@article{MuellerTjallingiiPlocienniketal.2021, author = {M{\"u}ller, Daniela and Tjallingii, Rik and Plociennik, Mateusz and Luoto, Tomi P. and Kotrys, Bartosz and Plessen, Birgit and Ramisch, Arne and Schwab, Markus Julius and Blaszkiewicz, Miroslaw and Slowinski, Michal and Brauer, Achim}, title = {New insights into lake responses to rapid climate change}, series = {Boreas}, volume = {50}, journal = {Boreas}, number = {2}, publisher = {Wiley}, address = {Hoboken}, issn = {0300-9483}, doi = {10.23689/fidgeo-4033}, pages = {535 -- 555}, year = {2021}, abstract = {The sediment profile from Lake Goscia(z) over dot in central Poland comprises a continuous, seasonally resolved and exceptionally well-preserved archive of the Younger Dryas (YD) climate variation. This provides a unique opportunity for detailed investigation of lake system responses during periods of rapid climate cooling (YD onset) and warming (YD termination). The new varve record of Lake Goscia(z) over dot presented here spans 1662 years from the late Allerod (AL) to the early Preboreal (PB). Microscopic varve counting provides an independent chronology with a YD duration of 1149+14/-22 years, which confirms previous results of 1140 +/- 40 years. We link stable oxygen isotopes and chironomid-based air temperature reconstructions with the response of various geochemical and varve microfacies proxies especially focusing on the onset and termination of the YD. Cooling at the YD onset lasted similar to 180 years, which is about a century longer than the terminal warming that was completed in similar to 70 years. During the AL/YD transition, environmental proxy data lagged the onset of cooling by similar to 90 years and revealed an increase of lake productivity and internal lake re-suspension as well as slightly higher detrital sediment input. In contrast, rapid warming and environmental changes during the YD/PB transition occurred simultaneously. However, initial changes such as declining diatom deposition and detrital input occurred already a few centuries before the rapid warming at the YD/PB transition. These environmental changes likely reflect a gradual increase in summer air temperatures already during the YD. Our data indicate complex and differing environmental responses to the major climate changes related to the YD, which involve different proxy sensitivities and threshold processes.}, language = {en} } @article{HeineckeFletcherMischkeetal.2018, author = {Heinecke, Liv and Fletcher, W. J. and Mischke, Steffen and Tian, Fang and Herzschuh, Ulrike}, title = {Vegetation change in the eastern Pamir Mountains, Tajikistan, inferred from Lake Karakul pollen spectra of the last 28 kyr}, series = {Palaeogeography, palaeoclimatology, palaeoecology : an international journal for the geo-sciences}, volume = {511}, journal = {Palaeogeography, palaeoclimatology, palaeoecology : an international journal for the geo-sciences}, publisher = {Elsevier}, address = {Amsterdam}, issn = {0031-0182}, doi = {10.1016/j.palaeo.2018.08.010}, pages = {232 -- 242}, year = {2018}, abstract = {We present a pollen record for last 28 cal kyr BP from the eastern basin of Lake Karakul, the largest lake in Tajikistan, located in the eastern Pamir Mountains at 3915 m asl, a geographically complex region. The pollen record is dominated by Artemisia and Chenopodiaceae, while other taxa, apart from Poaceae, are present in low quantities and rarely exceed 5\% in total. Arboreal pollen occur predominantly from similar to 28 to similar to 13 cal kyr BP, but as likely no trees occurred in the high mountain regions of the eastern Pamir during this time due to the high altitude and cold climate, arboreal taxa are attributed to long distance transport, probably by the Westerlies, the dominant atmospheric circulation. Tree pollen influx decreases strongly after similar to 13 cal kyr BP, allowing the pollen spectra to be interpreted as a regional vegetation signal. We infer that from 27.6 to 19.4 cal kyr BP the eastern Pamir was dominated by dry mountain steppe with low vegetation cover, while from 19.0 to 13.6 cal kyr BP Artemisia values increase and Chenopodiaceae, most herb taxa, and inferred far distant input from arboreal taxa decrease. Between 12.9 and 6.7 cal kyr BP open steppe vegetation dominated with maximum values in Ephedra, and while steppe taxa still dominated the spectra from 5.4 to 1 cal kyr BP, meadow taxa start to increase. During the last millennium, alpine steppe and alpine meadows expanded and a weak human influence can be ascertained from the increase of Asteraceae and the occurrence of Plantago pollen in the spectra.}, language = {en} } @article{LauterbachWittPlessenetal.2014, author = {Lauterbach, Stefan and Witt, Roman and Plessen, Birgit and Dulski, Peter and Prasad, Sushma and Mingram, Jens and Gleixner, Gerd and Hettler-Riedel, Sabine and Stebich, Martina and Schnetger, Bernhard and Schwalb, Antje and Schwarz, Anja}, title = {Climatic imprint of the mid-latitude Westerlies in the Central Tian Shan of Kyrgyzstan and teleconnections to North Atlantic climate variability during the last 6000 years}, series = {The Holocene : an interdisciplinary journal focusing on recent environmental change}, volume = {24}, journal = {The Holocene : an interdisciplinary journal focusing on recent environmental change}, number = {8}, publisher = {Sage Publ.}, address = {London}, issn = {0959-6836}, doi = {10.1177/0959683614534741}, pages = {970 -- 984}, year = {2014}, abstract = {In general, a moderate drying trend is observed in mid-latitude arid Central Asia since the Mid-Holocene, attributed to the progressively weakening influence of the mid-latitude Westerlies on regional climate. However, as the spatio-temporal pattern of this development and the underlying climatic mechanisms are yet not fully understood, new high-resolution paleoclimate records from this region are needed. Within this study, a sediment core from Lake Son Kol (Central Kyrgyzstan) was investigated using sedimentological, (bio) geochemical, isotopic, and palynological analyses, aiming at reconstructing regional climate development during the last 6000 years. Biogeochemical data, mainly reflecting summer moisture conditions, indicate predominantly wet conditions until 4950 cal. yr BP, succeeded by a pronounced dry interval between 4950 and 3900 cal. yr BP. In the following, a return to wet conditions and a subsequent moderate drying trend until present times are observed. This is consistent with other regional paleoclimate records and likely reflects the gradual Late Holocene diminishment of the amount of summer moisture provided by the mid-latitude Westerlies. However, climate impact of the Westerlies was apparently not only restricted to the summer season but also significant during winter as indicated by recurrent episodes of enhanced allochthonous input through snowmelt, occurring before 6000 cal. yr BP and at 5100-4350, 3450-2850, and 1900-1500 cal. yr BP. The distinct similar to 1500year periodicity of these episodes of increased winter precipitation in Central Kyrgyzstan resembles similar cyclicities observed in paleoclimate records around the North Atlantic, likely indicating a hemispheric-scale climatic teleconnection and an impact of North Atlantic Oscillation (NAO) variability in Central Asia.}, language = {en} } @article{MishratAnoopJehangiretal.2014, author = {Mishrat, Praveen K. and Anoop, A. and Jehangir, A. and Prasad, Sushma and Menze, R. and Schettler, Georg and Naumann, R. and Weise, S. and Andersen, N. and Yousuf, A. R. and Gaye, Birgit}, title = {Limnology and modern sedimentation patterns in high altitude Tso Moriri Lake, NW Himalaya - implications for proxy development}, series = {Fundamental and applied limnology : official journal of the International Association of Theoretical and Applied Limnology}, volume = {185}, journal = {Fundamental and applied limnology : official journal of the International Association of Theoretical and Applied Limnology}, number = {3-4}, publisher = {Schweizerbart}, address = {Stuttgart}, issn = {1863-9135}, doi = {10.1127/fal/2014/0664}, pages = {329 -- 348}, year = {2014}, abstract = {We report the results of our investigations on the catchment area, lake surface sediments, and hydrology of the high altitude alpine Tso Moriri Lake, NW Himalayas (India). Our results indicate that the lake is currently alkaline, and thermally stratified with an oxic bottom layer. Results from hydrochemistry and isotopic composition (delta O-18 and delta D) of inflowing streams and lake waters show that Tso Moriri Lake is an evaporative lake with contributions from both westerly source (snow melt) and Indian summer monsoon precipitation. Geochemical and mineralogical investigations on the catchment and lake surface sediments reveal the presence of authigenic aragonite in modern lake sediment. The lithogenic components reflect the inflow and sorting processes during transport into the lake, whereas the authigenic carbonate fraction can be linked to the changes in ([precipitation+meltwater]/evaporation) (I/E) balance within the lake. The spatial variability in grain size distribution within the lake surface sediments shows that the grain size data can be utilised as a proxy for transport energy and shoreline proximity in the lake basin. We have evaluated the applicability of commonly applied environmentally sensitive proxies (isotopes, mineralogy, weathering indices) for palaeoenvironmental reconstruction in the Tso Moriri Lake. Our results show that the commonly used weathering index (Rb/Sr) is not applicable due to Sr contribution from authigenic carbonates. The useful weathering indices in Tso Moriri Lake are the Si/Al and the Chemical Proxy of Alteration (CPA). Since the carbonates are formed by evaporative processes, their presence and isotopic values can be used as indicators of I/E changes in the lake.}, language = {en} } @article{EppStoofLeichsenringTrauthetal.2011, author = {Epp, Laura Saskia and Stoof-Leichsenring, Kathleen Rosemarie and Trauth, Martin H. and Tiedemann, Ralph}, title = {Molecular profiling of diatom assemblages in tropical lake sediments using taxon-specific PCR and Denaturing High-Performance Liquid Chromatography (PCR-DHPLC)}, series = {Molecular ecology resources}, volume = {11}, journal = {Molecular ecology resources}, number = {5}, publisher = {Wiley-Blackwell}, address = {Hoboken}, issn = {1755-098X}, doi = {10.1111/j.1755-0998.2011.03022.x}, pages = {842 -- 853}, year = {2011}, abstract = {Here we present a protocol to genetically detect diatoms in sediments of the Kenyan tropical Lake Naivasha, based on taxon-specific PCR amplification of short fragments (approximately 100 bp) of the small subunit ribosomal (SSU) gene and subsequent separation of species-specific PCR products by PCR-based denaturing high-performance liquid chromatography (DHPLC). An evaluation of amplicons differing in primer specificity to diatoms and length of the fragments amplified demonstrated that the number of different diatom sequence types detected after cloning of the PCR products critically depended on the specificity of the primers to diatoms and the length of the amplified fragments whereby shorter fragments yielded more species of diatoms. The DHPLC was able to discriminate between very short amplicons based on the sequence difference, even if the fragments were of identical length and if the amplicons differed only in a small number of nucleotides. Generally, the method identified the dominant sequence types from mixed amplifications. A comparison with microscopic analysis of the sediment samples revealed that the sequence types identified in the molecular assessment corresponded well with the most dominant species. In summary, the PCR-based DHPLC protocol offers a fast, reliable and cost-efficient possibility to study DNA from sediments and other environmental samples with unknown organismic content, even for very short DNA fragments.}, language = {en} }