TY  - JOUR
A1  - Krüger, Johanna
A1  - Foerster, Verena Elisabeth
A1  - Trauth, Martin H.
A1  - Hofreiter, Michael
A1  - Tiedemann, Ralph
T1  - Exploring the Past Biosphere of Chew Bahir/Southern Ethiopia: Cross-Species Hybridization Capture of Ancient Sedimentary DNA from a Deep Drill Core
JF  - Frontiers in Earth Science
N2  - Eastern Africa has been a prime target for scientific drilling because it is rich in key paleoanthropological sites as well as in paleolakes, containing valuable paleoclimatic information on evolutionary time scales. The Hominin Sites and Paleolakes Drilling Project (HSPDP) explores these paleolakes with the aim of reconstructing environmental conditions around critical episodes of hominin evolution. Identification of biological taxa based on their sedimentary ancient DNA (sedaDNA) traces can contribute to understand past ecological and climatological conditions of the living environment of our ancestors. However, sedaDNA recovery from tropical environments is challenging because high temperatures, UV irradiation, and desiccation result in highly degraded DNA. Consequently, most of the DNA fragments in tropical sediments are too short for PCR amplification. We analyzed sedaDNA in the upper 70 m of the composite sediment core of the HSPDP drill site at Chew Bahir for eukaryotic remnants. We first tested shotgun high throughput sequencing which leads to metagenomes dominated by bacterial DNA of the deep biosphere, while only a small fraction was derived from eukaryotic, and thus probably ancient, DNA. Subsequently, we performed cross-species hybridization capture of sedaDNA to enrich ancient DNA (aDNA) from eukaryotic remnants for paleoenvironmental analysis, using established barcoding genes (cox1 and rbcL for animals and plants, respectively) from 199 species that may have had relatives in the past biosphere at Chew Bahir. Metagenomes yielded after hybridization capture are richer in reads with similarity to cox1 and rbcL in comparison to metagenomes without prior hybridization capture. Taxonomic assignments of the reads from these hybridization capture metagenomes also yielded larger fractions of the eukaryotic domain. For reads assigned to cox1, inferred wet periods were associated with high inferred relative abundances of putative limnic organisms (gastropods, green algae), while inferred dry periods showed increased relative abundances for insects. These findings indicate that cross-species hybridization capture can be an effective approach to enhance the information content of sedaDNA in order to explore biosphere changes associated with past environmental conditions, enabling such analyses even under tropical conditions.
KW  - Chew Bahir
KW  - hybridization capture
KW  - ICDP
KW  - paleoclimate
KW  - past biosphere
KW  - sedaDNA
KW  - sediment core
Y1  - 2021
U6  - https://doi.org/10.3389/feart.2021.683010
SN  - 2296-6463
SP  - 1
EP  - 20
PB  - Frontiers in Earth Science
CY  - Lausanne, Schweiz
ER  - 
TY  - GEN
A1  - Krüger, Johanna
A1  - Foerster, Verena Elisabeth
A1  - Trauth, Martin H.
A1  - Hofreiter, Michael
A1  - Tiedemann, Ralph
T1  - Exploring the Past Biosphere of Chew Bahir/Southern Ethiopia: Cross-Species Hybridization Capture of Ancient Sedimentary DNA from a Deep Drill Core
T2  - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe
N2  - Eastern Africa has been a prime target for scientific drilling because it is rich in key paleoanthropological sites as well as in paleolakes, containing valuable paleoclimatic information on evolutionary time scales. The Hominin Sites and Paleolakes Drilling Project (HSPDP) explores these paleolakes with the aim of reconstructing environmental conditions around critical episodes of hominin evolution. Identification of biological taxa based on their sedimentary ancient DNA (sedaDNA) traces can contribute to understand past ecological and climatological conditions of the living environment of our ancestors. However, sedaDNA recovery from tropical environments is challenging because high temperatures, UV irradiation, and desiccation result in highly degraded DNA. Consequently, most of the DNA fragments in tropical sediments are too short for PCR amplification. We analyzed sedaDNA in the upper 70 m of the composite sediment core of the HSPDP drill site at Chew Bahir for eukaryotic remnants. We first tested shotgun high throughput sequencing which leads to metagenomes dominated by bacterial DNA of the deep biosphere, while only a small fraction was derived from eukaryotic, and thus probably ancient, DNA. Subsequently, we performed cross-species hybridization capture of sedaDNA to enrich ancient DNA (aDNA) from eukaryotic remnants for paleoenvironmental analysis, using established barcoding genes (cox1 and rbcL for animals and plants, respectively) from 199 species that may have had relatives in the past biosphere at Chew Bahir. Metagenomes yielded after hybridization capture are richer in reads with similarity to cox1 and rbcL in comparison to metagenomes without prior hybridization capture. Taxonomic assignments of the reads from these hybridization capture metagenomes also yielded larger fractions of the eukaryotic domain. For reads assigned to cox1, inferred wet periods were associated with high inferred relative abundances of putative limnic organisms (gastropods, green algae), while inferred dry periods showed increased relative abundances for insects. These findings indicate that cross-species hybridization capture can be an effective approach to enhance the information content of sedaDNA in order to explore biosphere changes associated with past environmental conditions, enabling such analyses even under tropical conditions.
T3  - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 1244 
KW  - Chew Bahir
KW  - hybridization capture
KW  - ICDP
KW  - paleoclimate
KW  - past biosphere
KW  - sedaDNA
KW  - sediment core
Y1  - 2022
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-550071
SN  - 1866-8372
SP  - 1
EP  - 20
PB  - Universitätsverlag Potsdam
CY  - Potsdam
ER  - 
TY  - JOUR
A1  - Owen, Richard Bernhart
A1  - Muiruri, Veronica M.
A1  - Lowenstein, Tim K.
A1  - Renaut, Robin W.
A1  - Rabideaux, Nathan
A1  - Luo, Shangde
A1  - Deino, Alan L.
A1  - Sier, Mark J.
A1  - Dupont-Nivet, Guillaume
A1  - McNulty, Emma P.
A1  - Leet, Kennie
A1  - Cohen, Andrew
A1  - Campisano, Christopher
A1  - Deocampo, Daniel
A1  - Shen, Chuan-Chou
A1  - Billingsley, Anne
A1  - Mbuthia, Anthony
T1  - Progressive aridification in East Africa over the last half million years and implications for human evolution
JF  - Proceedings of the National Academy of Sciences of the United States of America
N2  - Evidence for Quaternary climate change in East Africa has been derived from outcrops on land and lake cores and from marine dust, leaf wax, and pollen records. These data have previously been used to evaluate the impact of climate change on hominin evolution, but correlations have proved to be difficult, given poor data continuity and the great distances between marine cores and terrestrial basins where fossil evidence is located. Here, we present continental coring evidence for progressive aridification since about 575 thousand years before present (ka), based on Lake Magadi (Kenya) sediments. This long-term drying trend was interrupted by many wet-dry cycles, with the greatest variability developing during times of high eccentricity-modulated precession. Intense aridification apparent in the Magadi record took place between 525 and 400 ka, with relatively persistent arid conditions after 350 ka and through to the present. Arid conditions in the Magadi Basin coincide with the Mid-Brunhes Event and overlap with mammalian extinctions in the South Kenya Rift between 500 and 400 ka. The 525 to 400 ka arid phase developed in the South Kenya Rift between the period when the last Acheulean tools are reported (at about 500 ka) and before the appearance of Middle Stone Age artifacts (by about 320 ka). Our data suggest that increasing Middle- to Late-Pleistocene aridification and environmental variability may have been drivers in the physical and cultural evolution of Homo sapiens in East Africa.
KW  - Quaternary
KW  - paleoclimate
KW  - paleolimnology
KW  - hominins
KW  - Lake Magadi
Y1  - 2018
U6  - https://doi.org/10.1073/pnas.1801357115
SN  - 0027-8424
SN  - 1091-6490
VL  - 115
IS  - 44
SP  - 11174
EP  - 11179
PB  - National Academy of Sciences
CY  - Washington
ER  - 
TY  - JOUR
A1  - Khider, D.
A1  - Emile-Geay, J.
A1  - McKay, N. P.
A1  - Gil, Y.
A1  - Garijo, D.
A1  - Ratnakar, V
A1  - Alonso-Garcia, M.
A1  - Bertrand, S.
A1  - Bothe, O.
A1  - Brewer, P.
A1  - Bunn, A.
A1  - Chevalier, M.
A1  - Comas-Bru, L.
A1  - Csank, A.
A1  - Dassie, E.
A1  - DeLong, K.
A1  - Felis, T.
A1  - Francus, P.
A1  - Frappier, A.
A1  - Gray, W.
A1  - Goring, S.
A1  - Jonkers, L.
A1  - Kahle, M.
A1  - Kaufman, D.
A1  - Kehrwald, N. M.
A1  - Martrat, B.
A1  - McGregor, H.
A1  - Richey, J.
A1  - Schmittner, A.
A1  - Scroxton, N.
A1  - Sutherland, E.
A1  - Thirumalai, Kaustubh
A1  - Allen, K.
A1  - Arnaud, F.
A1  - Axford, Y.
A1  - Barrows, T.
A1  - Bazin, L.
A1  - Birch, S. E. Pilaar
A1  - Bradley, E.
A1  - Bregy, J.
A1  - Capron, E.
A1  - Cartapanis, O.
A1  - Chiang, H-W
A1  - Cobb, K. M.
A1  - Debret, M.
A1  - Dommain, Réne
A1  - Du, J.
A1  - Dyez, K.
A1  - Emerick, S.
A1  - Erb, M. P.
A1  - Falster, G.
A1  - Finsinger, W.
A1  - Fortier, D.
A1  - Gauthier, Nicolas
A1  - George, S.
A1  - Grimm, E.
A1  - Hertzberg, J.
A1  - Hibbert, F.
A1  - Hillman, A.
A1  - Hobbs, W.
A1  - Huber, M.
A1  - Hughes, A. L. C.
A1  - Jaccard, S.
A1  - Ruan, J.
A1  - Kienast, M.
A1  - Konecky, B.
A1  - Le Roux, G.
A1  - Lyubchich, V
A1  - Novello, V. F.
A1  - Olaka, L.
A1  - Partin, J. W.
A1  - Pearce, C.
A1  - Phipps, S. J.
A1  - Pignol, C.
A1  - Piotrowska, N.
A1  - Poli, M-S
A1  - Prokopenko, A.
A1  - Schwanck, F.
A1  - Stepanek, C.
A1  - Swann, G. E. A.
A1  - Telford, R.
A1  - Thomas, E.
A1  - Thomas, Z.
A1  - Truebe, S.
A1  - von Gunten, L.
A1  - Waite, A.
A1  - Weitzel, N.
A1  - Wilhelm, B.
A1  - Williams, J.
A1  - Winstrup, M.
A1  - Zhao, N.
A1  - Zhou, Y.
T1  - PaCTS 1.0: A Crowdsourced Reporting Standard for Paleoclimate Data
JF  - Paleoceanography and paleoclimatology
N2  - The progress of science is tied to the standardization of measurements, instruments, and data. This is especially true in the Big Data age, where analyzing large data volumes critically hinges on the data being standardized. Accordingly, the lack of community-sanctioned data standards in paleoclimatology has largely precluded the benefits of Big Data advances in the field. Building upon recent efforts to standardize the format and terminology of paleoclimate data, this article describes the Paleoclimate Community reporTing Standard (PaCTS), a crowdsourced reporting standard for such data. PaCTS captures which information should be included when reporting paleoclimate data, with the goal of maximizing the reuse value of paleoclimate data sets, particularly for synthesis work and comparison to climate model simulations. Initiated by the LinkedEarth project, the process to elicit a reporting standard involved an international workshop in 2016, various forms of digital community engagement over the next few years, and grassroots working groups. Participants in this process identified important properties across paleoclimate archives, in addition to the reporting of uncertainties and chronologies; they also identified archive-specific properties and distinguished reporting standards for new versus legacy data sets. This work shows that at least 135 respondents overwhelmingly support a drastic increase in the amount of metadata accompanying paleoclimate data sets. Since such goals are at odds with present practices, we discuss a transparent path toward implementing or revising these recommendations in the near future, using both bottom-up and top-down approaches.
KW  - standards
KW  - FAIR
KW  - paleoclimate
KW  - paleoceanography
KW  - data
KW  - best practices
Y1  - 2019
U6  - https://doi.org/10.1029/2019PA003632
SN  - 2572-4517
SN  - 2572-4525
VL  - 34
IS  - 10
SP  - 1570
EP  - 1596
PB  - American Geophysical Union
CY  - Washington
ER  - 
TY  - JOUR
A1  - Aichner, Bernhard
A1  - Makhmudov, Zafar
A1  - Rajabov, Iljomjon
A1  - Zhang, Qiong
A1  - Pausata, Francesco Salvatore R.
A1  - Werner, Martin
A1  - Heinecke, Liv
A1  - Kuessner, Marie L.
A1  - Feakins, Sarah J.
A1  - Sachse, Dirk
A1  - Mischke, Steffen
T1  - Hydroclimate in the Pamirs Was Driven by Changes in Precipitation-Evaporation Seasonality Since theLast Glacial Period
JF  - Geophysical research letters
N2  - The Central Asian Pamir Mountains (Pamirs) are a high-altitude region sensitive to climatic change, with only few paleoclimatic records available. To examine the glacial-interglacial hydrological changes in the region, we analyzed the geochemical parameters of a 31-kyr record from Lake Karakul and performed a set of experiments with climate models to interpret the results. delta D values of terrestrial biomarkers showed insolation-driven trends reflecting major shifts of water vapor sources. For aquatic biomarkers, positive delta D shifts driven by changes in precipitation seasonality were observed at ca. 31-30, 28-26, and 17-14 kyr BP. Multiproxy paleoecological data and modelling results suggest that increased water availability, induced by decreased summer evaporation, triggered higher lake levels during those episodes, possibly synchronous to northern hemispheric rapid climate events. We conclude that seasonal changes in precipitation-evaporation balance significantly influenced the hydrological state of a large waterbody such as Lake Karakul, while annual precipitation amount and inflows remained fairly constant.
KW  - climate
KW  - biomarker
KW  - geochemistry
KW  - modelling
KW  - paleoclimate
KW  - hydrology
Y1  - 2019
U6  - https://doi.org/10.1029/2019GL085202
SN  - 0094-8276
SN  - 1944-8007
VL  - 46
IS  - 23
SP  - 13972
EP  - 13983
PB  - American Geophysical Union
CY  - Washington
ER  - 
TY  - JOUR
A1  - Menges, Johanna
A1  - Hovius, Niels
A1  - Andermann, Christoff
A1  - Dietze, Michael
A1  - Swoboda, Charlie
A1  - Cook, Kristen L.
A1  - Adhikari, Basanta R.
A1  - Vieth-Hillebrand, Andrea
A1  - Bonnet, Stephane
A1  - Reimann, Tony
A1  - Koutsodendris, Andreas
A1  - Sachse, Dirk
T1  - Late holocene landscape collapse of a trans-himalayan dryland
BT  - human impact and aridification
JF  - Geophysical research letters
N2  - Soil degradation is a severe and growing threat to ecosystem services globally. Soil loss is often nonlinear, involving a rapid deterioration from a stable eco-geomorphic state once a tipping point is reached. Soil loss thresholds have been studied at plot scale, but for landscapes, quantitative constraints on the necessary and sufficient conditions for tipping points are rare. Here, we document a landscape-wide eco-geomorphic tipping point at the edge of the Tibetan Plateau and quantify its drivers and erosional consequences. We show that in the upper Kali Gandaki valley, Nepal, soil formation prevailed under wetter conditions during much of the Holocene. Our data suggest that after a period of human pressure and declining vegetation cover, a 20% reduction of relative humidity and precipitation below 200 mm/year halted soil formation after 1.6 ka and promoted widespread gullying and rapid soil loss, with irreversible consequences for ecosystem services.
KW  - geomorphology
KW  - paleoclimate
KW  - human activity
KW  - Tibetan plateau
KW  - late Holocene
Y1  - 2019
U6  - https://doi.org/10.1029/2019GL084192
SN  - 0094-8276
SN  - 1944-8007
VL  - 46
IS  - 23
SP  - 13814
EP  - 13824
PB  - American Geophysical Union
CY  - Washington
ER  - 
TY  - GEN
A1  - Duy, Nguyen Le
A1  - Heidbüchel, Ingo
A1  - Meyer, Hanno
A1  - Merz, Bruno
A1  - Apel, Heiko
T1  - What controls the stable isotope composition of precipitation in the Mekong Delta?
BT  - a model-based statistical approach
T2  - Postprints der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe
N2  - This study analyzes the influence of local and regional climatic factors on the stable isotopic composition of rainfall in the Vietnamese Mekong Delta (VMD) as part of the Asian monsoon region. It is based on 1.5 years of weekly rainfall samples. In the first step, the isotopic composition of the samples is analyzed by local meteoric water lines (LMWLs) and single-factor linear correlations. Additionally, the contribution of several regional and local factors is quantified by multiple linear regression (MLR) of all possible factor combinations and by relative importance analysis. This approach is novel for the interpretation of isotopic records and enables an objective quantification of the explained variance in isotopic records for individual factors. In this study, the local factors are extracted from local climate records, while the regional factors are derived from atmospheric backward trajectories of water particles. The regional factors, i.e., precipitation, temperature, relative humidity and the length of backward trajectories, are combined with equivalent local climatic parameters to explain the response variables delta O-18, delta H-2, and d-excess of precipitation at the station of measurement.

The results indicate that (i) MLR can better explain the isotopic variation in precipitation (R-2 = 0.8) compared to single-factor linear regression (R-2 = 0.3); (ii) the isotopic variation in precipitation is controlled dominantly by regional moisture regimes (similar to 70 %) compared to local climatic conditions (similar to 30 %); (iii) the most important climatic parameter during the rainy season is the precipitation amount along the trajectories of air mass movement; (iv) the influence of local precipitation amount and temperature is not sig-nificant during the rainy season, unlike the regional precipitation amount effect; (v) secondary fractionation processes (e.g., sub-cloud evaporation) can be identified through the d-excess and take place mainly in the dry season, either locally for delta O-18 and delta H-2, or along the air mass trajectories for d-excess. The analysis shows that regional and local factors vary in importance over the seasons and that the source regions and transport pathways, and particularly the climatic conditions along the pathways, have a large influence on the isotopic composition of rainfall. Although the general results have been reported qualitatively in previous studies (proving the validity of the approach), the proposed method provides quantitative estimates of the controlling factors, both for the whole data set and for distinct seasons. Therefore, it is argued that the approach constitutes an advancement in the statistical analysis of isotopic records in rainfall that can supplement or precede more complex studies utilizing atmospheric models. Due to its relative simplicity, the method can be easily transferred to other regions, or extended with other factors.

The results illustrate that the interpretation of the isotopic composition of precipitation as a recorder of local climatic conditions, as for example performed for paleorecords of water isotopes, may not be adequate in the southern part of the Indochinese Peninsula, and likely neither in other regions affected by monsoon processes. However, the presented approach could open a pathway towards better and seasonally differentiated reconstruction of paleoclimates based on isotopic records.
T3  - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 927 
KW  - Asian summer monsoon
KW  - interannuel variability
KW  - climate controls
KW  - deuterium excess
KW  - oxygen isotopes
KW  - paleoclimate
KW  - water
KW  - system
KW  - trajectories
KW  - circulation
Y1  - 2020
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-445743
SN  - 1866-8372
IS  - 927
SP  - 1239
EP  - 1262
ER  - 
TY  - THES
A1  - Genderjahn, Steffi
T1  - Biosignatures of Present and Past Microbial Life in Southern African Geoarchives
T1  - Biosignaturen von gegenwärtigem und vergangenem mikrobiellen Leben in 
südafrikanischen Geoarchiven
N2  - Global climate change is one of the greatest challenges of the 21st century, with influence on the environment, societies, politics and economies. The (semi-)arid areas of Southern Africa already suffer from water scarcity. There is a great variety of ongoing research related to global climate history but important questions on regional differences still exist.
In southern African regions terrestrial climate archives are rare, which makes paleoclimate studies challenging. Based on the assumption that continental pans (sabkhas) represent a suitable geo-archive for the climate history, two different pans were studied in the southern and western Kalahari Desert. A combined approach of molecular biological and biogeochemical analyses is utilized to investigate the diversity and abundance of microorganisms and to trace temporal and spatial changes in paleoprecipitation in arid environments. The present PhD thesis demonstrates the applicability of pan sediments as a late Quaternary geo-archive based on microbial signature lipid biomarkers, such as archaeol, branched and isoprenoid glycerol dialkyl glycerol tetraethers (GDGTs) as well as phospholipid fatty acids (PLFA). The microbial signatures contained in the sediment provide information on the current or past microbial community from the Last Glacial Maximum to the recent epoch, the Holocene. The results are discussed in the context of regional climate evolution in southwestern Africa. The seasonal shift of the Innertropical Convergence Zone (ITCZ) along the equator influences the distribution of precipitation- and climate zones. The different expansion of the winter- and summer rainfall zones in southern Africa was confirmed by the frequency of certain microbial biomarkers. A period of increased precipitation in the south-western Kalahari could be described as a result of the extension of the winter rainfall zone during the last glacial maximum (21 ± 2 ka). Instead a period of increased paleoprecipitation in the western Kalahari was indicated during the Late Glacial to Holocene transition. This was possibly caused by a southwestern shift in the position of the summer rainfall zone associated to the southward movement of the ITCZ.
Furthermore, for the first time this study characterizes the bacterial and archaeal life based on 16S rRNA gene high-throughput sequencing in continental pan sediments and provides an insight into the recent microbial community structure. Near-surface processes play an important role for the modern microbial ecosystem in the pans. Water availability as well as salinity might determine the abundance and composition of the microbial communities. The microbial community of pan sediments is dominated by halophilic and dry-adapted archaea and bacteria. Frequently occurring microorganisms such as, Halobacteriaceae, Bacillus and Gemmatimonadetes are described in more detail in this study.
N2  - Der globale Klimawandel beeinflusst Umwelt, Gesellschaft, Politik sowie Wirtschaft und ist eine der größten Herausforderungen des 21. Jahrhunderts. Die semi-ariden bzw. ariden Gebiete im südlichen Afrika leiden bereits unter Wasserknappheit. Eine Vielzahl laufender Forschungsprojekte befasst sich mit der globalen Klimageschichte, wobei häufig Fragen zu regionalen Unterschieden offen bleiben.
In den südafrikanischen Gebieten sind terrestrische Klimaarchive (wie z.B. Seen) selten, so dass die Durchführung von Paleoklimastudien schwierig ist. Basierend auf der Annahme, dass kontinentale Pfannen (Sabkhas) zur Klimarekonstruktion geeignet sind, wurden in der vorliegenden Doktorarbeit zwei unterschiedliche Pfannen in der süd- und in der westlichen Kalahari untersucht. Mittels eines kombinierten Ansatzes aus molekularbiologischen und biogeochemischen Methoden wurde die Diversität und Abundanz der Mikroorganismen analysiert, um räumliche und zeitliche Veränderungen in Bezug auf den Niederschlag in diesen trockenen Gebieten zu rekonstruieren. Diese Dissertation betrachtet u.a. das Potential der Pfannensedimente als Geoarchiv auf Basis der mikrobiellen Biomarkeranalyse, wie Archaeol, verzweigte und isoprenoiden Glycerol Dialkyl Glycerol Tetraethern (GDGTs) sowie Phospholipidfettsäuren (PLFAs). Die im Sediment enthaltenen mikrobiellen Signaturen geben Auskunft über die gegenwärtige bzw. vergangene mikrobielle Gemeinschaft vom Letzten Glazialen Maximum bis zur jüngsten Epoche, dem Holozän. Die Ergebnisse werden im Kontext der regionalen Klimaentwicklung im südwestlichen Afrika diskutiert. Bedingt durch die saisonale Verschiebung der Innertropischen Konvergenzzone (ITCZ) entlang des Äquators verändert sich die Verteilung von Niederschlags- und Klimazonen.
Die unterschiedliche Ausdehnung der Winter- und Sommerregenzonen im südlichen Afrika konnte anhand der Häufigkeit bestimmter mikrobieller Biomarker bestätigt werden. Aufgrund der Ausdehnung der Winterregenzone während des Letzten Glazialen Maximums (LGM, 21 ± 2 ka) konnte eine Periode erhöhten Niederschlags in der südwestlichen Kalahari beschrieben werden. Im Gegensatz dazu konnte eine Niederschlagszunahme zwischen dem letzten Glazial bis zum Holozän (17 – 12 ka) in der westlichen Kalahari aufgezeigt werden, ausgelöst durch eine Verschiebung der ITCZ in Richtung Süden.
Darüber hinaus charakterisiert diese Studie erstmals das bakterielle und archaelle Leben auf Basis der 16S rRNA Gen Hochdurchsatz-Sequenzierung in kontinentalen Pfannensedimenten und gibt einen Einblick in die Struktur der mikrobiellen Gemeinschaft. Oberflächennahe Prozesse spielen eine wichtige Rolle für das moderne mikrobielle Ökosystem in den Pfannen. Wasserverfügbarkeit sowie der Salzgehalt bestimmen die Abundanz und Diversität der mikrobiellen Gemeinschaften. Gelegentliche Regenschauer können die Bedingungen an den oberflächennahen Sedimenten schnell verändern und das mikrobielle Leben beeinflussen. Die mikrobielle Gemeinschaft der Pfannensedimente wird von halophilen und an die Trockenheit angepassten Archaeen und Bakterien dominiert. Häufig vorkommende Mikroorganismen, wie zum Beispiel Halobacteriaceae, Bacillus und Gemmatimonadetes werden in der vorliegenden Arbeit näher beschrieben.
Diese Arbeit gibt einen Einblick in die Diversität und Verteilung der mikrobiellen Gemeinschaft in nährstoffarmen und niederschlagsarmen, semi-ariden Habitaten. Sie beschreibt die Verwendung von Lipidbiomarkern als Proxy der mikrobiellen Abundanz in Bezug auf vergangene klimatische Veränderungen in der Kalahari.
KW  - biomarker
KW  - paleoclimate
KW  - Kalahari
KW  - halophiles
KW  - next generation sequencing
KW  - Biomarker
KW  - Paläoklima
KW  - Kalahari
KW  - Halophile
KW  - Hochdurchsatzsequenzierung
Y1  - 2018
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-410110
ER  - 
TY  - JOUR
A1  - Sachse, Dirk
A1  - Billault, Isabelle
A1  - Bowen, Gabriel J.
A1  - Chikaraishi, Yoshito
A1  - Dawson, Todd E.
A1  - Feakins, Sarah J.
A1  - Freeman, Katherine H.
A1  - Magill, Clayton R.
A1  - McInerney, Francesca A.
A1  - van der Meer, Marcel T. J.
A1  - Polissar, Pratigya
A1  - Robins, Richard J.
A1  - Sachs, Julian P.
A1  - Schmidt, Hanns-Ludwig
A1  - Sessions, Alex L.
A1  - White, James W. C.
A1  - West, Jason B.
A1  - Kahmen, Ansgar
ED  - Jeanloz, R
T1  - Molecular Paleohydrology interpreting the Hydrogen- Isotopic Composition of Lipid Biomarkers from Photosynthesizing Organisms
JF  - Annual review of earth and planetary sciences
JF  - Annual Review of Earth and Planetary Sciences
N2  - Hydrogen-isotopic abundances of lipid biomarkers are emerging as important proxies in the study of ancient environments and ecosystems. A decade ago, pioneering studies made use of new analytical methods and demonstrated that the hydrogen-isotopic composition of individual lipids from aquatic and terrestrial organisms can be related to the composition of their growth (i.e., environmental) water. Subsequently, compound-specific deuterium/hydrogen (D/H) ratios of sedimentary biomarkers have been increasingly used as paleohydrological proxies over a range of geological timescales. Isotopic fractionation observed between hydrogen in environmental water and hydrogen in lipids, however, is sensitive to biochemical, physiological, and environmental influences on the composition of hydrogen available for biosynthesis in cells. Here we review the factors and processes that are known to influence the hydrogen-isotopic compositions of lipids-especially n-alkanes-from photosynthesizing organisms, and we provide a framework for interpreting their D/H ratios from ancient sediments and identify future research opportunities.
KW  - paleoclimate
KW  - paleoclimate proxy
KW  - deuterium
KW  - organic geochemistry
Y1  - 2012
SN  - 978-0-8243-2040-9
U6  - https://doi.org/10.1146/annurev-earth-042711-105535
SN  - 0084-6597
VL  - 40
IS  - 1
SP  - 221
EP  - 249
PB  - Annual Reviews
CY  - Palo Alto
ER  - 
TY  - JOUR
A1  - Bookhagen, Bodo
A1  - Strecker, Manfred
T1  - Spatiotemporal trends in erosion rates across a pronounced rainfall gradient: Examples from the southern Central Andes
JF  - Earth & planetary science letters
N2  - The tectonic and climatic boundary conditions of the broken foreland and the orogen interior of the southern Central Andes of northwestern Argentina cause strong contrasts in elevation, rainfall, and surface-process regimes. The climatic gradient in this region ranges from the wet, windward eastern flanks (similar to 2 m/yr rainfall) to progressively drier western basins and ranges (similar to 0.1 m/yr) bordering the arid Altiplano-Puna Plateau. In this study, we analyze the impact of spatiotemporal climatic gradients on surface erosion: First, we present 41 new catchment-mean erosion rates derived from cosmogenic nuclide inventories to document spatial erosion patterns. Second, we re-evaluate paleoclimatic records from the Calchaquies basin (66 W, 26 S), a large intermontane basin bordered by high (> 4.5 km) mountain ranges, to demonstrate temporal variations in erosion rates associated with changing climatic boundary conditions during the late Pleistocene and Holocene. Three key observations in this region emphasize the importance of climatic parameters on the efficiency of surface processes in space and time: (1) First-order spatial patterns of erosion rates can be explained by a simple specific stream power (SSP) approach. We explicitly account for discharge by routing high-resolution, satellite derived rainfall. This is important as the steep climatic gradient results in a highly non-linear relation between drainage area and discharge. This relation indicates that erosion rates (ER) scale with ER similar to SSP1.4 on cosmogenic-nuclide time scales. (2) We identify an intrinsic channel-slope behavior in different climatic compartments. Channel slopes in dry areas (< 0.25 m/yr rainfall) are slightly steeper than in wet areas (> 0.75 m/yr) with equal drainage areas, thus compensating lower amounts of discharge with steeper slopes. (3) Erosion rates can vary by an order of magnitude between presently dry (similar to 0.05 mm/yr) and well-defined late Pleistocene humid (similar to 0.5 mm/yr) conditions within an intemontane basin. Overall, we document a strong climatic impact on erosion rates and channel slopes. We suggest that rainfall reaching areas with steeper channel slopes in the orogen interior during wetter climate periods results in intensified sediment mass transport, which is primarily responsible for maintaining the balance between surface uplift, erosion, sediment routing and transient storage in the orogen.
KW  - erosion
KW  - landscape evolution
KW  - specific stream power
KW  - cosmogenic radionuclides
KW  - paleoclimate
KW  - climate-tectonic feedback processes
Y1  - 2012
U6  - https://doi.org/10.1016/j.epsl.2012.02.005
SN  - 0012-821X
VL  - 327
IS  - 8
SP  - 97
EP  - 110
PB  - Elsevier
CY  - Amsterdam
ER  -