Glacial Vegetation Research Articles

Different sensitivity of postglacial vegetation to climate and human disturbance between Tibetan Plateau and its surrounding regions

Characterizing the ecosystems' response to environmental changes on Tibetan Plateau (TP), as well as elucidating the regional disparities of these changes across the plateau's surface and its neighboring regions, holds significance for safeguarding the ecological security of Asia. Here, an improved pollen-based biomization procedure, incorporating weighted taxa, was conducted to illustrate the spatial and temporal differences of vegetation changes in TP, Xinjiang and southwestern China over the past 21,000 years. Results showed that the vegetation changes in TP and Xinjiang were characterized by alternations among herbaceous biomes, while the southwestern China were featured by changes among various woody biomes. Asynchronous vegetation change rates (ROCs) were discovered among TP, Xinjiang and southwestern China. The ROCs in TP were generally low during the Last Glacial Maximum but rose abruptly and peaked in the late deglacial period, whereas Xinjiang and southwestern China had high and increasing ROCs during Holocene. Those trajectories might relate to different sensitivities of vegetation to climate change and human disturbances. Habitat limitation on TP should be pretty intense during glacial period, leading to rapid vegetation establishment after glacier retreat. While in Xinjiang, water availability was the most obvious limitation, making the vegetation change sensitive to moisture and atmospheric CO2 variations. The forest in Yunnan behaved the most stability but was characterized by vertical migration responding to deglacial warming. Holocene acceleration of ROCs aligned with intensified human activities in Xinjiang and southwestern China. To sum up, environmental conditions have been always important in determining post glacial vegetation changes in west China, but the ROCs were asynchronous due to different sensitivities of vegetation to climate change and human activity. Although the plateau's vegetation was quite stable during Holocene, the plateau terrestrial ecosystem may subject to increasing risk under accelerating global warming and intensifying human activities.

Elevated Southern Hemisphere moisture availability during glacial periods.

Late Pleistocene ice-age climates are routinely characterized as having imposed moisture stress on low- to mid-latitude ecosystems1-5. This idea is largely based on fossil pollen evidence for widespread, low-biomass glacial vegetation, interpreted as indicating climatic dryness6. However, woody plant growth is inhibited under low atmospheric CO2(refs. 7,8), so understanding glacial environments requires the development of new palaeoclimate indicators that are independent of vegetation9. Here we show that, contrary to expectations, during the past 350 kyr, peaks in southern Australian climatic moisture availability were largely confined to glacial periods, including the Last Glacial Maximum, whereas warm interglacials were relatively dry. By measuring the timing of speleothem growth in the Southern Hemisphere subtropics, which today has a predominantly negative annual moisture balance, we developed a record of climatic moisture availability that is independent of vegetation and extends through multiple glacial-interglacial cycles. Our results demonstrate that a cool-moist response is consistent across the austral subtropics and, in part, may result from reduced evaporation under cool glacial temperatures. Insofar as cold glacial environments in the Southern Hemisphere subtropics have been portrayed as uniformly arid3,10,11, our findings suggest that their characterization as evolutionary or physiological obstacles to movement and expansion of animal, plant and, potentially, human populations10 should be reconsidered.

Late Glacial vegetation changes in the Kostroma Volga region based on pollen study of Lake Chukhlomskoye bottom sediments

The article presents the results of a palynological study of Lake Chukhlomskoye bottom sediments. Pollen analysis in combination with the results from 14C and 137Cs dating made it possible to reconstruct the main stages of changes in plant communities in the Kostroma Volga region at the end of the Pleniglacial and during the Late Glacial: 19.5–16.9 cal. ka BP – periglacial steppe, 16.9–14.7 cal. ka BP – birch periglacial forest-steppe, 14.7–12.7 cal. ka BP – spruce and birch-spruce forests and open woods with periglacial-steppe and meadow communities, 12.7–11.7 cal. ka BP – birch periglacial forest-steppe with rare participation of spruce.

Climate amelioration, abrupt vegetation recovery, and the dispersal of Homo sapiens in Baikal Siberia.

The dispersal of Homo sapiens in Siberia and Mongolia occurred by 45 to 40 thousand years (ka) ago; however, the climatic and environmental context of this event remains poorly understood. We reconstruct a detailed vegetation history for the Last Glacial period based on pollen spectra from Lake Baikal. While herb and shrub taxa including Artemisia and Alnus dominated throughout most of this period, coniferous forests rapidly expanded during Dansgaard-Oeschger (D-O) events 14 (55 ka ago) and 12 to 10 (48 to 41 ka ago), with the latter presenting the strongest signal for coniferous forest expansion and Picea trees, indicating remarkably humid conditions. These abrupt forestation events are consistent with obliquity maxima, so that we interpret last glacial vegetation changes in southern Siberia as being driven by obliquity change. Likewise, we posit that major climate amelioration and pronounced forestation precipitated H. sapiens dispersal into Baikal Siberia 45 ka ago, as chronicled by the appearance of the Initial Upper Paleolithic.

Well-hidden forests? Modern pollen spectra from Central Yakutia (Eastern Siberia) contribute to the interpretation of the last glacial vegetation in Central Europe

Well-hidden forests? Modern pollen spectra from Central Yakutia (Eastern Siberia) contribute to the interpretation of the last glacial vegetation in Central Europe

Aspects from the evolution of past vegetation in Southern Transylvania (Sibiu region)

The article reviews the results obtained through the palynological study of sequences obtained from the Sibiu region and adjacent areas. The oldest Upper Pleistocene sequences we refer to seem to reflect snapshots from the Last Glacial Maximum. The history of the Late Glacial and Holocene vegetation here is broadly part of the succession known for the territory of Romania, in the Carpathians and the surrounding areas of medium and low altitudes. The dynamics of the main forest and grasses taxa were highlighted, influenced both by natural factors and, more recently, by human activity. The reference area is characterized by the domination of the forests during the interstadials and by open landscape of forested steppe during the cold, stadial periods.

1.36 million years of Mediterranean forest refugium dynamics in response to glacial–interglacial cycle strength

The sediment record from Lake Ohrid (Southwestern Balkans) represents the longest continuous lake archive in Europe, extending back to 1.36 Ma. We reconstruct the vegetation history based on pollen analysis of the DEEP core to reveal changes in vegetation cover and forest diversity during glacial-interglacial (G-IG) cycles and early basin development. The earliest lake phase saw a significantly different composition rich in relict tree taxa and few herbs. Subsequent establishment of a permanent steppic herb association around 1.2 Ma implies a threshold response to changes in moisture availability and temperature and gradual adjustment of the basin morphology. A change in the character of G-IG cycles during the Early-Middle Pleistocene Transition is reflected in the record by reorganization of the vegetation from obliquity- to eccentricity-paced cycles. Based on a quantitative analysis of tree taxa richness, the first large-scale decline in tree diversity occurred around 0.94 Ma. Subsequent variations in tree richness were largely driven by the amplitude and duration of G-IG cycles. Significant tree richness declines occurred in periods with abundant dry herb associations, pointing to aridity affecting tree population survival. Assessment of long-term legacy effects between global climate and regional vegetation change reveals a significant influence of cool interglacial conditions on subsequent glacial vegetation composition and diversity. This effect is contrary to observations at high latitudes, where glacial intensity is known to control subsequent interglacial vegetation, and the evidence demonstrates that the Lake Ohrid catchment functioned as a refugium for both thermophilous and temperate tree species.

The palaeoendemic conifer Pherosphaera hookeriana (Podocarpaceae) exhibits high genetic diversity despite Quaternary range contraction and post glacial bottlenecking

Glacial relict plants are often endangered because extant populations can be small, geographically isolated and persist in suboptimal environments, leading to increased clonality and reduced genetic diversity putting their survival at further risk. This study examines how restriction to interglacial refugia has impacted the genetic diversity and structure of the threatened Tasmanian palaeoendemic, Pherosphaera hookeriana W. Archer bis. This species is a poorly dispersed, dioecious conifer that, having once been a major component of Last Glacial vegetation, is now limited to 30 known populations. Genetic diversity and structure were assessed using fifteen nuclear and nine chloroplast SSRs in 23 populations representing the species’ entire range. Changes in distribution and abundance from the Last Glacial to present were investigated by examining the fossil record, approximate Bayesian computation (ABC) and species distribution modelling. Despite fossil and ABC based evidence for a postglacial bottleneck, species-level genetic diversity (He = 0.56 and Ne = 2.86) exceeded that of some conifers with far wider distributions. Significant genetic structure (Fst = 0.127, Jost’s D = 0.203) was present, with most populations dominated by distinct nuclear SSR genetic clusters and having unique chloroplast haplotypes. Unexpectedly, clonality plays only a small role in population level regeneration. Genetic diversity has likely been maintained due to dioecy, persistence in multiple parts of its range and extant populations being directly descended from proximate glacial populations. Protecting populations from the mounting threat of fire will remain crucial for the in situ conservation of P. hookeriana.

Late glacial aster prairie at the Aubrey Clovis site, North Texas, USA

Pollen analysis of pond and spring deposits at the Aubrey Clovis site in North Texas provides a 1300-year record of late glacial grassland vegetation from 17,200 to 15,900 cal years BP. Forty-six pollen taxa are identified in the well-preserved assemblages. The late glacial pollen record at the Aubrey site represents three environments: upland, riparian, and lacustrine-wetland. The pond-related sediments are dominated by 80% Poaceae pollen, an unusually high amount in pollen records; the spring tufa sediments are dominated by Cyperaceae. Cattail (Typha latifolia) and other wetland plants, including green algae Botryococcus, Pediastrum, and Chara were present. The riparian habitat of the wide late glacial alluvial valley had alder (Alnus), willow (Salix), cottonwood (Populus), and water elm (Planera aquatica). The upland vegetation was a treeless grassland with comparatively high amounts of Asteraceae-type pollen; it is therefore called the aster prairie. Quercus, Juniperus, Carya, Ulmus, Ambrosia, and Chenopodiaceae pollen are much less abundant than found in modern grassland pollen records. Small amounts of Artemisia, Pinus, and Picea pollen are present, a consequence of long-distance transport. Regional late glacial cool-wet climate produced moist prairie soils. The Cross Timbers oak forest that occurs near the site today had not yet formed. Dissimilarity analysis of the pollen data shows that the late glacial aster prairie has no analog with modern shortgrass, mixed-grass, or tallgrass prairies. In contrast, a favorable analog exists with fossil pollen data from a lower zone at Patschke Bog, central Texas, and Muscotah Marsh, northeastern Kansas, indicating that a grassland characterized by high amounts of Asteraceae pollen formed a unique late glacial vegetation type in the region, earlier in Texas and later in Kansas. Because of its chronology and location in the eastern Great Plains, the late glacial aster prairie may be ancestral to the modern tallgrass prairie.

Using the fossil flora composition analysis for the reconstruction of vegetation and palaeoecological conditions during late glacial time in Karelia

The paper summarizes the results of pollen and macrofossil studies of late glacial deposits in Karelia, encompassing the Older Dryas, Allerod, and Younger Dryas – 12350–10300 14С yrs BP (14100–11900 cal. yrs BP). Specific features of the composition and formation of spore-pollen spectra (SPS) are considered. SPS of late glacial deposits in Karelia were found to contain pollen and spores of plants from surrounding habitats, as well as redeposited pollen grains and those coming from long-range transport. Interpretation of late glacial palaeobotanical data and reconstruction of the respective plant cover employed palaeoecological analysis and the method of measuring pollen concentration in deposits. The geographical and eco-sociological analysis of the fossil flora was carried out. A majority of species were found to have had circumpolar distribution; somewhat fewer species had Eurasian ranges; the third position is shared by Holarctic, circumboreal, and European species. The flora includes arctic-alpine, low-arctic, arctic, steppe, and boreal species. Having analyzed micro- and macrofossils, we identified plants belonging to forest, tundra, forest-tundra, steppe, and meadow communities, pioneer groupings on immature or disturbed soils, stony and gravely substrates. The identified plants are indicators of late glacial ecological conditions. They have different requirements to heat and moisture, texture and geochemical composition of the underlying deposits. The integrated analysis of the fossil flora and pollen concentration measurements have enabled more accurate reconstructions of late glacial vegetation. According to them, the complex natural and climatic conditions, as well as the high variation of landforms and Quaternary deposits composition have resulted in a very specific plant cover, with no modern analogs to be found. The cover did not form a closed canopy, was mosaic, and included species that were diverse both ecologically and in terms of geographic provenance. In Karelia at 12350–10300 14С yrs BP (14100–11900 cal. yrs BP), periglacial-steppe and tundra communities were widespread, and there occurred also birch and alder forest-tundra communities. Climate change during late glacial cooling (stadial) and warming (interstadial) events altered their spatial shares, but the composition of the flora persisted.

Late Quaternary Environments of the Teton Mountains, Wyoming: A Pollen Record from Green Lake

Late Quaternary forest succession in Wyoming’s Rocky Mountains, occurred in random patterns, because it reflects differences between the Glacial vegetation at lower elevations on the east vs. the west of the Rockies, as well as along the mountain crest to the south. Differential melting of mountain glaciers resulted in differences in the timing of recolonization. Significant variations in the composition of plant assemblages occurred due to delays in species’ arrival, and even in the exclusion of species. Holocene climate variability, especially ongoing global warming, added to the complex dynamics of plant assemblages with warm climate species replacing early Holocene, cooler climate species. The pollen record from Green Lake (located in a glacial cirque on the west side of the Teton Mountains in Teton County, Wyoming) addresses the local vegetation response from just before the fall of Mazama ash to the end of the middle Holocene warm period. Although the earlier portion of the pollen sequence records some of the last adjustments as some plant species were still arriving after de-glaciation, by the time Mazama ash fell it was climate variation that determined most of the dynamics observed in the Green Lake record. The results reveal a sequence of wetter and drier periods based upon the presence of diagnostic tree species. A moist late early Holocene was followed by a dry middle Holocene, which ended about 6,400 cal. B.P., and was followed between 5,000 to 2,800 cal. B.P. by a sequence of drier and moister climate episodes.

Statistical reconstruction of global vegetation for the last glacial maximum

We provide an estimate of global vegetation density for the Last Glacial Maximum (LGM) using a simple statistic model. For today's climate, vegetation is divided into 11 vegetation types plus bare soil, for each of which an empirical relationship between the probability of its occurrence and climate controls is derived. The relationships are then used to reconstruct the glacial vegetation patterns with and without considering CO2 modifications. For the LGM, the climate drivers are estimated from an ensemble-average of global paleo-climate simulations. The reconstruction suggests that vegetation types existing in today's cooler and drier regimes prevailed during the LGM and today's desert areas had more vegetation then. The vegetation patterns of the Amazon and Sahara are examined in detail. In the Amazon, tropical rainforest cover is reduced from 80% in today's climate to 40% in the LGM climate. The Sahara was partly covered by shrubs and grassland, with bare ground fraction reduced from 80% today to 30% in the LGM. The reconstructed vegetation patterns are compared with available biome data.

Glacial-relict symptoms in the Western Carpathian flora

Glacial relicts have been regionally more common in glacial than in recent times. A rigorous assessment of which species are indeed glacial relicts is extremely difficult because direct evidence is untraceable or equivocal for many species. We aimed to identify species of the Western Carpathian flora (vascular plants, bryophytes and terrestrial lichens) that display apparent biogeographical and ecological symptoms, suggesting a wider regional or supra-regional distribution during glacial times, or at least before the middle-Holocene climate optimum. We worked with the premise that exemplary relict species should tolerate continental and/or arctic climates, should have large distribution ranges with disjunctions, being regionally rare and ecologically conservative nowadays, should be associated with habitats that occurred during glacial times (tundra, steppe, peatland, open coniferous forest) and should display a restriction of ecological niches in the study region. The assessed species were primarily those with boreo-continental or artcic-alpine distribution. We demonstrated a conspicuous gradient of glacial-relict symptoms, with Carex vaginata, Betula nana, Trichophorum pumilum, Nephroma arcticum, Saxifraga hirculus and Cladonia stellaris topping the ranking. Based on the arbitrary ranking, 289 taxa can be considered high-probability relicts. For only a minority of them, there are any phylogeographical and/or palaeoecological data available from the study area. Biogeographical and ecological symptoms of 144 taxa suggest that they retreated rapidly after the Last Glacial Maximum whereas other species probably retreated later. The first principal component of biogeographical symptoms sorted species from circumpolar arctic-alpine species of acidic peatlands and wet tundra to strongly continental species of steppe, steppe-tundra and mineral-rich fens. This differentiation may mirror the altitudinal zonation of glacial vegetation in the Western Carpathians.

Landscape-scale drivers of glacial ecosystem change in the montane forests of the eastern Andean flank, Ecuador

Understanding the impact of landscape-scale disturbance events during the last glacial period is vital in accurately reconstructing the ecosystem dynamics of montane environments. Here, a sedimentary succession from the tropical montane cloud forest of the eastern Andean flank of Ecuador provides evidence of the role of non-climate drivers of vegetation change (volcanic events, fire regime and herbivory) during the late-Pleistocene. Multiproxy analysis (pollen, non-pollen palynomorphs, charcoal, geochemistry and carbon content) of the sediments, radiocarbon dated to ca. 45–42ka, provide a snap shot of the depositional environment, vegetation community and non-climate drivers of ecosystem dynamics. The geomorphology of the Vinillos study area, along with the organic‑carbon content, and aquatic remains suggest deposition took place near a valley floor in a swamp or shallow water environment. The pollen assemblage initially composed primarily of herbaceous types (Poaceae-Asteraceae-Solanaceae) is replaced by assemblages characterised by Andean forest taxa, (first Melastomataceae-Weinmannia-Ilex, and later, Alnus-Hedyosmum-Myrica). The pollen assemblages have no modern analogues in the tropical montane cloud forest of Ecuador. High micro-charcoal and rare macro-charcoal abundances co-occur with volcanic tephra deposits suggesting transportation from extra-local regions and that volcanic eruptions were an important source of ignition in the wider glacial landscape. The presence of the coprophilous fungi Sporormiella reveals the occurrence of herbivores in the glacial montane forest landscape. Pollen analysis indicates a stable regional vegetation community, with changes in vegetation population co-varying with large volcanic tephra deposits suggesting that the structure of glacial vegetation at Vinillos was driven by volcanic activity.

Vegetation assemblages of central Mexico through the late Quaternary: modern analogs and compositional turnover

AbstractQuestionWhen did vegetation assemblages that occupy modern central Mexico appear within the context of the late Quaternary?LocationCentral Mexico.MethodsWe used modern and fossil pollen data sets from central Mexico to explore the evolution of regional vegetation through the late Quaternary. A total of 1397 samples (1357 fossil samples distributed in 17 records and 40 modern samples) were analysed through detrended correspondence analysis to evaluate the degree of analogy between modern and past vegetation assemblages, and regional vegetation compositional turnover through time.ResultsThere was a high degree of analogy between modern and glacial vegetation, whereas the early and mid‐Holocene were characterized by a high frequency of no‐modern‐analogue pollen assemblages. Vegetation turnover during the glacial time was characterized by both pulses of abrupt change and episodes of stability. In contrast, vegetation turnover was high through most of the Holocene. Both vegetation turnover and past vegetation analogy to modern were not synchronous in altitudinal zones, except for the past 2000 yrs, when pollen assemblages suggest a high vegetation analogy to modern‐day throughout the region.ConclusionsHuman impacts on central Mexico regional vegetation were consistently evident during the last 2000 yrs, suggesting that biodiversity expressed in the modern vegetation assemblages incorporates a high anthropogenic imprint. High resemblance of glacial and modern landscapes suggests that the effect of human occupation on the landscape is similar to that exerted by glacial time environmental stress. However, loss of ecosystem connectivity under the modern pattern of landscape homogenization represents an unprecedented threat for regional biodiversity.

Glacial legacies on interglacial vegetation at the Pliocene-Pleistocene transition in NE Asia.

Broad-scale climate control of vegetation is widely assumed. Vegetation-climate lags are generally thought to have lasted no more than a few centuries. Here our palaeoecological study challenges this concept over glacial–interglacial timescales. Through multivariate analyses of pollen assemblages from Lake El'gygytgyn, Russian Far East and other data we show that interglacial vegetation during the Plio-Pleistocene transition mainly reflects conditions of the preceding glacial instead of contemporary interglacial climate. Vegetation–climate disequilibrium may persist for several millennia, related to the combined effects of permafrost persistence, distant glacial refugia and fire. In contrast, no effects from the preceding interglacial on glacial vegetation are detected. We propose that disequilibrium was stronger during the Plio-Pleistocene transition than during the Mid-Pliocene Warm Period when, in addition to climate, herbivory was important. By analogy to the past, we suggest today's widespread larch ecosystem on permafrost is not in climate equilibrium. Vegetation-based reconstructions of interglacial climates used to assess atmospheric CO2–temperature relationships may thus yield misleading simulations of past global climate sensitivity.

Vegetation stability and the habitat associations of the endemic taxa of the Olympic Peninsula, Washington, USA

Explanations for areas of endemism often involve relative climatic stability, or low climate ve- locity, over time scales ranging from the Pleistocene to the late Cenozoic. Given that many narrowly en- demic taxa in forested landscapes display discrete habitat associations, habitat stability should be simi- larly important for endemic persistence. Furthermore, while past climate variability is exceedingly diffi- cult to quantify on millennial time scales, past distributions of habitats may be robustly inferred from paleoecological records. The Olympic Peninsula, Washington, supports a biota with several insular fea- tures including 29 endemic plant and animal taxa. Here I present the geographic distribution and habitat of the endemic taxa, and then examine the vegetation stability of the past 14,300 years from five pollen records associated with discrete vegetation zones on the peninsula. I show that 11 endemics have distri- butions centered on dry alpine scree and rock in the northeastern quadrant of the peninsula, and nine occur in shaded riparian forests in the southwest. Vegetation turnover during the post -glacial period was smallest in these areas. However, another long pollen record from the western peninsula reveals existence of shrub tundra and greatly reduced forest cover, indicating southward displacement of shad- ed riparian habitats by perhaps as much as 100 km. Although this study supports an association of post - glacial vegetation stability with endemism, records spanning the glacial maximum indicate widespread tundra during long periods of the late Pleistocene and therefore suggest southern displacement of for- est-associated endemics. While some of the alpine scree-associated endemics may have persisted in situ, many others likely arrived via a variety of dispersal trajectories. These histories include dispersal from southern refugia towards ocean barriers preventing further northward dispersal, contraction from more widespread distributions, and recent divergence from sister taxa. This study shows that paleoeco- logical records can cast strong doubt on the inference that areas of endemism necessarily imply in situ glacial survival.

Late Glacial and Holocene vegetation history in the northern foothills of the Adirondack Mountains

The postglacial history of vegetation at a regional scale is mainly governed by climate. However, the action of other environmental factors can lead to differentiation of the long-term vegetation dynamics in locations that are in proximity. In this context, the vegetation history of Covey Hill, at the northern tip of the Adirondack Mountains, was reconstructed using pollen analysis of a sediment core collected in a bog near the hilltop. This history was then compared with that of other sites in the Adirondacks, in the St. Lawrence Lowlands and in the Appalachian foothills to determine whether differentiations had occurred between sites across the landscape. Regionally, climate seems to have been the main driver of vegetation development. Differences between sites are most pronounced in regard to relative abundance of aspen and alder, and mostly occurred during the Late Glacial and early Holocene. Unlike other sites, fires occurred frequently on Covey Hill for several millennia, and most probably allowed the long-term maintenance of a rare pine barren. Finally, drier conditions are probably partly responsible for the hemlock decline evident around 5100 cal BP.

Vegetation response to climate forcing during the last glacial maximum and deglaciation in the East Carpathians: attenuated response to maximum cooling and increased biomass burning

The Carpathian Mountains were one of the main mountain reserves of the boreal and cool temperate flora during the Last Glacial Maximum (LGM) in East-Central Europe. Previous studies demonstrated late glacial vegetation dynamics in this area; however, our knowledge on the LGM vegetation composition is limited due to the scarcity of suitable sedimentary archives. Here we present a new record of vegetation, fire and lacustrine sedimentation from the youngest volcanic crater of the Carpathians (Lake St Anne, Lacul Sfânta Ana, Szent-Anna-to) to examine environmental change in this region during the LGM and the subsequent deglaciation. Our record indicates the persistence of boreal forest steppe vegetation ( Pinus sylvestris , Pinus mugo , Pinus cembra , Betula , Salix , Populus , Picea abies ) in the foreland and low mountain zone of the East Carpathians and Juniperus shrubland at higher elevation. We demonstrate attenuated response of the regional vegetation to maximum global cooling. Between ~22,870 and 19,150 cal yr BP we find increased regional biomass burning that is antagonistic with the global trend. Increased regional fire activity suggests extreme continentality likely with relatively warm and dry summers. We also demonstrate xerophytic steppe expansion directly after the LGM, from ~19,150 cal yr BP, and regional increase in boreal woodland cover with Pinus and Betula from 16,300 cal yr BP. Plant macrofossils indicate local (950 m a.s.l.) establishment of Betula nana and B . pubescens at 15,150 cal yr BP, Pinus sylvestris at 14,700 cal yr BP and Larix decidua at 12,870 cal yr BP. Pollen data furthermore hints at the regional presence of some temperate deciduous trees during the LGM ( Fagus sylvatica , Carpinus betulus , Corylus avellana , Fraxinus excelsior , Ulmus ). We also present pollen based quantitative climate reconstruction from this site and discuss its connection with other climate reconstructions and climate modeling results.

Orbital- and millennial-scale environmental changes between 64 and 20 ka BP recorded in Black Sea sediments

Abstract. High-resolution pollen and dinoflagellate cyst records from sediment core M72/5-25-GC1 were used to reconstruct vegetation dynamics in northern Anatolia and surface conditions of the Black Sea between 64 and 20 ka BP. During this period, the dominance of Artemisia in the pollen record indicates a steppe landscape and arid climate conditions. However, the concomitant presence of temperate arboreal pollen suggests the existence of glacial refugia in northern Anatolia. Long-term glacial vegetation dynamics reveal two major arid phases ~64–55 and 40–32 ka BP, and two major humid phases ~54–45 and 28–20 ka BP, correlating with higher and lower summer insolation, respectively. Dansgaard–Oeschger (D–O) cycles are clearly indicated by the 25-GC1 pollen record. Greenland interstadials are characterized by a marked increase in temperate tree pollen, indicating a spread of forests due to warm/wet conditions in northern Anatolia, whereas Greenland stadials reveal cold and arid conditions as indicated by spread of xerophytic biomes. There is evidence for a phase lag of ~500 to 1500 yr between initial warming and forest expansion, possibly due to successive changes in atmospheric circulation in the North Atlantic sector. The dominance of Pyxidinopsis psilata and Spiniferites cruciformis in the dinocyst record indicates brackish Black Sea conditions during the entire glacial period. The decrease of marine indicators (marine dinocysts, acritarchs) at ~54 ka BP and increase of freshwater algae (Pediastrum, Botryococcus) from 32 to 25 ka BP reveals freshening of the Black Sea surface water. This freshening is possibly related to humid phases in the region, to connection between Caspian Sea and Black Sea, to seasonal freshening by floating ice, and/or to closer position of river mouths due to low sea level. In the southern Black Sea, Greenland interstadials are clearly indicated by high dinocyst concentrations and calcium carbonate content, as a result of an increase in primary productivity. Heinrich events show a similar impact on the environment in the northern Anatolia/Black Sea region as Greenland stadials.