TY  - JOUR
A1  - Scheingross, Joel S.
A1  - Hovius, Niels
A1  - Dellinger, M.
A1  - Hilton, R. G.
A1  - Repasch, M.
A1  - Sachse, Dirk
A1  - Grocke, D. R.
A1  - Vieth-Hillebrand, Andrea
A1  - Turowski, Jens M.
T1  - Preservation of organic carbon during active fluvial transport and particle abrasion
JF  - Geology
N2  - Oxidation of particulate organic carbon (POC) during fluvial transit releases CO2 to the atmosphere and can influence global climate. Field data show large POC oxidation fluxes in lowland rivers; however, it is unclear if POC losses occur predominantly during in-river transport, where POC is in continual motion within an aerated environment, or during transient storage in floodplains, which may be anoxic. Determination of the locus of POC oxidation in lowland rivers is needed to develop process-based models to predict POC losses, constrain carbon budgets, and unravel links between climate and erosion. However, sediment exchange between rivers and floodplains makes differentiating POC oxidation during in-river transport from oxidation during floodplain storage difficult. Here, we isolated inriver POC oxidation using flume experiments transporting petrogenic and biospheric POC without floodplain storage. Our experiments showed solid phase POC losses of 0%-10% over similar to 10(3) km of fluvial transport, compared to similar to 7% to >50% losses observed in rivers over similar distances. The production of dissolved organic carbon (DOC) and dissolved rhenium (a proxy for petrogenic POC oxidation) was consistent with small POC lasses, and replicate experiments in static water tanks gave similar results. Our results show that fluvial sediment transport, particle abrasion, and turbulent mixing have a minimal role on POC oxidation, and they suggest that POC losses may accrue primarily in floodplain storage.
Y1  - 2019
U6  - https://doi.org/10.1130/G46442.1
SN  - 0091-7613
SN  - 1943-2682
VL  - 47
IS  - 10
SP  - 958
EP  - 962
PB  - American Institute of Physics
CY  - Boulder
ER  - 
TY  - JOUR
A1  - Szalay, J. R.
A1  - Poppe, A. R.
A1  - Agarwal, J.
A1  - Britt, D.
A1  - Belskaya, I.
A1  - Horanyi, M.
A1  - Nakamura, T.
A1  - Sachse, M.
A1  - Spahn, Frank
T1  - Dust Phenomena Relating to Airless Bodies
JF  - Space science reviews
N2  - Airless bodies are directly exposed to ambient plasma and meteoroid fluxes, making them characteristically different from bodies whose dense atmospheres protect their surfaces from such fluxes. Direct exposure to plasma and meteoroids has important consequences for the formation and evolution of planetary surfaces, including altering chemical makeup and optical properties, generating neutral gas and/or dust exospheres, and leading to the generation of circumplanetary and interplanetary dust grain populations. In the past two decades, there have been many advancements in our understanding of airless bodies and their interaction with various dust populations. In this paper, we describe relevant dust phenomena on the surface and in the vicinity of airless bodies over a broad range of scale sizes from to , with a focus on recent developments in this field.
KW  - Dust
KW  - Airless bodies
KW  - Interplanetary dust
Y1  - 2018
U6  - https://doi.org/10.1007/s11214-018-0527-0
SN  - 0038-6308
SN  - 1572-9672
VL  - 214
IS  - 5
PB  - Springer
CY  - Dordrecht
ER  - 
TY  - JOUR
A1  - Prasad, Sushma
A1  - Anoop, A.
A1  - Riedel, N.
A1  - Sarkar, Saswati
A1  - Menzel, P.
A1  - Basavaiah, Nathani
A1  - Krishnan, R.
A1  - Fuller, D.
A1  - Plessen, Birgit
A1  - Gaye, B.
A1  - Roehl, U.
A1  - Wilkes, H.
A1  - Sachse, Dirk
A1  - Sawant, R.
A1  - Wiesner, M. G.
A1  - Stebich, M.
T1  - Prolonged monsoon droughts and links to Indo-Pacific warm pool: A Holocene record from Lonar Lake, central India
JF  - Earth & planetary science letters
N2  - Concerns about the regional impact of global climate change in a warming scenario have highlighted the gaps in our understanding of the Indian Summer Monsoon (ISM, also referred to as the Indian Ocean summer monsoon) and the absence of long term palaeoclimate data from the central Indian core monsoon zone (CMZ). Here we present the first high resolution, well-dated, multiproxy reconstruction of Holocene palaeoclimate from a 10 m long sediment core raised from the Lonar Lake in central India. We show that while the early Holocene onset of-intensified monsoon in the CMZ is similar to that reported from other ISM records, the Lonar data shows two prolonged droughts (PD, multidecadal to centennial periods of weaker monsoon) between 4.6-3.9 and 2-0.6 cal ka. A comparison of our record with available data from other ISM influenced sites shows that the impact of these PD was observed in varying degrees throughout the ISM realm and coincides with intervals of higher solar irradiance. We demonstrate that (i) the regional warming in the Indo-Pacific Warm Pool (IPWP) plays an important role in causing ISM PD through changes in meridional overturning circulation and position of the anomalous Walker cell; (ii) the long term influence of conditions like El Nino-Southern Oscillation (ENSO) on the ISM began only ca. 2 cal ka BP and is coincident with the warming of the southern IPWP; (iii) the first settlements in central India coincided with the onset of the first PD and agricultural populations flourished between the two PD, highlighting the significance of natural climate variability and PD as major environmental factors affecting human settlements.
KW  - Indian summer monsoon
KW  - ENSO
KW  - prolonged droughts
KW  - Holocene
KW  - Lonar Lake
Y1  - 2014
U6  - https://doi.org/10.1016/j.epsl.2014.01.043
SN  - 0012-821X
SN  - 1385-013X
VL  - 391
SP  - 171
EP  - 182
PB  - Elsevier
CY  - Amsterdam
ER  - 
TY  - JOUR
A1  - Aichner, Bernhard
A1  - Ott, Florian
A1  - Slowinski, Michal
A1  - Norygkiewicz, Agnieszka M.
A1  - Brauer, Achim
A1  - Sachse, Dirk
T1  - Leaf wax n-alkane distributions record ecological changes during the Younger Dryas at Trzechowskie paleolake (northern Poland) without temporal delay
JF  - Climate of the past : an interactive open access journal of the European Geosciences Union
N2  - While of higher plant origin, a specific source assignment of sedimentary leaf wax n-alkanes remains difficult. In addition, it is unknown how fast a changing catchment vegetation would be reflected in sedimentary leaf wax archives. In particular, for a quantitative interpretation of n-alkane C and H isotope ratios in terms of paleohydrological and paleoecological changes, a better understanding of transfer times and dominant sedimentary sources of leaf wax n-alkanes is required. In this study we tested to what extent compositional changes in leaf wax n-alkanes can be linked to known vegetation changes by comparison with high-resolution palynological data from the same archive. We analyzed leaf wax n-alkane concentrations and distributions in decadal resolution from a sedimentary record from Trzechowskie paleolake (TRZ, northern Poland), covering the Late Glacial to early Holocene (13 360-9940 yr BP). As an additional source indicator of targeted n-alkanes, compound-specific carbon isotopic data have been generated in lower time resolution. The results indicated rapid responses of n-alkane distribution patterns coinciding with major climatic and paleoecological transitions. We found a shift towards higher average chain length (ACL) values at the Allerod-Younger Dryas (YD) transition between 12 680 and 12 600 yr BP, co-evaled with a decreasing contribution of arboreal pollen (mainly Pinus and Betula) and a subsequently higher abundance of pollen derived from herbaceous plants (Poaceae, Cyperaceae, Artemisia), shrubs, and dwarf shrubs (Juniperus and Salix). The termination of the YD was characterized by a successive increase in n-alkane concentrations coinciding with a sharp decrease in ACL values between 11 580 and 11 490 yr BP, reflecting the expansion of woodland vegetation at the YD-Holocene transition. A gradual reversal to longer chain lengths after 11 200 yr BP, together with decreasing n-alkane concentrations, most likely reflects the early Holocene vegetation succession with a decline of Betula. These results show that n-alkane distributions reflect vegetation changes and that a fast (i.e., subdecadal) signal transfer occurred. However, our data also indicate that a standard interpretation of directional changes in biomarker ratios remains difficult. Instead, responses such as changes in ACL need to be discussed in the context of other proxy data. In addition, we find that organic geochemical data integrate different ecological information compared to pollen, since some gymnosperm genera, such as Pinus, produce only a very low amount of n-alkanes and for this reason their contribution may be largely absent from biomarker records. Our results demonstrate that a combination of palynological and n-alkane data can be used to infer the major sedimentary leaf wax sources and constrain leaf wax transport times from the plant source to the sedimentary sink and thus pave the way towards quantitative interpretation of compound-specific hydrogen isotope ratios for paleohydrological reconstructions.
Y1  - 2018
U6  - https://doi.org/10.5194/cp-14-1607-2018
SN  - 1814-9324
SN  - 1814-9332
VL  - 14
IS  - 11
SP  - 1607
EP  - 1624
PB  - Copernicus
CY  - Göttingen
ER  - 
TY  - JOUR
A1  - Buratti, Bonnie J.
A1  - Thomas, P. C.
A1  - Roussos, E.
A1  - Howett, Carly
A1  - Seiss, Martin
A1  - Hendrix, A. R.
A1  - Helfenstein, Paul
A1  - Brown, R. H.
A1  - Clark, R. N.
A1  - Denk, Tilmann
A1  - Filacchione, Gianrico
A1  - Hoffmann, Holger
A1  - Jones, Geraint H.
A1  - Khawaja, N.
A1  - Kollmann, Peter
A1  - Krupp, Norbert
A1  - Lunine, Jonathan
A1  - Momary, T. W.
A1  - Paranicas, Christopher
A1  - Postberg, Frank
A1  - Sachse, Manuel
A1  - Spahn, Frank
A1  - Spencer, John
A1  - Srama, Ralf
A1  - Albin, T.
A1  - Baines, K. H.
A1  - Ciarniello, Mauro
A1  - Economou, Thanasis
A1  - Hsu, Hsiang-Wen
A1  - Kempf, Sascha
A1  - Krimigis, Stamatios M.
A1  - Mitchell, Donald
A1  - Moragas-Klostermeyer, Georg
A1  - Nicholson, Philip D.
A1  - Porco, C. C.
A1  - Rosenberg, Heike
A1  - Simolka, Jonas
A1  - Soderblom, Laurence A.
T1  - Close Cassini flybys of Saturn’s ring moons Pan, Daphnis, Atlas, Pandora, and Epimetheus
JF  - Science
N2  - Saturn’s main ring system is associated with a set of small moons that either are embedded within it or interact with the rings to alter their shape and composition. Five close flybys of the moons Pan, Daphnis, Atlas, Pandora, and Epimetheus were performed between December 2016 and April 2017 during the ring-grazing orbits of the Cassini mission. Data on the moons’ morphology, structure, particle environment, and composition were returned, along with images in the ultraviolet and thermal infrared. We find that the optical properties of the moons’ surfaces are determined by two competing processes: contamination by a red material formed in Saturn’s main ring system and accretion of bright icy particles or water vapor from volcanic plumes originating on the moon Enceladus.
Y1  - 2019
U6  - https://doi.org/10.1126/science.aat2349
SN  - 0036-8075
SN  - 1095-9203
VL  - 364
IS  - 6445
SP  - 1053
PB  - American Assoc. for the Advancement of Science
CY  - Washington
ER  - 
TY  - JOUR
A1  - Menges, Johanna
A1  - Huguet, C.
A1  - Alcaniz, Josep M.
A1  - Fietz, Susanne
A1  - Sachse, Dirk
A1  - Rosell-Mele, A.
T1  - Influence of water availability in the distributions of branched glycerol dialkyl glycerol tetraether in soils of the Iberian Peninsula
JF  - Biogeosciences
Y1  - 2014
U6  - https://doi.org/10.5194/bg-11-2571-2014
SN  - 1726-4170
SN  - 1726-4189
VL  - 11
IS  - 10
SP  - 2571
EP  - 2581
PB  - Copernicus
CY  - Göttingen
ER  - 
TY  - JOUR
A1  - Sachse, Rene
A1  - Petzoldt, Thomas
A1  - Blumstock, Maria
A1  - Moreira, Santiago
A1  - Paetzig, Marlene
A1  - Ruecker, Jacqueline
A1  - Janse, Jan H.
A1  - Mooij, Wolf M.
A1  - Hilt, Sabine
T1  - Extending one-dimensional models for deep lakes to simulate the impact of submerged macrophytes on water quality
JF  - Environmental modelling & software with environment data news
N2  - Submerged macrophytes can stabilise clear water conditions in shallow lakes. However, many existing models for deep lakes neglect their impact. Here, we tested the hypothesis that submerged macrophytes can affect the water clarity in deep lakes. A one-dimensional, vertically resolved macrophyte model was developed based on PCLake and coupled to SALMO-1D and GOTM hydrophysics and validated against field data. Validation showed good coherence in dynamic growth patterns and colonisation depths. In our simulations the presence of submerged macrophytes resulted in up to 50% less phytoplankton biomass in the shallowest simulated lake (11 m) and still 15% less phytoplankton was predicted in 100 m deep oligotrophic lakes. Nutrient loading, lake depth, and lake shape had a strong influence on macrophyte effects. Nutrient competition was found to be the strongest biological interaction. Despite a number of limitations, the derived dynamic lake model suggests significant effects of submerged macrophytes on deep lake water quality. (C) 2014 Elsevier Ltd. All rights reserved.
KW  - Lake model
KW  - Macrophytes
KW  - Water quality
Y1  - 2014
U6  - https://doi.org/10.1016/j.envsoft.2014.05.023
SN  - 1364-8152
SN  - 1873-6726
VL  - 61
SP  - 410
EP  - 423
PB  - Elsevier
CY  - Oxford
ER  - 
TY  - JOUR
A1  - Kind, Barbara
A1  - Muster, Britta
A1  - Staroske, Wolfgang
A1  - Herce, Henry D.
A1  - Sachse, Rene
A1  - Rapp, Alexander
A1  - Schmidt, Franziska
A1  - Koss, Sarah
A1  - Cardoso, M. Cristina
A1  - Lee-Kirsch, Min Ae
T1  - Altered spatio-temporal dynamics of RNase H2 complex assembly at replication and repair sites in Aicardi-Goutieres syndrome
JF  - Human molecular genetics
N2  - Ribonuclease H2 plays an essential role for genome stability as it removes ribonucleotides misincorporated into genomic DNA by replicative polymerases and resolves RNA/DNA hybrids. Biallelic mutations in the genes encoding the three RNase H2 subunits cause Aicardi-Goutieres syndrome (AGS), an early-onset inflammatory encephalopathy that phenotypically overlaps with the autoimmune disorder systemic lupus erythematosus. Here we studied the intracellular dynamics of RNase H2 in living cells during DNA replication and in response to DNA damage using confocal time-lapse imaging and fluorescence cross-correlation spectroscopy. We demonstrate that the RNase H2 complex is assembled in the cytosol and imported into the nucleus in an RNase H2B-dependent manner. RNase H2 is not only recruited to DNA replication foci, but also to sites of PCNA-dependent DNA repair. By fluorescence recovery after photobleaching, we demonstrate a high mobility and fast exchange of RNase H2 at sites of DNA repair and replication. We provide evidence that recruitment of RNase H2 is not only PCNA-dependent, mediated by an interaction of the B subunit with PCNA, but also PCNA-independent mediated via the catalytic domain of the A subunit. We found that AGS-associated mutations alter complex formation, recruitment efficiency and exchange kinetics at sites of DNA replication and repair suggesting that impaired ribonucleotide removal contributes to AGS pathogenesis.
Y1  - 2014
U6  - https://doi.org/10.1093/hmg/ddu319
SN  - 0964-6906
SN  - 1460-2083
VL  - 23
IS  - 22
SP  - 5950
EP  - 5960
PB  - Oxford Univ. Press
CY  - Oxford
ER  - 
TY  - JOUR
A1  - Janssen, Annette B. G.
A1  - Arhonditsis, George B.
A1  - Beusen, Arthur
A1  - Bolding, Karsten
A1  - Bruce, Louise
A1  - Bruggeman, Jorn
A1  - Couture, Raoul-Marie
A1  - Downing, Andrea S.
A1  - Elliott, J. Alex
A1  - Frassl, Marieke A.
A1  - Gal, Gideon
A1  - Gerla, Daan J.
A1  - Hipsey, Matthew R.
A1  - Hu, Fenjuan
A1  - Ives, Stephen C.
A1  - Janse, Jan H.
A1  - Jeppesen, Erik
A1  - Joehnk, Klaus D.
A1  - Kneis, David
A1  - Kong, Xiangzhen
A1  - Kuiper, Jan J.
A1  - Lehmann, Moritz K.
A1  - Lemmen, Carsten
A1  - Oezkundakci, Deniz
A1  - Petzoldt, Thomas
A1  - Rinke, Karsten
A1  - Robson, Barbara J.
A1  - Sachse, Rene
A1  - Schep, Sebastiaan A.
A1  - Schmid, Martin
A1  - Scholten, Huub
A1  - Teurlincx, Sven
A1  - Trolle, Dennis
A1  - Troost, Tineke A.
A1  - Van Dam, Anne A.
A1  - Van Gerven, Luuk P. A.
A1  - Weijerman, Mariska
A1  - Wells, Scott A.
A1  - Mooij, Wolf M.
T1  - Exploring, exploiting and evolving diversity of aquatic ecosystem models: a community perspective
JF  - Aquatic ecology : the international forum covering research in freshwater and marine environments
N2  - Here, we present a community perspective on how to explore, exploit and evolve the diversity in aquatic ecosystem models. These models play an important role in understanding the functioning of aquatic ecosystems, filling in observation gaps and developing effective strategies for water quality management. In this spirit, numerous models have been developed since the 1970s. We set off to explore model diversity by making an inventory among 42 aquatic ecosystem modellers, by categorizing the resulting set of models and by analysing them for diversity. We then focus on how to exploit model diversity by comparing and combining different aspects of existing models. Finally, we discuss how model diversity came about in the past and could evolve in the future. Throughout our study, we use analogies from biodiversity research to analyse and interpret model diversity. We recommend to make models publicly available through open-source policies, to standardize documentation and technical implementation of models, and to compare models through ensemble modelling and interdisciplinary approaches. We end with our perspective on how the field of aquatic ecosystem modelling might develop in the next 5-10 years. To strive for clarity and to improve readability for non-modellers, we include a glossary.
KW  - Water quality
KW  - Ecology
KW  - Geochemistry
KW  - Hydrology
KW  - Hydraulics
KW  - Hydrodynamics
KW  - Physical environment
KW  - Socio-economics
KW  - Model availability
KW  - Standardization
KW  - Linking
Y1  - 2015
U6  - https://doi.org/10.1007/s10452-015-9544-1
SN  - 1386-2588
SN  - 1573-5125
VL  - 49
IS  - 4
SP  - 513
EP  - 548
PB  - Springer
CY  - Dordrecht
ER  - 
TY  - JOUR
A1  - Kahmen, Ansgar
A1  - Sachse, Dirk
A1  - Arndt, Stefan K.
A1  - Tu, Kevin P.
A1  - Farrington, Heraldo
A1  - Vitousek, Peter M.
A1  - Dawson, Todd E.
T1  - Cellulose delta O-18 is an index of leaf-to-air vapor pressure difference (VPD) in tropical plants
JF  - Proceedings of the National Academy of Sciences of the United States of America
N2  - Cellulose in plants contains oxygen that derives in most cases from precipitation. Because the stable oxygen isotope composition, delta O-18, of precipitation is associated with environmental conditions, cellulose delta O-18 should be as well. However, plant physiological models using delta O-18 suggest that cellulose delta O-18 is influenced by a complex mix of both climatic and physiological drivers. This influence complicates the interpretation of cellulose delta O-18 values in a paleo-context. Here, we combined empirical data analyses with mechanistic model simulations to i) quantify the impacts that the primary climatic drivers humidity (e(a)) and air temperature (T-air) have on cellulose delta O-18 values in different tropical ecosystems and ii) determine which environmental signal is dominating cellulose delta O-18 values. Our results revealed that e(a) and T-air equally influence cellulose delta O-18 values and that distinguishing which of these factors dominates the delta O-18 values of cellulose cannot be accomplished in the absence of additional environmental information. However, the individual impacts of e(a) and T-air on the delta O-18 values of cellulose can be integrated into a single index of plant-experienced atmospheric vapor demand: the leaf-to-air vapor pressure difference (VPD). We found a robust relationship between VPD and cellulose delta O-18 values in both empirical and modeled data in all ecosystems that we investigated. Our analysis revealed therefore that delta O-18 values in plant cellulose can be used as a proxy for VPD in tropical ecosystems. As VPD is an essential variable that determines the biogeochemical dynamics of ecosystems, our study has applications in ecological-, climate-, or forensic-sciences.
KW  - stable isotopes
KW  - plant-water relations
KW  - paleoecology
KW  - climate change
KW  - Hawaii
Y1  - 2011
U6  - https://doi.org/10.1073/pnas.1018906108
SN  - 0027-8424
VL  - 108
IS  - 5
SP  - 1981
EP  - 1986
PB  - National Acad. of Sciences
CY  - Washington
ER  - 
TY  - JOUR
A1  - Vogeli, Natalie
A1  - Najman, Yani
A1  - van der Beek, Peter
A1  - Huyghe, Pascale
A1  - Wynn, Peter M.
A1  - Govin, Gwladys
A1  - van der Veen, Iris
A1  - Sachse, Dirk
T1  - Lateral variations in vegetation in the Himalaya since the Miocene and implications for climate evolution
JF  - Earth & planetary science letters
N2  - The Himalaya has a major influence on global and regional climate, in particular on the Asian monsoon system. The foreland basin of the Himalaya contains a record of tectonics and paleoclimate since the Miocene. Previous work on the evolution of vegetation and climate has focused on the central and western Himalaya, where a shift from C3 to C4 vegetation has been observed at similar to 7 Ma and linked to increased seasonality, but the climatic evolution of the eastern part of the orogen is less well understood. In order to track vegetation as a marker of monsoon intensity and seasonality, we analyzed delta C-13 and 8180 values of soil carbonate and associated delta C-13 values of bulk organic carbon from previously dated sedimentary sections exposing the syn-orogenic detrital Dharamsala and Siwalik Groups in the west, and, for the first time, the Siwalik Group in the east of the Himalayan foreland basin. Sedimentary records span from 20 to 1 Myr in the west (Joginder Nagar, Jawalamukhi, and Haripur Kolar sections) and from 13 to 1 Myr in the east (Kameng section), respectively. The presence of soil carbonate in the west and its absence in the east is a first indication of long-term lateral climatic variation, as soil carbonate requires seasonally arid conditions to develop. delta C-13 values in soil carbonate show a shift from around -10 parts per thousand to -2 parts per thousand at similar to 7 Ma in the west, which is confirmed by delta C-13 analyses on bulk organic carbon that show a shift from around -23 parts per thousand to -19 parts per thousand at the same time. Such a shift in isotopic values is likely to be associated with a change from C3 to C4 vegetation. In contrast, delta C-13 values of bulk organic carbon remain at 23 parts per thousand o in the east. Thus, our data show that the current east -west variation in climate was established at similar to 7 Ma. We propose that the regional change towards a more seasonal climate in the west is linked to a decrease of the influence of the Westerlies, delivering less winter precipitation to the western Himalaya, while the east remained annually humid due to its proximity to the monsoonal moisture source. (C) 2017 Elsevier B.V. All rights reserved.
KW  - Himalaya
KW  - stable carbon isotopes
KW  - paleovegetation
KW  - Siwalik
KW  - pre-Siwalik
KW  - monsoon
Y1  - 2017
U6  - https://doi.org/10.1016/j.epsl.2017.04.037
SN  - 0012-821X
SN  - 1385-013X
VL  - 471
SP  - 1
EP  - 9
PB  - Elsevier
CY  - Amsterdam
ER  - 
TY  - JOUR
A1  - Hernandez, Martin A.
A1  - Gleixner, Gerd
A1  - Sachse, Dirk
A1  - Alvarez, Hector M.
T1  - Carbon Allocation in Rhodococcus jostii RHA1 in Response to Disruption and Overexpression of nlpR Regulatory Gene, Based on C-13-labeling Analysis
JF  - Frontiers in microbiology
N2  - Nitrogen lipid regulator (NlpR) is a pleiotropic regulator that positively controls genes associated with both nitrogen and lipid metabolism in the oleaginous bacterium Rhodococcus jostii RHA1. In this study, we investigated the effect of nlpR disruption and overexpression on the assimilation of C-13-labeled glucose as carbon source, during cultivation of cells under nitrogen-limiting and nitrogen-rich conditions, respectively. Label incorporation into the total lipid extract (TLE) fraction was about 30% lower in the mutant strain in comparison with the wild type strain under low-nitrogen conditions. Moreover, a higher C-13 abundance (similar to 60%) into the extracellular polymeric substance fraction was observed in the mutant strain, nlpR disruption also promoted a decrease in the label incorporation into several TLE-derivative fractions including neutral lipids (NL), glycolipids (GL), phospholipids (PL), triacylglycerols (TAG), diacylglycerols (DAG), and free fatty acids (FFA), with the DAG being the most affected. In contrast, the nlpR overexpression in RHA1 cells under nitrogen-rich conditions produced an increase of the label incorporation into the TLE and its derivative NL and PL fractions, the last one being the highest C-13 enriched. In addition, a higher C-13 enrichment occurred in the TAG, DAG, and FFA fractions after nlpR induction, with the FFA fraction being the most affected within the TLE. Isotopic-labeling experiments demonstrated that NlpR regulator is contributing in oleaginous phenotype of R. jostii RHA1 to the allocation of carbon into the different lipid fractions in response to nitrogen levels, increasing the rate of carbon flux into lipid metabolism.
KW  - Rhodococcus
KW  - RHA1
KW  - NlpR
KW  - regulation
KW  - C-13-glucose
KW  - lipid metabolism
Y1  - 2017
U6  - https://doi.org/10.3389/fmicb.2017.01992
SN  - 1664-302X
VL  - 8
PB  - Frontiers Research Foundation
CY  - Lausanne
ER  - 
TY  - JOUR
A1  - Meese, Bernd
A1  - Bookhagen, Bodo
A1  - Olen, Stephanie M.
A1  - Barthold, Frauke Katrin
A1  - Sachse, Dirk
T1  - The effect of Indian Summer Monsoon rainfall on surface water delta D values in the central Himalaya
JF  - Hydrological processes
N2  - Stable isotope proxy records, such as speleothems, plant-wax biomarker records, and ice cores, are suitable archives for the reconstruction of regional palaeohydrologic conditions. But the interpretation of these records in the tropics, especially in the Indian Summer Monsoon (ISM) domain, is difficult due to differing moisture and water sources: precipitation from the ISM and Winter Westerlies, as well as snow- and glacial meltwater. In this study, we use interannual differences in ISM strength (2011-2012) to understand the stable isotopic composition of surface water in the Arun River catchment in eastern Nepal. We sampled main stem and tributary water (n = 204) for stable hydrogen and oxygen isotope analysis in the postmonsoon phase of two subsequent years with significantly distinct ISM intensities. In addition to the 2011/2012 sampling campaigns, we collected a 12-month time series of main stem waters (2012/2013, n = 105) in order to better quantify seasonal effects on the variability of surface water delta O-18/delta D. Furthermore, remotely sensed satellite data of rainfall, snow cover, glacial coverage, and evapotranspiration was evaluated. The comparison of datasets from both years revealed that surface waters of the main stem Arun and its tributaries were D-enriched by similar to 15 parts per thousand when ISM rainfall decreased by 20%. This strong response emphasizes the importance of the ISM for surface water run-off in the central Himalaya. However, further spatio-temporal analysis of remote sensing data in combination with stream water d-excess revealed that most high-altitude tributaries and the Tibetan part of the Arun receive high portions of glacial melt water and likely Winter Westerly Disturbances precipitation. We make the following two implications: First, palaeohydrologic archives found in high-altitude tributaries and on the southern Tibetan Plateau record a mixture of past precipitation delta D values and variable amounts of additional water sources. Second, surface water isotope ratios of lower elevated tributaries strongly reflect the isotopic composition of ISM rainfall implying a suitable region for the analysis of potential delta D value proxy records.
KW  - Himalaya
KW  - palaeoclimate records
KW  - snow melt
KW  - stream water
KW  - water isotopes
Y1  - 2018
U6  - https://doi.org/10.1002/hyp.13281
SN  - 0885-6087
SN  - 1099-1085
VL  - 32
IS  - 24
SP  - 3662
EP  - 3674
PB  - Wiley
CY  - Hoboken
ER  - 
TY  - JOUR
A1  - Hoffmann, Bernd
A1  - Feakins, Sarah J.
A1  - Bookhagen, Bodo
A1  - Olen, Stephanie M.
A1  - Adhikari, Danda P.
A1  - Mainali, Janardan
A1  - Sachse, Dirk
T1  - Climatic and geomorphic drivers of plant organic matter transport in the Arun River, E Nepal
JF  - Earth & planetary science letters
KW  - plant wax biomarker
KW  - leaf wax delta D
KW  - carbon cycle
KW  - remote sensing
KW  - erosion
Y1  - 2016
U6  - https://doi.org/10.1016/j.epsl.2016.07.008
SN  - 0012-821X
SN  - 1385-013X
VL  - 452
SP  - 104
EP  - 114
PB  - Elsevier
CY  - Amsterdam
ER  - 
TY  - JOUR
A1  - Nieto-Moreno, Vanesa
A1  - Rohrmann, Alexander
A1  - van der Meer, Marcel T. J.
A1  - Damste, Jaap S. Sinninghe
A1  - Sachse, Dirk
A1  - Tofelde, Stefanie
A1  - Niedermeyer, Eva M.
A1  - Strecker, Manfred
A1  - Mulch, Andreas
T1  - Elevation-dependent changes in n-alkane delta D and soil GDGTs across the South Central Andes
JF  - Earth & planetary science letters
N2  - Surface uplift of large plateaus may significantly influence regional climate and more specifically precipitation patterns and temperature, sometimes complicating paleoaltimetry interpretations. Thus, understanding the topographic evolution of tectonically active mountain belts benefits from continued development of reliable proxies to reduce uncertainties in paleoaltimetry reconstructions. Lipid biomarker-based proxies provide a novel approach to stable isotope paleoaltimetry and complement authigenic or pedogenic mineral proxy materials, in particular outside semi-arid climate zones where soil carbonates are not abundant but (soil) organic matter has a high preservation potential. Here we present delta D values of soil-derived n-alkanes and mean annual air temperature (MAT) estimates based on branched glycerol dialkyl glycerol tetraether (brGDGT) distributions to assess their potential for paleoelevation reconstructions in the southern central Andes. We analyzed soil samples across two environmental and hydrological gradients that include a hillslope (26-28 degrees S) and a valley (22-24 degrees S) transect on the windward flanks of Central Andean Eastern Cordillera in NW Argentina. Our results show that present-day n-alkane delta D values and brGDGT-based MAT estimates are both linearly related with elevation and in good agreement with present-day climate conditions. Soil n-alkanes show a delta D lapse rate (A(delta D)) of -1.64 parts per thousand/100 m (R-2 = 0.91, p < 0.01) at the hillslope transect, within the range of delta D lapse rates from precipitation and surface waters in other tropical regions in the Andes like the Eastern Cordillera in Colombia and Bolivia and the Equatorial and Peruvian Andes. BrGDGT-derived soil temperatures are similar to monitored winter temperatures in the region and show a lapse rate of Delta T = -0.51 degrees C/100 m (R-2 = 0.91, p < 0.01), comparable with lapse rates from in situ soil temperature measurements, satellite derived land-surface temperatures at this transect, and weather stations from the Eastern Cordillera at similar latitude. As a result of an increasing leeward sampling position along the valley transect lapse rates are biased towards lower values and display higher scatter (Delta(delta D) = -0.9 parts per thousand/100 m, R-2 = 0.76, p < 0.01 and Delta T = -0.19 degrees C/100 m, R-2 = 0.48, p < 0.05). Despite this higher complexity, they are in line with lapse rates from stream-water samples and in situ soil temperature measurements along the same transect. Our results demonstrate that both soil n-alkane delta D values and MAT reconstructions based on brGDGTs distributions from the hillslope transect (Delta(delta D) = -1.64 parts per thousand/100 m, R-2 = 0.91, p < 0.01 and Delta T = -0.51 degrees C/100 m, R-2 = 0.91, p < 0.01) track the direct effects of orography on precipitation and temperature and hence the combined effects of local and regional hydrology as well as elevation. (C) 2016 Elsevier B.V. All rights reserved.
KW  - South Central Andes
KW  - leaf-wax n-alkane delta D
KW  - branched GDGTs
KW  - MAT(mr) paleothermometer
KW  - paleoaltimetry proxies
KW  - attitudinal transects
Y1  - 2016
U6  - https://doi.org/10.1016/j.epsl.2016.07.049
SN  - 0012-821X
SN  - 1385-013X
VL  - 453
SP  - 234
EP  - 242
PB  - Elsevier
CY  - Amsterdam
ER  - 
TY  - JOUR
A1  - Olen, Stephanie M.
A1  - Bookhagen, Bodo
A1  - Hoffmann, Bernd
A1  - Sachse, Dirk
A1  - Adhikari, Danda P.
A1  - Strecker, Manfred
T1  - Understanding erosion rates in the Himalayan orogen: A case study from the Arun Valley
JF  - Journal of geophysical research : Earth surface
N2  - Understanding the rates and pattern of erosion is a key aspect of deciphering the impacts of climate and tectonics on landscape evolution. Denudation rates derived from terrestrial cosmogenic nuclides (TCNs) are commonly used to quantify erosion and bridge tectonic (Myr) and climatic (up to several kiloyears) time scales. However, how the processes of erosion in active orogens are ultimately reflected in Be-10 TCN samples remains a topic of discussion. We investigate this problem in the Arun Valley of eastern Nepal with 34 new Be-10-derived catchment-mean denudation rates. The Arun Valley is characterized by steep north-south gradients in topography and climate. Locally, denudation rates increase northward, from <0.2mmyr(-1) to similar to 1.5mmyr(-1) in tributary samples, while main stem samples appear to increase downstream from similar to 0.2mmyr(-1) at the border with Tibet to 0.91mmyr(-1) in the foreland. Denudation rates most strongly correlate with normalized channel steepness (R-2=0.67), which has been commonly interpreted to indicate tectonic activity. Significant downstream decrease of Be-10 concentration in the main stem Arun suggests that upstream sediment grains are fining to the point that they are operationally excluded from the processed sample. This results in Be-10 concentrations and denudation rates that do not uniformly represent the upstream catchment area. We observe strong impacts on Be-10 concentrations from local, nonfluvial geomorphic processes, such as glaciation and landsliding coinciding with areas of peak rainfall rates, pointing toward climatic modulation of predominantly tectonically driven denudation rates.
Y1  - 2015
U6  - https://doi.org/10.1002/2014JF003410
SN  - 2169-9003
SN  - 2169-9011
VL  - 120
IS  - 10
SP  - 2080
EP  - 2102
PB  - American Geophysical Union
CY  - Washington
ER  - 
TY  - JOUR
A1  - Garcin, Yannick
A1  - Deschamps, Pierre
A1  - Menot, Guillemette
A1  - de Saulieu, Geoffroy
A1  - Schefuss, Enno
A1  - Sebag, David
A1  - Dupont, Lydie M.
A1  - Oslisly, Richard
A1  - Brademann, Brian
A1  - Mbusnum, Kevin G.
A1  - Onana, Jean-Michel
A1  - Ako, Andrew A.
A1  - Epp, Laura Saskia
A1  - Tjallingii, Rik
A1  - Strecker, Manfred
A1  - Brauer, Achim
A1  - Sachse, Dirk
T1  - Early anthropogenic impact on Western Central African rainforests 2,600 y ago
JF  - Proceedings of the National Academy of Sciences of the United States of America
N2  - A potential human footprint on Western Central African rainforests before the Common Era has become the focus of an ongoing controversy. Between 3,000 y ago and 2,000 y ago, regional pollen sequences indicate a replacement of mature rainforests by a forest-savannah mosaic including pioneer trees. Although some studies suggested an anthropogenic influence on this forest fragmentation, current interpretations based on pollen data attribute the "rainforest crisis" to climate change toward a drier, more seasonal climate. A rigorous test of this hypothesis, however, requires climate proxies independent of vegetation changes. Here we resolve this controversy through a continuous 10,500-y record of both vegetation and hydrological changes from Lake Barombi in Southwest Cameroon based on changes in carbon and hydrogen isotope compositions of plant waxes. delta C-13-inferred vegetation changes confirm a prominent and abrupt appearance of C-4 plants in the Lake Barombi catchment, at 2,600 calendar years before AD 1950 (cal y BP), followed by an equally sudden return to rainforest vegetation at 2,020 cal y BP. delta D values from the same plant wax compounds, however, show no simultaneous hydrological change. Based on the combination of these data with a comprehensive regional archaeological database we provide evidence that humans triggered the rainforest fragmentation 2,600 y ago. Our findings suggest that technological developments, including agricultural practices and iron metallurgy, possibly related to the large-scale Bantu expansion, significantly impacted the ecosystems before the Common Era.
KW  - Western Central Africa
KW  - late Holocene
KW  - rainforest crisis
KW  - paleohydrology
KW  - human activity
Y1  - 2018
U6  - https://doi.org/10.1073/pnas.1715336115
SN  - 0027-8424
VL  - 115
IS  - 13
SP  - 3261
EP  - 3266
PB  - National Acad. of Sciences
CY  - Washington
ER  - 
TY  - GEN
A1  - Garcin, Yannick
A1  - Deschamps, Pierre
A1  - Menot, Guillemette
A1  - de Saulieu, Geoffroy
A1  - Schefuss, Enno
A1  - Sebag, David
A1  - Dupont, Lydie M.
A1  - Oslisly, Richard
A1  - Brademann, Brian
A1  - Mbusnum, Kevin G.
A1  - Onana, Jean-Michel
A1  - Ako, Andrew A.
A1  - Epp, Laura Saskia
A1  - Tjallingii, Rik
A1  - Strecker, Manfred
A1  - Brauer, Achim
A1  - Sachse, Dirk
T1  - No evidence for climate variability during the late Holocene rainforest crisis in Western Central Africa REPLY
T2  - Proceedings of the National Academy of Sciences of the United States of America
Y1  - 2018
U6  - https://doi.org/10.1073/pnas.1808481115
SN  - 0027-8424
VL  - 115
IS  - 29
SP  - E6674
EP  - E6675
PB  - National Acad. of Sciences
CY  - Washington
ER  - 
TY  - GEN
A1  - Garcin, Yannick
A1  - Deschamps, Pierre
A1  - Menot, Guillemette
A1  - de Saulieu, Geoffroy
A1  - Schefuss, Enno
A1  - Sebag, David
A1  - Dupont, Lydie M.
A1  - Oslisly, Richard
A1  - Brademann, Brian
A1  - Mbusnum, Kevin G.
A1  - Onana, Jean-Michel
A1  - Ako, Andrew A.
A1  - Epp, Laura Saskia
A1  - Tjallingii, Rik
A1  - Strecker, Manfred
A1  - Brauer, Achim
A1  - Sachse, Dirk
T1  - Human activity is the most probable trigger of the late Holocene rainforest crisis in Western Central Africa Reply
T2  - Proceedings of the National Academy of Sciences of the United States of America
Y1  - 2018
U6  - https://doi.org/10.1073/pnas.1805582115
SN  - 0027-8424
VL  - 115
IS  - 21
SP  - E4735
EP  - E4736
PB  - National Acad. of Sciences
CY  - Washington
ER  -