Terrestrial biosphere changes over the last 120 kyr

A new global synthesis and biomization of long (> 40 kyr) pollen-data records is presented and used with simulations from the HadCM3 and FAMOUS climate models and the BIOME4 vegetation model to analyse the dynamics of the global terrestrial biosphere and carbon storage over the last glacial–interglacial cycle. Simulated biome distributions using BIOME4 driven by HadCM3 and FAMOUS at the global scale over time generally agree well with those inferred from pollen data. Global average areas of grassland and dry shrubland, desert, and tundra biomes show large-scale increases during the Last Glacial Maximum, between ca. 64 and 74 ka BP and cool substages of Marine Isotope Stage 5, at the expense of the tropical forest, warm-temperate forest, and temperate forest biomes. These changes are reflected in BIOME4 simulations of global net primary productivity, showing good agreement between the two models. Such changes are likely to affect terrestrial carbon storage, which in turn influences the stable carbon isotopic composition of seawater as terrestrial carbon is depleted in 13C

Vegetation and climate variability during the Last Interglacial evidenced in the pollen record from Lake Baikal

A high-resolution pollen record from the core sediments collected in the northern part of Lake Baikal represents the latest stage of the Taz (Saale) Glaciation, Kazantsevo (Eemian) Interglacial (namely the Last Interglacial), and the earliest stage of the Zyryanka (Weichselian) Glaciation. According to the palaeomagnetic-based age model applied to the core, the Last Interglacial in the Lake Baikal record lasted about 10.6 kyrs from 128 kyr to 117.4 kyr BP, being more or less synchronous with the Marine Isotope Stage 5e. The reconstructed changes in the south Siberian vegetation and climate are following. A major spread of shrub alder (Duschekia fruticosa = Alnus fruticosa) and shrub birches (Betula sect. Nanae/Fruticosae) in the study area was a characteristic feature during the late glacial phase of the Taz Glaciation. Boreal trees e.g. spruce (Picea obovata) and birch (Betula sect. Albae) started to play an important role in the regional vegetation with the onset of the interglacial conditions. Optimal conditions for Abies sibirica-Picea obovata taiga development occurred ca. 126.3 kyr BP. The maximum spread of birch forest-steppe communities took place at the low altitudes ca. 126.5-125.5 kyr BP and Pinus sylvestris started to form forests in the northern Baikal area after ca. 124.4 kyr BP. Re-expansion of the steppe communities, as well as shrubby alder and willow communities and the disappearance of forest vegetation occurred at about 117.4 kyr BP, suggesting the end of the interglacial succession. The changes in the pollen assemblages recorded in the sediments from northern Baikal point to a certain instability of the interglacial climate. Three phases of climate deterioration have been distinguished: 126-125.5, 121.5-120, and 119.5-119 kyr BP. The penultimate cooling signal may be correlated with the cool oscillation recorded in European pollen records. However, such far distant correlation requires more careful investigation

Pleistocene climate changes based on palynological data

The paper presents general climate changes during the last 2.6 Ma in the Northern Hemisphere. Plant formations of warm intervals (interglacials and interstadials) are briefly described. Disappearance of some more climate-sensitive tree taxa as well as climate changes during the Pleistocene in Northern Europe are also portrayed

The course and correlation of the Late Pleistocene pollen sequences from Poland and Belarus

The most representative and long Late Pleistocene pollen sequences covering the late glacial of the penultimate glaciation (Warta/Pripiat), the last interglacial (Eemian/Muravian) and the early glacial of the Last Glaciation (Vistulian/Poozerie) from the territory of Poland and Belarus have been correlated. The resemblance ofpollen spectra in these pollen sequences and a parallel succession of Regional Pollen Assemblage Zones in the considered time intervals suggest that the natural environment of Poland and Belarus underwent synchronous changes under unidirectional climatic transformations. Qualitative and quantitative features of the Regional Pollen Assemblage Zones show similarities and differences in vegetation and climate changes in the study area. A comparison of the pollen spectra from Poland and Belarus suggests that both territories were affected by a similar climate particularly during the cold intervals. Some differences between the compositions of the pollen spectra were noticed as concerns the interglacial period. For instance, Abies and Taxus pollen as well as significantly high percentages of Calluna vulgaris pollen in NE Poland towards the end of the period are present only in the Polish sections. This may suggest a more Atlantic type of the climate during the Last Interglacial in Poland than in Belarus

Quaternary environmental changes at Starunia palaeontological site and vicinity (Carpathian region, Ukraine) based on palaeobotanical studies

The unique nature of the Starunia palaeontological site, where nearly perfectly preserved large mammals were discovered at the beginning of the 20th century, and also the incompletely researched history of the Pleistocene vegetation of the region, provided the necessary stimulus to undertake further complex palaeobotanical investigations. The Pleistocene and Holocene sediments filling the Velyky Lukavets River valley are the object of this type of investigation. Both the succession of vegetation and radiocarbon dating indicate that the formation of biogenic sediments began in the Weichselian Middle Pleniglacial, in the Moershoofd interstadial, and lasted through the Hengelo/Denekamp Interstadial Complex and the Late Glacial and Holocene. Palaeobotanical investigations show the Middle Pleniglacial to have been characterized by an open, forestless landscape. Grassland steppe communities dominated with extremely high proportions of Poaceae, as well as Artemisia, Chenopodiaceae, and a number of herbaceous plant taxa. More moist places were occupied by dwarf shrub tundra with Betula nana, Alnus viridis, and Cyperaceae. Small changes in the character of the vegetation resulting from climatic oscillations made their mark through a slight increase in the proportion of tree-birches, fir and pine. The record of Late Weichselian plant succession in the Velyky Lukavets River valley also documents the dominance of open habitats with a preponderance of steppe and steppe-tundra communities and a dry, continental climate. Only with the beginning of the Holocene did an improvement in climate conditions lead to the rapid expansion of forest communities with a dominance of pine accompanied by fir, larch, and trees, which are more demanding in terms of temperature, e.g. elm, oak, lime, hornbeam and hazel

Was the climate of the Eemian stable? A quantitative climate reconstruction from seven European pollen records

International audienceThe aim of the present study is to estimate the range of the climatic variability during the Eemian interglacial, which lasted about 10,000 years (marine isotopic stage 5e). The modem pollen analogue technique is applied to seven high resolution pollen records from France and poland to infer the annual precipitation and the mean temperature of the coldest month. The succession of pollen taxa and the reconstructed climate can be interpreted coherently. The warmest winter temperatures are centred in the first three millennia of the Eemian interglacial, during the mixed oak forest phase with Quercus and Corylus as dominant trees. A rapid shift to cooler winter temperatures of about 6 degrees to 10 degrees C occurred between 4000 and 5000 years after the beginning of the Eemian, related to the spread of the Carpinus forest. This shift is more obvious for the reconstructed temperatures than for precipitation and is unique and irreversible for the whole Eemian period. Following this climatic shift of the Eemian, variations of temperature and precipitation during the fast 5000 years were only slight with an amplitude of about 2 degrees to 4 degrees C and 200 to 400 mm/yr. The estimated temperature changes were certainly not as strong as those reconstructed for the stage 6/5e termination or the transition 5e/5d. This is consistent with the constantly high ratio of tree pollen throughout the Eemian, indicative of a succession of temperate forest types. This gradual transition between different forest landscapes can be related to intrinsic competition between the species rather than to a drastic climatic change. (C) 1998 Elsevier Science B.V. All rights reserved

Weathering in the Lake Baikal watershed during the Kazantsevo (Eemian) interglacial: Evidence from the lacustrine clay record

The clay-mineralogical record of a piston core recovered on an elevated plateau in the northern basin of Lake Baikal has been investigated for the Kazantsevo interglacial period (i.e., Eemian s.s. equivalent in northern Europe). The age model (as inferred from palaeomagnetic intensity) suggests that this stage spans ca. 128 to 117 kyr BP. Relative clay mineral abundances and clay-mineral ratios are used to reconstruct the weathering conditions within the Baikal watershed at a sub-millennial resolution, and suggest that the clay record is highly variable. A bimodal clay-data distribution is in agreement with different clay sources and/or formation between the studied glacial and interglacial periods. High amounts of smectites in the Taz glacial samples (128.7-136.4 kyr BP) may be explained by an additional source of neoformed smectites during the glacial stage. In addition to the classically used smectite/illite ratio, the mineralogical results are integrated by the calculation of a hydrolysis index that takes into account the abundance of all clay species and their sensitivity to chemical weathering. A principal components analysis (PCA) of the Baikal clay minerals allows the comparison of the clay parameters with regard to weathering conditions. Clay data are further compared (i) with diatom and pollen profiles, (ii) with pollen-based quantitative reconstructions for the same core material, and (iii) with other climate reconstructions for the Lake Baikal region and Siberia. Several features of our record are highlighted here. During the early period of the Kazantsevo interglacial (128.4-125.2 kyr BP), weathering processes remain controlled by physical reworking for more than 2 kyr after the initial transition from cold to warm conditions. Inception of chemical weathering starts only after ca. 125 kyr BP, a period coincident with the warmest conditions according to both the pollen record and by the strongest chernozem development in Siberian soils. Within the interglacial interval, the hydrolysis index displays a two-step increase, punctuated by a minimum value ca. 122 kyr BP. The increasing but irregular trend persists after the transition from the Kazantsevo interglacial to the Zyryanka glacial (similar to 117 kyr BP). Peak chemical weathering, as inferred by clay changes, lags the interglacial/ glacial transition by at least 2 kyr. This suggests that pedogenesis remains active after the interval of surface stabilization. Lake Baikal clay minerals trace the nature of the main weathering conditions within the watershed. We note any increase in physical weathering is rapidly recorded in sedimentary clay assemblages but the mineral imprint to chemical weathering changes is more gradual, lagging reconstructed climate conditions over the lake by ca. 2 kyr. 0 2007 Elsevier B.V.. All rights reserved.Continen

Instability of the environment at the end of the Eemian Interglacial as illustrated by the isopollen maps for Poland

Many terrestrial pollen profiles from Poland (and a few pollen records from other parts of Central Europe) show the end of the last interglacial (Eemian, MIS 5e) to have been characterized by climatic and environmental instability. This is expressed by a strong, rapid cooling in the middle part of the pine phase ending this interglacial (E7 regional pollen assemblage zone), and then a re-warming at the very end of this phase, immediately before the transition to the glacial conditions of the last glaciation (Vistulian, Weichselian, MIS 5d). We have characterized the regional distribution of these climatic fluctuations in Poland on the basis of isopollen maps prepared for the Eemian Interglacial based on palynological data from 31 Polish pollen profiles. These maps show unequivocally that the intra-interglacial cooling at the end of the Eemian Interglacial was a transregional phenomenon, which was reflected very clearly by a temporary openness of vegetation across the whole of Poland. It was associated with a distinct decrease in pine forest areas and an increase in birch forests and open communities of cold steppe type with a domination of Artemisia. The pronounced climate and environment instability during the last phase of the Eemian Interglacial may be consistent with it being a natural phenomenon, characteristic of transitional stages. Taking into consideration the currently observed global warming, coinciding with a natural cooling trend, the study of such transitional stages is important for understanding the underlying processes of climate change