Atlas of modern dinoflagellate cyst distributions in the Black Sea Corridor: From Aegean to Aral Seas, including Marmara, Black, Azov and Caspian Seas

We present the first comprehensive taxonomic and environmental study of dinoflagellate cysts in 185 surface sediment samples from the Black Sea Corridor (BSC) which is a series of marine basins extending from the Aegean to the Aral Seas (including Marmara, Black, Azov and Caspian Seas). For decades, these low-salinity, semi-enclosed or endorheic basins have experienced large-scale changes because of intensive agriculture and industrialisation, with consequent eutrophication and increased algal blooms. The BSC atlas data provide a baseline for improved understanding of linkages between surface water conditions and dinoflagellate cyst (dinocyst) distribution, diversity and morphological variations. By cross-reference to dinocyst occurrences in sediment cores with radiocarbon ages covering the past c. 11,700 years, the history of recent biodiversity changes can be evaluated. The seabed cyst samples integrate seasonal and multi-year data which are not usually captured by plankton samples, and the cyst composition can point to presence of previously unrecorded motile dinoflagellate species in the BSC. Results show the presence of at least 71 dinocyst taxa of which 36% can be related to motile stages recorded in the plankton. Comparison with sediment core records shows that five new taxa appear to have entered or re-entered the region over the past century. Statistical analysis of the atlas data reveals the presence of four ecological assemblages which are primarily correlated with seasonal and annual surface water salinity and temperature; correlation with phosphate, nitrate and silicate nutrients, chlorophyll-a and bottom water oxygen is less clear but may be important for some taxa. Biodiversity indices reveal strong west − east biogeographical differences among the basins that reflect the different histories of Mediterranean versus Ponto-Caspian connections. The atlas data provide a standardised taxonomy and regional database for interpreting downcore cyst variations in terms of quantitative oceanographic changes. The atlas also provides a baseline for monitoring further changes in the BSC dinocysts that may accompany the accelerating development of the region

Quantitative reconstruction of precipitation changes on the NE Tibetan Plateau since the Last Glacial Maximum – extending the concept of pollen source area to pollen-based climate reconstructions from large lakes

Pollen records from large lakes have been used for quantitative palaeoclimate reconstruction, but the influences that lake size (as a result of species-specific variations in pollen dispersal patterns that smaller pollen grains are more easily transported to lake centre) and taphonomy have on these climatic signals have not previously been systematically investigated. We introduce the concept of pollen source area to pollen-based climate calibration using the north-eastern Tibetan Plateau as our study area. We present a pollen data set collected from large lakes in the arid to semi-arid region of central Asia. The influences that lake size and the inferred pollen source areas have on pollen compositions have been investigated through comparisons with pollen assemblages in neighbouring lakes of various sizes. Modern pollen samples collected from different parts of Lake Donggi Cona (in the north-eastern part of the Tibetan Plateau) reveal variations in pollen assemblages within this large lake, which are interpreted in terms of the species-specific dispersal and depositional patterns for different types of pollen, and in terms of fluvial input components. We have estimated the pollen source area for each lake individually and used this information to infer modern climate data with which to then develop a modern calibration data set, using both the multivariate regression tree (MRT) and weighted-averaging partial least squares (WA-PLS) approaches. Fossil pollen data from Lake Donggi Cona have been used to reconstruct the climate history of the north-eastern part of the Tibetan Plateau since the Last Glacial Maximum (LGM). The mean annual precipitation was quantitatively reconstructed using WA-PLS: extremely dry conditions are found to have dominated the LGM, with annual precipitation of around 100 mm, which is only 32% of present-day precipitation. A gradually increasing trend in moisture conditions during the Late Glacial is terminated by an abrupt reversion to a dry phase that lasts for about 1000 yr and coincides with "Heinrich event 1" in the North Atlantic region. Subsequent periods corresponding to the Bølling/Allerød interstadial, with annual precipitation (<i>P</i>_ann) of about 350 mm, and the Younger Dryas event (about 270 mm <i>P</i>_ann) are followed by moist conditions in the early Holocene, with annual precipitation of up to 400 mm. A drier trend after 9 cal. ka BP is followed by a second wet phase in the middle Holocene, lasting until 4.5 cal. ka BP. Relatively steady conditions with only slight fluctuations then dominate the late Holocene, resulting in the present climatic conditions. The climate changes since the LGM have been primarily driven by deglaciation and fluctuations in the intensity of the Asian summer monsoon that resulted from changes in the Northern Hemisphere summer solar insolation, as well as from changes in the North Atlantic climate through variations in the circulation patterns and intensity of the westerlies

PALEOLIMNOLOGICAL TRANSECT (PLOT) PROJECT: THE PREGLACIAL TO POSTGLACIAL HISTORY OF THE RUSSIAN ARCTIC BASED ON THE PRELIMINARY POLLEN RESULTS

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Northern Eurasian large lakes history: sediment records obtained in the frame of Russian-German research project PLOT

Russian-German project PLOT (Paleolimnological Transect) aims at investigating the regional responses of the quaternary climate and environment on external forcing and feedback mechanisms along a more than 6000 km long longitudinal transect crossing Northern Eurasia. The well-dated record from Lake El´gygytgyn used as reference site for comparison the local climatic and environmental histories. Seismic surveys and sediment coring up to 54 m below lake floor performed in the frame of the project on Ladoga Lake (North-West of Russia; 2013), Lake Bolshoye Shchuchye (Polar Ural; 2016), Lake Levinson-Lessing and Lake Taymyr (Taymyr Peninsula; 2016-2017), Lake Emanda (Verkhoyansk Range; 2017). Fieldwork at Polar Ural and Taymyr Peninsula was conducted in collaboration with the Russian-Norwegian CHASE (Climate History along the Arctic Seaboard of Eurasia) project. Here, we present the major results of the project obtained so far

Corrigendum to "Quantitative reconstruction of precipitation changes on the NE Tibetan Plateau since the Last Glacial Maximum &ndash; extending the concept of pollen source area to pollen-based climate reconstructions from large lakes" published in Clim. Past, 10, 21&ndash;39, 2014

No abstract available

История растительности и пожаров арктической части Пур-Тазовского междуречья в голоцене

The global climate change and significantly increased anthropogenic pressure on the Arctic and Subarctic regions require modern ecosystem monitoring and understanding of the past environmental changes. Vegetation history is reflected by pollen spectra recorded in peat deposits, investigation of which is one of the main methods in the research of long-term climatic changes. In order to reconstruct the vegetation and fire history of today’s south tundra in the lower reaches of the Taz river, we carried out palynological exploration of peat and underlying lake sediments covering the last 11.2 cal ka BP in the Tazovsky district of the Yamalo-Nenets Autonomous Okrug (Russia). In the course of the research, we found 31 pollen taxa, 4 taxa of spore plants, 2 types of fungal spores, one species of shell amoeba and green algae. We have identified several stages in the development of the local wetland biocenosis at the study site and reconstructed the history of changes in the vegetation cover of the region, including changes in the composition of the woody vegetation. Grasslands, with groups of trees among thickets of shrubs and lake-mire complexes dominated in the study area by 11.2 cal ka BP. The grasslands were gradually supplemented by wet grass communities, which were then replaced by swamps and tundra complexes in the mid-Holocene. The time periods of the local fires have been established. The fire that had the greatest effect on the vegetation at the study site was detected in the period of 8.1 cal ka BP. We have revealed periods of the least fire activity – 7.6–5.5 cal ka BP and the highest fire activity – 12.5–8 cal ka BP.Чтобы реконструировать голоценовую историю растительности и пожаров современной южной тундры в нижнем течении р. Таз, мы провели палинологические исследования торфяных и подстилающих озерных отложений, сформированных за последние 11,2 кал. тыс. л. согласно полученным 8 радиоуглеродным датировкам. В ходе исследования были обнаружены: 31 пыльцевой таксон, 4 таксона споровых растений, 2 типа спор грибов, один вид раковинной амебы и зеленая водоросль. На исследуемом участке выделено несколько этапов в развитии местного водно-болотного биоценоза, реконструирована история растительного покрова региона. 11,2 кал. тыс. л. н. на исследуемой территории преобладали луга, группы деревьев в зарослях кустарников и озерно-болотные комплексы. Луга постепенно дополнялись высокопродуктивными травянистыми сообществами влаголюбивых растений, которые затем преобразовались в болота и тундровые комплексы в середине голоцена. Установлены временные периоды локальных пожаров. Пожар, который в наибольшей степени затронул растительность на исследуемом участке, произошел в период 8,1 кал. тыс. л. н. Выявлены периоды наименьшей и наибольшей пожарной активности – 7,6–5,5 кал. тыс. л. н. и 11,2–8 кал. тыс. л. н. соответственно

LegacyClimate 1.0: a dataset of pollen-based climate reconstructions from 2594 Northern Hemisphere sites covering the last 30&thinsp;kyr and beyond

Here we describe LegacyClimate 1.0, a dataset of the reconstruction of the mean July temperature (TJuly), mean annual temperature (Tann), and annual precipitation (Pann) from 2594 fossil pollen records from the Northern Hemisphere, spanning the entire Holocene, with some records reaching back to the Last Glacial Period. Two reconstruction methods, the modern analog technique (MAT) and weighted averaging partial least squares regression (WA-PLS), reveal similar results regarding spatial and temporal patterns. To reduce the impact of precipitation on temperature reconstruction, and vice versa, we also provide reconstructions using tailored modern pollen data, limiting the range of the corresponding other climate variables. We assess the reliability of the reconstructions, using information from the spatial distributions of the root mean squared error in the prediction and reconstruction significance tests. The dataset is beneficial for synthesis studies of proxy-based reconstructions and to evaluate the output of climate models and thus help to improve the models themselves. We provide our compilation of reconstructed TJuly, Tann, and Pann as open-access datasets at PANGAEA (https://doi.org/10.1594/PANGAEA.930512; Herzschuh et al., 2023a). The R code for the reconstructions is provided at Zenodo (https://doi.org/10.5281/zenodo.7887565; Herzschuh et al., 2023b), including the harmonized open-access modern and fossil datasets used for the reconstructions, so that customized reconstructions can be easily established.</p

The Eurasian Modern Pollen Database (EMPD), version 2

The Eurasian (née European) Modern Pollen Database (EMPD) was established in 2013 to provide a public database of high-quality modern pollen surface samples to help support studies of past climate, land cover, and land use using fossil pollen. The EMPD is part of, and complementary to, the European Pollen Database (EPD) which contains data on fossil pollen found in Late Quaternary sedimentary archives throughout the Eurasian region. The EPD is in turn part of the rapidly growing Neotoma database, which is now the primary home for global palaeoecological data. This paper describes version 2 of the EMPD in which the number of samples held in the database has been increased by 60 % from 4826 to 8134. Much of the improvement in data coverage has come from northern Asia, and the database has consequently been renamed the Eurasian Modern Pollen Database to reflect this geographical enlargement. The EMPD can be viewed online using a dedicated map-based viewer at https://empd2.github.io and downloaded in a variety of file formats at https://doi.pangaea.de/10.1594/PANGAEA.909130 (Chevalier et al., 2019)Swiss National Science Foundation | Ref. 200021_16959

The Eurasian Modern Pollen Database (EMPD), version 2

The Eurasian (nee European) Modern Pollen Database (EMPD) was established in 2013 to provide a public database of high-quality modern pollen surface samples to help support studies of past climate, land cover, and land use using fossil pollen. The EMPD is part of, and complementary to, the European Pollen Database (EPD) which contains data on fossil pollen found in Late Quaternary sedimentary archives throughout the Eurasian region. The EPD is in turn part of the rapidly growing Neotoma database, which is now the primary home for global palaeoecological data. This paper describes version 2 of the EMPD in which the number of samples held in the database has been increased by 60% from 4826 to 8134. Much of the improvement in data coverage has come from northern Asia, and the database has consequently been renamed the Eurasian Modern Pollen Database to reflect this geographical enlargement. The EMPD can be viewed online using a dedicated map-based viewer at https://empd2.github.io and downloaded in a variety of file formats at https://doi.pangaea.de/10.1594/PANGAEA.909130 (Chevalier et al., 2019).Peer reviewe

Long-term ecology and conservation of the Kungur forest-steppe (pre-Urals, Russia): case study Spasskaya Gora

The Kungur forest-steppe is the northernmost outpost of European forest-steppe, located in the western pre-Urals within the boreal climatic zone. The co-existence of boreal, nemoral and steppe species with relicts and endemics results in a high plant diversity, making it an important biodiversity hotspot. Under current climate change and strong agricultural impacts, the Kungur forest-steppe is rapidly degrading. In order to develop sustainable management strategies, we studied the vegetation history over the last 3500 years in the natural reserve area Spasskaya Gora. Palynological data indicate that the territory of Spasskaya Gora was largely covered by hemiboreal forests with high proportion of elm during the late Holocene. An opening of the vegetation strongly correlates with erosion, both indicating anthropogenic activities such as lumbering, agriculture, grazing and hay making. The modern Pinus and Betula dominated forests combined with large areas dominated by grasses and herbs appear in the last 300 years and caused by human activity. The data support the ‘anthropogenic’ hypothesis of the Kungur forest-steppe development, suggesting that Pleistocene steppe was replaced by hemiboreal forests during the Holocene. Steppe elements survived on exposed rocks. The recent forest-steppe landscapes dominated by pioneer birch and poplar were formed due to anthropogenic deforestation. With respect to nature conservation, our data demonstrate that prohibition of any anthropogenic activities at Spasskaya Gora will lead to loss of diversity of steppe assemblages over the mid-term. We emphasize that conservation of the high plant diversity of the Kungur forest-steppe must include disturbance factors in the form of selective lumbering, prescribed burning, moderate grazing or traditional mowing