variability, and situations of multi-centennial resilience or accommodation to climatic changes. Regional characteristics emerged as soon as for the Middle Pleistocene, if not earlier: Ericaceae in the Atlantic coast indicating wetter climate, thermo-mediterranean elements in the south as currently, and broad-leaf trees in the northeastern. Overall, steppe landscapes and open Pinus woodlands prevailed over many continental regions during the cold spells of the Late Pleistocene. The maintenance of a high phytodiversity during the glacials was linked to several refuge zones in the coastal shelves of the Mediterranean and intramountainous valleys. Northern Iberia, especially on coastal areas, was also patched with populations of tree species, and this is not only documented by palaeobotanical data (pollen and charcoal) but also postulated by phylogeographical models.