TY - JOUR A1 - Allan, Eric A1 - Bossdorf, Oliver A1 - Dormann, Carsten F. A1 - Prati, Daniel A1 - Gossner, Martin M. A1 - Tscharntke, Teja A1 - Blüthgen, Nico A1 - Bellach, Michaela A1 - Birkhofer, Klaus A1 - Boch, Steffen A1 - Böhm, Stefan A1 - Börschig, Carmen A1 - Chatzinotas, Antonis A1 - Christ, Sabina A1 - Daniel, Rolf A1 - Diekötter, Tim A1 - Fischer, Christiane A1 - Friedl, Thomas A1 - Glaser, Karin A1 - Hallmann, Christine A1 - Hodac, Ladislav A1 - Hölzel, Norbert A1 - Jung, Kirsten A1 - Klein, Alexandra-Maria A1 - Klaus, Valentin H. A1 - Kleinebecker, Till A1 - Krauss, Jochen A1 - Lange, Markus A1 - Morris, E. Kathryn A1 - Müller, Jörg A1 - Nacke, Heiko A1 - Pasalic, Esther A1 - Rillig, Matthias C. A1 - Rothenwoehrer, Christoph A1 - Schally, Peter A1 - Scherber, Christoph A1 - Schulze, Waltraud X. A1 - Socher, Stephanie A. A1 - Steckel, Juliane A1 - Steffan-Dewenter, Ingolf A1 - Türke, Manfred A1 - Weiner, Christiane N. A1 - Werner, Michael A1 - Westphal, Catrin A1 - Wolters, Volkmar A1 - Wubet, Tesfaye A1 - Gockel, Sonja A1 - Gorke, Martin A1 - Hemp, Andreas A1 - Renner, Swen C. A1 - Schöning, Ingo A1 - Pfeiffer, Simone A1 - König-Ries, Birgitta A1 - Buscot, Francois A1 - Linsenmair, Karl Eduard A1 - Schulze, Ernst-Detlef A1 - Weisser, Wolfgang W. A1 - Fischer, Markus T1 - Interannual variation in land-use intensity enhances grassland multidiversity JF - Proceedings of the National Academy of Sciences of the United States of America N2 - Although temporal heterogeneity is a well-accepted driver of biodiversity, effects of interannual variation in land-use intensity (LUI) have not been addressed yet. Additionally, responses to land use can differ greatly among different organisms; therefore, overall effects of land-use on total local biodiversity are hardly known. To test for effects of LUI (quantified as the combined intensity of fertilization, grazing, and mowing) and interannual variation in LUI (SD in LUI across time), we introduce a unique measure of whole-ecosystem biodiversity, multidiversity. This synthesizes individual diversity measures across up to 49 taxonomic groups of plants, animals, fungi, and bacteria from 150 grasslands. Multidiversity declined with increasing LUI among grasslands, particularly for rarer species and aboveground organisms, whereas common species and belowground groups were less sensitive. However, a high level of interannual variation in LUI increased overall multidiversity at low LUI and was even more beneficial for rarer species because it slowed the rate at which the multidiversity of rare species declined with increasing LUI. In more intensively managed grasslands, the diversity of rarer species was, on average, 18% of the maximum diversity across all grasslands when LUI was static over time but increased to 31% of the maximum when LUI changed maximally over time. In addition to decreasing overall LUI, we suggest varying LUI across years as a complementary strategy to promote biodiversity conservation. KW - biodiversity loss KW - agricultural grasslands KW - Biodiversity Exploratories Y1 - 2014 U6 - https://doi.org/10.1073/pnas.1312213111 SN - 0027-8424 VL - 111 IS - 1 SP - 308 EP - 313 PB - National Acad. of Sciences CY - Washington ER - TY - JOUR A1 - Penone, Caterina A1 - Allan, Eric A1 - Soliveres, Santiago A1 - Felipe-Lucia, Maria R. A1 - Gossner, Martin M. A1 - Seibold, Sebastian A1 - Simons, Nadja K. A1 - Schall, Peter A1 - van der Plas, Fons A1 - Manning, Peter A1 - Manzanedo, Ruben D. A1 - Boch, Steffen A1 - Prati, Daniel A1 - Ammer, Christian A1 - Bauhus, Juergen A1 - Buscot, Francois A1 - Ehbrecht, Martin A1 - Goldmann, Kezia A1 - Jung, Kirsten A1 - Mueller, Joerg A1 - Mueller, Joerg C. A1 - Pena, Rodica A1 - Polle, Andrea A1 - Renner, Swen C. A1 - Ruess, Liliane A1 - Schoenig, Ingo A1 - Schrumpf, Marion A1 - Solly, Emily F. A1 - Tschapka, Marco A1 - Weisser, Wolfgang W. A1 - Wubet, Tesfaye A1 - Fischer, Markus T1 - Specialisation and diversity of multiple trophic groups are promoted by different forest features JF - Ecology letters N2 - While forest management strongly influences biodiversity, it remains unclear how the structural and compositional changes caused by management affect different community dimensions (e.g. richness, specialisation, abundance or completeness) and how this differs between taxa. We assessed the effects of nine forest features (representing stand structure, heterogeneity and tree composition) on thirteen above- and belowground trophic groups of plants, animals, fungi and bacteria in 150 temperate forest plots differing in their management type. Canopy cover decreased light resources, which increased community specialisation but reduced overall diversity and abundance. Features increasing resource types and diversifying microhabitats (admixing of oaks and conifers) were important and mostly affected richness. Belowground groups responded differently to those aboveground and had weaker responses to most forest features. Our results show that we need to consider forest features rather than broad management types and highlight the importance of considering several groups and community dimensions to better inform conservation. KW - biodiversity exploratories KW - dark diversity KW - forest management KW - global change KW - land-use KW - multidiversity KW - specialisation KW - temperate forests Y1 - 2018 U6 - https://doi.org/10.1111/ele.13182 SN - 1461-023X SN - 1461-0248 VL - 22 IS - 1 SP - 170 EP - 180 PB - Wiley CY - Hoboken ER - TY - JOUR A1 - Fischer, Eric Wolfgang A1 - Anders, Janet A1 - Saalfrank, Peter T1 - Cavity-altered thermal isomerization rates and dynamical resonant localization in vibro-polaritonic chemistry JF - The journal of chemical physics : bridges a gap between journals of physics and journals of chemistr N2 - It has been experimentally demonstrated that reaction rates for molecules embedded in microfluidic optical cavities are altered when compared to rates observed under "ordinary" reaction conditions. However, precise mechanisms of how strong coupling of an optical cavity mode to molecular vibrations affects the reactivity and how resonance behavior emerges are still under dispute. In the present work, we approach these mechanistic issues from the perspective of a thermal model reaction, the inversion of ammonia along the umbrella mode, in the presence of a single-cavity mode of varying frequency and coupling strength. A topological analysis of the related cavity Born-Oppenheimer potential energy surface in combination with quantum mechanical and transition state theory rate calculations reveals two quantum effects, leading to decelerated reaction rates in qualitative agreement with experiments: the stiffening of quantized modes perpendicular to the reaction path at the transition state, which reduces the number of thermally accessible reaction channels, and the broadening of the barrier region, which attenuates tunneling. We find these two effects to be very robust in a fluctuating environment, causing statistical variations of potential parameters, such as the barrier height. Furthermore, by solving the time-dependent Schrodinger equation in the vibrational strong coupling regime, we identify a resonance behavior, in qualitative agreement with experimental and earlier theoretical work. The latter manifests as reduced reaction probability when the cavity frequency omega(c) is tuned resonant to a molecular reactant frequency. We find this effect to be based on the dynamical localization of the vibro-polaritonic wavepacket in the reactant well. Y1 - 2022 U6 - https://doi.org/10.1063/5.0076434 SN - 0021-9606 SN - 1089-7690 VL - 156 IS - 15 PB - American Institute of Physics CY - Melville, NY ER - TY - JOUR A1 - Soliveres, Santiago A1 - Maestre, Fernando T. A1 - Ulrich, Werner A1 - Manning, Peter A1 - Boch, Steffen A1 - Bowker, Matthew A. A1 - Prati, Daniel A1 - Delgado-Baquerizo, Manuel A1 - Quero, Jose L. A1 - Schöning, Ingo A1 - Gallardo, Antonio A1 - Weisser, Wolfgang W. A1 - Müller, Jörg A1 - Socher, Stephanie A. A1 - Garcia-Gomez, Miguel A1 - Ochoa, Victoria A1 - Schulze, Ernst-Detlef A1 - Fischer, Markus A1 - Allan, Eric T1 - Intransitive competition is widespread in plant communities and maintains their species richness JF - Ecology letters N2 - Intransitive competition networks, those in which there is no single best competitor, may ensure species coexistence. However, their frequency and importance in maintaining diversity in real-world ecosystems remain unclear. We used two large data sets from drylands and agricultural grasslands to assess: (1) the generality of intransitive competition, (2) intransitivity-richness relationships and (3) effects of two major drivers of biodiversity loss (aridity and land-use intensification) on intransitivity and species richness. Intransitive competition occurred in >65% of sites and was associated with higher species richness. Intransitivity increased with aridity, partly buffering its negative effects on diversity, but was decreased by intensive land use, enhancing its negative effects on diversity. These contrasting responses likely arise because intransitivity is promoted by temporal heterogeneity, which is enhanced by aridity but may decline with land-use intensity. We show that intransitivity is widespread in nature and increases diversity, but it can be lost with environmental homogenisation. KW - Aridity KW - biodiversity KW - coexistence KW - drylands KW - land use KW - mesic grasslands KW - rock-paper-scissors game Y1 - 2015 U6 - https://doi.org/10.1111/ele.12456 SN - 1461-023X SN - 1461-0248 VL - 18 IS - 8 SP - 790 EP - 798 PB - Wiley-Blackwell CY - Hoboken ER - TY - JOUR A1 - Allan, Eric A1 - Manning, Pete A1 - Alt, Fabian A1 - Binkenstein, Julia A1 - Blaser, Stefan A1 - Blüthgen, Nico A1 - Böhm, Stefan A1 - Grassein, Fabrice A1 - Hölzel, Norbert A1 - Klaus, Valentin H. A1 - Kleinebecker, Till A1 - Morris, E. Kathryn A1 - Oelmann, Yvonne A1 - Prati, Daniel A1 - Renner, Swen C. A1 - Rillig, Matthias C. A1 - Schaefer, Martin A1 - Schloter, Michael A1 - Schmitt, Barbara A1 - Schöning, Ingo A1 - Schrumpf, Marion A1 - Solly, Emily A1 - Sorkau, Elisabeth A1 - Steckel, Juliane A1 - Steffen-Dewenter, Ingolf A1 - Stempfhuber, Barbara A1 - Tschapka, Marco A1 - Weiner, Christiane N. A1 - Weisser, Wolfgang W. A1 - Werner, Michael A1 - Westphal, Catrin A1 - Wilcke, Wolfgang A1 - Fischer, Markus T1 - Land use intensification alters ecosystem multifunctionality via loss of biodiversity and changes to functional composition JF - Ecology letters N2 - Global change, especially land-use intensification, affects human well-being by impacting the delivery of multiple ecosystem services (multifunctionality). However, whether biodiversity loss is a major component of global change effects on multifunctionality in real-world ecosystems, as in experimental ones, remains unclear. Therefore, we assessed biodiversity, functional composition and 14 ecosystem services on 150 agricultural grasslands differing in land-use intensity. We also introduce five multifunctionality measures in which ecosystem services were weighted according to realistic land-use objectives. We found that indirect land-use effects, i.e. those mediated by biodiversity loss and by changes to functional composition, were as strong as direct effects on average. Their strength varied with land-use objectives and regional context. Biodiversity loss explained indirect effects in a region of intermediate productivity and was most damaging when land-use objectives favoured supporting and cultural services. In contrast, functional composition shifts, towards fast-growing plant species, strongly increased provisioning services in more inherently unproductive grasslands. KW - Biodiversity-ecosystem functioning KW - ecosystem services KW - global change KW - land use KW - multifunctionality Y1 - 2015 U6 - https://doi.org/10.1111/ele.12469 SN - 1461-023X SN - 1461-0248 VL - 18 IS - 8 SP - 834 EP - 843 PB - Wiley-Blackwell CY - Hoboken ER - TY - JOUR A1 - Heinze, Eric A1 - Boch, Steffen A1 - Fischer, Markus A1 - Hessenmöller, Dominik A1 - Klenk, Bernd A1 - Müller, Jörg A1 - Prati, Daniel A1 - Schulze, Ernst-Detlef A1 - Seele, Carolin A1 - Socher, Stephanie A1 - Halle, Stefan T1 - Habitat use of large ungulates in northeastern Germany in relation to forest management JF - Forest ecology and management N2 - Estimating large herbivore density has been a major area of research in recent decades. Previous studies monitoring ungulate density, however, focused mostly on determining animal abundance, and did not interpret animal distribution in relation to habitat parameters. We surveyed large ungulates in the Biodiversity Exploratory Schorfheide-Chorin using faecal pellet group counts. This allowed us to explore the link between relative ungulate abundance, habitat use, and browsing damage on trees in a region with several types of forest, including unharvested and age-class beech forests, as well as age-class pine forests. Our results demonstrate that roe deer and fallow deer relative abundance is negatively correlated with large tree cover, and positively correlated with the cover of small shrubs (Rubus spec., Vaccinium spec.), and winter food supply. Habitat use of roe deer and fallow deer, as estimated by counting faecal pellet groups, revealed a preference for mature pine forests, and avoidance of deciduous forests. This differential habitat use is explained by different distributions of high quality food resources during winter. The response of deer to understory cover differed between roe deer and fallow deer at high cover percentages. The amount of browsing damage we observed on coniferous trees was not consistent with the relative deer abundance. Browsing damage was consistently higher on most deciduous trees, except for beech saplings which sustained less damage when roe deer density was low. Because roe deer is a highly selective feeder, it was reported to affect tree diversity by feeding only on trees with high nutritional value. Consequently, we propose that managing the number of all deer species by hunting is necessary to allow successful forest regeneration. Such an adjustment to deer numbers would need to account for both current tree diversity and alternative food resources. Our findings may be applicable to other forest landscapes in northeastern Germany including mature pine stands and differently harvested deciduous forests. KW - Large ungulates KW - Faecal pellet group count KW - Forest management KW - Browsing damage Y1 - 2011 U6 - https://doi.org/10.1016/j.foreco.2010.10.022 SN - 0378-1127 VL - 261 IS - 2 SP - 288 EP - 296 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Soliveres, Santiago A1 - van der Plas, Fons A1 - Manning, Peter A1 - Prati, Daniel A1 - Gossner, Martin M. A1 - Renner, Swen C. A1 - Alt, Fabian A1 - Arndt, Hartmut A1 - Baumgartner, Vanessa A1 - Binkenstein, Julia A1 - Birkhofer, Klaus A1 - Blaser, Stefan A1 - Blüthgen, Nico A1 - Boch, Steffen A1 - Böhm, Stefan A1 - Börschig, Carmen A1 - Buscot, Francois A1 - Diekötter, Tim A1 - Heinze, Johannes A1 - Hölzel, Norbert A1 - Jung, Kirsten A1 - Klaus, Valentin H. A1 - Kleinebecker, Till A1 - Klemmer, Sandra A1 - Krauss, Jochen A1 - Lange, Markus A1 - Morris, E. Kathryn A1 - Müller, Jörg A1 - Oelmann, Yvonne A1 - Overmann, Jörg A1 - Pasalic, Esther A1 - Rillig, Matthias C. A1 - Schaefer, H. Martin A1 - Schloter, Michael A1 - Schmitt, Barbara A1 - Schöning, Ingo A1 - Schrumpf, Marion A1 - Sikorski, Johannes A1 - Socher, Stephanie A. A1 - Solly, Emily F. A1 - Sonnemann, Ilja A1 - Sorkau, Elisabeth A1 - Steckel, Juliane A1 - Steffan-Dewenter, Ingolf A1 - Stempfhuber, Barbara A1 - Tschapka, Marco A1 - Türke, Manfred A1 - Venter, Paul C. A1 - Weiner, Christiane N. A1 - Weisser, Wolfgang W. A1 - Werner, Michael A1 - Westphal, Catrin A1 - Wilcke, Wolfgang A1 - Wolters, Volkmar A1 - Wubet, Tesfaye A1 - Wurst, Susanne A1 - Fischer, Markus A1 - Allan, Eric T1 - Biodiversity at multiple trophic levels is needed for ecosystem multifunctionality JF - Nature : the international weekly journal of science Y1 - 2016 U6 - https://doi.org/10.1038/nature19092 SN - 0028-0836 SN - 1476-4687 VL - 536 SP - 456 EP - + PB - Nature Publ. Group CY - London ER - TY - JOUR A1 - Fischer, Eric Wolfgang A1 - Werther, Michael A1 - Bouakline, Foudhil A1 - Grossmann, Frank A1 - Saalfrank, Peter T1 - Non-Markovian vibrational relaxation dynamics at surfaces JF - The journal of chemical physics : bridges a gap between journals of physics and journals of chemistr N2 - Vibrational dynamics of adsorbates near surfaces plays both an important role for applied surface science and as a model lab for studying fundamental problems of open quantum systems. We employ a previously developed model for the relaxation of a D-Si-Si bending mode at a D:Si(100)-(2 x 1) surface, induced by a "bath " of more than 2000 phonon modes [Lorenz and P. Saalfrank, Chem. Phys. 482, 69 (2017)], to extend previous work along various directions. First, we use a Hierarchical Effective Mode (HEM) model [Fischer et al., J. Chem. Phys. 153, 064704 (2020)] to study relaxation of higher excited vibrational states than hitherto done by solving a high-dimensional system-bath time-dependent Schrodinger equation (TDSE). In the HEM approach, (many) real bath modes are replaced by (much less) effective bath modes. Accordingly, we are able to examine scaling laws for vibrational relaxation lifetimes for a realistic surface science problem. Second, we compare the performance of the multilayer multiconfigurational time-dependent Hartree (ML-MCTDH) approach with that of the recently developed coherent-state-based multi-Davydov-D2 Ansatz [Zhou et al., J. Chem. Phys. 143, 014113 (2015)]. Both approaches work well, with some computational advantages for the latter in the presented context. Third, we apply open-system density matrix theory in comparison with basically "exact " solutions of the multi-mode TDSEs. Specifically, we use an open-system Liouville-von Neumann (LvN) equation treating vibration-phonon coupling as Markovian dissipation in Lindblad form to quantify effects beyond the Born-Markov approximation. Published under an exclusive license by AIP Publishing. KW - phonons KW - Vibrational states KW - Chemical dynamics KW - Adsorption KW - Surface science KW - Open quantum systems KW - Density-matrix KW - Coherent states KW - Markov processes Y1 - 2022 U6 - https://doi.org/10.1063/5.0092836 SN - 0021-9606 SN - 1089-7690 SN - 1520-9032 VL - 156 IS - 21 PB - AIP Publishing CY - Melville ER - TY - JOUR A1 - Fischer, Eric W. A1 - Werther, Michael A1 - Bouakline, Foudhil A1 - Saalfrank, Peter T1 - A hierarchical effective mode approach to phonon-driven multilevel vibrational relaxation dynamics at surfaces JF - The journal of chemical physics : bridges a gap between journals of physics and journals of chemistry N2 - We discuss an efficient Hierarchical Effective Mode (HEM) representation of a high-dimensional harmonic oscillator bath, which describes phonon-driven vibrational relaxation of an adsorbate-surface system, namely, deuterium adsorbed on Si(100). Starting from the original Hamiltonian of the adsorbate-surface system, the HEM representation is constructed via iterative orthogonal transformations, which are efficiently implemented with Householder matrices. The detailed description of the HEM representation and its construction are given in the second quantization representation. The hierarchical nature of this representation allows access to the exact quantum dynamics of the adsorbate-surface system over finite time intervals, controllable via the truncation order of the hierarchy. To study the convergence properties of the effective mode representation, we solve the time-dependent Schrodinger equation of the truncated system-bath HEM Hamiltonian, with the help of the multilayer extension of the Multiconfigurational Time-Dependent Hartree (ML-MCTDH) method. The results of the HEM representation are compared with those obtained with a quantum-mechanical tier-model. The convergence of the HEM representation with respect to the truncation order of the hierarchy is discussed for different initial conditions of the adsorbate-surface system. The combination of the HEM representation with the ML-MCTDH method provides information on the time evolution of the system (adsorbate) and multiple effective modes of the bath (surface). This permits insight into mechanisms of vibration-phonon coupling of the adsorbate-surface system, as well as inter-mode couplings of the effective bath. Y1 - 2020 U6 - https://doi.org/10.1063/5.0017716 SN - 0021-9606 SN - 1089-7690 VL - 153 IS - 6 PB - American Institute of Physics CY - Melville ER - TY - THES A1 - Fischer, Eric Wolfgang T1 - Quantum vibrational dynamics in complex environments: from vibrational strong coupling in molecular cavity QED to phonon-induced adsorbate relaxation N2 - Molecules are often naturally embedded in a complex environment. As a consequence, characteristic properties of a molecular subsystem can be substantially altered or new properties emerge due to interactions between molecular and environmental degrees of freedom. The present thesis is concerned with the numerical study of quantum dynamical and stationary properties of molecular vibrational systems embedded in selected complex environments. In the first part, we discuss "strong-coupling" model scenarios for molecular vibrations interacting with few quantized electromagnetic field modes of an optical Fabry-Pérot cavity. We thoroughly elaborate on properties of emerging "vibrational polariton" light-matter hybrid states and examine the relevance of the dipole self-energy. Further, we identify cavity-induced quantum effects and an emergent dynamical resonance in a cavity-altered thermal isomerization model, which lead to significant suppression of thermal reaction rates. Moreover, for a single rovibrating diatomic molecule in an optical cavity, we observe non-adiabatic signatures in dynamics due to "vibro-polaritonic conical intersections" and discuss spectroscopically accessible "rovibro-polaritonic" light-matter hybrid states. In the second part, we study a weakly coupled but numerically challenging quantum mechanical adsorbate-surface model system comprising a few thousand surface modes. We introduce an efficient construction scheme for a "hierarchical effective mode" approach to reduce the number of surface modes in a controlled manner. In combination with the multilayer multiconfigurational time-dependent Hartree (ML-MCTDH) method, we examine the vibrational adsorbate relaxation dynamics from different excited adsorbate states by solving the full non-Markovian system-bath dynamics for the characteristic relaxation time scale. We examine half-lifetime scaling laws from vibrational populations and identify prominent non-Markovian signatures as deviations from Markovian reduced system density matrix theory in vibrational coherences, system-bath entanglement and energy transfer dynamics. In the final part of this thesis, we approach the dynamics and spectroscopy of vibronic model systems at finite temperature by formulating the ML-MCTDH method in the non-stochastic framework of thermofield dynamics. We apply our method to thermally-altered ultrafast internal conversion in the well-known vibronic coupling model of pyrazine. Numerically beneficial representations of multilayer wave functions ("ML-trees") are identified for different temperature regimes, which allow us to access thermal effects on both electronic and vibrational dynamics as well as spectroscopic properties for several pyrazine models. N2 - Moleküle sind für gewöhnlich in komplexe Umgebungen eingebettet. In Folge werden charakteristische Eigenschaften des molekularen Subsystems durch Wechselwirkung mit Umgebungsfreitheitsgraden potentiell deutlich verändert. Die vorliegende Dissertation behandelt die numerische Untersuchung von quantendynamischen und stationären Eigenschaften molekularer Schwingungen unter dem Einfluss ausgewählter komplexer Umgebungen. Im ersten Teil werden stark gekoppelte Modelsysteme betrachtet, die durch Wechselwirkung von molekulare Schwingungen mit wenigen quantisierten, elektromagnetischen Feldmoden einer Fabry-Pérot Kavität realisiert werden. Die Eigenschaften von Schwingungspolaritonen und die Relevanz der Dipolselbstenergie werden im Detail untersucht. Weiterhin werden quantenmechanische Effekte sowie ein dynamisches Resonanzphänomen in einem Modelsystem für thermische Isomerisierung unter dem Einfluss einer Kavität identifiziert, die zu signifikant reduzierten thermischen Reaktionsraten führen. Für ein frei rotierendes, schwingendes CO Molekül in einer Kavität finden sich nicht-adiabatische Signaturen in Form von schwingungspolaritonischen konischen Durchschneidungen sowie spektroskopisch identifizierbaren rovibratorischen Licht-Materie-Hybridzustände. Im zweiten Teil wird ein schwach gekoppeltes, numerisch anspruchsvolles Adsorbat-Oberflächen-Model mit einigen tausend Oberflächenmoden diskutiert. Es wird ein numerisch effizientes Verfahren zur Konstruktion einer Hierarchie effektiver Moden vorgestellt, wodurch die Anzahl an Oberflächenmoden kontrolliert reduziert wird. In Kombination mit der "multilayer multiconfigurational time-dependent Hartree" (ML-MCTDH) Methode, wird der Relaxationsprozess der Adsorbatmode für verschiedene Anfangszustände durch Lösung der nicht-Markovschen System-Bad Dynamik auf der charakteristische Relaxationszeitskala untersucht. Skalierungsgesetze von Halbwertszeiten werden aus Schwingungspopulationen erhalten und prominente nicht-markovsche Signaturen in Schwingungskohärenzen, in System-Bad-Verschränkung und in der Energietransferdynamik werden durch Vergleich mit markovscher reduzierter Dichtematrixtheorie identifiziert. Im letzten Teil wird vibronische Dynamik bei endlichen Temperaturen untersucht und die ML-MCTDH Methode im Rahmen der nicht-stochastischen "Thermofield Theory" formuliert. Der thermisch beeinflusste, ultraschnelle interne Konversionsprozess in Pyrazin wird betrachtet. Numerisch effiziente Darstellungen der ML-MCTDH Wellenfunktionen für verschiedene Temperaturen werden vorgestellt und thermische Effekte auf Dynamik und Spektroskopie werden diskutiert. KW - theoretical chemistry KW - theoretische Chemie KW - quantum dynamics KW - Quantendynamik Y1 - 2022 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-567214 ER - TY - JOUR A1 - Fischer, Eric W. A1 - Saalfrank, Peter T1 - Cavity-induced non-adiabatic dynamics and spectroscopy of molecular rovibrational polaritons studied by multi-mode quantum models JF - The journal of chemical physics : bridges a gap between journals of physics and journals of chemistr N2 - We study theoretically the quantum dynamics and spectroscopy of rovibrational polaritons formed in a model system composed of a single rovibrating diatomic molecule, which interacts with two degenerate, orthogonally polarized modes of an optical Fabry-Perot cavity. We employ an effective rovibrational Pauli-Fierz Hamiltonian in length gauge representation and identify three-state vibro-polaritonic conical intersections (VPCIs) between singly excited vibro-polaritonic states in a two-dimensional angular coordinate branching space. The lower and upper vibrational polaritons are of mixed light-matter hybrid character, whereas the intermediate state is purely photonic in nature. The VPCIs provide effective population transfer channels between singly excited vibrational polaritons, which manifest in rich interference patterns in rotational densities. Spectroscopically, three bright singly excited states are identified when an external infrared laser field couples to both a molecular and a cavity mode. The non-trivial VPCI topology manifests as pronounced multi-peak progression in the spectral region of the upper vibrational polariton, which is traced back to the emergence of rovibro-polaritonic light-matter hybrid states. Experimentally, ubiquitous spontaneous emission from cavity modes induces a dissipative reduction of intensity and peak broadening, which mainly influences the purely photonic intermediate state peak as well as the rovibro-polaritonic progression. Published under an exclusive license by AIP Publishing. Y1 - 2022 U6 - https://doi.org/10.1063/5.0098006 SN - 0021-9606 SN - 1089-7690 VL - 157 IS - 3 PB - American Institute of Physics CY - Melville ER - TY - JOUR A1 - Fischer, Eric W. A1 - Saalfrank, Peter T1 - Ground state properties and infrared spectra of anharmonic vibrational polaritons of small molecules in cavities JF - The journal of chemical physics : bridges a gap between journals of physics and journals of chemistr N2 - Recent experiments and theory suggest that ground state properties and reactivity of molecules can be modified when placed inside a nanoscale cavity, giving rise to strong coupling between vibrational modes and the quantized cavity field. This is commonly thought to be caused either by a cavity-distorted Born-Oppenheimer ground state potential or by the formation of light-matter hybrid states, vibrational polaritons. Here, we systematically study the effect of a cavity on ground state properties and infrared spectra of single molecules, considering vibration-cavity coupling strengths from zero up to the vibrational ultrastrong coupling regime. Using single-mode models for Li-H and O-H stretch modes and for the NH3 inversion mode, respectively, a single cavity mode in resonance with vibrational transitions is coupled to position-dependent molecular dipole functions. We address the influence of the cavity mode on polariton ground state energies, equilibrium bond lengths, dissociation energies, activation energies for isomerization, and on vibro-polaritonic infrared spectra. In agreement with earlier work, we observe all mentioned properties being strongly affected by the cavity, but only if the dipole self-energy contribution in the interaction Hamiltonian is neglected. When this term is included, these properties do not depend significantly on the coupling anymore. Vibro-polaritonic infrared spectra, in contrast, are always affected by the cavity mode due to the formation of excited vibrational polaritons. It is argued that the quantized nature of vibrational polaritons is key to not only interpreting molecular spectra in cavities but also understanding the experimentally observed modification of molecular reactivity in cavities. Y1 - 2021 U6 - https://doi.org/10.1063/5.0040853 SN - 0021-9606 SN - 1089-7690 VL - 154 IS - 10 PB - American Institute of Physics CY - Melville ER - TY - JOUR A1 - Fischer, Eric W. A1 - Saalfrank, Peter T1 - A thermofield-based multilayer multiconfigurational time-dependent Hartree approach to non-adiabatic quantum dynamics at finite temperature JF - The journal of chemical physics : bridges a gap between journals of physics and journals of chemistry N2 - We introduce a thermofield-based formulation of the multilayer multiconfigurational time-dependent Hartree (MCTDH) method to study finite temperature effects on non-adiabatic quantum dynamics from a non-stochastic, wave function perspective. Our approach is based on the formal equivalence of bosonic many-body theory at zero temperature with a doubled number of degrees of freedom and the thermal quasi-particle representation of bosonic thermofield dynamics (TFD). This equivalence allows for a transfer of bosonic many-body MCTDH as introduced by Wang and Thoss to the finite temperature framework of thermal quasi-particle TFD. As an application, we study temperature effects on the ultrafast internal conversion dynamics in pyrazine. We show that finite temperature effects can be efficiently accounted for in the construction of multilayer expansions of thermofield states in the framework presented herein. Furthermore, we find our results to agree well with existing studies on the pyrazine model based on the pMCTDH method. Y1 - 2021 U6 - https://doi.org/10.1063/5.0064013 SN - 0021-9606 SN - 1089-7690 VL - 155 IS - 13 PB - American Institute of Physics CY - Melville ER - TY - JOUR A1 - Gossner, Martin M. A1 - Lewinsohn, Thomas M. A1 - Kahl, Tiemo A1 - Grassein, Fabrice A1 - Boch, Steffen A1 - Prati, Daniel A1 - Birkhofer, Klaus A1 - Renner, Swen C. A1 - Sikorski, Johannes A1 - Wubet, Tesfaye A1 - Arndt, Hartmut A1 - Baumgartner, Vanessa A1 - Blaser, Stefan A1 - Blüthgen, Nico A1 - Börschig, Carmen A1 - Buscot, Francois A1 - Diekötter, Tim A1 - Jorge, Leonardo Re A1 - Jung, Kirsten A1 - Keyel, Alexander C. A1 - Klein, Alexandra-Maria A1 - Klemmer, Sandra A1 - Krauss, Jochen A1 - Lange, Markus A1 - Müller, Jörg A1 - Overmann, Jörg A1 - Pasalic, Esther A1 - Penone, Caterina A1 - Perovic, David J. A1 - Purschke, Oliver A1 - Schall, Peter A1 - Socher, Stephanie A. A1 - Sonnemann, Ilja A1 - Tschapka, Marco A1 - Tscharntke, Teja A1 - Türke, Manfred A1 - Venter, Paul Christiaan A1 - Weiner, Christiane N. A1 - Werner, Michael A1 - Wolters, Volkmar A1 - Wurst, Susanne A1 - Westphal, Catrin A1 - Fischer, Markus A1 - Weisser, Wolfgang W. A1 - Allan, Eric T1 - Land-use intensification causes multitrophic homogenization of grassland communities JF - Nature : the international weekly journal of science N2 - Land-use intensification is a major driver of biodiversity loss(1,2). Alongside reductions in local species diversity, biotic homogenization at larger spatial scales is of great concern for conservation. Biotic homogenization means a decrease in beta-diversity (the compositional dissimilarity between sites). Most studies have investigated losses in local (alpha)-diversity(1,3) and neglected biodiversity loss at larger spatial scales. Studies addressing beta-diversity have focused on single or a few organism groups (for example, ref. 4), and it is thus unknown whether land-use intensification homogenizes communities at different trophic levels, above-and belowground. Here we show that even moderate increases in local land-use intensity (LUI) cause biotic homogenization across microbial, plant and animal groups, both above- and belowground, and that this is largely independent of changes in alpha-diversity. We analysed a unique grassland biodiversity dataset, with abundances of more than 4,000 species belonging to 12 trophic groups. LUI, and, in particular, high mowing intensity, had consistent effects on beta-diversity across groups, causing a homogenization of soil microbial, fungal pathogen, plant and arthropod communities. These effects were nonlinear and the strongest declines in beta-diversity occurred in the transition from extensively managed to intermediate intensity grassland. LUI tended to reduce local alpha-diversity in aboveground groups, whereas the alpha-diversity increased in belowground groups. Correlations between the alpha-diversity of different groups, particularly between plants and their consumers, became weaker at high LUI. This suggests a loss of specialist species and is further evidence for biotic homogenization. The consistently negative effects of LUI on landscape-scale biodiversity underscore the high value of extensively managed grasslands for conserving multitrophic biodiversity and ecosystem service provision. Indeed, biotic homogenization rather than local diversity loss could prove to be the most substantial consequence of land-use intensification. Y1 - 2016 U6 - https://doi.org/10.1038/nature20575 SN - 0028-0836 SN - 1476-4687 VL - 540 SP - 266 EP - + PB - Nature Publ. Group CY - London ER - TY - JOUR A1 - Soliveres, Santiago A1 - Manning, Peter A1 - Prati, Daniel A1 - Gossner, Martin M. A1 - Alt, Fabian A1 - Arndt, Hartmut A1 - Baumgartner, Vanessa A1 - Binkenstein, Julia A1 - Birkhofer, Klaus A1 - Blaser, Stefan A1 - Bluethgen, Nico A1 - Boch, Steffen A1 - Boehm, Stefan A1 - Boerschig, Carmen A1 - Buscot, Francois A1 - Diekoetter, Tim A1 - Heinze, Johannes A1 - Hoelzel, Norbert A1 - Jung, Kirsten A1 - Klaus, Valentin H. A1 - Klein, Alexandra-Maria A1 - Kleinebecker, Till A1 - Klemmer, Sandra A1 - Krauss, Jochen A1 - Lange, Markus A1 - Morris, E. Kathryn A1 - Mueller, Joerg A1 - Oelmann, Yvonne A1 - Overmann, Jörg A1 - Pasalic, Esther A1 - Renner, Swen C. A1 - Rillig, Matthias C. A1 - Schaefer, H. Martin A1 - Schloter, Michael A1 - Schmitt, Barbara A1 - Schoening, Ingo A1 - Schrumpf, Marion A1 - Sikorski, Johannes A1 - Socher, Stephanie A. A1 - Solly, Emily F. A1 - Sonnemann, Ilja A1 - Sorkau, Elisabeth A1 - Steckel, Juliane A1 - Steffan-Dewenter, Ingolf A1 - Stempfhuber, Barbara A1 - Tschapka, Marco A1 - Tuerke, Manfred A1 - Venter, Paul A1 - Weiner, Christiane N. A1 - Weisser, Wolfgang W. A1 - Werner, Michael A1 - Westphal, Catrin A1 - Wilcke, Wolfgang A1 - Wolters, Volkmar A1 - Wubet, Tesfaye A1 - Wurst, Susanne A1 - Fischer, Markus A1 - Allan, Eric T1 - Locally rare species influence grassland ecosystem multifunctionality JF - Philosophical transactions of the Royal Society of London : B, Biological sciences N2 - Species diversity promotes the delivery of multiple ecosystem functions (multifunctionality). However, the relative functional importance of rare and common species in driving the biodiversity multifunctionality relationship remains unknown. We studied the relationship between the diversity of rare and common species (according to their local abundances and across nine different trophic groups), and multifunctionality indices derived from 14 ecosystem functions on 150 grasslands across a land use intensity (LUI) gradient. The diversity of above- and below-ground rare species had opposite effects, with rare above-ground species being associated with high levels of multifunctionality, probably because their effects on different functions did not trade off against each other. Conversely, common species were only related to average, not high, levels of multifunctionality, and their functional effects declined with LUI. Apart from the community level effects of diversity, we found significant positive associations between the abundance of individual species and multifunctionality in 6% of the species tested. Species specific functional effects were best predicted by their response to LUI: species that declined in abundance with land use intensification were those associated with higher levels of multifunctionality. Our results highlight the importance of rare species for ecosystem multifunctionality and help guiding future conservation priorities. KW - biodiversity KW - common species KW - ecosystem function KW - identity hypothesis KW - land use KW - multitrophic Y1 - 2016 U6 - https://doi.org/10.1098/rstb.2015.0269 SN - 0962-8436 SN - 1471-2970 VL - 371 SP - 3175 EP - 3185 PB - Royal Society CY - London ER - TY - JOUR A1 - Allan, Eric A1 - Weisser, Wolfgang W. A1 - Fischer, Markus A1 - Schulze, Ernst-Detlef A1 - Weigelt, Alexandra A1 - Roscher, Christiane A1 - Baade, Jussi A1 - Barnard, Romain L. A1 - Bessler, Holger A1 - Buchmann, Nina A1 - Ebeling, Anne A1 - Eisenhauer, Nico A1 - Engels, Christof A1 - Fergus, Alexander J. F. A1 - Gleixner, Gerd A1 - Gubsch, Marlen A1 - Halle, Stefan A1 - Klein, Alexandra-Maria A1 - Kertscher, Ilona A1 - Kuu, Annely A1 - Lange, Markus A1 - Le Roux, Xavier A1 - Meyer, Sebastian T. A1 - Migunova, Varvara D. A1 - Milcu, Alexandru A1 - Niklaus, Pascal A. A1 - Oelmann, Yvonne A1 - Pasalic, Esther A1 - Petermann, Jana S. A1 - Poly, Franck A1 - Rottstock, Tanja A1 - Sabais, Alexander C. W. A1 - Scherber, Christoph A1 - Scherer-Lorenzen, Michael A1 - Scheu, Stefan A1 - Steinbeiss, Sibylle A1 - Schwichtenberg, Guido A1 - Temperton, Vicky A1 - Tscharntke, Teja A1 - Voigt, Winfried A1 - Wilcke, Wolfgang A1 - Wirth, Christian A1 - Schmid, Bernhard T1 - A comparison of the strength of biodiversity effects across multiple functions JF - Oecologia N2 - In order to predict which ecosystem functions are most at risk from biodiversity loss, meta-analyses have generalised results from biodiversity experiments over different sites and ecosystem types. In contrast, comparing the strength of biodiversity effects across a large number of ecosystem processes measured in a single experiment permits more direct comparisons. Here, we present an analysis of 418 separate measures of 38 ecosystem processes. Overall, 45 % of processes were significantly affected by plant species richness, suggesting that, while diversity affects a large number of processes not all respond to biodiversity. We therefore compared the strength of plant diversity effects between different categories of ecosystem processes, grouping processes according to the year of measurement, their biogeochemical cycle, trophic level and compartment (above- or belowground) and according to whether they were measures of biodiversity or other ecosystem processes, biotic or abiotic and static or dynamic. Overall, and for several individual processes, we found that biodiversity effects became stronger over time. Measures of the carbon cycle were also affected more strongly by plant species richness than were the measures associated with the nitrogen cycle. Further, we found greater plant species richness effects on measures of biodiversity than on other processes. The differential effects of plant diversity on the various types of ecosystem processes indicate that future research and political effort should shift from a general debate about whether biodiversity loss impairs ecosystem functions to focussing on the specific functions of interest and ways to preserve them individually or in combination. KW - Bottom-up effects KW - Carbon cycling KW - Ecological synthesis KW - Ecosystem processes KW - Grasslands KW - Jena experiment KW - Nitrogen cycling Y1 - 2013 U6 - https://doi.org/10.1007/s00442-012-2589-0 SN - 0029-8549 VL - 173 IS - 1 SP - 223 EP - 237 PB - Springer CY - New York ER - TY - JOUR A1 - Manning, Pete A1 - Gossner, Martin M. A1 - Bossdorf, Oliver A1 - Allan, Eric A1 - Zhang, Yuan-Ye A1 - Prati, Daniel A1 - Blüthgen, Nico A1 - Boch, Steffen A1 - Böhm, Stefan A1 - Börschig, Carmen A1 - Hölzel, Norbert A1 - Jung, Kirsten A1 - Klaus, Valentin H. A1 - Klein, Alexandra-Maria A1 - Kleinebecker, Till A1 - Krauss, Jochen A1 - Lange, Markus A1 - Müller, Jörg A1 - Pasalic, Esther A1 - Socher, Stephanie A. A1 - Tschapka, Marco A1 - Türke, Manfred A1 - Weiner, Christiane A1 - Werner, Michael A1 - Gockel, Sonja A1 - Hemp, Andreas A1 - Renner, Swen C. A1 - Wells, Konstans A1 - Buscot, Francois A1 - Kalko, Elisabeth K. V. A1 - Linsenmair, Karl Eduard A1 - Weisser, Wolfgang W. A1 - Fischer, Markus T1 - Grassland management intensification weakens the associations among the diversities of multiple plant and animal taxa JF - Ecology : a publication of the Ecological Society of America N2 - Land-use intensification is a key driver of biodiversity change. However, little is known about how it alters relationships between the diversities of different taxonomic groups, which are often correlated due to shared environmental drivers and trophic interactions. Using data from 150 grassland sites, we examined how land-use intensification (increased fertilization, higher livestock densities, and increased mowing frequency) altered correlations between the species richness of 15 plant, invertebrate, and vertebrate taxa. We found that 54% of pairwise correlations between taxonomic groups were significant and positive among all grasslands, while only one was negative. Higher land-use intensity substantially weakened these correlations(35% decrease in rand 43% fewer significant pairwise correlations at high intensity), a pattern which may emerge as a result of biodiversity declines and the breakdown of specialized relationships in these conditions. Nevertheless, some groups (Coleoptera, Heteroptera, Hymenoptera and Orthoptera) were consistently correlated with multidiversity, an aggregate measure of total biodiversity comprised of the standardized diversities of multiple taxa, at both high and lowland-use intensity. The form of intensification was also important; increased fertilization and mowing frequency typically weakened plant-plant and plant-primary consumer correlations, whereas grazing intensification did not. This may reflect decreased habitat heterogeneity under mowing and fertilization and increased habitat heterogeneity under grazing. While these results urge caution in using certain taxonomic groups to monitor impacts of agricultural management on biodiversity, they also suggest that the diversities of some groups are reasonably robust indicators of total biodiversity across a range of conditions. KW - Biodiversity indicators KW - correlation KW - fertilization KW - grassland management KW - grazing KW - land-use change KW - land-use intensity KW - mowing KW - multidiversity KW - multitrophic interactions Y1 - 2015 U6 - https://doi.org/10.1890/14-1307.1 SN - 0012-9658 SN - 1939-9170 VL - 96 IS - 6 SP - 1492 EP - 1501 PB - Wiley CY - Washington ER - TY - JOUR A1 - Scherber, Christoph A1 - Eisenhauer, Nico A1 - Weisser, Wolfgang W. A1 - Schmid, Bernhard A1 - Voigt, Winfried A1 - Fischer, Markus A1 - Schukze, Ernst-Detlef A1 - Roscher, Christiane A1 - Weigelt, Alexandra A1 - Allan, Eric A1 - Beßler, Holger A1 - Bonkowski, Michael A1 - Buchmann, Nina A1 - Buscot, François A1 - Clement, Lars W. A1 - Ebeling, Anne A1 - Engels, Christof A1 - Halle, Stefan A1 - Kertscher, Ilona A1 - Klein, Alexandra-Maria A1 - Koller, Robert A1 - König, Stephan A1 - Kowalski, Esther A1 - Kummer, Volker A1 - Kuu, Annely A1 - Lange, Markus A1 - Lauterbach, Dirk T1 - Bottom-up effects of plant diversity on multitrophic interactions in a biodiversity experiment Y1 - 2010 UR - http://www.nature.com/nature/journal/v468/n7323/full/nature09492.html SN - 0028-0836 ER - TY - GEN A1 - Zhou, Lin A1 - Fischer, Eric A1 - Tunca, Can A1 - Brahms, Clemens Markus A1 - Ersoy, Cem A1 - Granacher, Urs A1 - Arnrich, Bert T1 - How We Found Our IMU BT - Guidelines to IMU Selection and a Comparison of Seven IMUs for Pervasive Healthcare Applications T2 - Postprints der Universität Potsdam : Reihe der Digital Engineering Fakultät N2 - Inertial measurement units (IMUs) are commonly used for localization or movement tracking in pervasive healthcare-related studies, and gait analysis is one of the most often studied topics using IMUs. The increasing variety of commercially available IMU devices offers convenience by combining the sensor modalities and simplifies the data collection procedures. However, selecting the most suitable IMU device for a certain use case is increasingly challenging. In this study, guidelines for IMU selection are proposed. In particular, seven IMUs were compared in terms of their specifications, data collection procedures, and raw data quality. Data collected from the IMUs were then analyzed by a gait analysis algorithm. The difference in accuracy of the calculated gait parameters between the IMUs could be used to retrace the issues in raw data, such as acceleration range or sensor calibration. Based on our algorithm, we were able to identify the best-suited IMUs for our needs. This study provides an overview of how to select the IMUs based on the area of study with concrete examples, and gives insights into the features of seven commercial IMUs using real data. T3 - Zweitveröffentlichungen der Universität Potsdam : Reihe der Digital Engineering Fakultät - 2 KW - inertial measurement unit KW - pervasive healthcare KW - gait analysis KW - comparison of devices Y1 - 2020 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-481628 IS - 2 ER - TY - JOUR A1 - Zhou, Lin A1 - Fischer, Eric A1 - Tunca, Can A1 - Brahms, Clemens Markus A1 - Ersoy, Cem A1 - Granacher, Urs A1 - Arnrich, Bert T1 - How We Found Our IMU BT - Guidelines to IMU Selection and a Comparison of Seven IMUs for Pervasive Healthcare Applications JF - Sensors N2 - Inertial measurement units (IMUs) are commonly used for localization or movement tracking in pervasive healthcare-related studies, and gait analysis is one of the most often studied topics using IMUs. The increasing variety of commercially available IMU devices offers convenience by combining the sensor modalities and simplifies the data collection procedures. However, selecting the most suitable IMU device for a certain use case is increasingly challenging. In this study, guidelines for IMU selection are proposed. In particular, seven IMUs were compared in terms of their specifications, data collection procedures, and raw data quality. Data collected from the IMUs were then analyzed by a gait analysis algorithm. The difference in accuracy of the calculated gait parameters between the IMUs could be used to retrace the issues in raw data, such as acceleration range or sensor calibration. Based on our algorithm, we were able to identify the best-suited IMUs for our needs. This study provides an overview of how to select the IMUs based on the area of study with concrete examples, and gives insights into the features of seven commercial IMUs using real data. KW - inertial measurement unit KW - pervasive healthcare KW - gait analysis KW - comparison of devices Y1 - 2020 U6 - https://doi.org/10.3390/s20154090 SN - 1424-8220 VL - 20 IS - 15 PB - MDPI CY - Basel ER -