TY - JOUR A1 - Zhilich, Snezhana A1 - Rudaya, Natalia A1 - Krivonogov, Sergei A1 - Nazarova, Larisa B. A1 - Pozdnyakov, Dmitry T1 - Environmental dynamics of the Baraba forest-steppe (Siberia) over the last 8000 years and their impact on the types of economic life of the population JF - Quaternary science reviews : the international multidisciplinary research and review journal N2 - This article offers a reconstruction of the vegetation and climate of the south-western Siberian Baraba forest-steppe area during the last ca. 8000 years. The analysis of palynological data from the sediment core of Lake Bolshie Toroki using quantitative methods has made it possible to reconstruct changes of the dominant types of vegetation and mean July air temperatures. Coniferous forests grew in the vicinity of the lake, and mean July air temperatures were similar to present-day ones between 7.9 and 7.0 kyr BP. The warmest and driest climate occurred at 7.0-5.0 kyr BP. At that time, the region had open steppe landscapes; birch groves began to spread. A cooling trend is seen after 5.5 kyr BP, when forest-steppe began to emerge. Steppe communities started to dominate again after 1.5 kyr BP. Mean July air temperatures lower than now are reconstructed for the period of 1.9-1 kyr BP, and then the temperatures became similar to present-day ones. Comparing the archaeological data on the types of economy of the population which inhabited the Baraba forest-steppe with the data on changes in the natural environment revealed a connection between the gradual transition from hunting and fishing to livestock breeding and the development of forest-steppe landscapes with a decrease in the area covered by forests. The development of the forest-steppe as an ecotonic landscape starting around 5 kyr BP might have contributed to the coexistence of several archaeological cultures with different types of economy on the same territory. (C) 2017 Elsevier Ltd. All rights reserved. KW - Holocene KW - Climate dynamics KW - Russia KW - Vegetation dynamics KW - Baraba forest-steppe KW - Archaeology KW - Transfer function Y1 - 2017 U6 - https://doi.org/10.1016/j.quascirev.2017.03.022 SN - 0277-3791 VL - 163 SP - 152 EP - 161 PB - Elsevier CY - Oxford ER - TY - JOUR A1 - Zhang, Chengjun A1 - Zhang, Wanyi A1 - Feng, Zhaodong A1 - Mischke, Steffen A1 - Gao, Xiang A1 - Gao, Dou A1 - Sun, Feifei T1 - Holocene hydrological and climatic change on the northern Mongolian Plateau based on multi-proxy records from Lake Gun Nuur JF - Palaeogeography, palaeoclimatology, palaeoecology : an international journal for the geo-sciences N2 - A multi-proxy study including analyses of delta C-13(org) for the lake sediment core GN-02 and grain size, TOC. CaCO3 content, delta C-13(carb) and delta O-18(carb) of bulk carbonate, and the mineralogy of the parallel core GN-04 from Gun Nuur was performed to reconstruct the Holocene hydrology and climate on the northern Mongolian Plateau. The chronology was established using 40 C-14 dates of bulk organic matter in addition to nine previously published radiocarbon dates for core GN-02, and further five C-14 dates for the new core GN-04. A lake reservoir effect of 1060 C-14 years was determined as the intercept of the high-resolution GN-02 age-depth model at the modern sediment surface. The size of the reservoir effect is supported by the age of the core-top sample (1200 +/- 40 C-14 years) and the determined difference between a wood-derived radiocarbon age from the GN-02 core base and the age-model inferred age for bulk organic matter at the same stratigraphic level (1000 C-14 years). Low lake level and prevailing aeolian sediment deposition at Gun Nuur under dry conditions were recorded during the earliest Holocene (> 10,800-10,300 cal a BP). Gun Nuur expanded under significantly wetter conditions between 10,300 and 7000 cal a BP. Unstable climate conditions existed in the mid Holocene (7000-2500 cal a BP) and three periods of low lake-levels and significantly drier conditions were recorded between 7000-5700, 4100-3600 and 3000-2500 cal a BP. Intermediate lake levels were inferred for the intervening periods. Around 2500 cal a BP, the climate change and wetter conditions were established again. As a consequence, the lake level of Gun Nuur rose again due to higher effective moisture and the relatively wet present conditions were achieved ca. 1600 cal a BP. Our results suggest that the initial Holocene climate change on the northern Mongolian Plateau was not accompanied by a rapid increase in precipitation as on the Tibetan Plateau. The establishment of wetter conditions in northern Mongolia lagged behind the early Holocene moisture increase on the Tibetan Plateau by ca. 1000 years. Subsiding dry air in the north of the Tibetan Plateau resulted from the strengthened summer monsoon on the Tibetan Plateau during the period of maximum summer insolation and probably inhibited a significant precipitation increase in Mongolia. The significant moisture increase in the Gun Nuur region at ca. 10.3 cal ka BP is probably not related to the northward shift of the present summer monsoon boundary or the moisture delivery from the northern Atlantic through the westerlies. Instead, water from melting snow, ice and frozen ground and the generation of precipitation from the local recycling of moisture are discussed as possible moisture source for the early onset of wetter conditions on the Mongolian Plateau. KW - Multi-proxy record KW - Sediment geochemistry KW - Mineralogy KW - Paleohydrology KW - Holocene KW - Mongolia Y1 - 2012 U6 - https://doi.org/10.1016/j.palaeo.2012.01.032 SN - 0031-0182 VL - 323 IS - 6 SP - 75 EP - 86 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Wang, Yongbo A1 - Herzschuh, Ulrike T1 - Reassessment of Holocene vegetation change on the upper Tibetan Plateau using the pollen-based REVEALS model JF - Review of palaeobotany and palynology : an international journal N2 - Previous studies based on fossil pollen data have reported significant changes in vegetation on the alpine Tibetan Plateau during the Holocene. However, since the relative proportions of fossil pollen taxa are largely influenced by individual pollen productivities and the dispersal characteristics, such inferences on vegetation have the potential to be considerably biased. We therefore examined the modern pollen-vegetation relationships for four common pollen species on the Tibetan Plateau, using Extended R-value (ERV) models. Assuming an average radius of 100 m for the sampled lakes, we estimated the relevant source area of pollen (RSAP) to be 2200 m (which represents the distance from the lake). Using Poaceae as the reference taxa (Pollen Productivity Estimate, PPE = 1), ERV Submodel 2 derived relative high PPEs for the steppe and desert taxa: 2.079 +/- 0.432 for Artemisia and 5.379 +/- 1.077 for Chenopodiaceae. Low PPEs were estimated for the Cyperaceae (1.036 +/- 0.012). whose plants are characteristic of the alpine Kobresia meadows. Applying these PPEs to four fossil pollen sequences since the Late Glacial, the plant abundances on the central and north-eastern Tibetan Plateau were quantified using the "Regional Estimates of Vegetation Abundance from Large Sites" (REVEALS) model. The proportions of Artemisia and Chenopodiaceae were greatly reduced compared to their original pollen percentages in the reconstructed vegetation, owing to their high productivities and their dispersal characteristics, while Cyperaceae showed a relative increase in the vegetation reconstruction. The reconstructed vegetation assemblages of the four pollen sequence sites always yielded smaller compositional species turnovers than suggested by the pollen spectra, as revealed by Detrended Canonical Correspondence Analyses (DCCA) of the Holocene sections. The strength of the previously reported vegetation changes may therefore have been overestimated, which indicates the importance of taking into account pollen-vegetation relationships when discussing the potential drivers (such as climate, land use, atmospheric CO(2) concentrations) and implications (such as for land surface-climate feedbacks, carbon storage, and biodiversity) of vegetation change. KW - pollen productivity KW - vegetation reconstruction KW - ERV model KW - REVEALS model KW - Holocene KW - Tibetan Plateau Y1 - 2011 U6 - https://doi.org/10.1016/j.revpalbo.2011.09.004 SN - 0034-6667 VL - 168 IS - 1 SP - 31 EP - 40 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Wang, Yongbo A1 - Bekeschus, Benjamin A1 - Handorf, Doerthe A1 - Liu, Xingqi A1 - Dallmeyer, Anne A1 - Herzschuh, Ulrike T1 - Coherent tropical-subtropical Holocene see-saw moisture patterns in the Eastern Hemisphere monsoon systems JF - Quaternary science reviews : the international multidisciplinary research and review journal N2 - The concept of a Global Monsoon (GM) has been proposed based on modern precipitation observations, but its application over a wide range of temporal scales is still under debate. Here, we present a synthesis of 268 continental paleo-moisture records collected from monsoonal systems in the Eastern Hemisphere, including the East Asian Monsoon (EAsM), the Indian Monsoon (IM), the East African Monsoon (EAfM), and the Australian Monsoon (AuM) covering the last 18,000 years. The overall pattern of late Glacial to Holocene moisture change is consistent with those inferred from ice cores and marine records. With respect to the last 10,000 years (10 ka), i.e. a period that has high spatial coverage, a Fuzzy c-Means clustering analysis of the moisture index records together with "Xie-Beni" index reveals four clusters of our data set. The paleoclimatic meaning of each cluster is interpreted considering the temporal evolution and spatial distribution patterns. The major trend in the tropical AuM, EAfM, and IM regions is a gradual decrease in moisture conditions since the early Holocene. Moisture changes in the EAsM regions show maximum index values between 8 and 6 ka. However, records located in nearby subtropical areas, i.e. in regions not influenced by the intertropical convergence zone, show an opposite trend compared to the tropical monsoon regions (AuM, EAfM and IM), i.e. a gradual increase. Analyses of modern meteorological data reveal the same spatial patterns as in the paleoclimate records such that, in times of overall monsoon strengthening, lower precipitation rates are observed in the nearby subtropical areas. We explain this pattern as the effect of a strong monsoon circulation suppressing air uplift in nearby subtropical areas, and hence hindering precipitation. By analogy to the modern system, this would mean that during the early Holocene strong monsoon period, the intensified ascending airflows within the monsoon domains led to relatively weaker ascending or even descending airflows in the adjacent subtropical regions, resulting in a precipitation deficit compared to the late Holocene. Our conceptual model therefore integrates regionally contrasting moisture changes into the Global Monsoon hypothesis. (C) 2017 Elsevier Ltd. All rights reserved. KW - Global monsoon KW - Holocene KW - Eastern hemisphere KW - Moisture evolution Y1 - 2017 U6 - https://doi.org/10.1016/j.quascirev.2017.06.006 SN - 0277-3791 VL - 169 SP - 231 EP - 242 PB - Elsevier CY - Oxford ER - TY - JOUR A1 - Trauth, Martin H. A1 - Foerster, Verena A1 - Junginger, Annett A1 - Asrat, Asfawossen A1 - Lamb, Henry F. A1 - Schäbitz, Frank T1 - Abrupt or gradual? BT - Change point analysis of the late Pleistocene-Holocene climate record from Chew Bahir, southern Ethiopia JF - Quaternary research : an interdisciplinary journal N2 - We used a change point analysis on a late Pleistocene-Holocene lake-sediment record from the Chew Bahir basin in the southern Ethiopian Rift to determine the amplitude and duration of past climate transitions. The most dramatic changes occurred over 240 yr (from similar to 15,700 to 15,460 yr) during the onset of the African Humid Period (AHP), and over 990 yr (from similar to 4875 to 3885 yr) during its protracted termination. The AHP was interrupted by a distinct dry period coinciding with the high-latitude Younger Dryas stadial, which had an abrupt onset (less than similar to 100 yr) at similar to 13,260 yr and lasted until similar to 11,730 yr. Wet-dry-wet transitions prior to the AHP may reflect the high-latitude Dansgaard-Oeschger cycles, as indicated by cross-correlation of the potassium record with the NorthGRIP ice core record between similar to 45-20 ka. These findings may contribute to the debates regarding the amplitude, and duration and mechanisms of past climate transitions, and their possible influence on the development of early modern human cultures. KW - Late Pleistocene KW - Holocene KW - Change point analysis KW - Principal component analysis KW - Paleoclimatology KW - Southern Ethiopian Rift KW - African Humid Period KW - Younger Dryas KW - Dansgaard-Oeschger cycles Y1 - 2018 U6 - https://doi.org/10.1017/qua.2018.30 SN - 0033-5894 SN - 1096-0287 VL - 90 IS - 2 SP - 321 EP - 330 PB - Cambridge Univ. Press CY - New York ER - TY - JOUR A1 - Trauth, Martin H. A1 - Asrat, Asfawossen A1 - Düsing, Walter A1 - Foerster, Verena A1 - Krämer, K. Hauke A1 - Marwan, Norbert A1 - Maslin, Mark A. A1 - Schäbitz, Frank T1 - Classifying past climate change in the Chew Bahir basin, southern Ethiopia, using recurrence quantification analysis JF - Climate dynamics : observational, theoretical and computational research on the climate system N2 - The Chew Bahir Drilling Project (CBDP) aims to test possible linkages between climate and evolution in Africa through the analysis of sediment cores that have recorded environmental changes in the Chew Bahir basin. In this statistical project we consider the Chew Bahir palaeolake to be a dynamical system consisting of interactions between its different components, such as the waterbody, the sediment beneath lake, and the organisms living within and around the lake. Recurrence is a common feature of such dynamical systems, with recurring patterns in the state of the system reflecting typical influences. Identifying and defining these influences contributes significantly to our understanding of the dynamics of the system. Different recurring changes in precipitation, evaporation, and wind speed in the Chew Bahir basin could result in similar (but not identical) conditions in the lake (e.g., depth and area of the lake, alkalinity and salinity of the lake water, species assemblages in the water body, and diagenesis in the sediments). Recurrence plots (RPs) are graphic displays of such recurring states within a system. Measures of complexity were subsequently introduced to complement the visual inspection of recurrence plots, and provide quantitative descriptions for use in recurrence quantification analysis (RQA). We present and discuss herein results from an RQA on the environmental record from six short (< 17 m) sediment cores collected during the CBDP, spanning the last 45 kyrs. The different types of variability and transitions in these records were classified to improve our understanding of the response of the biosphere to climate change, and especially the response of humans in the area. KW - Paleoclimate dynamics KW - Eastern Africa KW - Pleistocene KW - Holocene KW - Time-series analysis KW - Recurrence plot Y1 - 2019 U6 - https://doi.org/10.1007/s00382-019-04641-3 SN - 0930-7575 SN - 1432-0894 VL - 53 IS - 5-6 SP - 2557 EP - 2572 PB - Springer CY - New York ER - TY - JOUR A1 - Tian, Fang A1 - Cao, Xianyong A1 - Dallmeyer, Anne A1 - Zhao, Yan A1 - Ni, Jian A1 - Herzschuh, Ulrike T1 - Pollen-climate relationships in time (9 ka, 6 ka, 0 ka) and space (upland vs. lowland) in eastern continental Asia JF - Quaternary science reviews : the international multidisciplinary research and review journal N2 - Temporal and spatial stability of the vegetation climate relationship is a basic ecological assumption for pollen-based quantitative inferences of past climate change and for predicting future vegetation. We explore this assumption for the Holocene in eastern continental Asia (China, Mongolia). Boosted regression trees (BRT) between fossil pollen taxa percentages (Abies, Artemisia, Betula, Chenopodiaceae, Cyperaceae, Ephedra, Picea, Pinus, Poaceae and Quercus) and climate model outputs of mean annual precipitation (P-ann) and mean temperature of the warmest month (Mt(wa)) for 9 and 6 ka (ka = thousand years before present) were set up and results compared to those obtained from relating modern pollen to modern climate. Overall, our results reveal only slight temporal differences in the pollen climate relationships. Our analyses suggest that the importance of P-ann compared with Mt(wa) for taxa distribution is higher today than it was at 6 ka and 9 ka. In particular, the relevance of P-ann for Picea and Pinus increases and has become the main determinant. This change in the climate tree pollen relationship parallels a widespread tree pollen decrease in north-central China and the eastern Tibetan Plateau. We assume that this is at least partly related to vegetation climate disequilibrium originating from human impact. Increased atmospheric CO2 concentration may have permitted the expansion of moisture-loving herb taxa (Cyperaceae and Poaceae) during the late Holocene into arid/semi-arid areas. We furthermore find that the pollen climate relationship between north-central China and the eastern Tibetan Plateau is generally similar, but that regional differences are larger than temporal differences. In summary, vegetation climate relationships in China are generally stable in space and time, and pollen-based climate reconstructions can be applied to the Holocene. Regional differences imply the calibration-set should be restricted spatially. KW - Boosted regression trees KW - China KW - Holocene KW - Niche stability KW - Pollen-climate relationship KW - Uniformitarianism Y1 - 2016 U6 - https://doi.org/10.1016/j.quascirev.2016.11.027 SN - 0277-3791 VL - 156 SP - 1 EP - 11 PB - Elsevier CY - Oxford ER - TY - JOUR A1 - Syrykh, Lydmila S. A1 - Nazarova, Larisa B. A1 - Herzschuh, Ulrike A1 - Subetto, D. A. A1 - Grekov, I. M. T1 - Reconstruction of palaeoecological and palaeoclimatic conditions of the Holocene in the south of the Taimyr according to an analysis of lake sediments JF - Contemporary Problems of Ecology N2 - A sediment core from Khatanga-12 Lake (Taimyr Peninsula, Krasnoyarsk krai) has been studied. The 131.5-cm-long core covers ca. 7100 years of sedimentation. Chironomid analysis, a qualitative reconstruction of the paleoenvironment in the region, and a quantitative reconstruction of variations of the mean July air temperature and in the water depth of the lake have been performed using Northern Russia chironomid-inferred mean July temperature models (Nazarova et al., 2008, 2011, 2015). Khatanga-12 Lake was formed during the Middle Holocene warming as a result of thermokarst processes. The development of the lake ecosystem at different stages of its development was influenced by climatic and cryolithogenic factors. The Middle Holocene warming, which occurred around 7100-6250 cal. years BP, activated thermokarst processes and resulted in the formation of the lake basin. Later, between 6250 and 4500 cal. years BP, a period of cooling took place, as is proved by chironomid analysis. The bottom sediments of the lake during this period were formed by erosion processes on the lake shores. The reconstructed conditions were close to the modern after 2500 cal. years BP. KW - Chironomidae KW - paleolimnology KW - Holocene KW - climate reconstructions KW - Russian Arctic region KW - Khatanga Y1 - 2017 U6 - https://doi.org/10.1134/S1995425517040114 SN - 1995-4255 SN - 1995-4263 VL - 10 SP - 363 EP - 369 PB - Pleiades Publ. CY - New York ER - TY - JOUR A1 - Savi, Sara A1 - Delunel, Romain A1 - Schlunegger, Fritz T1 - Efficiency of frost-cracking processes through space and time: An example from the eastern Italian Alps JF - Geomorphology : an international journal on pure and applied geomorphology N2 - It is widely accepted that climate has a strong impact and exerts important feedbacks on erosional processes and sediment transport mechanisms. However, the extent at which climate influences erosion is still a matter of debate. In this paper we test whether frost-cracking processes and related temperature variations can influence the sediment production and surface erosion in a small catchment situated in the eastern Italian Alps. To this extent, we first present a geomorphic map of the region that we complement with published Be-10-based denudation rates. We then apply a preexisting heat-flow model in order to analyze the variations of the frost-cracking intensity (FCI) in the study area, which could have controlled the sediment production in the basin. Finally, we compare the model results with the pattern of denudation rates and Quaternary deposits in the geomorphic map. The model results, combined with field observations, mapping, and quantitative geomorphic analyses, reveal that frost-cracking processes have had a primary role in the production of sediment where the intensity of sediment supply has been dictated and limited by the combined effect of temperature variations and conditions of bedrock preservation. These results highlight the importance of a yet poorly understood process for the production of sediment in mountain areas. (C) 2015 Elsevier B.V. All rights reserved. KW - Frost-cracking KW - Sediment production KW - Sediment supply KW - Spatial and temporal denudation rate KW - Climatic variations KW - Holocene Y1 - 2015 U6 - https://doi.org/10.1016/j.geomorph.2015.01.009 SN - 0169-555X SN - 1872-695X VL - 232 SP - 248 EP - 260 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Sarkar, Saswati A1 - Prasad, Sushma A1 - Wilkes, Heinz A1 - Riedel, Nils A1 - Stebich, Martina A1 - Basavaiah, Nathani A1 - Sachse, Dirk T1 - Monsoon source shifts during the drying mid-Holocene: Biomarker isotope based evidence from the core 'monsoon zone' (CMZ) of India JF - Quaternary science reviews : the international multidisciplinary research and review journal N2 - A better understanding of past variations of the Indian Summer Monsoon (ISM), that plays a vital role for the still largely agro-based economy in India, can lead to a better assessment of its potential impact under global climate change scenarios. However, our knowledge of spatiotemporal patterns of ISM strength is limited due to the lack of high-resolution, continental paleohydrological records. Here, we reconstruct centennial-scale hydrological variability during the Holocene associated to changes in the intensity of the ISM based on a record of lipid biomarker abundances and compound-specific stable isotopic composition of a 10 m long sediment core from saline alkaline Lonar Lake, situated in the core 'monsoon zone' of central India. We identified three main periods of distinct hydrology during the Holocene in central India. The period between 10.1 and 6 cal ka BP was likely the wettest during the Holocene. Lower average chain length (ACL) index values (29.4-28.6) and negative delta C-13(wax) values (-34.8 parts per thousand to -27.8 parts per thousand) of leaf wax n-alkanes indicate the dominance of woody C-3 vegetation in the catchment, and negative delta D-wax values (concentration weighted average) (-171 parts per thousand to -147 parts per thousand) suggest a wet period due to an intensified monsoon. After 6 cal ka BP, a gradual shift to less negative delta C-13(wax) values (particularly for the grass derived n-C-31) and appearance of the triterpene lipid tetrahymanol, generally considered as a marker for salinity and water column stratification, mark the onset of drier conditions. At 5.1 cal ka BP an increasing flux of leaf wax n-alkanes along with the highest flux of tetrahymanol indicate a major lowering of the lake level. Between 4.8 and 4 cal ka BP, we find evidence for a transition to arid conditions, indicated by high and strongly variable tetrahymanol flux. In addition, a pronounced shift to less negative delta C-13(wax) values, in particular for n-C-31 (-25.2 parts per thousand to -22.8 parts per thousand), during this period indicates a change of dominant vegetation to C-4 grasses. In agreement with other proxy data, such as deposition of evaporite minerals, we interpret this period to reflect the driest conditions in the region during the last 10.1 ka. This transition led to protracted late Holocene arid conditions after 4 ka with the presence of a permanent saline lake, supported by the sustained presence of tetrahymanol and more positive average delta D-wax values (-122 parts per thousand to -141 parts per thousand). A late Holocene peak of cyanobacterial biomarker input at 1.3 cal ka BP might represent an event of lake eutrophication, possibly due to human impact and the onset of cattle/livestock farming in the catchment. A unique feature of our record is the presence of a distinct transitional period between 4.8 and 4 cal ka BP, which was characterized by some of the most negative delta D-wax values during the Holocene (up to -180 parts per thousand), when all other proxy data indicate the driest conditions during the Holocene. These negative delta D-wax values can as such most reasonably be explained by a shift in moisture source area and/or pathways or rainfall seasonality during this transitional period. We hypothesize that orbital induced weakening of the summer solar insolation and associated reorganization of the general atmospheric circulation, as a possible southward displacement of the tropical rainbelt, led to an unstable hydroclimate in central India between 4.8 and 4 ka. KW - Indian Summer Monsoon KW - Holocene KW - Lonar Lake KW - Lipid biomarkers KW - Compound-specific stable isotopic KW - composition Y1 - 2015 U6 - https://doi.org/10.1016/j.quascirev.2015.06.020 SN - 0277-3791 VL - 123 SP - 144 EP - 157 PB - Elsevier CY - Oxford ER -