@misc{AcevedoFallahReichetal.2017, author = {Acevedo, Walter and Fallah, Bijan and Reich, Sebastian and Cubasch, Ulrich}, title = {Assimilation of pseudo-tree-ring-width observations into an atmospheric general circulation model}, series = {Postprints der Universit{\"a}t Potsdam : Mathematisch Naturwissenschaftliche Reihe}, journal = {Postprints der Universit{\"a}t Potsdam : Mathematisch Naturwissenschaftliche Reihe}, number = {627}, issn = {1866-8372}, doi = {10.25932/publishup-41874}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-418743}, pages = {545 -- 557}, year = {2017}, abstract = {Paleoclimate data assimilation (DA) is a promising technique to systematically combine the information from climate model simulations and proxy records. Here, we investigate the assimilation of tree-ring-width (TRW) chronologies into an atmospheric global climate model using ensemble Kalman filter (EnKF) techniques and a process-based tree-growth forward model as an observation operator. Our results, within a perfect-model experiment setting, indicate that the "online DA" approach did not outperform the "off-line" one, despite its considerable additional implementation complexity. On the other hand, it was observed that the nonlinear response of tree growth to surface temperature and soil moisture does deteriorate the operation of the time-averaged EnKF methodology. Moreover, for the first time we show that this skill loss appears significantly sensitive to the structure of the growth rate function, used to represent the principle of limiting factors (PLF) within the forward model. In general, our experiments showed that the error reduction achieved by assimilating pseudo-TRW chronologies is modulated by the magnitude of the yearly internal variability in themodel. This result might help the dendrochronology community to optimize their sampling efforts.}, language = {en} } @misc{AgarwalMarwanMaheswaranetal.2017, author = {Agarwal, Ankit and Marwan, Norbert and Maheswaran, Rathinasamy and Merz, Bruno and Kurths, J{\"u}rgen}, title = {Multi-scale event synchronization analysis for unravelling climate processes}, series = {Postprints der Universit{\"a}t Potsdam : Mathematisch-Naturwissenschaftliche Reihe}, journal = {Postprints der Universit{\"a}t Potsdam : Mathematisch-Naturwissenschaftliche Reihe}, number = {661}, issn = {1866-8372}, doi = {10.25932/publishup-41827}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-418274}, pages = {13}, year = {2017}, abstract = {The temporal dynamics of climate processes are spread across different timescales and, as such, the study of these processes at only one selected timescale might not reveal the complete mechanisms and interactions within and between the (sub-) processes. To capture the non-linear interactions between climatic events, the method of event synchronization has found increasing attention recently. The main drawback with the present estimation of event synchronization is its restriction to analysing the time series at one reference timescale only. The study of event synchronization at multiple scales would be of great interest to comprehend the dynamics of the investigated climate processes. In this paper, the wavelet-based multi-scale event synchronization (MSES) method is proposed by combining the wavelet transform and event synchronization. Wavelets are used extensively to comprehend multi-scale processes and the dynamics of processes across various timescales. The proposed method allows the study of spatio-temporal patterns across different timescales. The method is tested on synthetic and real-world time series in order to check its replicability and applicability. The results indicate that MSES is able to capture relationships that exist between processes at different timescales.}, language = {en} } @misc{AngermannJackischAllroggenetal.2017, author = {Angermann, Lisa and Jackisch, Conrad and Allroggen, Niklas and Sprenger, Matthias and Zehe, Erwin and Tronicke, Jens and Weiler, Markus and Blume, Theresa}, title = {Form and function in hillslope hydrology}, series = {Postprints der Universit{\"a}t Potsdam : Mathematisch-Naturwissenschaftliche Reihe}, journal = {Postprints der Universit{\"a}t Potsdam : Mathematisch-Naturwissenschaftliche Reihe}, number = {658}, issn = {1866-8372}, doi = {10.25932/publishup-41916}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-419161}, pages = {22}, year = {2017}, abstract = {The phrase form and function was established in architecture and biology and refers to the idea that form and functionality are closely correlated, influence each other, and co-evolve. We suggest transferring this idea to hydrological systems to separate and analyze their two main characteristics: their form, which is equivalent to the spatial structure and static properties, and their function, equivalent to internal responses and hydrological behavior. While this approach is not particularly new to hydrological field research, we want to employ this concept to explicitly pursue the question of what information is most advantageous to understand a hydrological system. We applied this concept to subsurface flow within a hillslope, with a methodological focus on function: we conducted observations during a natural storm event and followed this with a hillslope-scale irrigation experiment. The results are used to infer hydrological processes of the monitored system. Based on these findings, the explanatory power and conclusiveness of the data are discussed. The measurements included basic hydrological monitoring methods, like piezometers, soil moisture, and discharge measurements. These were accompanied by isotope sampling and a novel application of 2-D time-lapse GPR (ground-penetrating radar). The main finding regarding the processes in the hillslope was that preferential flow paths were established quickly, despite unsaturated conditions. These flow paths also caused a detectable signal in the catchment response following a natural rainfall event, showing that these processes are relevant also at the catchment scale. Thus, we conclude that response observations (dynamics and patterns, i.e., indicators of function) were well suited to describing processes at the observational scale. Especially the use of 2-D time-lapse GPR measurements, providing detailed subsurface response patterns, as well as the combination of stream-centered and hillslope-centered approaches, allowed us to link processes and put them in a larger context. Transfer to other scales beyond observational scale and generalizations, however, rely on the knowledge of structures (form) and remain speculative. The complementary approach with a methodological focus on form (i.e., structure exploration) is presented and discussed in the companion paper by Jackisch et al. (2017).}, language = {en} } @misc{BaroniZinkKumaretal.2017, author = {Baroni, Gabriele and Zink, Matthias and Kumar, Rohini and Samaniego, Luis and Attinger, Sabine}, title = {Effects of uncertainty in soil properties on simulated hydrological states and fluxes at different spatio-temporal scales}, series = {Postprints der Universit{\"a}t Potsdam Mathematisch-Naturwissenschaftliche Reihe}, journal = {Postprints der Universit{\"a}t Potsdam Mathematisch-Naturwissenschaftliche Reihe}, number = {545}, issn = {1866-8372}, doi = {10.25932/publishup-41917}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-419174}, pages = {20}, year = {2017}, abstract = {Soil properties show high heterogeneity at different spatial scales and their correct characterization remains a crucial challenge over large areas. The aim of the study is to quantify the impact of different types of uncertainties that arise from the unresolved soil spatial variability on simulated hydrological states and fluxes. Three perturbation methods are presented for the characterization of uncertainties in soil properties. The methods are applied on the soil map of the upper Neckar catchment (Germany), as an example. The uncertainties are propagated through the distributed mesoscale hydrological model (mHM) to assess the impact on the simulated states and fluxes. The model outputs are analysed by aggregating the results at different spatial and temporal scales. These results show that the impact of the different uncertainties introduced in the original soil map is equivalent when the simulated model outputs are analysed at the model grid resolution (i.e. 500 m). However, several differences are identified by aggregating states and fluxes at different spatial scales (by subcatchments of different sizes or coarsening the grid resolution). Streamflow is only sensitive to the perturbation of long spatial structures while distributed states and fluxes (e.g. soil moisture and groundwater recharge) are only sensitive to the local noise introduced to the original soil properties. A clear identification of the temporal and spatial scale for which finer-resolution soil information is (or is not) relevant is unlikely to be universal. However, the comparison of the impacts on the different hydrological components can be used to prioritize the model improvements in specific applications, either by collecting new measurements or by calibration and data assimilation approaches. In conclusion, the study underlines the importance of a correct characterization of uncertainty in soil properties. With that, soil maps with additional information regarding the unresolved soil spatial variability would provide strong support to hydrological modelling applications.}, language = {en} } @misc{BaslerXenikoudakisWestburyetal.2017, author = {Basler, Nikolas and Xenikoudakis, Georgios and Westbury, Michael V. and Song, Lingfeng and Sheng, Guilian and Barlow, Axel}, title = {Reduction of the contaminant fraction of DNA obtained from an ancient giant panda bone}, series = {Postprints der Universit{\"a}t Potsdam Mathematisch-Naturwissenschaftliche Reihe}, journal = {Postprints der Universit{\"a}t Potsdam Mathematisch-Naturwissenschaftliche Reihe}, number = {715}, issn = {1866-8372}, doi = {10.25932/publishup-42815}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-428151}, pages = {7}, year = {2017}, abstract = {Objective: A key challenge in ancient DNA research is massive microbial DNA contamination from the deposition site which accumulates post mortem in the study organism's remains. Two simple and cost-effective methods to enrich the relative endogenous fraction of DNA in ancient samples involve treatment of sample powder with either bleach or Proteinase K pre-digestion prior to DNA extraction. Both approaches have yielded promising but vary-ing results in other studies. Here, we contribute data on the performance of these methods using a comprehensive and systematic series of experiments applied to a single ancient bone fragment from a giant panda (Ailuropoda melanoleuca).Results: Bleach and pre-digestion treatments increased the endogenous DNA content up to ninefold. However, the absolute amount of DNA retrieved was dramatically reduced by all treatments. We also observed reduced DNA damage patterns in pre-treated libraries compared to untreated ones, resulting in longer mean fragment lengths and reduced thymine over-representation at fragment ends. Guanine-cytosine (GC) contents of both mapped and total reads are consistent between treatments and conform to general expectations, indicating no obvious biasing effect of the applied methods. Our results therefore confirm the value of bleach and pre-digestion as tools in palaeog-enomic studies, providing sufficient material is available.}, language = {en} } @misc{BaumbachSiegmundMittermeieretal.2017, author = {Baumbach, Lukas and Siegmund, Jonatan Frederik and Mittermeier, Magdalena and Donner, Reik Volker}, title = {Impacts of temperature extremes on European vegetation during the growing season}, series = {Postprints der Universit{\"a}t Potsdam : Mathematisch Naturwissenschaftliche Reihe}, journal = {Postprints der Universit{\"a}t Potsdam : Mathematisch Naturwissenschaftliche Reihe}, number = {642}, issn = {1866-8372}, doi = {10.25932/publishup-41801}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-418018}, pages = {4891 -- 4903}, year = {2017}, abstract = {Temperature is a key factor controlling plant growth and vitality in the temperate climates of the mid-latitudes like in vast parts of the European continent. Beyond the effect of average conditions, the timings and magnitudes of temperature extremes play a particularly crucial role, which needs to be better understood in the context of projected future rises in the frequency and/or intensity of such events. In this work, we employ event coincidence analysis (ECA) to quantify the likelihood of simultaneous occurrences of extremes in daytime land surface temperature anomalies (LSTAD) and the normalized difference vegetation index (NDVI). We perform this analysis for entire Europe based upon remote sensing data, differentiating between three periods corresponding to different stages of plant development during the growing season. In addition, we analyze the typical elevation and land cover type of the regions showing significantly large event coincidences rates to identify the most severely affected vegetation types. Our results reveal distinct spatio-temporal impact patterns in terms of extraordinarily large co-occurrence rates between several combinations of temperature and NDVI extremes. Croplands are among the most frequently affected land cover types, while elevation is found to have only a minor effect on the spatial distribution of corresponding extreme weather impacts. These findings provide important insights into the vulnerability of European terrestrial ecosystems to extreme temperature events and demonstrate how event-based statistics like ECA can provide a valuable perspective on environmental nexuses.}, language = {en} } @misc{BeaumontWarringtonCavadinoetal.2017, author = {Beaumont, Robin N. and Warrington, Nicole M. and Cavadino, Alana and Tyrrell, Jessica and Nodzenski, Michael and Horikoshi, Momoko and Geller, Frank and Myhre, Ronny and Richmond, Rebecca C. and Paternoster, Lavinia and Bradfield, Jonathan P. and Kreiner-M{\o}ller, Eskil and Huikari, Ville and Metrustry, Sarah and Lunetta, Kathryn L. and Painter, Jodie N. and Hottenga, Jouke-Jan and Allard, Catherine and Barton, Sheila J. and Espinosa, Ana and Marsh, Julie A. and Potter, Catherine and Zhang, Ge and Ang, Wei and Berry, Diane J. and Bouchard, Luigi and Das, Shikta and Hakonarson, Hakon and Heikkinen, Jani and Helgeland, {\O}yvind and Hocher, Berthold and Hofman, Albert and Inskip, Hazel M. and Jones, Samuel E. and Kogevinas, Manolis and Lind, Penelope A. and Marullo, Letizia and Medland, Sarah E. and Murray, Anna and Murray, Jeffrey C. and Nj{\o}lstad, Pa ̊l R. and Nohr, Ellen A. and Reichetzeder, Christoph and Ring, Susan M. and Ruth, Katherine S. and Santa-Marina, Loreto and Scholtens, Denise M. and Sebert, Sylvain and Sengpiel, Verena and Tuke, Marcus A. and Vaudel, Marc and Weedon, Michael N. and Willemsen, Gonneke and Wood, Andrew R. and Yaghootkar, Hanieh and Muglia, Louis J. and Bartels, Meike and Relton, Caroline L. and Pennell, Craig E. and Chatzi, Leda and Estivill, Xavier and Holloway, John W. and Boomsma, Dorret I. and Montgomery, Grant W. and Murabito, Joanne M. and Spector, Tim D. and Power, Christine and Ja ̈rvelin, Marjo-Ritta and Bisgaard, Hans and Grant, Struan F.A. and S{\o}rensen, Thorkild I.A. and Jaddoe, Vincent W. and Jacobsson, Bo and Melbye, Mads and McCarthy, Mark I. and Hattersley, Andrew T. and Hayes, M. Geoffrey and Frayling, Timothy M. and Hivert, Marie-France and Felix, Janine F. and Hyppo ̈nen, Elina and Lowe, William L. , Jr and Evans, David M. and Lawlor, Debbie A. and Feenstra, Bjarke and Freathy, Rachel M.}, title = {Genome-wide association study of offspring birth weight in 86 577 women identifies five novel loci and highlights maternal genetic effects that are independent of fetal genetics}, series = {Postprints der Universit{\"a}t Potsdam : Mathematisch-Naturwissenschaftliche Reihe}, journal = {Postprints der Universit{\"a}t Potsdam : Mathematisch-Naturwissenschaftliche Reihe}, number = {628}, issn = {1866-8372}, doi = {10.25932/publishup-42310}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-423100}, pages = {15}, year = {2017}, abstract = {Genome-wide association studies of birth weight have focused on fetal genetics, whereas relatively little is known about the role of maternal genetic variation. We aimed to identify maternal genetic variants associated with birth weight that could highlight potentially relevant maternal determinants of fetal growth. We meta-analysed data on up to 8.7 million SNPs in up to 86 577 women of European descent from the Early Growth Genetics (EGG) Consortium and the UK Biobank. We used structural equation modelling (SEM) and analyses of mother-child pairs to quantify the separate maternal and fetal genetic effects. Maternal SNPs at 10 loci (MTNR1B, HMGA2, SH2B3, KCNAB1, L3MBTL3, GCK, EBF1, TCF7L2, ACTL9, CYP3A7) were associated with offspring birth weight at P < 5 {\^A} 10 {\`A}8 . In SEM analyses, at least 7 of the 10 associations were consistent with effects of the maternal genotype acting via the intrauterine environment, rather than via effects of shared alleles with the fetus. Variants, or correlated proxies, at many of the loci had been previously associated with adult traits, including fasting glucose (MTNR1B, GCK and TCF7L2) and sex hormone levels (CYP3A7), and one (EBF1) with gestational duration. The identified associations indicate that genetic effects on maternal glucose, cytochrome P450 activity and gestational duration, and potentially on maternal blood pressure and immune function, are relevant for fetal growth. Further characterization of these associations in mechanistic and causal analyses will enhance understanding of the potentially modifiable maternal determinants of fetal growth, with the goal of reducing the morbidity and mortality associated with low and high birth weights.}, language = {en} } @misc{BeniniSchenkel2017, author = {Benini, Marco and Schenkel, Alexander}, title = {Quantum field theories on categories fibered in groupoids}, series = {Postprints der Universit{\"a}t Potsdam : Mathematisch-Naturwissenschaftliche Reihe}, journal = {Postprints der Universit{\"a}t Potsdam : Mathematisch-Naturwissenschaftliche Reihe}, number = {895}, issn = {1866-8372}, doi = {10.25932/publishup-43154}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-431541}, pages = {48}, year = {2017}, abstract = {We introduce an abstract concept of quantum field theory on categories fibered in groupoids over the category of spacetimes. This provides us with a general and flexible framework to study quantum field theories defined on spacetimes with extra geometric structures such as bundles, connections and spin structures. Using right Kan extensions, we can assign to any such theory an ordinary quantum field theory defined on the category of spacetimes and we shall clarify under which conditions it satisfies the axioms of locally covariant quantum field theory. The same constructions can be performed in a homotopy theoretic framework by using homotopy right Kan extensions, which allows us to obtain first toy-models of homotopical quantum field theories resembling some aspects of gauge theories.}, language = {en} } @misc{BoersGoswamiGhil2017, author = {Boers, Niklas and Goswami, Bedartha and Ghil, Michael}, title = {A complete representation of uncertainties in layer-counted paleoclimatic archives}, series = {Postprints der Universit{\"a}t Potsdam : Mathematisch-Naturwissenschaftliche Reihe}, journal = {Postprints der Universit{\"a}t Potsdam : Mathematisch-Naturwissenschaftliche Reihe}, number = {641}, issn = {1866-8372}, doi = {10.25932/publishup-41803}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-418030}, pages = {12}, year = {2017}, abstract = {Accurate time series representation of paleoclimatic proxy records is challenging because such records involve dating errors in addition to proxy measurement errors. Rigorous attention is rarely given to age uncertainties in paleoclimatic research, although the latter can severely bias the results of proxy record analysis. Here, we introduce a Bayesian approach to represent layer-counted proxy records - such as ice cores, sediments, corals, or tree rings - as sequences of probability distributions on absolute, error-free time axes. The method accounts for both proxy measurement errors and uncertainties arising from layer-counting-based dating of the records. An application to oxygen isotope ratios from the North Greenland Ice Core Project (NGRIP) record reveals that the counting errors, although seemingly small, lead to substantial uncertainties in the final representation of the oxygen isotope ratios. In particular, for the older parts of the NGRIP record, our results show that the total uncertainty originating from dating errors has been seriously underestimated. Our method is next applied to deriving the overall uncertainties of the Suigetsu radiocarbon comparison curve, which was recently obtained from varved sediment cores at Lake Suigetsu, Japan. This curve provides the only terrestrial radiocarbon comparison for the time interval 12.5-52.8 kyr BP. The uncertainties derived here can be readily employed to obtain complete error estimates for arbitrary radiometrically dated proxy records of this recent part of the last glacial interval.}, language = {en} } @misc{BuschKlausPenoneetal.2017, author = {Busch, Verena and Klaus, Valentin H. and Penone, Caterina and Sch{\"a}fer, Deborah and Boch, Steffen and Prati, Daniel and M{\"u}ller, J{\"o}rg and Socher, Stephanie A. and Niinemets, {\"U}lo and Pe{\~n}uelas, Josep and H{\"o}lzel, Norbert and Fischer, Markus and Kleinebecker, Till}, title = {Nutrient stoichiometry and land use rather than species richness determine plant functional diversity}, series = {Postprints der Universit{\"a}t Potsdam : Mathematisch-Naturwissenschaftliche Reihe}, journal = {Postprints der Universit{\"a}t Potsdam : Mathematisch-Naturwissenschaftliche Reihe}, number = {651}, issn = {1866-8372}, doi = {10.25932/publishup-42461}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-424617}, pages = {16}, year = {2017}, abstract = {Plant functional traits reflect individual and community ecological strategies. They allow the detection of directional changes in community dynamics and ecosystemic processes, being an additional tool to assess biodiversity than species richness. Analysis of functional patterns in plant communities provides mechanistic insight into biodiversity alterations due to anthropogenic activity. Although studies have considered of either anthropogenic management or nutrient availability on functional traits in temperate grasslands, studies combining effects of both drivers are scarce. Here, we assessed the impacts of management intensity (fertilization, mowing, grazing), nutrient stoichiometry (C, N, P, K), and vegetation composition on community-weighted means (CWMs) and functional diversity (Rao's Q) from seven plant traits in 150 grasslands in three regions in Germany, using data of 6 years. Land use and nutrient stoichiometry accounted for larger proportions of model variance of CWM and Rao's Q than species richness and productivity. Grazing affected all analyzed trait groups; fertilization and mowing only impacted generative traits. Grazing was clearly associated with nutrient retention strategies, that is, investing in durable structures and production of fewer, less variable seed. Phenological variability was increased. Fertilization and mowing decreased seed number/mass variability, indicating competition-related effects. Impacts of nutrient stoichiometry on trait syndromes varied. Nutrient limitation (large N:P, C:N ratios) promoted species with conservative strategies, that is, investment in durable plant structures rather than fast growth, fewer seed, and delayed flowering onset. In contrast to seed mass, leaf-economics variability was reduced under P shortage. Species diversity was positively associated with the variability of generative traits. Synthesis. Here, land use, nutrient availability, species richness, and plant functional strategies have been shown to interact complexly, driving community composition, and vegetation responses to management intensity. We suggest that deeper understanding of underlying mechanisms shaping community assembly and biodiversity will require analyzing all these parameters.}, language = {en} }