TY - JOUR A1 - van der Kroef, Ilona A1 - Koszinski, Sylvia A1 - Grinat, Michael A1 - van der Meij, Marijn W. A1 - Hierold, Wilfried A1 - Südekum, Wolfgang A1 - Sommer, Michael T1 - Digital mapping of buried soil horizons using 2D and pseudo-3D geoelectrical measurements in a ground moraine landscape JF - European journal of soil science : EJSS N2 - The identification of buried soil horizons in agricultural landscapes helps to quantify sediment budgets and erosion-related carbon dynamics. High-resolution mapping of buried horizons using conventional soil surveys is destructive and time consuming. Geoelectrical sensors can offer a fast and non-destructive alternative for determining horizon positions and properties. In this paper, we compare the suitability of several geoelectrical methods for measuring the depth to buried horizons (Apb, Ahb and Hab) in the hummocky ground moraine landscape of northeastern Germany. Soil profile descriptions were developed for 269 locations within a 6-ha experimental field "CarboZALF-D". A stepwise linear discriminant analysis (LDA) estimated the lateral position of the buried horizons using electromagnetic induction data and terrain attributes. To predict the depth of a buried horizon, multiple linear regression (MLR) was used for both a 120-m transect and a 0.2-ha pseudo-three-dimensional (3D) area. At these scales, apparent electrical conductivity (ECa), electrical resistivity (ER) and terrain attributes were used as independent variables. The LDA accurately predicted Apb- and Ahb-horizons (a correct classification of 93%). The LDA of the Hab-horizon had a misclassification of 24%, which was probably related to the smaller test set and the higher depth of this horizon. The MLR predicted the depth of the Apb-, Ahb- and Hab-horizons with relative root mean square errors (RMSEs) of 7, 3 and 13%, respectively, in the pseudo-3D area. MLR had a lower accuracy for the 2D transect compared to the pseudo-3D area. Overall, the use of LDA and MLR has been an efficient methodological approach for predicting buried horizon positions. Highlights The suitability of geoelectrical measurements for digital modelling of diagnostic buried soil horizons was determined. LDA and MLR were used to detect multiple horizons with geoelectrical devices and terrain attributes. Geoelectrical variables were significant predictors of the position of the target soil horizons. The use of these tested digital technologies gives an opportunity to develop high-resolution soil mapping procedures. KW - colluvium depth modelling KW - electrical conductivity KW - electrical resistivity tomography KW - electromagnetic induction KW - EM38DD KW - linear discriminant analysis KW - linear regression KW - moraine soil landscape Y1 - 2019 SN - 1351-0754 SN - 1365-2389 VL - 71 IS - 1 SP - 10 EP - 26 PB - Wiley CY - Hoboken ER - TY - JOUR A1 - Chang, Dan A1 - Knapp, Michael A1 - Enk, Jacob A1 - Lippold, Sebastian A1 - Kircher, Martin A1 - Lister, Adrian M. A1 - MacPhee, Ross D. E. A1 - Widga, Christopher A1 - Czechowski, Paul A1 - Sommer, Robert A1 - Hodges, Emily A1 - Stümpel, Nikolaus A1 - Barnes, Ian A1 - Dalén, Love A1 - Derevianko, Anatoly A1 - Germonpré, Mietje A1 - Hillebrand-Voiculescu, Alexandra A1 - Constantin, Silviu A1 - Kuznetsova, Tatyana A1 - Mol, Dick A1 - Rathgeber, Thomas A1 - Rosendahl, Wilfried A1 - Tikhonov, Alexey N. A1 - Willerslev, Eske A1 - Hannon, Greg A1 - Lalueza i Fox, Carles A1 - Joger, Ulrich A1 - Poinar, Hendrik N. A1 - Hofreiter, Michael A1 - Shapiro, Beth T1 - The evolutionary and phylogeographic history of woolly mammoths BT - a comprehensive mitogenomic analysis JF - Scientific reports N2 - Near the end of the Pleistocene epoch, populations of the woolly mammoth (Mammuthus primigenius) were distributed across parts of three continents, from western Europe and northern Asia through Beringia to the Atlantic seaboard of North America. Nonetheless, questions about the connectivity and temporal continuity of mammoth populations and species remain unanswered. We use a combination of targeted enrichment and high-throughput sequencing to assemble and interpret a data set of 143 mammoth mitochondrial genomes, sampled from fossils recovered from across their Holarctic range. Our dataset includes 54 previously unpublished mitochondrial genomes and significantly increases the coverage of the Eurasian range of the species. The resulting global phylogeny confirms that the Late Pleistocene mammoth population comprised three distinct mitochondrial lineages that began to diverge ~1.0–2.0 million years ago (Ma). We also find that mammoth mitochondrial lineages were strongly geographically partitioned throughout the Pleistocene. In combination, our genetic results and the pattern of morphological variation in time and space suggest that male-mediated gene flow, rather than large-scale dispersals, was important in the Pleistocene evolutionary history of mammoths. Y1 - 2017 U6 - https://doi.org/10.1038/srep44585 SN - 2045-2322 VL - 7 PB - Nature Publishing Group CY - London ER - TY - JOUR A1 - Kaiser, Michael A1 - Ellerbrock, Ruth H. A1 - Sommer, Michael T1 - Separation of coarse organic particles from bulk surface soil samples by electrostatic attraction N2 - Different separation procedures are suggested for studying the stability and functionality of sod organic matter (OM). Density fractionation procedures using high-molarity, water-based salt solutions to separate organic particles may cause losses or transfers of C between particle and soluble OM fractions during separation, which may be a result of solution processes. The objective of this study was to separate coarse organic particles (>0.315 mm) from air- dried surface soil samples to avoid such solution processes as far as possible. Air-dried surface soil samples (<2 mm) from nine adjacent arable and forest sites were sieved into five soil particle size fractions (2-1.25, 1.25-0.8, 0.8- 0.5, 0.5-0.4, and 0.4-0.315 mm). Coarse organic particles were separated from each of these fractions using electrostatic attraction by a charged glass surface. The sum of the total dry matter content of the electrostatically separated coarse organic particles ranged from 0.05 to 140 g kg(-1). Scanning electron microscopy images and organic C (OC) analyses indicated, however, that the coarse organic particle fractions were also composed of 20 to 76% mineral particles (i.e., 200-760 g mineral kg(-1) fraction). The repeatability of the electrostatic attraction procedure falls within a range similar to that of accepted density fractionation methods using high-molarity salt solutions. Based on the similarity in repeatability, we suggest that the electrostatic attraction procedure will successfully remove coarse organic particles (>0.315 mm) from air-dried surface soil samples. Because aqueous solutions are not used, the electrostatic attraction procedure to separate coarse organic particles avoids C losses and transfers associated with solution-dependent techniques. Therefore, this method can be used as a pretreatment for subsequent density- or solubility-based soil OM fractionation procedures. Y1 - 2009 UR - https://www.soils.org/publications/sssaj U6 - https://doi.org/10.2136/sssaj2009.0046 SN - 0361-5995 ER - TY - JOUR A1 - Kaiser, Michael A1 - Berhe, Asmeret Asefaw A1 - Sommer, Michael A1 - Kleber, Markus T1 - Application of ultrasound to disperse soil aggregates of high mechanical stability JF - Journal of plant nutrition and soil science = Zeitschrift für Pflanzenernährung und Bodenkunde N2 - Questions remain about the exact ultrasonic energy level that is required to effectively disperse soil aggregates and to what extent this is accompanied by physical damage to individual soil particles. We found maximum aggregate dispersion at energy levels of 1500 J?cm3 and no evidence for the disintegration of particles < 20 mu m even at that energy level. Our findings suggest that sonication at energies much greater than those applied conventionally can disperse aggregates of high mechanical stability. KW - soil aggregates KW - ultrasonication KW - dispersion maxima KW - water-extractable elements Y1 - 2012 U6 - https://doi.org/10.1002/jpln.201200077 SN - 1436-8730 VL - 175 IS - 4 SP - 521 EP - 526 PB - Wiley-VCH CY - Weinheim ER - TY - JOUR A1 - Kaiser, Michael A1 - Walter, K. A1 - Ellerbrock, Ruth H. A1 - Sommer, Michael T1 - Effects of land use and mineral characteristics on the organic carbon content, and the amount and composition of Na-pyrophosphate-soluble organic matter, in subsurface soils JF - European journal of soil science N2 - Land use and mineral characteristics affect the ability of surface as well as subsurface soils to sequester organic carbon and their contribution to mitigation of the greenhouse effect. There is less information about the effects of land use and soil properties on the amount and composition of organic matter (OM) for subsurface soils as compared with surface soils. Here we aimed to analyse the long-term (>= 100 years) impact of arable and forest land use and soil mineral characteristics on subsurface soil organic carbon (SOC) contents, as well as on amount and composition of OM sequentially separated by Na pyrophosphate solution (OM(PY)) from subsurface soil samples. Seven soils with different mineral characteristics (Albic and Haplic Luvisol, Colluvic and Haplic Regosol, Haplic and Vertic Cambisol, Haplic Stagnosol) were selected from within Germany. Soil samples were taken from subsurface horizons of forest and adjacent arable sites continuously used for > 100 years. The OM(PY) fractions were analysed for their OC content (OC(PY)) and characterized by Fourier transform infrared spectroscopy. Multiple regression analyses for the arable subsurface soils indicated significant positive relationships between the SOC contents and combined effects of the (i) exchangeable Ca (Ca(ex)) and oxalate-soluble Fe (Fe(ox)) and (ii) the Ca(ex) and Al(ox) contents. For these soils the increase in OC (OC(PY) multiplied by the relative C=O content of OM(PY)) and increasing contents of Ca(ex) indicated that OM(PY) mainly interacts with Ca2+. For the forest subsurface soils (pH < 5), the OC(PY) contents were related to the contents of Na-pyrophosphate-soluble Fe and Al. The long-term arable and forest land use seems to result in different OM(PY)-mineral interactions in subsurface soils. On the basis of this, we hypothesize that a long-term land-use change from arable to forest may lead to a shift from mainly OM(PY)-Ca2+ to mainly OM(PY)-Fe3+ and -Al3+ interactions if the pH of subsurface soils significantly decreases to < 5. Y1 - 2011 U6 - https://doi.org/10.1111/j.1365-2389.2010.01340.x SN - 1351-0754 VL - 62 IS - 2 SP - 226 EP - 236 PB - Wiley-Blackwell CY - Malden ER - TY - JOUR A1 - Kayler, Z. E. A1 - Kaiser, Michael A1 - Gessler, A. A1 - Ellerbrock, Ruth H. A1 - Sommer, Michael T1 - Application of delta C-13 and delta N-15 isotopic signatures of organic matter fractions sequentially separated from adjacent arable and forest soils to identify carbon stabilization mechanisms JF - Biogeosciences N2 - Identifying the chemical mechanisms behind soil carbon bound in organo-mineral complexes is necessary to determine the degree to which soil organic carbon is stabilized belowground. Analysis of delta C-13 and delta N-15 isotopic signatures of stabilized OM fractions along with soil mineral characteristics may yield important information about OM-mineral associations and their processing history. We anlayzed the delta C-13 and delta N-15 isotopic signatures from two organic matter (OM) fractions along with soil mineral proxies to identify the likely binding mechanisms involved. We analyzed OM fractions hypothesized to contain carbon stabilized through organo-mineral complexes: (1) OM separated chemically with sodium pyrophosphate (OM(PY)) and (2) OM occluded in micro-structures found in the chemical extraction residue (OM(ER)). Because the OM fractions were separated from five different soils with paired forest and arable land use histories, we could address the impact of land use change on carbon binding and processing mechanisms. We used partial least squares regression to analyze patterns in the isotopic signature of OM with established mineral and chemical proxies indicative for certain binding mechanisms. We found different mechanisms predominate in each land use type. For arable soils, the formation of OM(PY)-Ca-mineral associations was identified as an important OM binding mechanism. Therefore, we hypothesize an increased stabilization of microbial processed OM(PY) through Ca2+ interactions. In general, we found the forest soils to contain on average 10% more stabilized carbon relative to total carbon stocks, than the agricultural counter part. In forest soils, we found a positive relationship between isotopic signatures of OM(PY) and the ratio of soil organic carbon content to soil surface area (SOC/SSA). This indicates that the OM(PY) fractions of forest soils represent layers of slower exchange not directly attached to mineral surfaces. From the isotopic composition of the OM(ER) fraction, we conclude that the OM in this fraction from both land use types have undergone a different pathway to stabilization that does not involve microbial processing, which may include OM which is highly protected within soil micro-structures. Y1 - 2011 U6 - https://doi.org/10.5194/bg-8-2895-2011 SN - 1726-4170 VL - 8 IS - 10 SP - 2895 EP - 2906 PB - Copernicus CY - Göttingen ER - TY - JOUR A1 - Kaiser, Michael A1 - Zederer, Dan P. A1 - Ellerbrock, Ruth H. A1 - Sommer, Michael A1 - Ludwig, Bernard T1 - Effects of mineral characteristics on content, composition, and stability of organic matter fractions separated from seven forest topsoils of different pedogenesis JF - Geoderma : an international journal of soil science N2 - Mineral topsoils possess large organic carbon (OC) contents but there is only limited knowledge on the mechanisms controlling the preservation of organic matter (OM) against microbial decay. Samples were taken from the uppermost mineral topsoil horizon (0 to 5 cm) of seven sites under mature deciduous forest showing OC contents between 69 and 164 g kg(-1) and a wide range in mineral characteristics. At first, organic particles and the water-extractable OM were removed from the soil samples. Thereafter, Na-pyrophosphate extractable organic matter (OM(PY)), assumed to be indicative for OM bound via cation mediated interactions, and the OM remaining in the extraction residue (OM(ER)), supposed to be indicative for OM occluded in mechanically highly stable micro-aggregates, were sequentially separated and quantified. The composition of OM(PY) and OM(ER) was analyzed by FTIR and their stability by C-14 measurements. The OC remaining in the extraction residues accounted for 38 to 59% of the bulk soil OC (SOC) suggesting a much larger relevance of OM(ER) for the OM dynamic in the analyzed soils as compared with OM(PY) that accounted for 1.6 to 7.5% of the SOC. The FUR analyses revealed a lower relative proportion of C=O groups in OM(ER) compared to OM(PY) indicating differences in the degree of microbial processing between these fractions. Correlation analyses suggest an increase in the stability of OM(PY) with the soil pH and contents of Na-pyrophosphate soluble Fe, Al, and Mg and an increase in the stability of OM(ER) with the soil pH and the contents of clay and oxalate-soluble Fe and Al. Despite the detected influence of soil mineral characteristics on the turnover of OM(PY) and OM(ER), the Delta C-14 signatures indicated mean residence times less than 100 years. The presence of less stabilized OM in these fractions can be derived from methodological uncertainties and/or the fast cycling compartment of mineral-associated OM. (C) 2015 Elsevier B.V. All rights reserved. KW - Forest mineral topsoil KW - Organic matter stabilization KW - Na-pyrophosphate soluble organic matter KW - Micro-aggregates KW - Infrared spectroscopy KW - C-14 analyses Y1 - 2016 U6 - https://doi.org/10.1016/j.geoderma.2015.08.029 SN - 0016-7061 SN - 1872-6259 VL - 263 SP - 1 EP - 7 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Hemme, Dorothea A1 - Veyel, Daniel A1 - Muehlhaus, Timo A1 - Sommer, Frederik A1 - Jueppner, Jessica A1 - Unger, Ann-Katrin A1 - Sandmann, Michael A1 - Fehrle, Ines A1 - Schoenfelder, Stephanie A1 - Steup, Martin A1 - Geimer, Stefan A1 - Kopka, Joachim A1 - Giavalisco, Patrick A1 - Schroda, Michael T1 - Systems-wide analysis of acclimation responses to long-term heat stress and recovery in the photosynthetic model organism Chlamydomonas reinhardtii JF - The plant cell N2 - We applied a top-down systems biology approach to understand how Chlamydomonas reinhardtii acclimates to long-term heat stress (HS) and recovers from it. For this, we shifted cells from 25 to 42 degrees C for 24 h and back to 25 degrees C for >= 8 h and monitored abundances of 1856 proteins/protein groups, 99 polar and 185 lipophilic metabolites, and cytological and photosynthesis parameters. Our data indicate that acclimation of Chlamydomonas to long-term HS consists of a temporally ordered, orchestrated implementation of response elements at various system levels. These comprise (1) cell cycle arrest; (2) catabolism of larger molecules to generate compounds with roles in stress protection; (3) accumulation of molecular chaperones to restore protein homeostasis together with compatible solutes; (4) redirection of photosynthetic energy and reducing power from the Calvin cycle to the de novo synthesis of saturated fatty acids to replace polyunsaturated ones in membrane lipids, which are deposited in lipid bodies; and (5) when sinks for photosynthetic energy and reducing power are depleted, resumption of Calvin cycle activity associated with increased photorespiration, accumulation of reactive oxygen species scavengers, and throttling of linear electron flow by antenna uncoupling. During recovery from HS, cells appear to focus on processes allowing rapid resumption of growth rather than restoring pre-HS conditions. Y1 - 2014 U6 - https://doi.org/10.1105/tpc.114.130997 SN - 1040-4651 SN - 1532-298X VL - 26 IS - 11 SP - 4270 EP - 4297 PB - American Society of Plant Physiologists CY - Rockville ER - TY - GEN A1 - Garbusow, Maria A1 - Sommer, Christian A1 - Nebe, Stephan A1 - Sebold, Miriam Hannah A1 - Kuitunen-Paul, Sören A1 - Wittchen, Hans-Ulrich A1 - Smolka, Michael N. A1 - Zimmermann, Ulrich S. A1 - Rapp, Michael Armin A1 - Huys, Quentin J. M. A1 - Schlagenhauf, Florian A1 - Heinz, Andreas T1 - Multi-level evidence of general pavlovian-to-instrumental transfer in alcohol use disorder T2 - Alcoholism : clinical and experimental research ; the official journal of the American Medical Society on Alcoholism and the Research Society on Alcoholism Y1 - 2018 SN - 0145-6008 SN - 1530-0277 VL - 42 SP - 128A EP - 128A PB - Wiley CY - Hoboken ER - TY - JOUR A1 - Premke, Katrin A1 - Attermeyer, Katrin A1 - Augustin, Jürgen A1 - Cabezas, Alvaro A1 - Casper, Peter A1 - Deumlich, Detlef A1 - Gelbrecht, Jörg A1 - Gerke, Horst H. A1 - Gessler, Arthur A1 - Großart, Hans-Peter A1 - Hilt, Sabine A1 - Hupfer, Michael A1 - Kalettka, Thomas A1 - Kayler, Zachary A1 - Lischeid, Gunnar A1 - Sommer, Michael A1 - Zak, Dominik T1 - The importance of landscape diversity for carbon fluxes at the landscape level: small-scale heterogeneity matters JF - Wiley Interdisciplinary Reviews : Water N2 - Landscapes can be viewed as spatially heterogeneous areas encompassing terrestrial and aquatic domains. To date, most landscape carbon (C) fluxes have been estimated by accounting for terrestrial ecosystems, while aquatic ecosystems have been largely neglected. However, a robust assessment of C fluxes on the landscape scale requires the estimation of fluxes within and between both landscape components. Here, we compiled data from the literature on C fluxes across the air–water interface from various landscape components. We simulated C emissions and uptake for five different scenarios which represent a gradient of increasing spatial heterogeneity within a temperate young moraine landscape: (I) a homogeneous landscape with only cropland and large lakes; (II) separation of the terrestrial domain into cropland and forest; (III) further separation into cropland, forest, and grassland; (IV) additional division of the aquatic area into large lakes and peatlands; and (V) further separation of the aquatic area into large lakes, peatlands, running waters, and small water bodies These simulations suggest that C fluxes at the landscape scale might depend on spatial heterogeneity and landscape diversity, among other factors. When we consider spatial heterogeneity and diversity alone, small inland waters appear to play a pivotal and previously underestimated role in landscape greenhouse gas emissions that may be regarded as C hot spots. Approaches focusing on the landscape scale will also enable improved projections of ecosystems’ responses to perturbations, e.g., due to global change and anthropogenic activities, and evaluations of the specific role individual landscape components play in regional C fluxes. WIREs Water 2016, 3:601–617. doi: 10.1002/wat2.1147 Y1 - 2016 U6 - https://doi.org/10.1002/wat2.1147 SN - 2049-1948 SN - 2049-1948 VL - 3 SP - 601 EP - 617 PB - Wiley CY - Hoboken ER - TY - GEN A1 - Garbusow, Maria A1 - Nebe, Stephan A1 - Sommer, Christian A1 - Kuitunen-Paul, Sören A1 - Sebold, Miriam Hannah A1 - Schad, Daniel A1 - Friedel, Eva A1 - Veer, Ilya M. A1 - Wittchen, Hans-Ulrich A1 - Rapp, Michael Armin A1 - Ripke, Stephan A1 - Walter, Henrik A1 - Huys, Quentin J. M. A1 - Schlagenhauf, Florian A1 - Smolka, Michael N. A1 - Heinz, Andreas T1 - Pavlovian-To-Instrumental Transfer and Alcohol Consumption in Young Male Social Drinkers BT - Behavioral, Neural and Polygenic Correlates T2 - Zweitveröffentlichungen der Universität Potsdam : Humanwissenschaftliche Reihe N2 - In animals and humans, behavior can be influenced by irrelevant stimuli, a phenomenon called Pavlovian-to-instrumental transfer (PIT). In subjects with substance use disorder, PIT is even enhanced with functional activation in the nucleus accumbens (NAcc) and amygdala. While we observed enhanced behavioral and neural PIT effects in alcohol-dependent subjects, we here aimed to determine whether behavioral PIT is enhanced in young men with high-risk compared to low-risk drinking and subsequently related functional activation in an a-priori region of interest encompassing the NAcc and amygdala and related to polygenic risk for alcohol consumption. A representative sample of 18-year old men (n = 1937) was contacted: 445 were screened, 209 assessed: resulting in 191 valid behavioral, 139 imaging and 157 genetic datasets. None of the subjects fulfilled criteria for alcohol dependence according to the Diagnostic and Statistical Manual of Mental Disorders-IV-TextRevision (DSM-IV-TR). We measured how instrumental responding for rewards was influenced by background Pavlovian conditioned stimuli predicting action-independent rewards and losses. Behavioral PIT was enhanced in high-compared to low-risk drinkers (b = 0.09, SE = 0.03, z = 2.7, p < 0.009). Across all subjects, we observed PIT-related neural blood oxygen level-dependent (BOLD) signal in the right amygdala (t = 3.25, p(SVC) = 0.04, x = 26, y = -6, z = -12), but not in NAcc. The strength of the behavioral PIT effect was positively correlated with polygenic risk for alcohol consumption (r(s) = 0.17, p = 0.032). We conclude that behavioral PIT and polygenic risk for alcohol consumption might be a biomarker for a subclinical phenotype of risky alcohol consumption, even if no drug-related stimulus is present. The association between behavioral PIT effects and the amygdala might point to habitual processes related to out PIT task. In non-dependent young social drinkers, the amygdala rather than the NAcc is activated during PIT; possible different involvement in association with disease trajectory should be investigated in future studies. T3 - Zweitveröffentlichungen der Universität Potsdam : Humanwissenschaftliche Reihe - 841 KW - Pavlovian-to-instrumental transfer KW - amygdala KW - alcohol KW - polygenic risk KW - high risk drinkers Y1 - 2019 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-473280 SN - 1866-8364 IS - 841 ER - TY - GEN A1 - Sebold, Miriam Hannah A1 - Nebe, Stephan A1 - Garbusow, Maria A1 - Schad, Daniel A1 - Sommer, Christian A1 - Rapp, Michael Armin A1 - Smolka, Michael N. A1 - Huys, Quentin J. M. A1 - Schlagenhauf, Florian A1 - Heinz, Andreas T1 - Neurobiological correlates of learning and decision-making in alcohol dependence T2 - European psychiatry : the journal of the Association of European Psychiatrists Y1 - 2017 U6 - https://doi.org/10.1016/j.eurpsy.2017.01.084 SN - 0924-9338 SN - 1778-3585 VL - 41 SP - S11 EP - S11 PB - Elsevier CY - Paris ER - TY - GEN A1 - Giraudier, Manon A1 - Ventura-Bort, Carlos A1 - Burger, Andreas M. A1 - Claes, Nathalie A1 - D'Agostini, Martina A1 - Fischer, Rico A1 - Franssen, Mathijs A1 - Kaess, Michael A1 - Koenig, Julian A1 - Liepelt, Roman A1 - Nieuwenhuis, Sander A1 - Sommer, Aldo A1 - Usichenko, Taras A1 - Van Diest, Ilse A1 - von Leupoldt, Andreas A1 - Warren, Christopher Michael A1 - Weymar, Mathias T1 - Evidence for a modulating effect of transcutaneous auricular vagus nerve stimulation (taVNS) on salivary alpha-amylase as indirect noradrenergic marker: A pooled mega-analysis T2 - Zweitveröffentlichungen der Universität Potsdam : Humanwissenschaftliche Reihe N2 - Background Non-invasive transcutaneous auricular vagus nerve stimulation (taVNS) has received tremendous attention as a potential neuromodulator of cognitive and affective functions, which likely exerts its effects via activation of the locus coeruleus-noradrenaline (LC-NA) system. Reliable effects of taVNS on markers of LC-NA system activity, however, have not been demonstrated yet. Methods The aim of the present study was to overcome previous limitations by pooling raw data from a large sample of ten taVNS studies (371 healthy participants) that collected salivary alpha-amylase (sAA) as a potential marker of central NA release. Results While a meta-analytic approach using summary statistics did not yield any significant effects, linear mixed model analyses showed that afferent stimulation of the vagus nerve via taVNS increased sAA levels compared to sham stimulation (b = 0.16, SE = 0.05, p = 0.001). When considering potential confounders of sAA, we further replicated previous findings on the diurnal trajectory of sAA activity. Conclusion(s) Vagal activation via taVNS increases sAA release compared to sham stimulation, which likely substantiates the assumption that taVNS triggers NA release. Moreover, our results highlight the benefits of data pooling and data sharing in order to allow stronger conclusions in research. T3 - Zweitveröffentlichungen der Universität Potsdam : Humanwissenschaftliche Reihe - 808 KW - Non-invasive vagus nerve stimulation KW - tVNS KW - sAA KW - Noradrenaline KW - Biomarker KW - Data pooling Y1 - 2023 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-577668 SN - 1866-8364 IS - 808 SP - 1378 EP - 1388 ER - TY - JOUR A1 - Giraudier, Manon A1 - Ventura-Bort, Carlos A1 - Burger, Andreas M. A1 - Claes, Nathalie A1 - D'Agostini, Martina A1 - Fischer, Rico A1 - Franssen, Mathijs A1 - Kaess, Michael A1 - Koenig, Julian A1 - Liepelt, Roman A1 - Nieuwenhuis, Sander A1 - Sommer, Aldo A1 - Usichenko, Taras A1 - Van Diest, Ilse A1 - von Leupoldt, Andreas A1 - Warren, Christopher Michael A1 - Weymar, Mathias T1 - Evidence for a modulating effect of transcutaneous auricular vagus nerve stimulation (taVNS) on salivary alpha-amylase as indirect noradrenergic marker: A pooled mega-analysis JF - Brain Stimulation N2 - Background Non-invasive transcutaneous auricular vagus nerve stimulation (taVNS) has received tremendous attention as a potential neuromodulator of cognitive and affective functions, which likely exerts its effects via activation of the locus coeruleus-noradrenaline (LC-NA) system. Reliable effects of taVNS on markers of LC-NA system activity, however, have not been demonstrated yet. Methods The aim of the present study was to overcome previous limitations by pooling raw data from a large sample of ten taVNS studies (371 healthy participants) that collected salivary alpha-amylase (sAA) as a potential marker of central NA release. Results While a meta-analytic approach using summary statistics did not yield any significant effects, linear mixed model analyses showed that afferent stimulation of the vagus nerve via taVNS increased sAA levels compared to sham stimulation (b = 0.16, SE = 0.05, p = 0.001). When considering potential confounders of sAA, we further replicated previous findings on the diurnal trajectory of sAA activity. Conclusion(s) Vagal activation via taVNS increases sAA release compared to sham stimulation, which likely substantiates the assumption that taVNS triggers NA release. Moreover, our results highlight the benefits of data pooling and data sharing in order to allow stronger conclusions in research. KW - Non-invasive vagus nerve stimulation KW - tVNS KW - sAA KW - Noradrenaline KW - Biomarker KW - Data pooling Y1 - 2022 U6 - https://doi.org/10.1016/j.brs.2022.09.009 SN - 1876-4754 VL - 15 SP - 1378 EP - 1388 PB - Elsevier CY - New York, NY, USA ET - 6 ER - TY - JOUR A1 - Wanner, Manfred A1 - Elmer, Michael A1 - Sommer, Michael A1 - Funk, Roger A1 - Puppe, Daniel T1 - Testate amoebae colonizing a newly exposed land surface are of airborne origin JF - Ecological indicators : integrating monitoring, assessment and management N2 - We hypothesized that at the very beginning of terrestrial ecosystem development, airborne testate amoebae play a pivotal role in facilitating organismic colonization and related soil processes. We, therefore, analyzed size and quantity of airborne testate amoebae and immigration and colonization success of airborne testate amoebae on a new land surface (experimental site "Chicken Creek", artificial post-mining water catchment). Within an altogether 91-day exposure of 70 adhesive traps, 12 species of testate amoebae were identified to be of airborne origin. Phryganella acropodia (51% of all individuals found, diameter about 35-45 mu m) and Centropyxis sphagnicola (23% of all individuals found, longest axis about 55-68 mu m), occurred most frequently in the adhesive traps. We extrapolated an aerial amoeba deposition of 61 individuals d(-1) m(-2) (living and dead individuals combined). Although it would be necessary to have a longer sequence (some additional years), our analysis of the "target substrate" of aerial immigration (catchment site) may point to a shift from a stochastic (variable) beginning of community assembly to a more deterministic (stable) course. This shift was assigned to an age of seven years of initial soil development. Although experienced specialists are necessary to conduct these time-consuming studies, the presented data suggest that terrestrial amoebae are suitable indicators for initial ecosystem development and utilization. KW - Artificial water catchment KW - Immigration by air KW - Biological indicator Y1 - 2015 U6 - https://doi.org/10.1016/j.ecolind.2014.07.037 SN - 1470-160X SN - 1872-7034 VL - 48 SP - 55 EP - 62 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Schad, Daniel A1 - Garbusow, Maria A1 - Friedel, Eva A1 - Sommer, Christian A1 - Sebold, Miriam Hannah A1 - Hägele, Claudia A1 - Bernhardt, Nadine A1 - Nebe, Stephan A1 - Kuitunen-Paul, Sören A1 - Liu, Shuyan A1 - Eichmann, Uta A1 - Beck, Anne A1 - Wittchen, Hans-Ulrich A1 - Walter, Henrik A1 - Sterzer, Philipp A1 - Zimmermann, Ulrich S. A1 - Smolka, Michael N. A1 - Schlagenhauf, Florian A1 - Huys, Quentin J. M. A1 - Heinz, Andreas A1 - Rapp, Michael Armin T1 - Neural correlates of instrumental responding in the context of alcohol-related cues index disorder severity and relapse risk JF - European archives of psychiatry and clinical neuroscience : official organ of the German Society for Biological Psychiatry N2 - The influence of Pavlovian conditioned stimuli on ongoing behavior may contribute to explaining how alcohol cues stimulate drug seeking and intake. Using a Pavlovian-instrumental transfer task, we investigated the effects of alcohol-related cues on approach behavior (i.e., instrumental response behavior) and its neural correlates, and related both to the relapse after detoxification in alcohol-dependent patients. Thirty-one recently detoxified alcohol-dependent patients and 24 healthy controls underwent instrumental training, where approach or non-approach towards initially neutral stimuli was reinforced by monetary incentives. Approach behavior was tested during extinction with either alcohol-related or neutral stimuli (as Pavlovian cues) presented in the background during functional magnetic resonance imaging (fMRI). Patients were subsequently followed up for 6 months. We observed that alcohol-related background stimuli inhibited the approach behavior in detoxified alcohol-dependent patients (t = -3.86, p < .001), but not in healthy controls (t = -0.92, p = .36). This behavioral inhibition was associated with neural activation in the nucleus accumbens (NAcc) (t((30)) = 2.06, p < .05). Interestingly, both the effects were only present in subsequent abstainers, but not relapsers and in those with mild but not severe dependence. Our data show that alcohol-related cues can acquire inhibitory behavioral features typical of aversive stimuli despite being accompanied by a stronger NAcc activation, suggesting salience attribution. The fact that these findings are restricted to abstinence and milder illness suggests that they may be potential resilience factors. KW - Alcohol dependence KW - Human neuroimaging KW - Nucleus accumbens KW - Pavlovian-instrumental transfer KW - Relapse Y1 - 2018 U6 - https://doi.org/10.1007/s00406-017-0860-4 SN - 0940-1334 SN - 1433-8491 VL - 269 IS - 3 SP - 295 EP - 308 PB - Springer CY - Heidelberg ER - TY - JOUR A1 - Garbusow, Maria A1 - Nebe, Stephan A1 - Sommer, Christian A1 - Kuitunen-Paul, Sören A1 - Sebold, Miriam Hannah A1 - Schad, Daniel A1 - Friedel, Eva A1 - Veer, Ilya M. A1 - Wittchen, Hans-Ulrich A1 - Rapp, Michael Armin A1 - Ripke, Stephan A1 - Walter, Henrik A1 - Huys, Quentin J. M. A1 - Schlagenhauf, Florian A1 - Smolka, Michael N. A1 - Heinz, Andreas T1 - Pavlovian-To-Instrumental Transfer and Alcohol Consumption in Young Male Social Drinkers BT - Behavioral, Neural and Polygenic Correlates JF - Journal of Clinical Medicine N2 - In animals and humans, behavior can be influenced by irrelevant stimuli, a phenomenon called Pavlovian-to-instrumental transfer (PIT). In subjects with substance use disorder, PIT is even enhanced with functional activation in the nucleus accumbens (NAcc) and amygdala. While we observed enhanced behavioral and neural PIT effects in alcohol-dependent subjects, we here aimed to determine whether behavioral PIT is enhanced in young men with high-risk compared to low-risk drinking and subsequently related functional activation in an a-priori region of interest encompassing the NAcc and amygdala and related to polygenic risk for alcohol consumption. A representative sample of 18-year old men (n = 1937) was contacted: 445 were screened, 209 assessed: resulting in 191 valid behavioral, 139 imaging and 157 genetic datasets. None of the subjects fulfilled criteria for alcohol dependence according to the Diagnostic and Statistical Manual of Mental Disorders-IV-TextRevision (DSM-IV-TR). We measured how instrumental responding for rewards was influenced by background Pavlovian conditioned stimuli predicting action-independent rewards and losses. Behavioral PIT was enhanced in high-compared to low-risk drinkers (b = 0.09, SE = 0.03, z = 2.7, p < 0.009). Across all subjects, we observed PIT-related neural blood oxygen level-dependent (BOLD) signal in the right amygdala (t = 3.25, p(SVC) = 0.04, x = 26, y = -6, z = -12), but not in NAcc. The strength of the behavioral PIT effect was positively correlated with polygenic risk for alcohol consumption (r(s) = 0.17, p = 0.032). We conclude that behavioral PIT and polygenic risk for alcohol consumption might be a biomarker for a subclinical phenotype of risky alcohol consumption, even if no drug-related stimulus is present. The association between behavioral PIT effects and the amygdala might point to habitual processes related to out PIT task. In non-dependent young social drinkers, the amygdala rather than the NAcc is activated during PIT; possible different involvement in association with disease trajectory should be investigated in future studies. KW - Pavlovian-to-instrumental transfer KW - amygdala KW - alcohol KW - polygenic risk KW - high risk drinkers Y1 - 2019 U6 - https://doi.org/10.3390/jcm8081188 SN - 2077-0383 VL - 8 IS - 8 PB - MDPI CY - Basel ER - TY - JOUR A1 - Garbusow, Maria A1 - Schad, Daniel A1 - Sebold, Miriam Hannah A1 - Friedel, Eva A1 - Bernhardt, Nadine A1 - Koch, Stefan P. A1 - Steinacher, Bruno A1 - Kathmann, Norbert A1 - Geurts, Dirk E. M. A1 - Sommer, Christian A1 - Mueller, Dirk K. A1 - Nebe, Stephan A1 - Paul, Soeren A1 - Wittchen, Hans-Ulrich A1 - Zimmermann, Ulrich S. A1 - Walter, Henrik A1 - Smolka, Michael N. A1 - Sterzer, Philipp A1 - Rapp, Michael Armin A1 - Huys, Quentin J. M. A1 - Schlagenhauf, Florian A1 - Heinz, Andreas T1 - Pavlovian-to-instrumental transfer effects in the nucleus accumbens relate to relapse in alcohol dependence JF - Addiction biology N2 - In detoxified alcohol-dependent patients, alcohol-related stimuli can promote relapse. However, to date, the mechanisms by which contextual stimuli promote relapse have not been elucidated in detail. One hypothesis is that such contextual stimuli directly stimulate the motivation to drink via associated brain regions like the ventral striatum and thus promote alcohol seeking, intake and relapse. Pavlovian-to-Instrumental-Transfer (PIT) may be one of those behavioral phenomena contributing to relapse, capturing how Pavlovian conditioned (contextual) cues determine instrumental behavior (e.g. alcohol seeking and intake). We used a PIT paradigm during functional magnetic resonance imaging to examine the effects of classically conditioned Pavlovian stimuli on instrumental choices in n=31 detoxified patients diagnosed with alcohol dependence and n=24 healthy controls matched for age and gender. Patients were followed up over a period of 3 months. We observed that (1) there was a significant behavioral PIT effect for all participants, which was significantly more pronounced in alcohol-dependent patients; (2) PIT was significantly associated with blood oxygen level-dependent (BOLD) signals in the nucleus accumbens (NAcc) in subsequent relapsers only; and (3) PIT-related NAcc activation was associated with, and predictive of, critical outcomes (amount of alcohol intake and relapse during a 3 months follow-up period) in alcohol-dependent patients. These observations show for the first time that PIT-related BOLD signals, as a measure of the influence of Pavlovian cues on instrumental behavior, predict alcohol intake and relapse in alcohol dependence. KW - human Pavlovian-to-instrumental transfer KW - nucleus accumbens KW - relapse in alcohol use disorder Y1 - 2016 U6 - https://doi.org/10.1111/adb.12243 SN - 1355-6215 SN - 1369-1600 VL - 21 SP - 719 EP - 731 PB - Wiley-Blackwell CY - Hoboken ER - TY - JOUR A1 - Sebold, Miriam Hannah A1 - Nebe, Stephan A1 - Garbusow, Maria A1 - Guggenmos, Matthias A1 - Schad, Daniel A1 - Beck, Anne A1 - Kuitunen-Paul, Sören A1 - Sommer, Christian A1 - Frank, Robin A1 - Neu, Peter A1 - Zimmermann, Ulrich S. A1 - Rapp, Michael Armin A1 - Smolka, Michael N. A1 - Huys, Quentin J. M. A1 - Schlagenhauf, Florian A1 - Heinz, Andreas T1 - When Habits Are Dangerous: Alcohol Expectancies and Habitual Decision Making Predict Relapse in Alcohol Dependence JF - Biological psychiatry : a journal of psychiatric neuroscience and therapeutics ; a publication of the Society of Biological Psychiatry N2 - BACKGROUND: Addiction is supposedly characterized by a shift from goal-directed to habitual decision making, thus facilitating automatic drug intake. The two-step task allows distinguishing between these mechanisms by computationally modeling goal-directed and habitual behavior as model-based and model-free control. In addicted patients, decision making may also strongly depend upon drug-associated expectations. Therefore, we investigated model-based versus model-free decision making and its neural correlates as well as alcohol expectancies in alcohol-dependent patients and healthy controls and assessed treatment outcome in patients. METHODS: Ninety detoxified, medication-free, alcohol-dependent patients and 96 age-and gender-matched control subjects underwent functional magnetic resonance imaging during the two-step task. Alcohol expectancies were measured with the Alcohol Expectancy Questionnaire. Over a follow-up period of 48 weeks, 37 patients remained abstinent and 53 patients relapsed as indicated by the Alcohol Timeline Followback method. RESULTS: Patients who relapsed displayed reduced medial prefrontal cortex activation during model-based decision making. Furthermore, high alcohol expectancies were associated with low model-based control in relapsers, while the opposite was observed in abstainers and healthy control subjects. However, reduced model-based control per se was not associated with subsequent relapse. CONCLUSIONS: These findings suggest that poor treatment outcome in alcohol dependence does not simply result from a shift from model-based to model-free control but is instead dependent on the interaction between high drug expectancies and low model-based decision making. Reduced model-based medial prefrontal cortex signatures in those who relapse point to a neural correlate of relapse risk. These observations suggest that therapeutic interventions should target subjective alcohol expectancies. KW - Alcohol dependence KW - Alcohol expectancy KW - Goal-directed control KW - Medial prefrontal cortex KW - Reinforcement learning KW - Treatment outcome Y1 - 2017 U6 - https://doi.org/10.1016/j.biopsych.2017.04.019 SN - 0006-3223 SN - 1873-2402 VL - 82 SP - 847 EP - 856 PB - Elsevier CY - New York ER - TY - JOUR A1 - van der Meij, Marijn W. A1 - Temme, Arnaud J. A. M. A1 - Lin, H. S. A1 - Gerke, Horst H. A1 - Sommer, Michael T1 - On the role of hydrologic processes in soil and landscape evolution modeling BT - concepts, complications and partial solutions JF - Earth science reviews : the international geological journal bridging the gap between research articles and textbooks N2 - The ability of water to transport and transform soil materials is one of the main drivers of soil and landscape development. In turn, soil and landscape properties determine how water is distributed in soil landscapes. Understanding the complex dynamics of this co-evolution of soils, landscapes and the hydrological system is fundamental in adapting land management to changes in climate. Soil-Landscape Evolution Models (SLEMs) are used to simulate the development and evolution of soils and landscapes. However, many hydrologic processes, such as preferential flow and subsurface lateral flow, are currently absent in these models. This limits the applicability of SLEMs to improve our understanding of feedbacks in the hydro-pedo-geomorphological system. Implementation of these hydrologic processes in SLEMs faces several complications related to calculation demands, limited methods for linking pedogenic and hydrologic processes, and limited data on quantification of changes in the hydrological system over time. In this contribution, we first briefly review processes and feedbacks in soil-landscape-hydrological systems. Next, we elaborate on the development required to include these processes in SLEMs. We discuss the state-of-the-art knowledge, identify complications, give partial solutions and suggest important future development. The main requirements for incorporating hydrologic processes in SLEMs are: (1) designing a model framework that can deal with varying timescales for different sets of processes, (2) developing and implementing methods for simulating pedogenesis as a function of water flow, (3) improving and implementing knowledge on the evolution and dynamics of soil hydraulic properties over different timescales, and (4) improving the database on temporal changes and dynamics of flow paths. Y1 - 2018 U6 - https://doi.org/10.1016/j.earscirev.2018.09.001 SN - 0012-8252 SN - 1872-6828 VL - 185 SP - 1088 EP - 1106 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Kaczorek, Danuta A1 - Puppe, Daniel A1 - Busse, Jacqueline A1 - Sommer, Michael T1 - Effects of phytolith distribution and characteristics on extractable silicon fractions in soils under different vegetation - An exploratory study on loess JF - Geoderma : an international journal of soil science N2 - The significance of phytoliths for the control of silicon (Si) fluxes from terrestrial to aquatic ecosystems has been recognized as a key factor. Humankind actively influences Si fluxes by intensified land use, i.e., agriculture and forestry, on a global scale. We hypothesized phytolith distribution and assemblages in soils of agricultural and forestry sites to be controlled by vegetation (which is directed by land use) with direct effects on extractable Si fractions driven mainly by phytolith characteristics, i.e., dissolution status (dissolution signs) and morphology (morphotype proportions). To test our hypothesis we combined different chemical extraction methods (calcium chloride, ammonium oxalate, Tiron) for the quantification of different Si fractions (plant available Si, Si adsorbed to/occluded in pedogenic oxides/hydroxides, amorphous Si) and microscopic techniques (light microscopy, confocal laser scanning microscopy, scanning electron microscopy) for detailed analyses of phytoliths extracted using gravimetric separation (physical extraction) from exemplary loess soils of agricultural (arable land and grassland/meadow) and forestry (beech and pine) sites in Poland. We found differences in dissolution signs, morphotype proportions, and vertical distribution of phytoliths in soil horizons per site. In general, dominant morphotypes of assignable phytoliths in the studied soil profiles were elongate phytoliths and short cells, both of which are typical for grass-dominated vegetation. However, the organic layers of forest soils were dominated by globular phytoliths, which are typical indicators for mosses. As expected soil horizons under different vegetation generally were characterized by differences in extractable Si fractions, especially in the upper soil horizons. However, phytogenic Si pools counter-intuitively showed no correlations with chemically extracted Si fractions and soil pH at all. Our findings indicate that it is necessary to combine microscopic analyses and Si extraction techniques for examinations of Si cycling in biogeosystems, because extractions of Si fractions alone do not allow drawing any conclusions about phytolith characteristics or interactions between phytolith pools and chemically extractable Si fractions and do not necessarily reflect phytogenic Si pool quantities in soils and vice versa. KW - Phytolith dissolution KW - Phytolith morphotypes KW - Si extraction KW - Surface roughness parameters KW - Si cycling Y1 - 2019 U6 - https://doi.org/10.1016/j.geoderma.2019.113917 SN - 0016-7061 SN - 1872-6259 VL - 356 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Steinhöfel, Grit A1 - Breuer, Jörn A1 - von Blanckenburg, Friedhelm A1 - Horn, Ingo A1 - Sommer, Michael T1 - The dynamics of Si cycling during weathering in two small catchments in the Black Forest (Germany) traced by Si isotopes JF - Chemical geology : official journal of the European Association for Geochemistry N2 - Silicon stable isotopes have emerged as a powerful proxy to investigate weathering because Si uptake from solution by secondary minerals or by the vegetation causes significant shifts in the isotope composition. In this study, we determined the Si isotope compositions of the principle Si pools within two small catchments located on sandstone and paragneiss, respectively, in the temperate Black Forest (Germany). At both settings, clay formation is dominated by mineral transformation preserving largely the signature of parental minerals with delta Si-30 values of around -0.7%. Bulk soils rich in primary minerals are similar to bulk parental material with delta Si-30 values close to -0.4%. Topsoils are partly different because organic matter degradation has promoted intense weathering leading to delta Si-30 values as low as -1.0%. Water samples expose highly dynamic weathering processes in the soil zone: 1) after spring snowmelt, increased release of DOC and high water fluxes trigger clay mineral dissolution which leads to delta Si-30 values down to -0.7% and 2) in course of the summer, Si uptake by the vegetation and secondary mineral formation drives dissolved Si to typical positive delta Si-30 values up to 1.1%. Groundwater with delta Si-30 values of around 0.4% records steady processes in bedrock reflecting plagioclase weathering together with kaolinite precipitation. An isotope mass balance approach reveals incongruent weathering conditions where denudation of Si is largely driven by physical erosion. Erosion of phytoliths contributes 3 to 21% to the total Si export flux, which is in the same order as the dissolved Si flux. These results elucidate the Si dynamics during weathering on catchments underlain of sedimentary origin, prevailing on the Earth surface and provide therefore valuable information to interpret the isotope signature of large river systems. KW - Weathering KW - Sedimentary rocks KW - Biogeochemical Si cycle KW - Silicon isotopes KW - UV femtosecond laser ablation Y1 - 2017 U6 - https://doi.org/10.1016/j.chemgeo.2017.06.026 SN - 0009-2541 SN - 1878-5999 VL - 466 SP - 389 EP - 402 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Hoffmann, Mathias A1 - Wirth, Stephan J. A1 - Bessler, Holger A1 - Engels, Christof A1 - Jochheim, Hubert A1 - Sommer, Michael A1 - Augustin, Jürgen T1 - Combining a root exclusion technique with continuous chamber and porous tube measurements for a pin-point separation of ecosystem respiration in croplands JF - Journal of plant nutrition and soil science = Zeitschrift für Pflanzenernährung und Bodenkunde N2 - To better assess ecosystem C budgets of croplands and understand their potential response to climate and management changes, detailed information on the mechanisms and environmental controls driving the individual C flux components are needed. This accounts in particular for the ecosystem respiration (R-eco) and its components, the autotrophic (R-a) and heterotrophic respiration (R-h) which vary tremendously in time and space. This study presents a method to separate R-eco into R-a [as the sum of R-a (shoot) and R-a (root)] and R-h in order to detect temporal and small-scale spatial dynamics within their relative contribution to overall R-eco. Thus, predominant environmental drivers and underlying mechanisms can be revealed. R-eco was derived during nighttime by automatic chamber CO2 flux measurements on plant covered plots. R-h was derived from CO2 efflux measurements, which were performed in parallel to R-eco measurements on a fallow plot using CO2 sampling tubes in 10 cm soil depth. R-a (root) was calculated as the difference between sampling tube CO2 efflux measurements on a plant covered plot and R-h. R-a (shoot) was calculated as R-eco - R-a (root) - R-h. Measurements were carried out for winter wheat (Triticum aestivum L.) during the crop season 2015 at an experimental plot located in the hummocky ground moraine landscape of NE Germany. R-eco varied seasonally from < 1 to 9.5 g C m(-2) d(-1), and was higher in adult (a) and reproductive (r) than juvenile (j) stands (gC m(-2) d(-1): j = 1.2, a = 4.6, r = 5.3). Observed R-a and R-h were in general smaller compared to the independently measured R-eco, contributing in average 58% and 42% to R-eco. However, both varied strongly regarding their environmental drivers and particular contribution throughout the study period, following the seasonal development of soil temperature and moisture (R-h) as well as crop development (R-a). Thus, our results consistently revealed temporal dynamics regarding the relative contribution of R-a (root) and R-a (shoot) to R-a, as well as of R-a and R-h to R-eco. Based on the observed results, implications for partitioning of R-eco in croplands are given. KW - automatic chambers KW - autotrophic respiration KW - heterotrophic respiration KW - soil CO2 sampling tubes Y1 - 2017 U6 - https://doi.org/10.1002/jpln.201600489 SN - 1436-8730 SN - 1522-2624 VL - 181 IS - 1 SP - 41 EP - 50 PB - Wiley-VCH CY - Weinheim ER - TY - JOUR A1 - Herbrich, Marcus A1 - Gerke, Horst H. A1 - Sommer, Michael T1 - Root development of winter wheat in erosion-affected soils depending on the position in a hummocky ground moraine soil landscape JF - Journal of plant nutrition and soil science = Zeitschrift für Pflanzenernährung und Bodenkunde N2 - Agricultural soil landscapes of hummocky ground moraines are characterized by 3D spatial patterns of soil types that result from profile modifications due to the combined effect of water and tillage erosion. We hypothesize that crops reflect such soil landscape patterns by increased or reduced plant and root growth. Root development may depend on the thickness and vertical sequence of soil horizons as well as on the structural development state of these horizons at different landscape positions. The hypotheses were tested using field data of the root density (RD) and the root lengths (RL) of winter wheat using the minirhizotron technique. We compared data from plots at the CarboZALF-D site (NE Germany) that are representing a non-eroded reference soil profile (Albic Luvisol) at a plateau position, a strongly eroded profile at steep slope (Calcaric Regosol), and a depositional profile at the footslope (Anocolluvic Regosol). At each of these plots, three Plexiglas access tubes were installed down to approx. 1.5 m soil depth. Root measurements were carried out during the growing season of winter wheat (September 2014-August 2015) on six dates. The root length density (RLD) and the root biomass density were derived from RD values assuming a mean specific root length of 100 m g(-1). Values of RD and RLD were highest for the Anocolluvic Regosol and lowest for the Calcaric Regosol. The maximum root penetration depth was lower in the Anocolluvic Regosol because of a relatively high and fluctuating water table at this landscape position. Results revealed positive relations between below-ground (root) and above-ground crop parameters (i.e., leaf area index, plant height, biomass, and yield) for the three soil types. Observed root densities and root lengths in soils at the three landscape positions corroborated the hypothesis that the root system was reflecting erosion-induced soil profile modifications. Soil landscape position dependent root growth should be considered when attempting to quantify landscape scale water and element balances as well as agricultural productivity. KW - minirhizotron KW - root density KW - root lengths density KW - root biomass KW - root penetration KW - soil erosion KW - soil horizonation Y1 - 2018 U6 - https://doi.org/10.1002/jpln.201600536 SN - 1436-8730 SN - 1522-2624 VL - 181 IS - 2 SP - 147 EP - 157 PB - Wiley-VCH CY - Weinheim ER - TY - CHAP A1 - Sommer, Michael T1 - Nicht-invasive Methoden in der Bodenlandschaftsforschung BT - Konzeption und Projekte N2 - Der Referent ist Leiter des Institutes für Bodenlandschaftsforschung am Leibniz-Zentrum für Agrarlandschaftsforschung (ZALF) e. V. in Müncheberg. Y1 - 2006 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-7117 N1 - Interdisziplinäres Zentrum für Musterdynamik und Angewandte Fernerkundung Workshop vom 9. - 10. Februar 2006 ER - TY - GEN A1 - Küken, Anika A1 - Sommer, Frederik A1 - Yaneva-Roder, Liliya A1 - Mackinder, Luke C.M. A1 - Höhne, Melanie A1 - Geimer, Stefan A1 - Jonikas, Martin C. A1 - Schroda, Michael A1 - Stitt, Mark A1 - Nikoloski, Zoran A1 - Mettler-Altmann, Tabea T1 - Effects of microcompartmentation on flux distribution and metabolic pools in Chlamydomonas reinhardtii chloroplasts T2 - Postprints der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe N2 - Cells and organelles are not homogeneous but include microcompartments that alter the spatiotemporal characteristics of cellular processes. The effects of microcompartmentation on metabolic pathways are however difficult to study experimentally. The pyrenoid is a microcompartment that is essential for a carbon concentrating mechanism (CCM) that improves the photosynthetic performance of eukaryotic algae. Using Chlamydomonas reinhardtii, we obtained experimental data on photosynthesis, metabolites, and proteins in CCM-induced and CCM-suppressed cells. We then employed a computational strategy to estimate how fluxes through the Calvin-Benson cycle are compartmented between the pyrenoid and the stroma. Our model predicts that ribulose-1,5-bisphosphate (RuBP), the substrate of Rubisco, and 3-phosphoglycerate (3PGA), its product, diffuse in and out of the pyrenoid, respectively, with higher fluxes in CCM-induced cells. It also indicates that there is no major diffusional barrier to metabolic flux between the pyrenoid and stroma. Our computational approach represents a stepping stone to understanding microcompartmentalized CCM in other organisms. T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 1122 KW - carbon concentrating mechanism KW - B12-dependent 1,2-propanediol degradation KW - green algae KW - co2 concentrating mechanism KW - salmonella typhimurium KW - co2 concentration KW - enzyme activities KW - anhydrase CAH3 KW - protein KW - expression Y1 - 2021 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-446358 SN - 1866-8372 IS - 1122 ER - TY - GEN A1 - Puppe, Daniel A1 - Wanner, Manfred A1 - Sommer, Michael T1 - Data on euglyphid testate amoeba densities, corresponding protozoic silicon pools, and selected soil parameters of initial and forested biogeosystems T2 - Postprints der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe N2 - The dataset in the present article provides information on protozoic silicon (Si) pools represented by euglyphid testate amoebae (TA) in soils of initial and forested biogeosystems. Protozoic Si pools were calculated from densities of euglyphid TA shells and corresponding Si contents. The article also includes data on potential annual biosilicification rates of euglyphid TA at the examined sites. Furthermore, data on selected soil parameters (e.g., readily-available Si, soil pH) and site characteristics (e.g., soil groups, climate data) can be found. The data might be interesting for researchers focusing on biological processes in Si cycling in general and euglyphid TA and corresponding protozoic Si pools in particular. T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 1039 KW - silicon cycling KW - biogenic silica KW - terrestrial biogeosystems KW - biosilicification KW - Euglyphida Y1 - 2020 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-471160 SN - 1866-8372 IS - 1039 ER - TY - JOUR A1 - Hoffmann, Mathias A1 - Jurisch, Nicole A1 - Alba, Juana Garcia A1 - Borraz, Elisa Albiac A1 - Schmidt, Marten A1 - Huth, Vytas A1 - Rogasik, Helmut A1 - Rieckh, Helene A1 - Verch, Gernot A1 - Sommer, Michael A1 - Augustin, Jürgen T1 - Detecting small-scale spatial heterogeneity and temporal dynamics of soil organic carbon (SOC) stocks BT - a comparison between automatic chamber-derived C budgets and repeated soil inventories JF - Biogeosciences N2 - Carbon (C) sequestration in soils plays a key role in the global C cycle. It is therefore crucial to adequately monitor dynamics in soil organic carbon (Delta SOC) stocks when aiming to reveal underlying processes and potential drivers. However, small-scale spatial (10-30 m) and temporal changes in SOC stocks, particularly pronounced in arable lands, are hard to assess. The main reasons for this are limitations of the well-established methods. On the one hand, repeated soil inventories, often used in long-term field trials, reveal spatial patterns and trends in Delta SOC but require a longer observation period and a sufficient number of repetitions. On the other hand, eddy covariance measurements of C fluxes towards a complete C budget of the soil-plant-atmosphere system may help to obtain temporal Delta SOC patterns but lack small-scale spatial resolution. To overcome these limitations, this study presents a reliable method to detect both short-term temporal dynamics as well as small-scale spatial differences of Delta SOC using measurements of the net ecosystem carbon balance (NECB) as a proxy. To estimate the NECB, a combination of automatic chamber (AC) measurements of CO2 exchange and empirically modeled aboveground biomass development (NPPshoot / were used. To verify our method, results were compared with Delta SOC observed by soil resampling. Soil resampling and AC measurements were performed from 2010 to 2014 at a colluvial depression located in the hummocky ground moraine landscape of northeastern Germany. The measurement site is characterized by a variable groundwater level (GWL) and pronounced small-scale spatial heterogeneity regarding SOC and nitrogen (Nt) stocks. Tendencies and magnitude of Delta SOC values derived by AC measurements and repeated soil inventories corresponded well. The period of maximum plant growth was identified as being most important for the development of spatial differences in annual Delta SOC. Hence, we were able to confirm that AC-based C budgets are able to reveal small-scale spatial differences and short-term temporal dynamics of Delta SOC. Y1 - 2017 U6 - https://doi.org/10.5194/bg-14-1003-2017 SN - 1726-4170 SN - 1726-4189 VL - 14 IS - 4 SP - 1003 EP - 1019 PB - Copernicus CY - Göttingen ER - TY - JOUR A1 - Hoffmann, Mathias A1 - Schulz-Hanke, Maximilian A1 - Alba, Juana Garcia A1 - Jurisch, Nicole A1 - Hagemann, Ulrike A1 - Sachs, Torsten A1 - Sommer, Michael A1 - Augustin, Jürgen T1 - A simple calculation algorithm to separate high-resolution CH4 flux measurements into ebullition- and diffusion-derived components JF - Atmospheric measurement techniques : an interactive open access journal of the European Geosciences Union N2 - Processes driving the production, transformation and transport of methane (CH4 / in wetland ecosystems are highly complex. We present a simple calculation algorithm to separate open-water CH4 fluxes measured with automatic chambers into diffusion-and ebullition-derived components. This helps to reveal underlying dynamics, to identify potential environmental drivers and, thus, to calculate reliable CH4 emission estimates. The flux separation is based on identification of ebullition-related sudden concentration changes during single measurements. Therefore, a variable ebullition filter is applied, using the lower and upper quartile and the interquartile range (IQR). Automation of data processing is achieved by using an established R script, adjusted for the purpose of CH4 flux calculation. The algorithm was validated by performing a laboratory experiment and tested using flux measurement data (July to September 2013) from a former fen grassland site, which converted into a shallow lake as a result of rewetting. Ebullition and diffusion contributed equally (46 and 55 %) to total CH4 emissions, which is comparable to ratios given in the literature. Moreover, the separation algorithm revealed a concealed shift in the diurnal trend of diffusive fluxes throughout the measurement period. The water temperature gradient was identified as one of the major drivers of diffusive CH4 emissions, whereas no significant driver was found in the case of erratic CH4 ebullition events. Y1 - 2017 U6 - https://doi.org/10.5194/amt-10-109-2017 SN - 1867-1381 SN - 1867-8548 VL - 10 IS - 1 SP - 109 EP - 118 PB - Copernicus CY - Göttingen ER - TY - JOUR A1 - Filipovic, Vilim A1 - Gerke, Horst H. A1 - Filipovic, Lana A1 - Sommer, Michael T1 - Quantifying subsurface lateral flow along sloping horizon boundaries in soil profiles of a hummocky ground moraine JF - Vadose zone journal N2 - Subsurface lateral flow in hillslope soils depends on lower permeability or texture-contrasting soil horizons. In the arable hummocky soil landscape, erosion processes caused glacial till appearance closer to the soil surface at upslope positions. The objective of this work was to quantify the potential for subsurface lateral flow depending on the erosion-affected spatial hydropedological complexity. The eroded Haplic Luvisol profile was studied due to the presence of a relatively dense C horizon that varied in depth, thickness, and sloping angle. A two-dimensional numerical modeling and sensitivity analysis for the saturated hydraulic conductivity (K-s) of the C horizon and the depth to C horizon (i.e., soil solum thickness) was performed for rainstorms in 2011 and 2012 using HYDRUS-2D. A K-s value of <2.5 cm d(-1) for the C horizon was required for lateral flow initiation. Lateral flow was (i) increasing with decreasing solum thickness, indicating an erosion-induced feedback on subsurface lateral flow, and (ii) dependent on the soil moisture regime prior to rainstorms. The effect of lateral flow on the movement of a conservative tracer was simulated in the form of a "virtual experiment". Simulation scenarios revealed only a relatively small lateral shift of the tracer plume caused by a local decoupling of water (already lateral) from subsequent tracer movement (still vertical). Longer term simulations suggested that, for the present conditions, lateral flow was limited mostly to occasional summer storm events. Even without considering preferential flow contribution to lateral flow, highly complex hydropedologic interactions are present in erosion-affected heterogeneous soil profiles. Y1 - 2016 U6 - https://doi.org/10.2136/vzj2017.05.0106 SN - 1539-1663 VL - 17 IS - 1 PB - Soil Science Society of America CY - Madison ER - TY - JOUR A1 - van der Meij, Marijn W. A1 - Reimann, Tony A1 - Vornehm, V. K. A1 - Temme, Arnaud J. A. M. A1 - Wallinga, Jakob A1 - van Beek, Roy A1 - Sommer, Michael T1 - Reconstructing rates and patterns of colluvial soil redistribution in agrarian (hummocky) landscapes JF - Earth surface processes and landforms : the journal of the British Geomorphological Research Group N2 - Humans have triggered or accelerated erosion processes since prehistoric times through agricultural practices. Optically stimulated luminescence (OSL) is widely used to quantify phases and rates of the corresponding landscape change, by measuring the last moment of daylight exposure of sediments. However, natural and anthropogenic mixing processes, such as bioturbation and tillage, complicate the use of OSL as grains of different depositional ages become mixed, and grains become exposed to light even long after the depositional event of interest. Instead, OSL determines the stabilization age, indicating when sediments were buried below the active mixing zone. These stabilization ages can cause systematic underestimation when calculating deposition rates. Our focus is on colluvial deposition in a kettle hole in the Uckermark region, northeastern Germany. We took 32 samples from five locations in the colluvium filling the kettle hole to study both spatial and temporal patterns in colluviation. We combined OSL dating with advanced age modelling to determine the stabilization age of colluvial sediments. These ages were combined with an archaeological reconstruction of historical ploughing depths to derive the levels of the soil surface at the moment of stabilization; the deposition depths, which were then used to calculate unbiased deposition rates. We identified two phases of colluvial deposition. The oldest deposits (similar to 5 ka) were located at the fringe of the kettle hole and accumulated relatively slowly, whereas the youngest deposits (<0.3 ka) rapidly filled the central kettle hole with rates of two orders of magnitude higher. We suggest that the latter phase is related to artificial drainage, facilitating accessibility in the central depression for agricultural practices. Our results show the need for numerical dating techniques that take archaeological and soil-geomorphological information into account to identify spatiotemporal patterns of landscape change, and to correctly interpret landscape dynamics in anthropogenically influenced hilly landscapes. (c) 2019 The Authors. Earth Surface Processes and Landforms Published by John Wiley & Sons Ltd. KW - geochronology KW - OSL KW - tillage KW - erosion KW - kettle hole KW - hummocky KW - landscape evolution Y1 - 2019 U6 - https://doi.org/10.1002/esp.4671 SN - 0197-9337 SN - 1096-9837 VL - 44 IS - 12 SP - 2408 EP - 2422 PB - Wiley CY - Hoboken ER - TY - JOUR A1 - Puppe, Daniel A1 - Wanner, Manfred A1 - Sommer, Michael T1 - Data on euglyphid testate amoeba densities, corresponding protozoic silicon pools, and selected soil parameters of initial and forested biogeosystems JF - Data in brief N2 - The dataset in the present article provides information on protozoic silicon (Si) pools represented by euglyphid testate amoebae (TA) in soils of initial and forested biogeosystems. Protozoic Si pools were calculated from densities of euglyphid TA shells and corresponding Si contents. The article also includes data on potential annual biosilicification rates of euglyphid TA at the examined sites. Furthermore, data on selected soil parameters (e.g., readily-available Si, soil pH) and site characteristics (e.g., soil groups, climate data) can be found. The data might be interesting for researchers focusing on biological processes in Si cycling in general and euglyphid TA and corresponding protozoic Si pools in particular. KW - Silicon cycling KW - Biogenic silica KW - Terrestrial biogeosystems KW - Biosilicification KW - Euglyphida Y1 - 2018 U6 - https://doi.org/10.1016/j.dib.2018.10.164 SN - 2352-3409 VL - 21 SP - 1697 EP - 1703 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Leue, Martin A1 - Hoffmann, Carsten A1 - Hierold, Wilfried A1 - Sommer, Michael T1 - In-situ multi-sensor characterization of soil cores along an erosion deposition gradient JF - Catena : an interdisciplinary journal of soil science, hydrology, geomorphology focusing on geoecology and landscape evolution N2 - Soil landscape research is faced with wide-ranging questions of soil erosion, precision farming, and agricultural risk management. Digital Soil Morphometrics is a powerful tool to provide respective answers or recommendations but requires soil data from the pedon-to-field scale with high horizontal and vertical resolutions, including the subsoil. We present an efficient sampling and measurement method for easily obtainable soil driving cores with low-destructive preparation. Elemental contents and soil organic and mineral matter composition were measured rapidly and in large numbers using a multi-sensor approach, i.e., visible and near infrared (Vis-NIR), diffuse reflectance infrared Fourier transform (DRIFT), and X-ray fluorescence (XRF) spectroscopy. The suitability of the approach with respect to three-dimensional soil landscape models was tested using soils along a slope representing different stages of erosion and deposition in a hummocky landscape under arable land use (Calcaric Regosols, Calcic Luvisols, Luvic Stagnosols, Gleyic-Colluvic Regosols). The combination of soil core sampling, pedological description, and three spectroscopic techniques enabled rapid determination and interpretation of horizontal and vertical spatial distributions of soil organic carbon (SOC), soil organic and mineral matter composition, as well as CaCO3, Fe, and Mn contents. Depth profiles for SOC, CaCO3, and Fe contents were suitable indicators for site-specific degrees of erosion and matter transport processes at the pedon-to-field scale. Fe and Mn profiles helped identifying zones of reductive and oxic domains in subsoils (gleyzation). Further methodical developments should implement plant-availability of nutrients, characterization of Fe oxides, and calibration of the spectroscopic techniques to field-moist samples. KW - Digital soil morphometrics KW - VIS-NIR spectroscopy KW - DRIFT spectroscopy KW - XRF spectroscopy KW - Soil organic carbon KW - Soil erosion Y1 - 2019 U6 - https://doi.org/10.1016/j.catena.2019.104140 SN - 0341-8162 SN - 1872-6887 VL - 182 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Puppe, Daniel A1 - Sommer, Michael T1 - Experiments, uptake mechanisms, and functioning of silicon foliar fertilization BT - a review focusing on Maize, Rice, and Wheat JF - Advances in Agronomy ; 152 N2 - Silicon (Si) is considered as a quasiessential element for higher plants as its uptake increases plant growth and resistance against abiotic as well as biotic stresses. Foliar application of fertilizers generally is assumed to be a comparably environment-friendly form of fertilization because only small quantities are needed. The interest in foliar fertilization and the use of Si as a fertilizer in general increased significantly within the last decades, but there are only few publications dealing with the foliar application of Si at all. In the present review, the effects of Si foliar fertilization, including nano-Si fertilizers, on the three most important crops on a global scale, that is, maize, rice, and wheat, are summarized. Additionally, different pathways (i.e., cuticular pathways, stomata, and trichomes) of foliar uptake and functioning of Si foliar fertilizers against biotic (i.e., fungal diseases and harmful insects), as well as abiotic (i.e., water stress, macronutrient imbalance, and heavy metal toxicity) stressors are discussed. Future research should especially focus on (1) the gathering of empirical data from field and greenhouse experiments, (2) the intensification of co-operations between practitioners and scientists, (3) interdisciplinary research, and (4) the analysis of results from multiple studies (meta-analysis, big data) to fully understand effects, uptake, and functioning of Si foliar fertilizers and to evaluate their potential in modern sustainable agriculture concepts. Y1 - 2018 SN - 978-0-12-815171-6 U6 - https://doi.org/10.1016/bs.agron.2018.07.003 SN - 0065-2113 VL - 152 SP - 1 EP - 49 PB - Elsevier CY - San Diego ER - TY - JOUR A1 - Hoffmann, Matthias A1 - Pohl, Madlen A1 - Jurisch, N. A1 - Prescher, Anne-Katrin A1 - Campa, E. Mendez A1 - Hagemann, Ulrike A1 - Remus, R. A1 - Verch, G. A1 - Sommer, Michael A1 - Augustin, J. T1 - Maize carbon dynamics are driven by soil erosion state and plant phenology rather than nitrogen fertilization form JF - Soil & tillage research : an international journal on research and development in soil tillage and field traffic, and their relationships with soil environment, land use and crop production N2 - Carbon (C) stored in soils represents the largest C pool of terrestrial ecosystems and consequently plays a crucial role in the global C cycle. So far, it is widely unclear to what extent different land uses and land use change influence soil C storage. The hummocky ground moraine landscape of northeastern Germany is characterized by distinct small-scale soil heterogeneity on the one hand, and intensive energy crop cultivation on the other. Both factors are assumed to significantly influence gaseous C exchange; as such, they likely drive soil organic carbon (SOC) stock dynamics in terrestrial agricultural ecosystems. To date, it is not clear to what extent N fertilization forms, which are associated with energy crop cultivation (e.g., application of biogas fermentation residues) and soil type relative to soil erosion state, influence soil C dynamics, nor is it clear whether one of these factors is more important than the other. To investigate the influence of soil erosion state and N fertilization form on soil C dynamics, we present dynamic and seasonal net ecosystem carbon balances (NECB) as a proxy for changes in soil organic carbon stocks. Measurements were conducted for maize (Zea mays L.) at five sites in the "CarboZALF-D" experimental field during the 2011 growing season. Measurement sites represent different soil erosion states (non-eroded Albic Luvisols, extremely eroded Calcaric Regosols and depositional Endogleyic Colluvic Regosols) and N fertilization forms (100% mineral fertilizer, 50% mineral and 50% organic fertilizer, and 100% organic fertilizer). Fertilization treatments were established on the Albic Luvisol. Net ecosystem CO2 exchange (NEE) and ecosystem respiration (R-eco) were measured every four weeks using a dynamic flow-through non-steady-state closed manual chamber system. Gap filling was performed based on empirical temperature and PAR dependency functions and was used to derive daily NEE values. In parallel, daily above-ground biomass production (NPFshoot) was estimated using a logistic growth equation, fitted on periodic biomass samples. Finally, C dynamics were calculated as the balance of daily NEE and NPPshoot based on the initial C input due to organic fertilization. Resulting NECB varied from pronounced soil C losses at the Endogleyic Colluvic Regosol (592 g C m(-2)) to soil C gains at the Calcaric Regosol (-124 g C m(-2)). Minor to modest C losses were observed for the Albic Luvisol. Compared to N fertilization forms, soil erosion states generally had a stronger impact on derived NECB. However, interannual variations in plant phonology and interactions between soil erosion states and fertilization forms might result in different NECB values over multiple years. Hence, long-term measurements of different fertilization treatments on characteristic soil landscape elements are needed. KW - Soil erosion KW - Net ecosystem carbon balance (NECB) KW - Closed chamber measurements KW - Biogas fermentation residues KW - Plant phenology Y1 - 2017 U6 - https://doi.org/10.1016/j.still.2017.09.004 SN - 0167-1987 SN - 1879-3444 VL - 175 SP - 255 EP - 266 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Frick, Daniel Alexander A1 - Schüßler, Jan Arne A1 - Sommer, Michael A1 - von Blanckenburg, Friedhelm T1 - Laser Ablation In Situ Silicon Stable Isotope Analysis of Phytoliths JF - Geostandards and geoanalytical research N2 - Silicon is a beneficial element for many plants and is deposited in plant tissue as amorphous bio-opal called phytoliths. The biochemical processes of silicon uptake and precipitation induce isotope fractionation: the mass-dependent shift in the relative abundances of the stable isotopes of silicon. At the bulk scale, delta Si-30 ratios span from -2 to +6 parts per thousand. To further constrain these variations in situ, at the scale of individual phytolith fragments, we used femtosecond laser ablation multi-collector inductively coupled plasma-mass spectrometry (fsLA-MC-ICP-MS). A variety of phytoliths from grasses, trees and ferns were prepared from plant tissue or extracted from soil. Good agreement between phytolith delta Si-30 ratios obtained by bulk solution MC-ICP-MS analysis and in situ isotope ratios from fsLA-MC-ICP-MS validates the method. Bulk solution analyses result in at least twofold better precision for delta Si-30 (2s on reference materials <= 0.11 parts per thousand) over that found for the means of in situ analyses (2s typically <= 0.24 parts per thousand). We find that bushgrass, common reed and horsetail show large internal variations up to 2 parts per thousand in delta Si-30, reflecting the various pathways of silicon from soil to deposition. Femtosecond laser ablation provides a means to identify the underlying processes involved in the formation of phytoliths using silicon isotope ratios. KW - In situ silicon isotope ratio analysis KW - phytolith KW - laser ablation inductively coupled plasma-mass spectrometry KW - biogenic silica Y1 - 2018 U6 - https://doi.org/10.1111/ggr.12243 SN - 1639-4488 SN - 1751-908X VL - 43 IS - 1 SP - 77 EP - 91 PB - Wiley CY - Hoboken ER - TY - JOUR A1 - Wilken, Florian A1 - Baur, Martin A1 - Sommer, Michael A1 - Deumlich, Detlef A1 - Bens, Oliver A1 - Fiener, Peter T1 - Uncertainties in rainfall kinetic energy-intensity relations for soil erosion modelling JF - Catena : an interdisciplinary journal of soil science, hydrology, geomorphology focusing on geoecology and landscape evolution N2 - For bare soil conditions, the most important process driving and initiating splash and interrill erosion is the detachment of soil particles via raindrop impact. The kinetic energy of a rainfall event is controlled by the drop size and fall velocity distribution, which is often directly or indirectly implemented in erosion models. Therefore, numerous theoretical functions have been developed for the estimation of rainfall kinetic energy from available rainfall intensity measurements. The aim of this study is to assess differences inherent in a wide number of kinetic energy-rainfall intensity (KE-I) relations and their role in soil erosion modelling. Therefore, 32 KE-I relations are compared against measured rainfall energies based on optical distrometer measurements carried out at five stations of two substantially different rainfall regimes. These allow for continuous high-resolution (1-min) direct measurements of rainfall kinetic energies from a detailed spectrum of measured drop sizes and corresponding fall velocities. To quantify the effect of different KE-I relations on sediment delivery, we apply the erosion model WATEM/SEDEM in an experimental setup to four catchments of NE-Germany. The distrometer data shows substantial differences between measured and theoretical models of drop size and fall velocity distributions. For low intensities the number of small drops is overestimated by the Marshall and Palmer (1948; MP) drop size distribution, while for high intensities the proportion of large drops is overestimated by the MP distribution. The distrometer measurements show a considerable proportion of large drops falling at slower velocities than predicted by the Gunn and Kinzer (1949) terminal velocity model. For almost all rainfall events at all stations, the KE-I relations predicted higher cumulative kinetic energy sums compared to the direct measurements of the optical distrometers. The different KE-I relations show individual characteristics over the course of rainfall intensity levels. Our results indicate a high sensitivity (up to a range from 10 to 27 t ha(-1)) of the simulated sediment delivery related to different KE-I relations. Hence, the uncertainty associated with KE-I relations for soil erosion modelling is of critical importance. KW - Rainfall kinetic energy KW - Drop size distribution KW - Drop fall velocity KW - Soil erosion modelling KW - Optical distrometer Y1 - 2018 U6 - https://doi.org/10.1016/j.catena.2018.07.002 SN - 0341-8162 SN - 1872-6887 VL - 171 SP - 234 EP - 244 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Webber, Heidi A1 - Lischeid, Gunnar A1 - Sommer, Michael A1 - Finger, Robert A1 - Nendel, Claas A1 - Gaiser, Thomas A1 - Ewert, Frank T1 - No perfect storm for crop yield failure in Germany JF - Environmental research letters N2 - Large-scale crop yield failures are increasingly associated with food price spikes and food insecurity and are a large source of income risk for farmers. While the evidence linking extreme weather to yield failures is clear, consensus on the broader set of weather drivers and conditions responsible for recent yield failures is lacking. We investigate this for the case of four major crops in Germany over the past 20 years using a combination of machine learning and process-based modelling. Our results confirm that years associated with widespread yield failures across crops were generally associated with severe drought, such as in 2018 and to a lesser extent 2003. However, for years with more localized yield failures and large differences in spatial patterns of yield failures between crops, no single driver or combination of drivers was identified. Relatively large residuals of unexplained variation likely indicate the importance of non-weather related factors, such as management (pest, weed and nutrient management and possible interactions with weather) explaining yield failures. Models to inform adaptation planning at farm, market or policy levels are here suggested to require consideration of cumulative resource capture and use, as well as effects of extreme events, the latter largely missing in process-based models. However, increasingly novel combinations of weather events under climate change may limit the extent to which data driven methods can replace process-based models in risk assessments. KW - crop yield failure KW - extreme events KW - support vector machine KW - process-based crop model KW - Germany Y1 - 2020 U6 - https://doi.org/10.1088/1748-9326/aba2a4 SN - 1748-9326 VL - 15 IS - 10 PB - IOP Publ. Ltd. CY - Bristol ER - TY - JOUR A1 - Küken, Anika A1 - Sommer, Frederik A1 - Yaneva-Roder, Liliya A1 - Mackinder, Luke C. M. A1 - Hoehne, Melanie A1 - Geimer, Stefan A1 - Jonikas, Martin C. A1 - Schroda, Michael A1 - Stitt, Mark A1 - Nikoloski, Zoran A1 - Mettler-Altmann, Tabea T1 - Effects of microcompartmentation on flux distribution and metabolic pools in Chlamydomonas reinhardtii chloroplasts JF - eLife N2 - Cells and organelles are not homogeneous but include microcompartments that alter the spatiotemporal characteristics of cellular processes. The effects of microcompartmentation on metabolic pathways are however difficult to study experimentally. The pyrenoid is a microcompartment that is essential for a carbon concentrating mechanism (CCM) that improves the photosynthetic performance of eukaryotic algae. Using Chlamydomonas reinhardtii, we obtained experimental data on photosynthesis, metabolites, and proteins in CCM-induced and CCM-suppressed cells. We then employed a computational strategy to estimate how fluxes through the Calvin-Benson cycle are compartmented between the pyrenoid and the stroma. Our model predicts that ribulose-1,5-bisphosphate (RuBP), the substrate of Rubisco, and 3-phosphoglycerate (3PGA), its product, diffuse in and out of the pyrenoid, respectively, with higher fluxes in CCM-induced cells. It also indicates that there is no major diffusional barrier to metabolic flux between the pyrenoid and stroma. Our computational approach represents a stepping stone to understanding microcompartmentalized CCM in other organisms. Y1 - 2018 U6 - https://doi.org/10.7554/eLife.37960 SN - 2050-084X VL - 7 PB - eLife Sciences Publications CY - Cambridge ER - TY - JOUR A1 - Sommer, Michael A1 - Kaczorek, Danuta A1 - Kuzyakov, Yakov A1 - Breuer, Jörn T1 - Silicon pools and fluxes in soils and landscapes : a review N2 - Silicon (Si) is the second-most abundant element in the earth's crust. In the pedosphere, however, huge spans of Si contents occur mainly caused by Si redistribution in soil profiles and landscapes. Here, we summarize the current knowledge on the different pools and fluxes of Si in soils and terrestrial biogeosystems. Weathering and subsequent release of soluble Si may lead to (1) secondarily bound Si in newly formed Al silicates, (2) amorphous silica precipitation on surfaces of other minerals, (3) plant uptake, formation of phytogenic Si, and subsequent retranslocation to soils, (4) translocation within soil profiles and formation of new horizons, or (5) translocation out of soils (desilication). The research carried out hitherto focused on the participation of Si in weathering processes, especially in clay neoformation, buffering mechanisms for acids in soils or chemical denudation of landscapes. There are, however, only few investigations on the characteristics and controls of the low-crystalline, almost pure silica compounds formed during pedogenesis. Further, there is strong demand to improve the knowledge of (micro)biological and rhizosphere processes contributing to Si mobilization, plant uptake, and formation of phytogenic Si in plants, and release due to microbial decomposition. The contribution of the biogenic Si sources to Si redistribution within soil profiles and desilication remains unknown concerning the pools, rates, processes, and driving forces. Comprehensive studies considering soil hydrological, chemical, and biological processes as well as their interactions at the scale of pedons and landscapes are necessary to make up and model the Si balance and to couple terrestrial processes with Si cycle of limnic, fluvial, or marine biogeosystems Y1 - 2006 ER - TY - JOUR A1 - Kühn, Jürgen A1 - Brenning, Alexander A1 - Wehrhan, Marc A1 - Koszinski, Sylvia A1 - Sommer, Michael T1 - Interpretation of electrical conductivity patterns by soil properties and geological maps for precision agriculture N2 - Precision farming needs management rules to apply spatially differentiated treatments in agricultural fields. Digital soil mapping (DSM) tools, for example apparent soil electrical conductivity, corrected to 25A degrees C (EC25), and digital elevation models, try to explain the spatial variation in soil type, soil properties (e.g. clay content), site and crop that are determined by landscape characteristics such as terrain, geology and geomorphology. We examined the use of EC25 maps to delineate management zones, and identified the main factors affecting the spatial pattern of EC25 at the regional scale in a study area in eastern Germany. Data of different types were compared: EC25 maps for 11 fields, soil properties measured in the laboratory, terrain attributes, geological maps and the description of 75 soil profiles. We identified the factors that influence EC25 in the presence of spatial autocorrelation and field-specific random effects with spatial linear mixed-effects models. The variation in EC25 could be explained to a large degree (R (2) of up to 61%). Primarily, soil organic matter and CaCO3, and secondarily clay and the presence of gleyic horizons were significantly related to EC25. Terrain attributes, however, had no significant effect on EC25. The geological map unit showed a significant relationship to EC25, and it was possible to determine the most important soil properties affecting EC25 by interpreting the geological maps. Including information on geology in precision agriculture could improve understanding of EC25 maps. The EC25 maps of fields should not be assumed to represent a map of clay content to form a basis for deriving management zones because other factors appeared to have a more important effect on EC25. Y1 - 2009 UR - http://www.springerlink.com/content/103317 U6 - https://doi.org/10.1007/s11119-008-9103-z SN - 1385-2256 ER - TY - JOUR A1 - Gerke, Horst H. A1 - Koszinski, Sylvia A1 - Kalettka, Thomas A1 - Sommer, Michael T1 - Structures and hydrologic function of soil landscapes with kettle holes using an integrated hydropedological approach N2 - The hummocky post-glacial soil landscapes with kettle holes as internal drainage systems are characterized by ponds that trap lateral fluxes in topographic depressions. A quantitative description is mostly limited by the unknown complexity of hydraulically relevant soil and sediment structures. This paper is focussing on a structure-based approach to identify relevant field-scale flow and transport processes. Illustrative examples demonstrate extreme variations in water table fluctuation for adjoining kettle holes. Explanations require a pedohydrologic concept of the arable soil landscape. Identification of structures is based on geophysical methods and soil hydraulic measurements. Electrical resistivity imaging yields 0.5 m-scale spatial structures that correspond with soil texture distributions. Electromagnetic induction provides larger-scale field maps that reflect major soil and sediment features. Results of both methods correspond within the limits of the different spatial resolutions. With geophysical exploration methods, colluvial areas with textural differences between upper and deeper soil layers, coarse-textured sediment lenses, and stony colluvial regions around kettle holes are identified as potentially relevant flow structures. The colluvial fringe around the pond seems to be a sensitive area with important lateral exchange fluxes. Tensiometer measurements perpendicular to this boundary indicate hydraulic gradients directed from the pond towards the partially saturated soil. The localized infiltration of trapped water in kettle holes can control large fractions of ground water recharge and may have implications for the fate of agricultural chemicals in post-glacial landscapes. While surface and subsurface hydraulic structures may be inferred using minimal-invasive techniques, better understanding of processes and properties governing lateral exchange fluxes between pond and surrounding soil are required. Y1 - 2010 UR - http://www.sciencedirect.com/science/journal/00221694 U6 - https://doi.org/10.1016/j.jhydrol.2009.12.047 SN - 0022-1694 ER - TY - JOUR A1 - Kaczorek, Danuta A1 - Bruemmer, Gerhard W. A1 - Sommer, Michael T1 - Content and binding forms of heavy metals, aluminium and phosphorus in bog iron ores from Poland N2 - Bog iron ores are widespread in Polish wetland soils used as meadows or pastures. They are suspected to contain high concentrations of heavy metals, which are precipitated together with Fe along a redox gradient. Therefore, soils with bog iron ore might be important sources for a heavy metal transfer from meadow plants into the food chain. However, this transfer depends on the different binding forms of heavy metals. The binding forms were quantified by sequential extraction analysis of heavy metals (Fe, Mn, Cr, Co, Ni, Cd, Pb) as well as Al and P on 13 representative samples of bog iron ores from central and southwestern Poland. Our results showed total contents of Cr, Co, Ni, Zn, Cd, and Pb not to exceed the natural values for sandy soils from Poland. Only the total Mn was slightly higher. The highest contents of all heavy metals have,been obtained in iron oxide fractions V (occluded in noncrystalline and poorly crystalline Fe oxides) and VI (occluded in crystalline Fe oxides). The results show a distinct relationship between the content of Fe and the quantity of Zn and Pb as well R Water soluble as well as plant available fractions were below the detection limit in most cases. From this we concluded bog iron ores not to be an actual, important source of heavy metals in the food chain. However, a remobilization of heavy metals might occur due to any reduction of iron oxides in bog iron ores, for example, by rising groundwater levels. Y1 - 2009 UR - https://www.soils.org/publications/jeq U6 - https://doi.org/10.2134/Jeq2008.0125 SN - 0047-2425 ER - TY - JOUR A1 - Koszinski, Sylvia A1 - Gerke, Horst H. A1 - Hierold, Wilfried A1 - Sommer, Michael T1 - Geophysical-based modeling of a kettle hole catchment of the morainic soil landscape JF - Vadose zone journal N2 - Soilscapes of the post-glacial morainic regions of the youngest glaciation are characterized by small hydrological kettle hole catchments forming hummocky soil landscapes. The spatial heterogeneity of subsurface structures as well as erosion-controlled pedogenesis under arable land use may complicate hydrological modeling. Our aim was to generate a soil landscape model for a small representative kettle hole catchment based on geoelectrical exploration and soil profile information. For a 1-ha catchment located in the northeastern German lowlands near the town of Prenzlau, electrical resistivity transects were determined by a multi electrode system (IMPETUS 12 Fs) and electrical conductivity (ECa) was mapped by using the electromagnetic induction (EMI) device EM38DD in both the vertical and horizontal modes. The 1-m digital elevation model (DEM) was obtained by kriging from high resolution manual elevation data determined with a leveling device (ZEISS Ni 40). Soil profile data from 26 boreholes distributed radially around the central pond were used to identify boundaries between soil horizons. The soil is characterized by varying topography and morphology of diagnostic horizons such as M- (colluvium), Bt- (clay illuviation), and C- (parent glacial till). By EMI mapping we identified (i) the boundary between erosive and colluvial areas around the kettle hole, and modeled (ii) the subsurface morphology of loamy horizons. Electrical resistivity tomography results coincide with these findings and allow for distinguishing between sandy and loamy dominated areas both in vertical and horizontal direction, respectively. This soil model of soil textural properties could be used for hydrological modeling. Y1 - 2013 U6 - https://doi.org/10.2136/vzj2013.02.0044 SN - 1539-1663 VL - 12 IS - 4 PB - Soil Science Society of America CY - Madison ER - TY - JOUR A1 - Gocke, Martina A1 - Liang, Wu A1 - Sommer, Michael A1 - Kuzyakov, Yakov T1 - Silicon uptake by wheat - effects of Si pools and pH JF - Journal of plant nutrition and soil science = Zeitschrift für Pflanzenernährung und Bodenkunde N2 - Silicon (Si), although not considered essential, has beneficial effects on plant growth which are mostly associated with the ability to accumulate amorphous (phytogenic) Si, e.g., as phytoliths. Phytogenic Si is the most active Si pool in the soil-plant system because of its great surface-to-volume ratio, amorphous structure, and high water solubility. Despite the high abundance of Si in terrestrial biogeosystems and its importance, e.g., for the global C cycle, little is known about Si fluxes between soil and plants and Si pools used by plants. This study aims at elucidating the contribution of various soil Si pools to Si uptake by wheat. As pH affects dissolution of Si pools and Si uptake by plants, the effect of pH (4.5 and 7) was evaluated. Wheat was grown on Si-free pellets mixed with one of the following Si pools: quartz sand (crystalline), anorthite powder (crystalline), or silica gel (amorphous). Silicon content was measured in aboveground biomass, roots, and soil solution 4 times in intervals of 7 d. At pH 4.5, plants grew best on anorthite, but pH did not significantly affect Si-uptake rates. Total Si contents in plant biomass were significantly higher in the silica-gel treatment compared to all other treatments, with up to 26 mg g(-1) in aboveground biomass and up to 17 mg g(-1) in roots. Thus, Si uptake depends on the conversion of Si into plant-available silicic acid. This conversion occurs too slowly for crystalline Si phases, therefore Si uptake from treatments with quartz sand and anorthite did not differ from the control. For plants grown on silica gel, real Si-uptake rates were higher than the theoretical value calculated based on water transpiration. This implies that Si uptake by wheat is driven not only by passive water flux but also by active transporters, depending on Si concentration in the aqueous phase, thus on type of Si pool. These results show that Si uptake by plants as well as plant growth are significantly affected by the type of Si pool and factors controlling its solubility. KW - anorthite KW - global Si cycle KW - phytogenic silica KW - quartz KW - silica gel KW - soil Si pools KW - Triticum aestivum L Y1 - 2013 U6 - https://doi.org/10.1002/jpln.201200098 SN - 1436-8730 SN - 1522-2624 VL - 176 IS - 4 SP - 551 EP - 560 PB - Wiley-VCH CY - Weinheim ER - TY - JOUR A1 - Kliegl, Reinhold A1 - Dambacher, Michael A1 - Dimigen, Olaf A1 - Jacobs, Arthur M. A1 - Sommer, Werner T1 - Eye movements and brain electric potentials during reading JF - Psychological research : an international journal of perception, attention, memory, and action N2 - The development of theories and computational models of reading requires an understanding of processing constraints, in particular of timelines related to word recognition and oculomotor control. Timelines of word recognition are usually determined with event-related potentials (ERPs) recorded under conditions of serial visual presentation (SVP) of words; timelines of oculomotor control are derived from parameters of eye movements (EMs) during natural reading. We describe two strategies to integrate these approaches. One is to collect ERPs and EMs in separate SVP and natural reading experiments for the same experimental material (but different subjects). The other strategy is to co-register EMs and ERPs during natural reading from the same subjects. Both strategies yield data that allow us to determine how lexical properties influence ERPs (e.g., the N400 component) and EMs (e.g., fixation durations) across neighboring words. We review our recent research on the effects of frequency and predictability of words on both EM and ERP measures with reference to current models of eye-movement control during reading. Results are in support of the proposition that lexical access is distributed across several fixations and across brain-electric potentials measured on neighboring words. Y1 - 2012 U6 - https://doi.org/10.1007/s00426-011-0376-x SN - 0340-0727 VL - 76 IS - 2 SP - 145 EP - 158 PB - Springer CY - Heidelberg ER - TY - JOUR A1 - Nordhues, Andre A1 - Schöttler, Mark Aurel A1 - Unger, Ann-Katrin A1 - Geimer, Stefan A1 - Schönfelder, Stephanie A1 - Schmollinger, Stefan A1 - Ruetgers, Mark A1 - Finazzi, Giovanni A1 - Soppa, Barbara A1 - Sommer, Frederik A1 - Mühlhaus, Timo A1 - Roach, Thomas A1 - Krieger-Liszkay, Anja A1 - Lokstein, Heiko A1 - Luis Crespo, Jose A1 - Schroda, Michael T1 - Evidence for a role of VIPP1 in the structural organization of the photosynthetic apparatus in chlamydomonas JF - The plant cell N2 - The vesicle-inducing protein in plastids (VIPP1) was suggested to play a role in thylakoid membrane formation via membrane vesicles. As this functional assignment is under debate, we investigated the function of VIPP1 in Chlamydomonas reinhardtii. Using immunofluorescence, we localized VIPP1 to distinct spots within the chloroplast. In VIPP1-RNA interference/artificial microRNA cells, we consistently observed aberrant, prolamellar body-like structures at the origin of multiple thylakoid membrane layers, which appear to coincide with the immunofluorescent VIPP1 spots and suggest a defect in thylakoid membrane biogenesis. Accordingly, using quantitative shotgun proteomics, we found that unstressed vipp1 mutant cells accumulate 14 to 20% less photosystems, cytochrome b(6)f complex, and ATP synthase but 30% more light-harvesting complex II than control cells, while complex assembly, thylakoid membrane ultrastructure, and bulk lipid composition appeared unaltered. Photosystems in vipp1 mutants are sensitive to high light, which coincides with a lowered midpoint potential of the Q(A)/Q(A)(-) redox couple and increased thermosensitivity of photosystem II (PSII), suggesting structural defects in PSII. Moreover, swollen thylakoids, despite reduced membrane energization, in vipp1 mutants grown on ammonium suggest defects in the supermolecular organization of thylakoid membrane complexes. Overall, our data suggest a role of VIPP1 in the biogenesis/assembly of thylakoid membrane core complexes, most likely by supplying structural lipids. Y1 - 2012 U6 - https://doi.org/10.1105/tpc.111.092692 SN - 1040-4651 VL - 24 IS - 2 SP - 637 EP - 659 PB - American Society of Plant Physiologists CY - Rockville ER - TY - JOUR A1 - Kaiser, Thomas A1 - Wehrhan, Marc A1 - Werner, Armin A1 - Sommer, Michael T1 - Regionalizing ecological moisture levels and groundwater levels in grassland areas using thermal remote sensing JF - Grassland science N2 - Site-specific soil moisture and groundwater levels are key input parameters for ecological modeling. Obtaining such information in a comprehensive manner is difficult for large regions. We studied a floodplain region in the Federal State of Brandenburg, Germany, to examine the degree to which the average depth of groundwater tables can be derived from surface temperatures obtained by the ASTER radiospectrometer (spatial resolution of 90 m per pixel). A floristic ecological indicator representing the site-specific moisture level was applied to develop a proxy between the thermal satellite data and groundwater table depth. The use of spring scenes (late April to early May) from 2 years proved to be well suited for minimizing the effects of weather and land use. Vegetation surveys along transects that were 2 m wide across the pixel diagonals allowed for the calculation of average ecological moisture values of pixel-sites by applying Ellenberg-numbers. These values were used to calibrate the satellite data locally. There was a close relationship between surface temperature and the average ecological moisture value (R2 = 0.73). Average ecological moisture values were highly indicative of the average groundwater levels during a 7-year measurement series (R2 = 0.93). Satellite-supported thermal data from spring were suitable for estimating the average groundwater levels of low-lying grasslands on a larger scale. Ecological moisture values from the transect surveys effectively allowed the incorporation of relief heterogeneity within the thermal grid and the establishment of the correlation between thermal data and average groundwater table depth. Regression functions were used to produce a map of groundwater levels at the study site. KW - Ellenberg indicator values KW - groundwater table KW - satellite data KW - soil moisture Y1 - 2012 U6 - https://doi.org/10.1111/j.1744-697X.2011.00240.x SN - 1744-6961 VL - 58 IS - 1 SP - 42 EP - 52 PB - Wiley-Blackwell CY - Malden ER - TY - JOUR A1 - Bell, M. J. A1 - Jones, E. A1 - Smith, J. A1 - Smith, P. A1 - Yeluripati, J. A1 - Augustin, Jürgen A1 - Juszczak, R. A1 - Olejnik, J. A1 - Sommer, Michael T1 - Simulation of soil nitrogen, nitrous oxide emissions and mitigation scenarios at 3 European cropland sites using the ECOSSE model JF - Nutrient cycling in agroecosystems N2 - The global warming potential of nitrous oxide (N2O) and its long atmospheric lifetime mean its presence in the atmosphere is of major concern, and that methods are required to measure and reduce emissions. Large spatial and temporal variations means, however, that simple extrapolation of measured data is inappropriate, and that other methods of quantification are required. Although process-based models have been developed to simulate these emissions, they often require a large amount of input data that is not available at a regional scale, making regional and global emission estimates difficult to achieve. The spatial extent of organic soils means that quantification of emissions from these soil types is also required, but will not be achievable using a process-based model that has not been developed to simulate soil water contents above field capacity or organic soils. The ECOSSE model was developed to overcome these limitations, and with a requirement for only input data that is readily available at a regional scale, it can be used to quantify regional emissions and directly inform land-use change decisions. ECOSSE includes the major processes of nitrogen (N) turnover, with material being exchanged between pools of SOM at rates modified by temperature, soil moisture, soil pH and crop cover. Evaluation of its performance at site-scale is presented to demonstrate its ability to adequately simulate soil N contents and N2O emissions from cropland soils in Europe. Mitigation scenarios and sensitivity analyses are also presented to demonstrate how ECOSSE can be used to estimate the impact of future climate and land-use change on N2O emissions. KW - Soil N2O emissions KW - Process-based models KW - Land-use KW - Climate change Y1 - 2012 U6 - https://doi.org/10.1007/s10705-011-9479-4 SN - 1385-1314 VL - 92 IS - 2 SP - 161 EP - 181 PB - Springer CY - Dordrecht ER - TY - JOUR A1 - Steinhoefel, Grit A1 - Breuer, Jörn A1 - von Blanckenburg, Friedhelm A1 - Horn, Ingo A1 - Kaczorek, Danuta A1 - Sommer, Michael T1 - Micrometer silicon isotope diagnostics of soils by UV femtosecond laser ablation JF - Chemical geology : official journal of the European Association for Geochemistry N2 - This study presents the first Si isotope data of the principle Si pools in soils determined by a UV femtosecond laser ablation system coupled to a multicollector inductively coupled plasma mass spectrometer (MC-ICP-MS). This method reveals accurate and precise Si isotope data on bulk materials, and at high spatial resolution, on the mineral scale. The following Si pools have been investigated: a) the Si source to soils on all major silicate minerals on thin sections from bedrock fragments in the soil profiles; b) bulk soils (particle size <2 mm) after fusion to glass beads with an iridium-strip heater or pressed into powder pellets: c) separated clay fractions as pressed powder pellets and e) separated phytoliths as pressed powder pellets. Multiple analyses of three rock standards, BHVO-2, AGV-1 and RGM-1 as fused glass beads and as pressed powder pellets, reveal delta(30)Si values within the expected range of igneous rocks. The MPI-DING reference glass KL2-G exhibits the same Si isotope composition after remelting by an iridium-strip heater showing that this technique does not alter the isotope composition of the glass. We used this approach to investigated two immature Cambisols developed on sandstone and paragneiss in the Black Forest (Germany), respectively. Bulk soils show a largely uniform Si isotope signature for different horizons and locations, which is close to those of primary quartz and feldspar with delta(30)Si values around -0.4 parts per thousand. Soil clay formation is associated with limited Si mobility, which preserves initial Si isotope signatures of parental minerals. An exception is the organic horizon of the paragneiss catchment where intense weathering leads to a high mobility of Si and significant negative isotope signatures as low as to -1.00 parts per thousand in bulk soils. Biogenic opal in the form of phytoliths, exhibits negative Si isotope signatures of about -0.4 parts per thousand. These results demonstrate that UV femtosecond laser ablation MC-ICP-MS provides a tool to characterize the Si isotope signature of the principle Si pools left behind after weathering and Si transport have altered soils. These results can now serve as a fingerprint of the residual solids that can be used to explain the isotope composition of dissolved Si in soil solutions and river water, which is mostly enriched in the heavy isotopes. KW - Silicon isotopes KW - Soils KW - UV femtosecond laser ablation KW - MC-ICP-MS Y1 - 2011 U6 - https://doi.org/10.1016/j.chemgeo.2011.05.013 SN - 0009-2541 VL - 286 IS - 3-4 SP - 280 EP - 289 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Ehrmann, Otto A1 - Puppe, Daniel A1 - Wanner, Manfred A1 - Kaczorek, Danuta A1 - Sommer, Michael T1 - Testate amoebae in 31 mature forest ecosystems - Densities and micro-distribution in soils JF - European journal of protistology N2 - We studied testate amoebae and possible correlated abiotic factors in soils of 31 mature forest ecosystems using an easily applicable and spatially explicit method. Simple counting on soil thin-sections with a light microscope resulted in amoeba densities comparable to previously reported values, i.e. 0.1 x 10(8) to 11.5 x 10(8) individuals m(-2) (upper 3 cm of soil). Soil moisture and soil acidity seem to be correlated with amoeba densities. At sites of moderate soil moisture regimes (SMR 2-7) we found higher densities of testate amoebae at pH < 4.5. At wetter sites (SMR >= 8) higher individual densities were recorded also at less acidic sites. The in situ description of amoebae, based on the analysis of a complete soil thin-section, showed a relatively uniform spatial micro-distribution throughout the organic and mineral soil horizons (no testate amoeba clusters). We discuss the pros and cons of the soil thin-section method and suggest it as an additional tool to improve knowledge of the spatial micro-distribution of testate amoebae. KW - Microhabitats KW - Soil thin-section KW - Soil moisture regimes KW - Soil reaction Y1 - 2012 U6 - https://doi.org/10.1016/j.ejop.2012.01.003 SN - 0932-4739 VL - 48 IS - 3 SP - 161 EP - 168 PB - Elsevier CY - Jena ER - TY - JOUR A1 - Mueller, Marina Elsa Herta A1 - Koszinski, Sylvia A1 - Brenning, Alexander A1 - Verch, Gernot A1 - Korn, Ulrike A1 - Sommer, Michael T1 - Within-field variation of mycotoxin contamination of winter wheat is related to indicators of soil moisture JF - Plant and soil N2 - Humidity is an important determinant of the mycotoxin production (DON, ZEA) by Fusarium species in the grain ears. From a landscape perspective humidity is not evenly distributed across fields. The topographically-controlled redistribution of water within a single field rather leads to spatially heterogeneous soil water content and air humidity. Therefore we hypothesized that the spatial distribution of mycotoxins is related to these topographically-controlled factors. To test this hypothesis we studied the mycotoxin concentrations at contrasting topographic relief positions, i.e. hilltops and depressions characterized by soils of different soil moisture regimes, on ten winter wheat fields in 2006 and 2007. Maize was the preceding crop and minimum tillage was practiced in the fields. The different topographic positions were associated with moderate differences in DON and ZEA concentrations in 2006, but with significant differences in 2007, with six times higher median ZEA and two times higher median DON detected at depression sites compared to the hilltops. The depression sites correspond to a higher topographic wetness index as well as redoximorphic properties in soil profiles, which empirically supports our hypothesis at least for years showing wetter conditions in sensitive time windows for Fusarium infections. KW - Wheat KW - Mycotoxins KW - Within-field variation KW - Topography KW - Humidity KW - Soil redoximorphic feature Y1 - 2011 U6 - https://doi.org/10.1007/s11104-010-0695-5 SN - 0032-079X SN - 1573-5036 VL - 342 IS - 1-2 SP - 289 EP - 300 PB - Springer CY - Dordrecht ER - TY - JOUR A1 - Rieckh, Helene A1 - Gerke, Horst H. A1 - Siemens, Jan A1 - Sommer, Michael T1 - Water and dissolved carbon fluxes in an eroding soil landscape depending on terrain position JF - Vadose zone journal N2 - Leaching of dissolved C in arable hummocky ground moraine soil landscapes is characterized by a spatial continuum of more or less erosion-affected Luvisols, Calcaric Regosols at exposed positions, and Colluvic Regosols in depressions. Our objective was to estimate the fluxes of dissolved C in four differently eroded soils as affected by erosion-induced pedological and soil structural alterations. In this model study, we considered landscape position effects by adapting the water table as the bottom boundary condition and erosion effects by using pedon-specific soil hydraulic properties. The one-dimensional vertical water movement was described with the Richards equation using HYDRUS-1D. Solute fluxes were obtained by combining calculated water fluxes with concentrations of dissolved organic and inorganic C (DOC and DIC, respectively) measured from soil solution extracted by suction cups at biweekly intervals. In the 3-yr period (2010-2012), DOC fluxes in the 2-m soil depth were similar at the three non-colluvic locations with -0.8 +/- 0.1 g m(-2) yr(-1) (i.e., outflow) but were 0.4 g m(-2) yr(-1) (i.e., input) in the depression. The DIC fluxes ranged from -10.2 g m(-2) yr(-1) for the eroded Luvisol, -9.2 g m(-2) yr(-1) for the Luvisol, and -6.1 g m(-2) yr(-1) for the Calcaric Regosol to 3.2 g m(-2) yr(-1) for the Colluvic Regosol. The temporal variations in DOC and DIC fluxes were controlled by water fluxes. The spatially distributed leaching results corroborate the hypothesis that the effects of soil erosion influence fluxes through modified hydraulic and transport properties and terrain-dependent boundary conditions. Y1 - 2014 U6 - https://doi.org/10.2136/vzj2013.10.0173 SN - 1539-1663 VL - 13 IS - 7 PB - Soil Science Society of America CY - Madison ER - TY - JOUR A1 - Wieland, Ralf A1 - Dalchow, Claus A1 - Sommer, Michael A1 - Fukuda, Kyoko T1 - Multi-Scale Landscape Analysis (MSLA) a method to identify correlation of relief with ecological point data JF - Ecological informatics : an international journal on ecoinformatics and computational ecolog N2 - A common problem in ecology is identifying the relationship between relief and site properties obtainable only by point measurements. The method of Multi-Scale Landscape Analysis (MSLA) identifies such correlations. MSLA combines frequency filtering of the digital elevation model (DEM) with an estimation of the optimum filter coefficients using an optimization procedure. Tested using point data of soil decarbonation from a German young moraine landscape, MSLA provided significant results. Implemented within open source software SAMT. MSLA is comfortable and flexible to use, offering applications for numerous other spatial analysis problems. KW - Landscape structure KW - DEM KW - Fourier transformation KW - Wavelet transformation KW - Singular value decomposition KW - SAMT Y1 - 2011 U6 - https://doi.org/10.1016/j.ecoinf.2010.09.002 SN - 1574-9541 VL - 6 IS - 2 SP - 164 EP - 169 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Rieckh, Helene A1 - Gerke, Horst H. A1 - Sommer, Michael T1 - Hydraulic properties of characteristic horizons depending on relief position and structure in a hummocky glacial soil landscape JF - Soil & tillage research : an international journal on research and development in soil tillage and field traffic, and their relationships with soil environment, land use and crop production N2 - The hummocky ground moraine soil landscape forms a spatial continuum of more or less eroded and depositional soils developed from glacial till under intensive agricultural cultivation. Measurements of soil hydraulic properties in the laboratory on soil cores are mostly limited to some characteristic horizons. However, these horizons can vary in thickness or structural and pedological development depending on relief position. This paper compares soil hydraulic properties of the same soil horizons sampled at different relief positions in a single field representing various degrees of soil erosion/deposition. Water retention curves were determined from undisturbed core samples using sand and kaolin beds with hanging water column and pressure chambers, and the unsaturated hydraulic conductivity using the double-membrane apparatus. Data were fitted to the van Genuchten-Mualem function (VGM) using the nonlinear curve fitting program RETC. The desorption water retention curves for the soil horizons were different and depended on the soil structural development that could be related with the intensity of erosion history at each landscape position. The greatest differences in hydraulic functions were found for the E, Bt, and C horizons. The fitted soil water retention curves reflected these differences mainly in the values of the VGM curve parameters n and theta(s). The landscape features that have the strongest differentiating effect are related to erosion and distance towards the water table. The results can help improving pedotransfer approaches for the estimation of spatially distributed hydraulic parameters for modelling the water movement in hummocky soil landscapes as basis for establishing landscape scale water and element balances. KW - Hydropedology KW - Structure effect KW - Soil development KW - RETC KW - van Genuchten-Mualem KW - Pedotransfer function Y1 - 2012 U6 - https://doi.org/10.1016/j.still.2012.07.004 SN - 0167-1987 VL - 125 IS - 1 SP - 123 EP - 131 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Puppe, Daniel A1 - Kaczorek, Danuta A1 - Wanner, Manfred A1 - Sommer, Michael T1 - Dynamics and drivers of the protozoic Si pool along a 10-year chronosequence of initial ecosystem states JF - Ecological engineering : the journal of ecotechnology N2 - The size and dynamics of biogenic silicon (BSi) pools influence silicon (Si) fluxes from terrestrial to aquatic ecosystems. The research focus up to now was on the role of plants in Si cycling. In recent studies on old forests annual biosilicification rates of idiosomic testate amoebae (i.e. TA producing self-secreted silica shells) were shown to be of the order of Si uptake by trees. However, no comparable data exist for initial ecosystems. We analyzed the protozoic BSi pool (idiosomic TA), corresponding annual biosilicification rates and readily available and amorphous Si fractions along a 10-year chronosequence in a post-mining landscape in Brandenburg, Germany. Idiosomic Si pools ranged from 3 to 680 g Si ha(-1) and were about 3-4 times higher at vegetated compared to uncovered spots. They increased significantly with age and were related to temporal development of soil chemical properties. The calculation of annual biosilicification resulted in maxima between 2 and 16 kg Si ha(-1) with rates always higher at vegetated spots. Our results showed that the BSi pool of idiosomic TA is built up rapidly during the initial phases of ecosystem development and is strongly linked to plant growth. Furthermore, our findings highlight the importance of TA for Si cycling in young artificial ecosystems. (C) 2014 Elsevier B.V. All rights reserved. KW - Idiosomic Si pool KW - Amorphous silica KW - Terrestrial ecosystem development KW - Artificial catchment KW - Si fractions KW - Biosilicification Y1 - 2014 U6 - https://doi.org/10.1016/j.ecoleng.2014.06.011 SN - 0925-8574 SN - 1872-6992 VL - 70 SP - 477 EP - 482 PB - Elsevier CY - Amsterdam ER - TY - GEN A1 - Wehrhan, Marc A1 - Rauneker, Philipp A1 - Sommer, Michael T1 - UAV-Based estimation of carbon exports from heterogeneous soil landscapes BT - a case study from the CarboZALF experimental area T2 - Sensors N2 - The advantages of remote sensing using Unmanned Aerial Vehicles (UAVs) are a high spatial resolution of images, temporal flexibility and narrow-band spectral data from different wavelengths domains. This enables the detection of spatio-temporal dynamics of environmental variables, like plant-related carbon dynamics in agricultural landscapes. In this paper, we quantify spatial patterns of fresh phytomass and related carbon (C) export using imagery captured by a 12-band multispectral camera mounted on the fixed wing UAV Carolo P360. The study was performed in 2014 at the experimental area CarboZALF-D in NE Germany. From radiometrically corrected and calibrated images of lucerne (Medicago sativa), the performance of four commonly used vegetation indices (VIs) was tested using band combinations of six near-infrared bands. The highest correlation between ground-based measurements of fresh phytomass of lucerne and VIs was obtained for the Enhanced Vegetation Index (EVI) using near-infrared band b(899). The resulting map was transformed into dry phytomass and finally upscaled to total C export by harvest. The observed spatial variability at field- and plot-scale could be attributed to small-scale soil heterogeneity in part. T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 451 KW - VI KW - soil landscape KW - carbon export KW - agriculture KW - multispectral KW - UAV Y1 - 2018 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-407706 ER - TY - GEN A1 - Pohl, Madlen A1 - Hoffmann, M. A1 - Hagemann, Ulrike A1 - Giebels, M. A1 - Albiac Borraz, E. A1 - Sommer, Michael A1 - Augustin, Jürgen T1 - Dynamic C and N stocks BT - key factors controlling the C gas exchange of maize in heterogenous peatland T2 - Postprints der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe N2 - The drainage and cultivation of fen peatlands create complex small-scale mosaics of soils with extremely variable soil organic carbon (SOC) stocks and groundwater levels (GWLs). To date, the significance of such sites as sources or sinks for greenhouse gases such as CO2 and CH4 is still unclear, especially if the sites are used for cropland. As individual control factors such as GWL fail to account for this complexity, holistic approaches combining gas fluxes with the underlying processes are required to understand the carbon (C) gas exchange of drained fens. It can be assumed that the stocks of SOC and N located above the variable GWL - defined as dynamic C and N stocks - play a key role in the regulation of the plant- and microbially mediated CO2 fluxes in these soils and, inversely, for CH4. To test this assumption, the present study analysed the C gas exchange (gross primary production - GPP; ecosystem respiration - R-eco; net ecosystem exchange - NEE; CH4) of maize using manual chambers for 4 years. The study sites were located near Paulinenaue, Germany, where we selected three soil types representing the full gradient of GWL and SOC stocks (0-1 m) of the landscape: (a) Haplic Arenosol (AR; 8 kg C m(-2)); (b) Mollic Gleysol (GL; 38 kg C m(-2)); and (c) Hemic Histosol (HS; 87 kg C m(-2)). Daily GWL data were used to calculate dynamic SOC (SOCdyn) and N (N-dyn) stocks. Average annual NEE differed considerably among sites, ranging from 47 +/- 30 g C m(-2) yr(-1) in AR to -305 +/- 123 g C m(-2) yr(-1) in GL and -127 +/- 212 g C m(-2) yr(-1) in HS. While static SOC and N stocks showed no significant effect on C fluxes, SOCdyn and N-dyn and their interaction with GWL strongly influenced the C gas exchange, particularly NEE and the GPP : R-eco ratio. Moreover, based on nonlinear regression analysis, 86% of NEE variability was explained by GWL and SOCdyn. The observed high relevance of dynamic SOC and N stocks in the aerobic zone for plant and soil gas exchange likely originates from the effects of GWL-dependent N availability on C formation and transformation processes in the plant-soil system, which promote CO2 input via GPP more than CO2 emission via R-eco. The process-oriented approach of dynamic C and N stocks is a promising, potentially generalisable method for system-oriented investigations of the C gas exchange of groundwater-influenced soils and could be expanded to other nutrients and soil characteristics. However, in order to assess the climate impact of arable sites on drained peatlands, it is always necessary to consider the entire range of groundwater-influenced mineral and organic soils and their respective areal extent within the soil landscape. T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 496 KW - soil organic-matter KW - Zea-mays L. KW - term management impacts KW - carbon-dioxide exchange KW - net ecosystem exchange KW - nitrogen-fertilization KW - water-table KW - northeast germany KW - CO2 fluxes KW - mineral fertilization Y1 - 2019 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-408184 SN - 1866-8372 IS - 496 ER - TY - JOUR A1 - Doetterl, Sebastian A1 - Berhe, Asmeret Asefaw A1 - Nadeu, Elisabet A1 - Wang, Zhengang A1 - Sommer, Michael A1 - Fiener, Peter T1 - Erosion, deposition and soil carbon: A review of process-level controls, experimental tools and models to address C cycling in dynamic landscapes JF - Earth science reviews : the international geological journal bridging the gap between research articles and textbooks N2 - The role of soil erosion in terrestrial carbon (C) sequestration and release remains one of the most important uncertainties in our attempts to determine the potential of soils to mediate climate change. Despite its widely recognized importance for terrestrial C sequestration, to date, no Earth System Model (ESM) implements soil erosion effects on carbon cycling in sufficient detail. So far, available studies have mostly investigated the magnitude of erosional C transport and in-situ measurements of vertical C fluxes on the catchment or regional scale. Recognizing the need to adequately represent C erosion processes and controls in ESMs, we provide a comprehensive cross-disciplinary review on lateral C redistribution in the landscape and discuss the implications for bio-geochemical cycling of carbon. We present current knowledge on the role of erosional C distribution in controlling the stabilization and release of C in soils, taking into consideration the important geomorphic, ecological, hydrologic, pedologic and micro-climatic processes and controls that affect soil organic carbon (SOC) stock, fluxes, and persistence in dynamic landscapes. Further, we provide an overview on latest experimental and modelling approaches that are being used to investigate the role of erosion in the carbon cycle. Finally, to advance our understanding of the role of soil redistribution in biogeochemical cycles of essential elements, we discuss the most promising topics for future research in this field. (C) 2015 Elsevier B.V. All rights reserved. KW - Soil erosion KW - Soil deposition KW - Carbon redistribution KW - Terrestrial C sink Y1 - 2016 U6 - https://doi.org/10.1016/j.earscirev.2015.12.005 SN - 0012-8252 SN - 1872-6828 VL - 154 SP - 102 EP - 122 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Gerke, Horst H. A1 - Rieckh, Helene A1 - Sommer, Michael T1 - Interactions between crop, water, and dissolved organic and inorganic carbon in a hummocky landscape with erosion-affected pedogenesis JF - Macromolecular rapid communications N2 - Hummocky soil landscapes are characterized by 3D spatial patterns of soil types that result from erosion-affected pedogenesis. Due to tillage and water erosion, truncated profiles have been formed at steep and mid slopes and colluvial soils at hollows, while intact profiles remained at plateau positions. Pedogenetic variations in soil horizons lead to spatial differences in the soil water balance at hillslope positions. Here, possible interactions between erosion affected soil properties, the water balances, and the crop growth and feedback effects of erosion on the leaching rates were assumed. The hypothesis was tested by water balance simulations comparing uniform with hillslope position-specific crop and root growths for soils at plateau, flat mid slope, steep slope, and hollow using the Hydrus-1D program. The boundary condition data were monitored at the CarboZALF-D experimental field site, which was cropped with perennial lucerne (Medicago sativa L.) in 2013 and 2014. Crop and root growth at the four hillslope positions was assumed proportional to observed leaf area index (LAI). Fluxes of dissolved organic and inorganic carbon (DOC, DIC) were obtained from simulated water fluxes and measured DOC and DIC concentrations. For the colluvic soil at hollow, the crop growth was initially highest and later limited by an increasing water table; here the predominately upward flow led to a net input in DIC and DOC. For the truncated soils at steep slopes, simulations support the hypothesis that reduced crop growth caused an increase in percolation and DIC leaching from the subsoil horizons, which in turn led to accelerated soil development and more soil variations along eroding hillslopes in arable soil landscapes. (C) 2015 Elsevier B.V. All rights reserved. KW - Hydrus-1D KW - LAI KW - Eroded soil types KW - Hillslope pedosequence KW - Soil C leaching KW - DOC vs. DIC KW - Soil water balance simulation KW - Root water uptake KW - Rooting depth Y1 - 2016 U6 - https://doi.org/10.1016/j.still.2015.09.003 SN - 0167-1987 SN - 1879-3444 VL - 156 SP - 230 EP - 244 PB - Elsevier CY - Amsterdam ER - TY - GEN A1 - Sommer, Michael A1 - Augustin, Jürgen A1 - Kleber, M. T1 - Feedbacks of soil erosion on SOC patterns and carbon dynamics in agricultural landscapes-The CarboZALF experiment T2 - Journal of real-time image processing Y1 - 2016 U6 - https://doi.org/10.1016/j.still.2015.09.015 SN - 0167-1987 SN - 1879-3444 VL - 156 SP - 182 EP - 184 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Wanner, Manfred A1 - Seidl-Lampa, Barbara A1 - Höhn, Axel A1 - Puppe, Daniel A1 - Meisterfeld, Ralf A1 - Sommer, Michael T1 - Culture growth of testate amoebae under different silicon concentrations JF - European journal of protistology N2 - Testate amoebae with self-secreted siliceous shell platelets ("idiosomes") play an important role in terrestrial silicon (Si) cycles. In this context, Si-dependent culture growth dynamics of idiosomic testate amoebae are of interest. Clonal cultures of idiosomic testate amoebae were analyzed under three different Si concentrations: low (50 mu mol L-1), moderate/site-specific (150 mu mol L-1) and high Si supply (500 mu mol L-1). Food (Saccharomyces cerevisiae) was provided in surplus. (i) Shell size of four different clones of idiosomic testate amoebae either decreased (Trinema galeata, Euglypha filifera cf.), increased (E. rotunda cf.), or did not change (E. rotunda) under the lowest Si concentration (50 mu mol Si L-1). (ii) Culture growth of idiosomic Euglypha rotunda was dependent on Si concentration. The more Si available in the culture medium, the earlier the entry into exponential growth phase. (iii) Culture growth of idiosomic Euglypha rotunda was dependent on origin of inoculum. Amoebae previously cultured under a moderate Si concentration revealed highest sustainability in consecutive cultures. Amoebae derived from cultures with high Si concentrations showed rapid culture growth which finished early in consecutive cultures. (iv) Si (diluted in the culture medium) was absorbed by amoebae and fixed in the amoeba shells resulting in decreased Si concentrations. (C) 2016 Elsevier GmbH. All rights reserved. KW - Amoebal silicon KW - Sommer et al. 2006 KW - Biosilicification KW - Consumption KW - Culture growth dynamics KW - Euglyphida KW - Terrestrial Si cycle Y1 - 2016 U6 - https://doi.org/10.1016/j.ejop.2016.08.008 SN - 0932-4739 SN - 1618-0429 VL - 56 SP - 171 EP - 179 PB - Royal Society of Chemistry CY - Jena ER - TY - JOUR A1 - Puppe, Daniel A1 - Höhn, Axel A1 - Kaczorek, Danuta A1 - Wanner, Manfred A1 - Sommer, Michael T1 - As time goes by-Spatiotemporal changes of biogenic Si pools in initial soils of an artificial catchment in NE Germany JF - Applied soil ecology : a section of agriculture, ecosystems & environment KW - Biogenic silica KW - Diatom frustule KW - Testate amoeba shell KW - Sponge spicule KW - Initial ecosystem Y1 - 2016 U6 - https://doi.org/10.1016/j.apsoil.2016.01.020 SN - 0929-1393 SN - 1873-0272 VL - 105 SP - 9 EP - 16 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Wehrhan, Marc A1 - Rauneker, Philipp A1 - Sommer, Michael T1 - UAV-Based Estimation of Carbon Exports from Heterogeneous Soil Landscapes-A Case Study from the CarboZALF Experimental Area JF - SENSORS N2 - The advantages of remote sensing using Unmanned Aerial Vehicles (UAVs) are a high spatial resolution of images, temporal flexibility and narrow-band spectral data from different wavelengths domains. This enables the detection of spatio-temporal dynamics of environmental variables, like plant-related carbon dynamics in agricultural landscapes. In this paper, we quantify spatial patterns of fresh phytomass and related carbon (C) export using imagery captured by a 12-band multispectral camera mounted on the fixed wing UAV Carolo P360. The study was performed in 2014 at the experimental area CarboZALF-D in NE Germany. From radiometrically corrected and calibrated images of lucerne (Medicago sativa), the performance of four commonly used vegetation indices (VIs) was tested using band combinations of six near-infrared bands. The highest correlation between ground-based measurements of fresh phytomass of lucerne and VIs was obtained for the Enhanced Vegetation Index (EVI) using near-infrared band b(899). The resulting map was transformed into dry phytomass and finally upscaled to total C export by harvest. The observed spatial variability at field- and plot-scale could be attributed to small-scale soil heterogeneity in part. KW - VI KW - soil landscape KW - carbon export KW - agriculture KW - multispectral KW - UAV Y1 - 2016 U6 - https://doi.org/10.3390/s16020255 SN - 1424-8220 VL - 16 PB - MDPI CY - Basel ER - TY - JOUR A1 - Puppe, Daniel A1 - Ehrmann, Otto A1 - Kaczorek, Danuta A1 - Wanner, Manfred A1 - Sommer, Michael T1 - The protozoic Si pool in temperate forest ecosystems - Quantification, abiotic controls and interactions with earthworms JF - Geoderma : an international journal of soil science N2 - Biogenic silicon (BSI) pools influence Si cycling in terrestrial ecosystems. As research has been focused mainly on phytogenic BSi pools until now, there is only little information available on quantities of other BSi pools. There are no systematic studies on protozoic Si pools - here represented by idiosomic testate amoebae (TA) - and abiotic and biotic influences in temperate forest ecosystems. We selected ten old forests along a strong gradient in soil forming factors (especially parent material and climate), soil properties and humus forms. We quantified idiosomic Si pools, corresponding annual biosilicification, plant-available and amorphous Si fractions of topsoil horizons. Furthermore, we analyzed the potential influences of abiotic factors (e.g. soil pH) and earthworms on idiosomic Si pools. While idiosomic Si pools were relatively small (up to 5 kg Si ha(-1)), annual biosilicification rates of living TA (17-80 kg Si ha(-1)) were comparable to or even exceeded reported data of annual Si uptake by trees. Soil pH exerted a strong, non-linear control on plant-available Si. Surprisingly, no relationship between Si supply and idiosomic Si pools could be found (no Si limitation). Instead, idiosomic Si pools showed a strong, negative relationship to earthworm biomasses, which corresponded to humus forms. We concluded that earthworms control idiosomic Si pools in forest soils by direct (feeding, competition) and/or indirect mechanisms (e.g. change of habitat structure). Earthworms themselves were strongly influenced by soil pH: Below a threshold of pH 3.8 no endogeic or anecic earthworms existed. As soil pH is a result of weathering and acidification idiosomic Si pools are indirectly, but ultimately controlled by soil forming factors, mainly parent material and climate. (C) 2014 Elsevier B.V. All rights reserved. KW - Biogenic silica KW - Testate amoebae KW - Biosilicification KW - Terrestrial Si cycle KW - Si fractions KW - Humus forms Y1 - 2015 U6 - https://doi.org/10.1016/j.geoderma.2014.12.018 SN - 0016-7061 SN - 1872-6259 VL - 243 SP - 196 EP - 204 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Pohl, M. A1 - Hoffmann, M. A1 - Hagemann, U. A1 - Giebels, M. A1 - Borraz, Elisa Albiac A1 - Sommer, Michael A1 - Augustin, Jürgen T1 - Dynamic C and N stocks - key factors controlling the C gas exchange of maize in heterogenous peatland JF - Biogeosciences N2 - The drainage and cultivation of fen peatlands create complex small-scale mosaics of soils with extremely variable soil organic carbon (SOC) stocks and groundwater levels (GWLs). To date, the significance of such sites as sources or sinks for greenhouse gases such as CO2 and CH4 is still unclear, especially if the sites are used for cropland. As individual control factors such as GWL fail to account for this complexity, holistic approaches combining gas fluxes with the underlying processes are required to understand the carbon (C) gas exchange of drained fens. It can be assumed that the stocks of SOC and N located above the variable GWL - defined as dynamic C and N stocks - play a key role in the regulation of the plant- and microbially mediated CO2 fluxes in these soils and, inversely, for CH4. To test this assumption, the present study analysed the C gas exchange (gross primary production - GPP; ecosystem respiration - R-eco; net ecosystem exchange - NEE; CH4) of maize using manual chambers for 4 years. The study sites were located near Paulinenaue, Germany, where we selected three soil types representing the full gradient of GWL and SOC stocks (0-1 m) of the landscape: (a) Haplic Arenosol (AR; 8 kg C m(-2)); (b) Mollic Gleysol (GL; 38 kg C m(-2)); and (c) Hemic Histosol (HS; 87 kg C m(-2)). Daily GWL data were used to calculate dynamic SOC (SOCdyn) and N (N-dyn) stocks. Average annual NEE differed considerably among sites, ranging from 47 +/- 30 g C m(-2) yr(-1) in AR to -305 +/- 123 g C m(-2) yr(-1) in GL and -127 +/- 212 g C m(-2) yr(-1) in HS. While static SOC and N stocks showed no significant effect on C fluxes, SOCdyn and N-dyn and their interaction with GWL strongly influenced the C gas exchange, particularly NEE and the GPP : R-eco ratio. Moreover, based on nonlinear regression analysis, 86% of NEE variability was explained by GWL and SOCdyn. The observed high relevance of dynamic SOC and N stocks in the aerobic zone for plant and soil gas exchange likely originates from the effects of GWL-dependent N availability on C formation and transformation processes in the plant-soil system, which promote CO2 input via GPP more than CO2 emission via R-eco. The process-oriented approach of dynamic C and N stocks is a promising, potentially generalisable method for system-oriented investigations of the C gas exchange of groundwater-influenced soils and could be expanded to other nutrients and soil characteristics. However, in order to assess the climate impact of arable sites on drained peatlands, it is always necessary to consider the entire range of groundwater-influenced mineral and organic soils and their respective areal extent within the soil landscape. Y1 - 2015 U6 - https://doi.org/10.5194/bg-12-2737-2015 SN - 1726-4170 SN - 1726-4189 VL - 12 IS - 9 SP - 2737 EP - 2752 PB - Copernicus CY - Göttingen ER - TY - GEN A1 - Hoffmann, Mathias A1 - Schulz-Hanke, Maximilian A1 - Alba, Juana Garcia A1 - Jurisch, Nicole A1 - Hagemann, Ulrike A1 - Sachs, Torsten A1 - Sommer, Michael A1 - Augustin, Jürgen T1 - A simple calculation algorithm to separate high-resolution CH4 flux measurements into ebullition- and diffusion-derived components T2 - Postprints der Universität Potsdam : Mathematisch Naturwissenschaftliche Reihe N2 - Processes driving the production, transformation and transport of methane (CH4) in wetland ecosystems are highly complex. We present a simple calculation algorithm to separate open-water CH4 fluxes measured with automatic chambers into diffusion- and ebullition-derived components. This helps to reveal underlying dynamics, to identify potential environmental drivers and, thus, to calculate reliable CH4 emission estimates. The flux separation is based on identification of ebullition-related sudden concentration changes during single measurements. Therefore, a variable ebullition filter is applied, using the lower and upper quartile and the interquartile range (IQR). Automation of data processing is achieved by using an established R script, adjusted for the purpose of CH4 flux calculation. The algorithm was validated by performing a laboratory experiment and tested using flux measurement data (July to September 2013) from a former fen grassland site, which converted into a shallow lake as a result of rewetting. Ebullition and diffusion contributed equally (46 and 55 %) to total CH4 emissions, which is comparable to ratios given in the literature. Moreover, the separation algorithm revealed a concealed shift in the diurnal trend of diffusive fluxes throughout the measurement period. The water temperature gradient was identified as one of the major drivers of diffusive CH4 emissions, whereas no significant driver was found in the case of erratic CH4 ebullition events. T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 604 KW - water methane emissions KW - chamber system KW - CO2 KW - lake KW - fen KW - exchange KW - mechanism KW - turbulence KW - transport KW - reservior Y1 - 2019 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-416659 SN - 1866-8372 IS - 604 SP - 109 EP - 118 ER - TY - GEN A1 - Hoffmann, Mathias A1 - Jurisch, Nicole A1 - Alba, Juana Garcia A1 - Borraz, Elisa Albiac A1 - Schmidt, Marten A1 - Huth, Vytas A1 - Rogasik, Helmut A1 - Rieckh, Helene A1 - Verch, Gernot A1 - Sommer, Michael A1 - Augustin, Jürgen T1 - Detecting small-scale spatial heterogeneity and temporal dynamics of soil organic carbon (SOC) stocks BT - a comparison between automatic chamber-derived C budgets and repeated soil inventories T2 - Postprints der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe N2 - Carbon (C) sequestration in soils plays a key role in the global C cycle. It is therefore crucial to adequately monitor dynamics in soil organic carbon (Delta SOC) stocks when aiming to reveal underlying processes and potential drivers. However, small-scale spatial (10-30 m) and temporal changes in SOC stocks, particularly pronounced in arable lands, are hard to assess. The main reasons for this are limitations of the well-established methods. On the one hand, repeated soil inventories, often used in long-term field trials, reveal spatial patterns and trends in Delta SOC but require a longer observation period and a sufficient number of repetitions. On the other hand, eddy covariance measurements of C fluxes towards a complete C budget of the soil-plant-atmosphere system may help to obtain temporal Delta SOC patterns but lack small-scale spatial resolution. To overcome these limitations, this study presents a reliable method to detect both short-term temporal dynamics as well as small-scale spatial differences of Delta SOC using measurements of the net ecosystem carbon balance (NECB) as a proxy. To estimate the NECB, a combination of automatic chamber (AC) measurements of CO2 exchange and empirically modeled aboveground biomass development (NPPshoot / were used. To verify our method, results were compared with Delta SOC observed by soil resampling. Soil resampling and AC measurements were performed from 2010 to 2014 at a colluvial depression located in the hummocky ground moraine landscape of northeastern Germany. The measurement site is characterized by a variable groundwater level (GWL) and pronounced small-scale spatial heterogeneity regarding SOC and nitrogen (Nt) stocks. Tendencies and magnitude of Delta SOC values derived by AC measurements and repeated soil inventories corresponded well. The period of maximum plant growth was identified as being most important for the development of spatial differences in annual Delta SOC. Hence, we were able to confirm that AC-based C budgets are able to reveal small-scale spatial differences and short-term temporal dynamics of Delta SOC. T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 666 KW - net ecosystem exchange KW - North Central region KW - no-till ecosystem KW - eddy covariance KW - CO2 fluxes KW - dioxide exchange KW - United States KW - gas-exchange KW - agricultural landscapes KW - monitoring networks Y1 - 2019 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-417118 SN - 1866-8372 IS - 666 ER - TY - GEN A1 - Puppe, Daniel A1 - Höhn, Axel A1 - Kaczorek, Danuta A1 - Wanner, Manfred A1 - Wehrhan, Marc A1 - Sommer, Michael T1 - How big is the influence of biogenic silicon pools on short-term changes in water-soluble silicon in soils? BT - Implications from a study of a 10-year-old soil–plant system T2 - Postprints der Universität Potsdam : Mathematisch Naturwissenschaftliche Reihe N2 - The significance of biogenic silicon (BSi) pools as a key factor for the control of Si fluxes from terrestrial to aquatic ecosystems has been recognized for decades. However, while most research has been focused on phytogenic Si pools, knowledge of other BSi pools is still limited. We hypothesized that different BSi pools influence short-term changes in the water-soluble Si fraction in soils to different extents. To test our hypothesis we took plant (Calamagrostis epigejos, Phragmites australis) and soil samples in an artificial catchment in a post-mining landscape in the state of Brandenburg, Germany. We quantified phytogenic (phytoliths), protistic (diatom frustules and testate amoeba shells) and zoogenic (sponge spicules) Si pools as well as Tironextractable and water-soluble Si fractions in soils at the beginning (t(0)) and after 10 years (t(10)) of ecosystem development. As expected the results of Tiron extraction showed that there are no consistent changes in the amorphous Si pool at Chicken Creek (Huhnerwasser) as early as after 10 years. In contrast to t(0) we found increased water-soluble Si and BSi pools at t(10); thus we concluded that BSi pools are the main driver of short-term changes in water-soluble Si. However, because total BSi represents only small proportions of water-soluble Si at t(0) (< 2 %) and t(10) (2.8-4.3 %) we further concluded that smaller (< 5 mu m) and/or fragile phytogenic Si structures have the biggest impact on short-term changes in water-soluble Si. In this context, extracted phytoliths (> 5 mu m) only amounted to about 16% of total Si con-tents of plant materials of C. epigejos and P. australis at t(10); thus about 84% of small-scale and/or fragile phytogenic Si is not quantified by the used phytolith extraction method. Analyses of small-scale and fragile phytogenic Si structures are urgently needed in future work as they seem to represent the biggest and most reactive Si pool in soils. Thus they are the most important drivers of Si cycling in terrestrial biogeosystems. T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 633 KW - brook experimental forest KW - protozoic Si pool KW - testate amebas KW - biochemical cycle KW - temperate forest KW - amorphous silica KW - dissolution KW - carbon KW - phytoliths KW - surface Y1 - 2019 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-417141 IS - 633 SP - 5239 EP - 5252 ER - TY - JOUR A1 - van der Meij, Marijn W. A1 - Temme, Arnaud J. A. M. A1 - Wallinga, J. A1 - Hierold, W. A1 - Sommer, Michael T1 - Topography reconstruction of eroding landscapes - A case study from a hummocky ground moraine (CarboZALF-D) JF - Geomorphology : an international journal on pure and applied geomorphology N2 - Erosion processes, aggravated by human activity, have a large impact on the spatial variation of soil and topographic properties. Knowledge of the topography prior to human-induced erosion (paleotopography) in naturally stable landscapes is valuable for identifying vulnerable landscape positions and is required as starting point for erosion modelling exercises. However, developing accurate reconstructions of paleotopography provide a major challenge for geomorphologists. Here, we present a set of paleotopographies for a closed kettle hole catchment in north-east Germany (4 ha), obtained through different reconstruction approaches. Current soil and colluvium thickness, estimated from a dataset of 264 soil descriptions using Ordinary Kriging, were used as input for a mass balance, or were compared with a set of undisturbed soil thicknesses to estimate the amount of erosion. The performance of the different approaches was assessed with cross-validation and the count of mispredicted eroded, depositional or stable landscape positions. The paleotopographic reconstruction approach based on the average thickness of undisturbed soils in the study area showed the best performance. This thickness (1.00 m) is comparable to the average undisturbed soil thickness in the region and in line with global correlations of soil thickness as a function of rainfall and initial CaCO3 content. The performance of the different approaches depended more on mispredictions of landscape position due to the assumption of a spatially constant initial soil depth than on small variations in this depth. To conclude, we mention several methodological and practical points of attention for future topography reconstruction studies, concerning data quality and availability, spatial configuration of data and other processes affecting topography. (C) 2017 Elsevier B.V. All rights reserved. KW - Topography reconstruction KW - Erosion KW - Tillage KW - Landscape change Y1 - 2017 U6 - https://doi.org/10.1016/j.geomorph.2017.08.015 SN - 0169-555X SN - 1872-695X VL - 295 SP - 758 EP - 772 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Puppe, Daniel A1 - Höhn, Axel A1 - Kaczorek, Danuta A1 - Wanner, Manfred A1 - Wehrhan, Marc A1 - Sommer, Michael T1 - How big is the influence of biogenic silicon pools on short-term changes in water-soluble silicon in soils? Implications from a study of a 10-year-old soil-plant system JF - Biogeosciences N2 - The significance of biogenic silicon (BSi) pools as a key factor for the control of Si fluxes from terrestrial to aquatic ecosystems has been recognized for decades. However, while most research has been focused on phytogenic Si pools, knowledge of other BSi pools is still limited. We hypothesized that different BSi pools influence short-term changes in the water-soluble Si fraction in soils to different extents. To test our hypothesis we took plant (Calamagrostis epigejos, Phragmites australis) and soil samples in an artificial catchment in a post-mining landscape in the state of Brandenburg, Germany. We quantified phytogenic (phytoliths), protistic (diatom frustules and testate amoeba shells) and zoogenic (sponge spicules) Si pools as well as Tironextractable and water-soluble Si fractions in soils at the beginning (t(0)) and after 10 years (t(10)) of ecosystem development. As expected the results of Tiron extraction showed that there are no consistent changes in the amorphous Si pool at Chicken Creek (Huhnerwasser) as early as after 10 years. In contrast to t(0) we found increased water-soluble Si and BSi pools at t(10); thus we concluded that BSi pools are the main driver of short-term changes in water-soluble Si. However, because total BSi represents only small proportions of water-soluble Si at t(0) (< 2 %) and t(10) (2.8-4.3 %) we further concluded that smaller (< 5 mu m) and/or fragile phytogenic Si structures have the biggest impact on short-term changes in water-soluble Si. In this context, extracted phytoliths (> 5 mu m) only amounted to about 16% of total Si con-tents of plant materials of C. epigejos and P. australis at t(10); thus about 84% of small-scale and/or fragile phytogenic Si is not quantified by the used phytolith extraction method. Analyses of small-scale and fragile phytogenic Si structures are urgently needed in future work as they seem to represent the biggest and most reactive Si pool in soils. Thus they are the most important drivers of Si cycling in terrestrial biogeosystems. Y1 - 2017 U6 - https://doi.org/10.5194/bg-14-5239-2017 SN - 1726-4170 SN - 1726-4189 VL - 14 PB - Copernicus CY - Göttingen ER - TY - JOUR A1 - Scharsich, Christina A1 - Lohwasser, Ruth H. A1 - Sommer, Michael A1 - Asawapirom, Udom A1 - Scherf, Ullrich A1 - Thelakkat, Mukundan A1 - Neher, Dieter A1 - Koehler, Anna T1 - Control of aggregate formation in poly(3-hexylthiophene) by solvent, molecular weight, and synthetic method JF - Journal of polymer science : B, Polymer physics N2 - Aggregate formation in poly(3-hexylthiophene) depends on molecular weight, solvent, and synthetic method. The interplay of these parameters thus largely controls device performance. In order to obtain a quantitative understanding on how these factors control the resulting electronic properties of P3HT, we measured absorption in solution and in thin films as well as the resulting field effect mobility in transistors. By a detailed analysis of the absorption spectra, we deduce the fraction of aggregates formed, the excitonic coupling within the aggregates, and the conjugation length within the aggregates, all as a function of solvent quality for molecular weights from 5 to 19 kDa. From this, we infer in which structure the aggregated chains pack. Although the 5 kDa samples form straight chains, the 11 and 19 kDa chains are kinked or folded, with conjugation lengths that increase as the solvent quality reduces. There is a maximum fraction of aggregated chains (about 55 +/- 5%) that can be obtained, even for poor solvent quality. We show that inducing aggregation in solution leads to control of aggregate properties in thin films. As expected, the field-effect mobility correlates with the propensity to aggregation. Correspondingly, we find that a well-defined synthetic approach, tailored to give a narrow molecular weight distribution, is needed to obtain high field effect mobilities of up to 0.01 cm2/Vs for low molecular weight samples (=11 kDa), while the influence of synthetic method is negligible for samples of higher molecular weight, if low molecular weight fractions are removed by extraction. KW - conformational analysis KW - conjugated polymers KW - crystallization KW - films KW - interaction parameter KW - molecular weight distribution KW - molar mass distribution KW - nucleation KW - photophysics KW - structure KW - UV-vis spectroscopy Y1 - 2012 U6 - https://doi.org/10.1002/polb.23022 SN - 0887-6266 VL - 50 IS - 6 SP - 442 EP - 453 PB - Wiley-Blackwell CY - Hoboken ER - TY - JOUR A1 - Wehrhan, Marc A1 - Sommer, Michael T1 - A parsimonious approach to estimate soil organic carbon applying Unmanned Aerial System (UAS) multispectral imagery and the topographic position index in a heterogeneous soil landscape JF - Remote sensing / Molecular Diversity Preservation International (MDPI) N2 - Remote sensing plays an increasingly key role in the determination of soil organic carbon (SOC) stored in agriculturally managed topsoils at the regional and field scales. Contemporary Unmanned Aerial Systems (UAS) carrying low-cost and lightweight multispectral sensors provide high spatial resolution imagery (<10 cm). These capabilities allow integrate of UAS-derived soil data and maps into digitalized workflows for sustainable agriculture. However, the common situation of scarce soil data at field scale might be an obstacle for accurate digital soil mapping. In our case study we tested a fixed-wing UAS equipped with visible and near infrared (VIS-NIR) sensors to estimate topsoil SOC distribution at two fields under the constraint of limited sampling points, which were selected by pedological knowledge. They represent all releva nt soil types along an erosion-deposition gradient; hence, the full feature space in terms of topsoils' SOC status. We included the Topographic Position Index (TPI) as a co-variate for SOC prediction. Our study was performed in a soil landscape of hummocky ground moraines, which represent a significant of global arable land. Herein, small scale soil variability is mainly driven by tillage erosion which, in turn, is strongly dependent on topography. Relationships between SOC, TPI and spectral information were tested by Multiple Linear Regression (MLR) using: (i) single field data (local approach) and (ii) data from both fields (pooled approach). The highest prediction performance determined by a leave-one-out-cross-validation (LOOCV) was obtained for the models using the reflectance at 570 nm in conjunction with the TPI as explanatory variables for the local approach (coefficient of determination (R-2) = 0.91; root mean square error (RMSE) = 0.11% and R-2 = 0.48; RMSE = 0.33, respectively). The local MLR models developed with both reflectance and TPI using values from all points showed high correlations and low prediction errors for SOC content (R-2 = 0.88, RMSE = 0.07%; R-2 = 0.79, RMSE = 0.06%, respectively). The comparison with an enlarged dataset consisting of all points from both fields (pooled approach) showed no improvement of the prediction accuracy but yielded decreased prediction errors. Lastly, the local MLR models were applied to the data of the respective other field to evaluate the cross-field prediction ability. The spatial SOC pattern generally remains unaffected on both fields; differences, however, occur concerning the predicted SOC level. Our results indicate a high potential of the combination of UAS-based remote sensing and environmental covariates, such as terrain attributes, for the prediction of topsoil SOC content at the field scale. The temporal flexibility of UAS offer the opportunity to optimize flight conditions including weather and soil surface status (plant cover or residuals, moisture and roughness) which, otherwise, might obscure the relationship between spectral data and SOC content. Pedologically targeted selection of soil samples for model development appears to be the key for an efficient and effective prediction even with a small dataset. KW - Unmanned Aerial System (UAS) KW - multispectral KW - Topographic Position Index KW - (TPI) KW - Multiple Linear Regression (MLR) KW - soil organic carbon (SOC) KW - agriculture KW - erosion KW - soil landscape KW - hummocky ground moraine Y1 - 2021 U6 - https://doi.org/10.3390/rs13183557 SN - 2072-4292 VL - 13 IS - 18 PB - MDPI CY - Basel ER - TY - GEN A1 - Garbusow, Maria A1 - Sommer, C. A1 - Nebe, S. A1 - Sebold, Miriam Hannah A1 - Kuitunen-Paul, Sören A1 - Wittchen, H. U. A1 - Smolka, M. A1 - Zimmermann, U. A1 - Rapp, Michael Armin A1 - Huys, Q. A1 - Schlagenhauf, Florian A1 - Heinz, A. T1 - Pavlovian-instrumental transfer in the course of alcohol use disorder T2 - European psychiatry : the journal of the Association of European Psychiatrists N2 - Background: Pavlovian processes are thought to play an important role in the development, maintenance and relapse of alcohol dependence, possibly by influencing and usurping on- going thought and behavior. The influence of Pavlovian stimuli on on-going behavior is paradigmatically measured by Pavlovian-to-instrumental-transfer (PIT) tasks. These involve multiple stages and are complex. Whether increased PIT is involved in human alcohol dependence is uncertain. We therefore aimed to establish and validate a modified PIT paradigm that would be robust, consistent, and tolerated by healthy controls as well as by patients suffering from alcohol dependence, and to explore whether alcohol dependence is associated with enhanced Pavlovian-Instrumental transfer. Methods: 32 recently detoxified alcohol-dependent patients and 32 age and gender matched healthy controls performed a PIT task with instrumental go/no-go approach behaviours. The task involved both Pavlovian stimuli associated with monetary rewards and losses, and images of drinks. Results: Both patients and healthy controls showed a robust and temporally stable PIT effect. Strengths of PIT effects to drug-related and monetary conditioned stimuli were highly correlated. Patients more frequently showed a PIT effect and the effect was stronger in response to aversively conditioned CSs (conditioned suppression), but there was no group difference in response to appetitive CSs. Conclusion: The implementation of PIT has favorably robust properties in chronic alcohol- dependent patients and in healthy controls. It shows internal consistency between monetary and drug-related cues. The findings support an association of alcohol dependence with an increased propensity towards PIT. Y1 - 2018 SN - 0924-9338 SN - 1778-3585 VL - 48 SP - S546 EP - S546 PB - Elsevier CY - ISSY-LES-MOULINEAUX ER - TY - JOUR A1 - Calitri, Francesca A1 - Sommer, Michael A1 - van der Meij, Marijn W. A1 - Egli, Markus T1 - Soil erosion along a transect in a forested catchment: recent or ancient processes? JF - Catena : an interdisciplinary journal of soil science, hydrology, geomorphology focusing on geoecology and landscape evolution N2 - Forested areas are assumed not to be influenced by erosion processes. However, forest soils of Northern Germany in a hummocky ground moraine landscape can sometimes exhibit a very shallow thickness on crest positions and buried soils on slope positions. The question consequently is: Are these on-going or ancient erosional and depositional processes? Plutonium isotopes act as soil erosion/deposition tracers for recent (last few decades) processes. Here, we quantified the 239+240PU inventories in a small, forested catchment (ancient forest "Melzower Forst", deciduous trees), which is characterised by a hummocky terrain including a kettle hole. Soil development depths (depth to C horizon) and 239+240PU inventories along a catena of sixteen different profiles were determined and correlated to relief parameters. Moreover, we compared different modelling approaches to derive erosion rates from Pu data.
We find a strong relationship between soil development depths, distance-to-sink and topography along the catena. Fully developed Retisols (thicknesses > 1 m) in the colluvium overlay old land surfaces as documented by fossil Ah horizons. However, we found no relationship of Pu-based erosion rates to any relief parameter. Instead, 239+240PU inventories showed a very high local, spatial variability (36-70 Bq m(-2)). Low annual rainfall, spatially distributed interception and stem flow might explain the high variability of the 239+240PU inventories, giving rise to a patchy input pattern. Different models resulted in quite similar erosion and deposition rates (max: -5 t ha(-1) yr(-1) to +7.3 t ha(-1) yr(-1)). Although some rates are rather high, the magnitude of soil erosion and deposition - in terms of soil thickness change - is negligible during the last 55 years. The partially high values are an effect of the patchy Pu deposition on the forest floor. This forest has been protected for at least 240 years. Therefore rather natural events and anthropogenic activities during medieval times or even earlier must have caused the observed soil pattern, which documents strong erosion and deposition processes. KW - Soil erosion KW - 239+240 Plutonium KW - Forest KW - Moraine landscape KW - Soil catena Y1 - 2020 U6 - https://doi.org/10.1016/j.catena.2020.104683 SN - 0341-8162 SN - 1872-6887 VL - 194 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Vaidya, Shrijana A1 - Schmidt, Marten A1 - Rakowski, Peter A1 - Bonk, Norbert A1 - Verch, Gernot A1 - Augustin, Jürgen A1 - Sommer, Michael A1 - Hoffmann, Mathias T1 - A novel robotic chamber system allowing to accurately and precisely determining spatio-temporal CO2 flux dynamics of heterogeneous croplands JF - Agricultural and forest meteorology N2 - The precise and accurate assessment of carbon dioxide (CO2) exchange is crucial to identify terrestrial carbon (C) sources and sinks and for evaluating their role within the global C budget. The substantial uncertainty in disentangling the management and soil impact on measured CO2 fluxes are largely ignored especially in cropland. The reasons for this lies in the limitation of the widely used eddy covariance as well as manual and automatic chamber systems, which either account for short-term temporal variability or small-scale spatial heterogeneity, but barely both. To address this issue, we developed a novel robotic chamber system allowing for dozens of spatial measurement repetitions, thus enabling CO2 exchange measurements in a sufficient temporal and high small-scale spatial resolution. The system was tested from 08th July to 09th September 2019 at a heterogeneous field (100 m x 16 m), located within the hummocky ground moraine landscape of northeastern Germany (CarboZALF-D). The field is foreseen for a longer-term block trial manipulation experiment extending over three erosion induced soil types and was covered with spring barley. Measured fluxes of nighttime ecosystem respiration (R-eco) and daytime net ecosystem exchange (NEE) showed distinct temporal patterns influenced by crop phenology, weather conditions and management practices. Similarly, we found clear small-scale spatial differences in cumulated (gap-filled) R-eco, gross primary productivity (GPP) and NEE fluxes affected by the three distinct soil types. Additionally, spatial patterns induced by former management practices and characterized by differences in soil pH and nutrition status (P and K) were also revealed between plots within each of the three soil types, which allowed compensating for prior to the foreseen block trial manipulation experiment. The results underline the great potential of the novel robotic chamber system, which not only detects short-term temporal CO2 flux dynamics but also reflects the impact of small-scale spatial heterogeneity. KW - Automatic chamber KW - Net ecosystem exchange (NEE) KW - Gross primary KW - productivity (GPP) KW - Ecosystem respiration (R-eco) KW - Soil erosion KW - Soil KW - heterogeneity Y1 - 2021 U6 - https://doi.org/10.1016/j.agrformet.2020.108206 SN - 0168-1923 SN - 1873-2240 VL - 296 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Puppe, Daniel A1 - Leue, Martin A1 - Sommer, Michael A1 - Schaller, Jörg A1 - Kaczorek, Danuta T1 - Auto-fluorescence in phytoliths BT - a mechanistic understanding derived from microscopic and spectroscopic analyses JF - Frontiers in Environmental Science N2 - The detection of auto-fluorescence in phytogenic, hydrated amorphous silica depositions (phytoliths) has been found to be a promising approach to verify if phytoliths were burnt or not, especially in archaeological contexts. However, it is unknown so far at what temperature and how auto-fluorescence is induced in phytoliths. We used fluorescence microscopy, scanning electron microscope-energy dispersive X-ray spectroscopy (SEM-EDX), and Fourier transform infrared spectroscopy to analyze auto-fluorescence in modern phytoliths extracted from plant samples or in intact leaves of winter wheat. Leaves and extracted phytoliths were heated at different temperatures up to 600 degrees C. The aims of our experiments were i) to find out what temperature is needed to induce auto-fluorescence in phytoliths, ii) to detect temperature-dependent changes in the molecular structure of phytoliths related to auto-fluorescence, and iii) to derive a mechanistic understanding of auto-fluorescence in phytoliths. We found organic compounds associated with phytoliths to cause auto-fluorescence in phytoliths treated at temperatures below approx. 400 degrees C. In phytoliths treated at higher temperatures, i.e., 450 and 600 degrees C, phytolith auto-fluorescence was mainly caused by molecular changes of phytolith silica. Based on our results we propose that auto-fluorescence in phytoliths is caused by clusterization-triggered emissions, which are caused by overlapping electron clouds forming non-conventional chromophores. In phytoliths heated at temperatures above about 400 degrees C dihydroxylation and the formation of siloxanes result in oxygen clusters that serve as non-conventional chromophores in fluorescence events. Furthermore, SEM-EDX analyses revealed that extractable phytoliths were dominated by lumen phytoliths (62%) compared to cell wall phytoliths (38%). Our findings might be not only relevant in archaeological phytolith-based examinations, but also for studies on the temperature-dependent release of silicon from phytoliths and the potential of long-term carbon sequestration in phytoliths. KW - fluorescence microscopy KW - FTIR spectroscopy KW - SEM-EDX KW - burnt phytoliths; KW - carbon sequestration Y1 - 2022 U6 - https://doi.org/10.3389/fenvs.2022.915947 SN - 2296-665X VL - 10 PB - Frontiers Media CY - Lausanne ER - TY - JOUR A1 - Mettler, Tabea A1 - Mühlhaus, Timo A1 - Hemme, Dorothea A1 - Schöttler, Mark Aurel A1 - Rupprecht, Jens A1 - Idoine, Adam A1 - Veyel, Daniel A1 - Pal, Sunil Kumar A1 - Yaneva-Roder, Liliya A1 - Winck, Flavia Vischi A1 - Sommer, Frederik A1 - Vosloh, Daniel A1 - Seiwert, Bettina A1 - Erban, Alexander A1 - Burgos, Asdrubal A1 - Arvidsson, Samuel Janne A1 - Schoenfelder, Stephanie A1 - Arnold, Anne A1 - Guenther, Manuela A1 - Krause, Ursula A1 - Lohse, Marc A1 - Kopka, Joachim A1 - Nikoloski, Zoran A1 - Müller-Röber, Bernd A1 - Willmitzer, Lothar A1 - Bock, Ralph A1 - Schroda, Michael A1 - Stitt, Mark T1 - Systems analysis of the response of photosynthesis, metabolism, and growth to an increase in irradiance in the photosynthetic model organism chlamydomonas reinhardtii JF - The plant cell N2 - We investigated the systems response of metabolism and growth after an increase in irradiance in the nonsaturating range in the algal model Chlamydomonas reinhardtii. In a three-step process, photosynthesis and the levels of metabolites increased immediately, growth increased after 10 to 15 min, and transcript and protein abundance responded by 40 and 120 to 240 min, respectively. In the first phase, starch and metabolites provided a transient buffer for carbon until growth increased. This uncouples photosynthesis from growth in a fluctuating light environment. In the first and second phases, rising metabolite levels and increased polysome loading drove an increase in fluxes. Most Calvin-Benson cycle (CBC) enzymes were substrate-limited in vivo, and strikingly, many were present at higher concentrations than their substrates, explaining how rising metabolite levels stimulate CBC flux. Rubisco, fructose-1,6-biosphosphatase, and seduheptulose-1,7-bisphosphatase were close to substrate saturation in vivo, and flux was increased by posttranslational activation. In the third phase, changes in abundance of particular proteins, including increases in plastidial ATP synthase and some CBC enzymes, relieved potential bottlenecks and readjusted protein allocation between different processes. Despite reasonable overall agreement between changes in transcript and protein abundance (R-2 = 0.24), many proteins, including those in photosynthesis, changed independently of transcript abundance. Y1 - 2014 U6 - https://doi.org/10.1105/tpc.114.124537 SN - 1040-4651 SN - 1532-298X VL - 26 IS - 6 SP - 2310 EP - 2350 PB - American Society of Plant Physiologists CY - Rockville ER - TY - JOUR A1 - Calitri, Francesca A1 - Sommer, Michael A1 - Norton, Kevin A1 - Temme, Arnaud A1 - Brandova, Dagmar A1 - Portes, Raquel A1 - Christl, Marcus A1 - Ketterer, Mike E. A1 - Egli, Markus T1 - Tracing the temporal evolution of soil redistribution rates in an agricultural landscape using Pu239+240 and Be-10 JF - Earth surface processes and landforms : the journal of the British Geomorphological Research Group N2 - Two principal groups of processes shape mass fluxes from and into a soil: vertical profile development and lateral soil redistribution. Periods having predominantly progressive soil forming processes (soil profile development) alternate with periods having predominantly regressive processes (erosion). As a result, short‐term soil redistribution – years to decades – can differ substantially from long‐term soil redistribution; i.e. centuries to millennia. However, the quantification of these processes is difficult and consequently their rates are poorly understood. To assess the competing roles of erosion and deposition we determined short‐ and long‐term soil redistribution rates in a formerly glaciated area of the Uckermark, northeast Germany. We compared short‐term erosion or accumulation rates using plutonium‐239 and ‐240 (239+240Pu) and long‐term rates using both in situ and meteoric cosmogenic beryllium‐10 (10Be). Three characteristic process domains have been analysed in detail: a flat landscape position having no erosion/deposition, an erosion‐dominated mid‐slope, and a deposition‐dominated lower‐slope site. We show that the short‐term mass erosion and accumulation rates are about one order of magnitude higher than long‐term redistribution rates. Both, in situ and meteoric 10Be provide comparable results. Depth functions, and therefore not only an average value of the topsoil, give the most meaningful rates. The long‐term soil redistribution rates were in the range of −2.1 t ha‐1 yr‐1 (erosion) and +0.26 t ha‐1 yr‐1 (accumulation) whereas the short‐term erosion rates indicated strong erosion of up to 25 t ha‐1 yr‐1 and accumulation of 7.6 t ha‐1 yr‐1. Our multi‐isotope method identifies periods of erosion and deposition, confirming the ‘time‐split approach’ of distinct different phases (progressive/regressive) in soil evolution. With such an approach, temporally‐changing processes can be disentangled, which allows the identification of both the dimensions of and the increase in soil erosion due to human influence KW - soil erosion KW - Be-10 KW - Pu239+240 KW - temporal evolution KW - moraine landscape KW - agricultural soils Y1 - 2019 U6 - https://doi.org/10.1002/esp.4612 SN - 0197-9337 SN - 1096-9837 VL - 44 IS - 9 SP - 1783 EP - 1798 PB - Wiley CY - Hoboken ER - TY - JOUR A1 - Garbusow, Maria A1 - Schad, Daniel A1 - Sommer, Christian A1 - Juenger, Elisabeth A1 - Sebold, Miriam Hannah A1 - Friedel, Eva A1 - Wendt, Jean A1 - Kathmann, Norbert A1 - Schlagenhauf, Florian A1 - Zimmermann, Ulrich S. A1 - Heinz, Andreas A1 - Huys, Quentin J. M. A1 - Rapp, Michael Armin T1 - Pavlovian-to-instrumental transfer in alcohol dependence: a pilot study JF - Neuropsychobiology : international journal of experimental and clinical research in biological psychiatry, pharmacopsychiatry, Biological Psychology/Pharmacopsychology and Pharmacoelectroencephalography N2 - Background: Pavlovian processes are thought to play an important role in the development, maintenance and relapse of alcohol dependence, possibly by influencing and usurping ongoing thought and behavior. The influence of pavlovian stimuli on ongoing behavior is paradigmatically measured by pavlovian-to-instrumental transfer (PIT) tasks. These involve multiple stages and are complex. Whether increased PIT is involved in human alcohol dependence is uncertain. We therefore aimed to establish and validate a modified PIT paradigm that would be robust, consistent and tolerated by healthy controls as well as by patients suffering from alcohol dependence, and to explore whether alcohol dependence is associated with enhanced PIT. Methods: Thirty-two recently detoxified alcohol-dependent patients and 32 age- and gender-matched healthy controls performed a PIT task with instrumental go/no-go approach behaviors. The task involved both pavlovian stimuli associated with monetary rewards and losses, and images of drinks. Results: Both patients and healthy controls showed a robust and temporally stable PIT effect. Strengths of PIT effects to drug-related and monetary conditioned stimuli were highly correlated. Patients more frequently showed a PIT effect, and the effect was stronger in response to aversively conditioned CSs (conditioned suppression), but there was no group difference in response to appetitive CSs. Conclusion: The implementation of PIT has favorably robust properties in chronic alcohol-dependent patients and in healthy controls. It shows internal consistency between monetary and drug-related cues. The findings support an association of alcohol dependence with an increased propensity towards PIT. KW - Pavlovian-to-instrumental transfer KW - Alcohol dependence KW - Human Y1 - 2014 U6 - https://doi.org/10.1159/000363507 SN - 0302-282X SN - 1423-0224 VL - 70 IS - 2 SP - 111 EP - 121 PB - Karger CY - Basel ER - TY - JOUR A1 - Obst, Elisabeth A1 - Schad, Daniel A1 - Huys, Quentin J. M. A1 - Sebold, Miriam Hannah A1 - Nebe, Stephan A1 - Sommer, Christian A1 - Smolka, Michael N. A1 - Zimmermann, Ulrich S. T1 - Drunk decisions BT - Alcohol shifts choice from habitual towards goal-directed control in adolescent intermediate-risk drinkers JF - Journal of Psychopharmacology N2 - Background: Studies in humans and animals suggest a shift from goal-directed to habitual decision-making in addiction. We therefore tested whether acute alcohol administration reduces goal-directed and promotes habitual decision-making, and whether these effects are moderated by self-reported drinking problems. Methods: Fifty-three socially drinking males completed the two-step task in a randomised crossover design while receiving an intravenous infusion of ethanol (blood alcohol level=80 mg%), or placebo. To minimise potential bias by long-standing heavy drinking and subsequent neuropsychological impairment, we tested 18- to 19-year-old adolescents. Results: Alcohol administration consistently reduced habitual, model-free decisions, while its effects on goal-directed, model-based behaviour varied as a function of drinking problems measured with the Alcohol Use Disorders Identification Test. While adolescents with low risk for drinking problems (scoring <8) exhibited an alcohol-induced numerical reduction in goal-directed choices, intermediate-risk drinkers showed a shift away from habitual towards goal-directed decision-making, such that alcohol possibly even improved their performance. Conclusions: We assume that alcohol disrupted basic cognitive functions underlying habitual and goal-directed decisions in low-risk drinkers, thereby enhancing hasty choices. Further, we speculate that intermediate-risk drinkers benefited from alcohol as a negative reinforcer that reduced unpleasant emotional states, possibly displaying a novel risk factor for drinking in adolescence. KW - Computer-assisted Alcohol Infusion System KW - habitual learning KW - model-free and model-based decision-making KW - two-stage Markov decision task KW - subjective response to ethanol KW - drinking problems KW - real-life drinking behaviour Y1 - 2018 U6 - https://doi.org/10.1177/0269881118772454 SN - 0269-8811 SN - 1461-7285 VL - 32 IS - 8 SP - 855 EP - 866 PB - Sage Publ. CY - London ER - TY - JOUR A1 - Wehrhan, Marc A1 - Puppe, Daniel A1 - Kaczorek, Danuta A1 - Sommer, Michael T1 - Spatial patterns of aboveground phytogenic Si stocks in a grass-dominated catchment BT - results from UAS-based high-resolution remote sensing JF - Biogeosciences : BG N2 - Various studies have been performed to quantify silicon (Si) stocks in plant biomass and related Si fluxes in terrestrial biogeosystems. Most studies are deliberately designed on the plot scale to ensure low heterogeneity in soils and plant composition, hence similar environmental conditions. Due to the immanent spatial soil variability, the transferability of results to larger areas, such as catchments, is therefore limited. However, the emergence of new technical features and increasing knowledge on details in Si cycling lead to a more complex picture at landscape and catchment scales. Dynamic and static soil properties change along the soil continuum and might influence not only the species composition of natural vegetation but also its biomass distribution and related Si stocks. Maximum likelihood (ML) classification was applied to multispectral imagery captured by an unmanned aerial system (UAS) aiming at the identification of land cover classes (LCCs). Subsequently, the normalized difference vegetation index (NDVI) and ground-based measurements of biomass were used to quantify aboveground Si stocks in two Si-accumulating plants (Calamagrostis epige-jos and Phragmites australis) in a heterogeneous catchment and related corresponding spatial patterns of these stocks to soil properties. We found aboveground Si stocks of C. epige-jos and P. australis to be surprisingly high (maxima of Si stocks reach values up to 98 g Sim(-2)), i.e. comparable to or markedly exceeding reported values for the Si storage in aboveground vegetation of various terrestrial ecosystems. We further found spatial patterns of plant aboveground Si stocks to reflect spatial heterogeneities in soil properties. From our results, we concluded that (i) aboveground biomass of plants seems to be the main factor of corresponding phytogenic Si stock quantities, and (ii) a detection of biomass heterogeneities via UAS-based remote sensing represents a promising tool for the quantification of lifelike phytogenic Si pools at landscape scales. Y1 - 2021 U6 - https://doi.org/10.5194/bg-18-5163-2021 SN - 1726-4170 SN - 1726-4189 VL - 18 IS - 18 SP - 5163 EP - 5183 PB - Copernicus CY - Göttingen ER - TY - JOUR A1 - Lorenz, Robert C. A1 - Gleich, Tobias A1 - Beck, Anne A1 - Poehland, Lydia A1 - Raufelder, Diana A1 - Sommer, Werner A1 - Rapp, Michael Armin A1 - Kuehn, Simone A1 - Gallinat, Jürgen T1 - Reward anticipation in the adolescent and aging brain JF - Human brain mapping : a journal devoted to functional neuroanatomy and neuroimaging N2 - Processing of reward is the basis of adaptive behavior of the human being. Neural correlates of reward processing seem to be influenced by developmental changes from adolescence to late adulthood. The aim of this study is to uncover these neural correlates during a slot machine gambling task across the lifespan. Therefore, we used functional magnetic resonance imaging to investigate 102 volunteers in three different age groups: 34 adolescents, 34 younger adults, and 34 older adults. We focused on the core reward areas ventral striatum (VS) and ventromedial prefrontal cortex (VMPFC), the valence processing associated areas, anterior cingulate cortex (ACC) and insula, as well as information integration associated areas, dorsolateral prefrontal cortex (DLPFC), and inferior parietal lobule (IPL). Results showed that VS and VMPFC were characterized by a hyperactivation in adolescents compared with younger adults. Furthermore, the ACC and insula were characterized by a U-shape pattern (hypoactivation in younger adults compared with adolescents and older adults), whereas the DLPFC and IPL were characterized by a J-shaped form (hyperactivation in older adults compared with younger groups). Furthermore, a functional connectivity analysis revealed an elevated negative functional coupling between the inhibition-related area rIFG and VS in younger adults compared with adolescents. Results indicate that lifespan-related changes during reward anticipation are characterized by different trajectories in different reward network modules and support the hypothesis of an imbalance in maturation of striatal and prefrontal cortex in adolescents. Furthermore, these results suggest compensatory age-specific effects in fronto-parietal regions. Hum Brain Mapp 35:5153-5165, 2014. (c) 2014 Wiley Periodicals, Inc. KW - reward anticipation KW - lifespan KW - aging KW - adolescence KW - fMRI KW - connectivity Y1 - 2014 U6 - https://doi.org/10.1002/hbm.22540 SN - 1065-9471 SN - 1097-0193 VL - 35 IS - 10 SP - 5153 EP - 5165 PB - Wiley-Blackwell CY - Hoboken ER - TY - JOUR A1 - Singhal, Puja A1 - Pahle, Michael A1 - Kalkuhl, Matthias A1 - Sommer, Stephan A1 - Levesque, Antoine A1 - Berneiser, Jessica T1 - Beyond good faith BT - why evidence-based policy is necessary to decarbonize buildings cost-effectively JF - SSRN eLibrary / Social Science Research Network N2 - The ambitious climate targets set by industrialized nations worldwide cannot be met without decarbonizing the building stock. Using Germany as a case study, this paper takes stock of the extensive set of energy efficiency policies that are already in place and clarifies that they have been designed “in good faith” but lack in overall effectiveness as well as cost-efficiency in achieving these climate targets. We map out the market failures and behavioural considerations that are potential reasons for why realized energy savings fall below expectations and why the household adoption of energy-efficient and low-carbon technologies has remained low. We highlight the pressing need for data and modern empirical research to develop targeted and cost-effective policies seeking to correct these market failures. To this end, we identify some key research questions and identify gaps in the data required for evidence-based policy. KW - energy efficiency KW - decarbonization KW - housing sector KW - heat demand KW - evidence-based policy Y1 - 2021 U6 - https://doi.org/10.2139/ssrn.3947800 SN - 1556-5068 PB - SSRN - Elsevier CY - Rochester, NY ER - TY - JOUR A1 - Funk, Roger A1 - Li, Yong A1 - Hoffmann, Carsten A1 - Reiche, Matthias A1 - Zhang, Zhuodong A1 - Li, Junjie A1 - Sommer, Michael T1 - Using Cs-137 to estimate wind erosion and dust deposition on grassland in Inner Mongolia-selection of a reference site and description of the temporal variability JF - Plant and soil N2 - The aims of this study were to identify areas of wind erosion and dust deposition and to quantify the effects of different grazing intensities on soil redistribution rates in grasslands based on the Cs-137 technique. Because the method uses a reference inventory as threshold for erosion or deposition, the classification of any other site as source or sink for dust depends on the accurate selection of this reference site. Measurements of Cs-137 inventories and depth distributions were carried out at pasture sites with predominant species of Stipa grandis and Leymus chinensis which are grazed with different intensities. Additional measurements were made at arable land, plant-covered sand dunes and alluvial plains. Wind-induced soil erosion and dust deposition rates were calculated from Cs-137 inventories by means of the "Profile-Distribution" and the "Mass Balance II" models. The selection of the reference site was based on fluid dynamical and process-determining parameters. The chosen site should meet the following four conditions: (i) located at a summit position with obviously low deposition rates, (ii) sufficient vegetation cover to prevent wind erosion, (iii) plane to exclude water erosion and (iv) in the wind/dust shadow of a higher elevation. The measured reference inventory of Cs-137 was 1967(+/- 102) Bqm(-2) located at a summit position of moderately grazed Leymus chinensis steppe. The Cs-137 inventories at other sites ranged from 1330 Bqm(-2) at heavily grazed sites to 5119 Bqm(-2) at river deposits, representing annual average soil losses of up to 130 tkm(-2) and deposits of up to 540 tkm(-2), respectively. The calculated annual averages of dust depositions at ungrazed Leymus chinensis sites were related to the dust storm frequencies of the last 50 years resulting in a description of the temporal variability of annual dust depositions from about 154 tkm(-2) in the 1960s to 26 tkm(-2) at recent times. Based on this quantification already 80% of the total dust depositions can be related to the 20 years between the 1960s and the end of the 1970s and only 20% to the time between 1980 and 2001. Cs-137 technique is a promising method to assess the effect of grazing intensity and land use types on the spatial variability of wind-induced soil and dust redistribution processes in semi-arid grasslands. However, considerable efforts are needed to identify a reliable reference site, because erosion and deposition induced by wind may occur at the same places. The combination of the dust deposition rates derived from Cs-137 profile data with the dust storm frequencies is helpful for a better reconstruction of the temporal variability of dust deposition and wind erosion in this region. The calculated recent deposition rates of about 20 tkm(-2) are in good agreement with data of other authors. KW - Cs-137 KW - Grassland KW - Wind erosion KW - Dust deposition KW - Reference site Y1 - 2012 U6 - https://doi.org/10.1007/s11104-011-0964-y SN - 0032-079X VL - 351 IS - 1-2 SP - 293 EP - 307 PB - Springer CY - Dordrecht ER - TY - JOUR A1 - Reiche, Matthias A1 - Funk, Roger A1 - Zhang, Zhuodong A1 - Hoffmann, Carsten A1 - Reiche, Johannes A1 - Wehrhan, Marc A1 - Li, Yong A1 - Sommer, Michael T1 - Application of satellite remote sensing for mapping wind erosion risk and dust emission-deposition in Inner Mongolia grassland, China JF - Grassland science N2 - Intensive grazing leads to land degradation and desertification of grassland ecosystems followed by serious environmental and social problems. The Xilingol steppe grassland in Inner Mongolia, China, which has been a sink area for dust for centuries, is strongly affected by the negative effects of overgrazing and wind erosion. The aim of this study is the provision of a wind erosion risk map with a spatial high resolution of 25 m to identify actual source and sink areas. In an integrative approach, field measurements of vegetation features and surface roughness length z0 were combined with Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) image data for a land use classification. To determine the characteristics of the different land use classes, a field observation (ground truth) was performed in April 2009. The correlation of vegetation height and z0 (R2 = 0.8, n = 55) provided the basis for a separation of three main classes, grassland, non-vegetation and other. The integration of the soil-adjusted vegetation index (SAVI) and the spectral information from the atmospheric corrected ASTER bands 1, 2 and 3 (visible to near-infrared) led to a classification of the overall accuracy (OA) of 0.79 with a kappa () statistic of 0.74, respectively. Additionally, a digital elevation model (DEM) was used to identify topographical effects in relation to the main wind direction, which enabled a qualitative estimation of potential dust deposition areas. The generated maps result in a significantly higher description of the spatial variability in the Xilingol steppe grassland reflecting the different land use intensities on the current state of the grassland less, moderately and highly degraded. The wind erosion risk map enables the identification of characteristic mineral dust sources, sinks and transition zones. KW - Advanced Spaceborne Thermal Emission and Reflection Radiometer data KW - dust emission and deposition KW - soil-adjusted vegetation index KW - semiarid grassland KW - wind erosion Y1 - 2012 U6 - https://doi.org/10.1111/j.1744-697X.2011.00235.x SN - 1744-6961 VL - 58 IS - 1 SP - 8 EP - 19 PB - Wiley-Blackwell CY - Malden ER - TY - JOUR A1 - Zhang, Zhuodong A1 - Wieland, Ralf A1 - Reiche, Matthias A1 - Funk, Roger A1 - Hoffmann, Carsten A1 - Li, Yong A1 - Sommer, Michael T1 - Identifying sensitive areas to wind erosion in the xilingele grassland by computational fluid dynamics modelling JF - Ecological informatics : an international journal on ecoinformatics and computational ecolog N2 - In order to identify the areas in the Xilingele grassland which are sensitive to wind erosion, a computational fluid dynamics model (CFD-WEM) was used to simulate the wind fields over a region of 37 km(2) which contains different topography and land use types. Previous studies revealed the important influences of topography and land use on wind erosion in the Xilingele grassland. Topography influences wind fields at large scale, and land use influences wind fields near the ground. Two steps were designed to implement the CFD wind simulation, and they were respectively to simulate the influence of topography and surface roughness on the wind. Digital elevation model (DEM) and surface roughness length were the key inputs for the CFD simulation. The wind simulation by CFD-WEM was validated by a wind data set which was measured simultaneously at six positions in the field. Three scenarios with different wind velocities were designed based on observed dust storm events, and wind fields were simulated according to these scenarios to predict the sensitive areas to wind erosion. General assumptions that cropland is the most sensitive area to wind erosion and heavily and moderately grazed grasslands are both sensitive etc. can be refined by the modelling of CFD-WEM. Aided by the results of this study, the land use planning and protection measures against wind erosion can be more efficient. Based on the case study in the Xilingele grassland, a method of regional wind erosion assessment aided by CFD wind simulation is summarized. The essence of this method is a combination of CFD wind simulation and determination of threshold wind velocity for wind erosion. Because of the physically-based simulation and the flexibility of the method, it can be generalised to other regions. KW - Sensitive areas KW - Wind erosion KW - Computational fluid dynamics KW - Grassland KW - Surface roughness Y1 - 2012 U6 - https://doi.org/10.1016/j.ecoinf.2011.12.002 SN - 1574-9541 VL - 8 IS - 5 SP - 37 EP - 47 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Zhang, Zhuo-dong A1 - Wieland, Ralf A1 - Reiche, Matthias A1 - Funk, Roger A1 - Hoffmann, Carsten A1 - Li, Yong A1 - Sommer, Michael T1 - A computational fluid dynamics model for wind simulation: model implementation and experimental validation JF - Journal of Zhejiang University : an international journal ; Science A, Applied physics & engineering : an international applied physics & engineering journal N2 - To provide physically based wind modelling for wind erosion research at regional scale, a 3D computational fluid dynamics (CFD) wind model was developed. The model was programmed in C language based on the Navier-Stokes equations, and it is freely available as open source. Integrated with the spatial analysis and modelling tool (SAMT), the wind model has convenient input preparation and powerful output visualization. To validate the wind model, a series of experiments was conducted in a wind tunnel. A blocking inflow experiment was designed to test the performance of the model on simulation of basic fluid processes. A round obstacle experiment was designed to check if the model could simulate the influences of the obstacle on wind field. Results show that measured and simulated wind fields have high correlations, and the wind model can simulate both the basic processes of the wind and the influences of the obstacle on the wind field. These results show the high reliability of the wind model. A digital elevation model (DEM) of an area (3800 m long and 1700 m wide) in the Xilingele grassland in Inner Mongolia (autonomous region, China) was applied to the model, and a 3D wind field has been successfully generated. The clear implementation of the model and the adequate validation by wind tunnel experiments laid a solid foundation for the prediction and assessment of wind erosion at regional scale. KW - Wind model KW - Computational fluid dynamics (CFD) KW - Wind erosion KW - Wind tunnel experiments KW - Spatial analysis and modelling tool (SAMT) KW - Open source Y1 - 2012 U6 - https://doi.org/10.1631/jzus.A1100231 SN - 1673-565X VL - 13 IS - 4 SP - 274 EP - 283 PB - Zhejiang University Press CY - Hangzou ER - TY - JOUR A1 - Zhang, Zhuodong A1 - Wieland, Ralf A1 - Reiche, Matthias A1 - Funk, Roger A1 - Hoffmann, Carsten A1 - Li, Yong A1 - Sommer, Michael T1 - Wind modelling for wind erosion research by open source computational fluid dynamics JF - Ecological informatics : an international journal on ecoinformatics and computational ecolog N2 - The open source computational fluid dynamics (CFD) wind model (CFD-WEM) for wind erosion research in the Xilingele grassland in Inner Mongolia (autonomous region, China) is compared with two open source CFD models Gerris and OpenFOAM. The evaluation of these models was made according to software technology, implemented methods, handling, accuracy and calculation speed. All models were applied to the same wind tunnel data set. Results show that the simplest CFD-WEM has the highest calculation speed with acceptable accuracy, and the most powerful OpenFOAM produces the simulation with highest accuracy and the lowest calculation speed. Gerris is between CFD-WEM and OpenFOAM. It calculates faster than OpenFOAM, and it is capable to solve different CFD problems. CFD-WEM is the optimal model to be further developed for wind erosion research in Inner Mongolia grassland considering its efficiency and the uncertainties of other input data. However, for other applications using CFD technology, Gerris and OpenFOAM can be good choices. This paper shows the powerful capability of open source CFD software in wind erosion study, and advocates more involvement of open source technology in wind erosion and related ecological researches. KW - Computational fluid dynamics KW - Wind modelling KW - Open source KW - Wind erosion KW - Gerris KW - OpenFOAM KW - SAMT Y1 - 2011 U6 - https://doi.org/10.1016/j.ecoinf.2011.02.001 SN - 1574-9541 VL - 6 IS - 5 SP - 316 EP - 324 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Lischeid, Gunnar A1 - Webber, Heidi A1 - Sommer, Michael A1 - Nendel, Claas A1 - Ewert, Frank T1 - Machine learning in crop yield modelling BT - A powerful tool, but no surrogate for science JF - Agricultural and forest meteorology N2 - Provisioning a sufficient stable source of food requires sound knowledge about current and upcoming threats to agricultural production. To that end machine learning approaches were used to identify the prevailing climatic and soil hydrological drivers of spatial and temporal yield variability of four crops, comprising 40 years yield data each from 351 counties in Germany. Effects of progress in agricultural management and breeding were subtracted from the data prior the machine learning modelling by fitting smooth non-linear trends to the 95th percentiles of observed yield data. An extensive feature selection approach was followed then to identify the most relevant predictors out of a large set of candidate predictors, comprising various soil and meteorological data. Particular emphasis was placed on studying the uniqueness of identified key predictors. Random Forest and Support Vector Machine models yielded similar although not identical results, capturing between 50% and 70% of the spatial and temporal variance of silage maize, winter barley, winter rapeseed and winter wheat yield. Equally good performance could be achieved with different sets of predictors. Thus identification of the most reliable models could not be based on the outcome of the model study only but required expert's judgement. Relationships between drivers and response often exhibited optimum curves, especially for summer air temperature and precipitation. In contrast, soil moisture clearly proved less relevant compared to meteorological drivers. In view of the expected climate change both excess precipitation and the excess heat effect deserve more attention in breeding as well as in crop modelling. KW - Crop modelling KW - Machine learning KW - Random forests KW - Support vector KW - machine KW - Feature selection KW - Equivocality Y1 - 2021 U6 - https://doi.org/10.1016/j.agrformet.2021.108698 SN - 0168-1923 SN - 1873-2240 VL - 312 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Siegmund, Nicole A1 - Funk, Roger A1 - Sommer, Michael A1 - Avecilla, Fernando A1 - Esteban Panebianco, Juan A1 - Iturri, Laura Antonela A1 - Buschiazzo, Daniel T1 - Horizontal and vertical fluxes of particulate matter during wind erosion on arable land in the province La Pampa, Argentina JF - International journal of sediment research N2 - A detailed analysis of horizontal and vertical particulate matter (PM) fluxes during wind erosion has been done, based on measurements of PM smaller than 10, 2.5, and 1.0 mu mm, at windward and leeward positions on a measuring field. The three fractions of PM measurement are differently influenced by the increasing wind and shear velocities of the wind. The measured concentrations of the coarser fractions of the fine dust, PM10, and PM2.5, increase with wind and shear velocity, whereas the PM1.0 concentrations show no clear correlation to the shear velocity. The share of PM2.5 on PM10 depends on the measurement height and wind speed and varies between 4 and 12 m/s at the 1 m height ranging from 25% to 7% (average 10%), and at the 4 m height from 39% to 23% (average 30%). Although general relationships between wind speed, PM concentration, and horizontal and vertical fluxes could be found, the contribution of the measuring field was very low, as balances of incoming and outgoing fluxes show. Consequently, the measured PM concentrations are determined from a variety of sources, such as traffic on unpaved roads, cattle drives, tillage operations, and wind erosion, and thus, represent all components of land use and landscape structure in the near and far surroundings of the measuring field. The current results may reflect factors from the landscape scale rather than the influence of field-related variables. The measuring devices used to monitor PM concentrations showed differences of up to 20%, which led to considerable deviations when determining total balances. Differences up to 67% between the calculated fluxes prove the necessity of a previous calibration of the devices used. (c) 2022 International Research and Training Centre on Erosion and Sedimentation/the World Association for Sedimentation and Erosion Research. KW - PM10, PM2.5 and PM1.0 concentrations KW - Field measurements KW - Horizontal KW - flux KW - Vertical flux KW - PM balances Y1 - 2022 U6 - https://doi.org/10.1016/j.ijsrc.2022.01.004 SN - 1001-6279 SN - 2589-7284 VL - 37 IS - 5 SP - 539 EP - 552 PB - IRTCES CY - Beijing ER - TY - JOUR A1 - Siegmund, Nicole A1 - Panebianco, Juan E. A1 - Avecilla, Fernando A1 - Iturri, Laura Antonela A1 - Sommer, Michael A1 - Buschiazzo, Daniel A1 - Funk, Roger T1 - From gustiness to dustiness BT - the impact of wind gusts on particulate matter emissions in field experiments in La Pampa, Argentina JF - Atmosphere N2 - This study delivers the first empirical data-driven analysis of the impact of turbulence induced gustiness on the fine dust emissions from a measuring field. For quantification of the gust impact, a new measure, the Gust uptake Efficiency (GuE) is introduced. GuE provides a percentage of over- or under-proportional dust uptake due to gust activity during a wind event. For the three analyzed wind events, GuE values of up to 150% could be found, yet they significantly differed per particle size class with a tendency for lower values for smaller particles. In addition, a high-resolution correlation analysis among 31 particle size classes and wind speed was conducted; it revealed strong negative correlation coefficients for very small particles and positive correlations for bigger particles, where 5 mu m appears to be an empirical threshold dividing both directions. We conclude with a number of suggestions for further investigations: an optimized field experiment setup, a new particle size ratio (PM1/PM0.5 in addition to PM10/PM2.5), as well as a comprehensive data-driven search for an optimal wind gust definition in terms of soil erosivity. KW - wind gusts KW - wind erosion KW - particle uptake KW - dust plumes Y1 - 2022 U6 - https://doi.org/10.3390/atmos13081173 SN - 2073-4433 VL - 13 IS - 8 PB - MDPI CY - Basel ER - TY - JOUR A1 - Siegmund, Nicole A1 - Funk, Roger A1 - Koszinsky, Sylvia A1 - Buschiazzo, Daniel A1 - Sommer, Michael T1 - Effects of low-scale landscape structures on aeolian transport processes on arable land JF - Aeolian Research N2 - The landscape of the semiarid Pampa in central Argentina is characterized by late Pleistocene aeolian deposits, covering large plains with sporadic dune structures. Since the current land use changed from extensive livestock production within the Caldenal forest ecosystem to arable land, the wind erosion risk increased distinctly. We measured wind erosion and deposition patterns at the plot scale and investigated the spatial variability of the erosion processes. The wind-induced mass-transport was measured with 18 Modified Wilson and Cooke samplers (MWAC), installed on a 1.44 ha large field in a 20 x 40 m grid. Physical and chemical soil properties from the upper soil as well as a digital elevation model were recorded in a 20 x 20 m grid. In a 5-month measuring campaign data from seven storms with three different wind directions was obtained. Results show very heterogeneous patterns of erosion and deposition for each storm and indicate favoured erosion on windward and deposits on leeward terrain positions. Furthermore, a multiple regression model was build, explaining up to 70% of the spatial variance of erosion by just using four predictors: topsoil thickness, relative elevation, soil organic carbon content and slope direction. Our findings suggest a structure-process-structure complex where the landscape structure determines the effects of recent wind erosion processes which again slowly influence the structure, leading to a gradual increase of soil heterogeneity. KW - Argentina KW - La Pampa KW - Wind erosion KW - Deposition KW - Topography KW - Mass transport KW - MWAC KW - Multiple regression Y1 - 2018 U6 - https://doi.org/10.1016/j.aeolia.2018.03.003 SN - 1875-9637 SN - 2212-1684 VL - 32 SP - 181 EP - 191 PB - Elsevier CY - Oxford ER - TY - JOUR A1 - Iturri, Laura Antonela A1 - Funk, Roger A1 - Sommer, Michael A1 - Buschiazzo, Daniel T1 - Transport preferences of P forms in wind-blown sediments of two susceptible soils JF - Aeolian research : an international journal on wind erosion research / International Society of Aeolian Research N2 - Wind erosion of agricultural soils affects their stock of essential elements for plants, like phosphorus (P). It is known that the composition of the eroded sediments varies with height, according to the size and density of the transported substances. Aim of this study was to analyze the concentration and enrichment ratios of P forms in sediments transported by the wind. A wind-tunnel study was performed on a sandy-and a sandy loam soil in order to measure P forms concentrations in the saltating sediments. P concentrations were also measured in the particulate matter (PM) of each soil, gained with the Easy Dust Generator. In both soils, inorganic-(Pi) and organic P (Po) were preferentially transported in PM, with enrichment ratios of 1.8 and 5.5, respectively. Nevertheless, a Pi/Po of 0.9 indicated that the accumulation of the minor Po in PM was more pronounced than Pi. This agrees with P-rich light and easily erodible organic compounds, almost exclusively accumulated in PM, and in relatively heavy and less erodible minerals, like apatites, in lower height sediments. Labile P (Pl) was preferentially transported in saltating sediments of both soils. This was attributed to the selective Bray & Kurtz I's extraction of the abundant inorganic P forms of these sediments. Total P (Pt) copied the transport trends of Pi, the major form. According to the transporting trends, Pi and Po would be re-sedimented at longer distances from the source than Pl. Outcomes become useful for modeling the influence of wind erosion on P cycling. KW - Nutrient KW - Soil fertility KW - Wind erosion KW - Semiarid KW - Wind tunnel Y1 - 2022 U6 - https://doi.org/10.1016/j.aeolia.2022.100776 SN - 1875-9637 VL - 55 PB - Elsevier CY - Amsterdam [u.a.] ER - TY - JOUR A1 - Schaller, Jörg A1 - Puppe, Daniel A1 - Kaczorek, Danuta A1 - Ellerbrock, Ruth A1 - Sommer, Michael T1 - Silicon cycling in soils revisited JF - Plants : open access journal N2 - Silicon (Si) speciation and availability in soils is highly important for ecosystem functioning, because Si is a beneficial element for plant growth. Si chemistry is highly complex compared to other elements in soils, because Si reaction rates are relatively slow and dependent on Si species. Consequently, we review the occurrence of different Si species in soil solution and their changes by polymerization, depolymerization, and condensation in relation to important soil processes. We show that an argumentation based on thermodynamic endmembers of Si dependent processes, as currently done, is often difficult, because some reactions such as mineral crystallization require months to years (sometimes even centuries or millennia). Furthermore, we give an overview of Si reactions in soil solution and the predominance of certain solid compounds, which is a neglected but important parameter controlling the availability, reactivity, and function of Si in soils. We further discuss the drivers of soil Si cycling and how humans interfere with these processes. The soil Si cycle is of major importance for ecosystem functioning; therefore, a deeper understanding of drivers of Si cycling (e.g., predominant speciation), human disturbances and the implication for important soil properties (water storage, nutrient availability, and micro aggregate stability) is of fundamental relevance. KW - andosols KW - clay neoformation KW - crop yield KW - land use change KW - micro KW - aggregate stability KW - phytoliths KW - sediments KW - silicon cycling KW - silicon KW - extraction methods KW - silicon pore water speciation Y1 - 2021 U6 - https://doi.org/10.3390/plants10020295 SN - 2223-7747 VL - 10 IS - 2 PB - MDPI CY - Basel ER - TY - JOUR A1 - Sommer, C. A1 - Garbusow, Maria A1 - Juenger, E. A1 - Pooseh, S. A1 - Bernhardt, Nadine A1 - Birkenstock, J. A1 - Schad, Daniel A1 - Jabs, B. A1 - Gloeckler, T. A1 - Huys, Quentin J. M. A1 - Heinz, A. A1 - Smolka, Michael N. A1 - Zimmermann, Ulrich S. T1 - Strong seduction: impulsivity and the impact of contextual cues on instrumental behavior in alcohol dependence JF - Translational Psychiatry N2 - Alcohol-related cues acquire incentive salience through Pavlovian conditioning and then can markedly affect instrumental behavior of alcohol-dependent patients to promote relapse. However, it is unclear whether similar effects occur with alcohol-unrelated cues. We tested 116 early-abstinent alcohol-dependent patients and 91 healthy controls who completed a delay discounting task to assess choice impulsivity, and a Pavlovian-to-instrumental transfer (PIT) paradigm employing both alcohol-unrelated and alcohol-related stimuli. To modify instrumental choice behavior, we tiled the background of the computer screen either with conditioned stimuli (CS) previously generated by pairing abstract pictures with pictures indicating monetary gains or losses, or with pictures displaying alcohol or water beverages. CS paired to money gains and losses affected instrumental choices differently. This PIT effect was significantly more pronounced in patients compared to controls, and the group difference was mainly driven by highly impulsive patients. The PIT effect was particularly strong in trials in which the instrumental stimulus required inhibition of instrumental response behavior and the background CS was associated to monetary gains. Under that condition, patients performed inappropriate approach behavior, contrary to their previously formed behavioral intention. Surprisingly, the effect of alcohol and water pictures as background stimuli resembled that of aversive and appetitive CS, respectively. These findings suggest that positively valenced background CS can provoke dysfunctional instrumental approach behavior in impulsive alcohol-dependent patients. Consequently, in real life they might be easily seduced by environmental cues to engage in actions thwarting their long-term goals. Such behaviors may include, but are not limited to, approaching alcohol. Y1 - 2017 U6 - https://doi.org/10.1038/tp.2017.158 SN - 2158-3188 VL - 7 SP - 1209 EP - 1222 PB - Nature Publ. Group CY - New York ER - TY - JOUR A1 - Puppe, Daniel A1 - Kaczorek, Danuta A1 - Schaller, Jörg A1 - Barkusky, Dietmar A1 - Sommer, Michael T1 - Crop straw recycling prevents anthropogenic desilication of agricultural soil-plant systems in the temperate zone BT - results from a long-term field experiment in NE Germany JF - Geoderma : an international journal of soil science N2 - Due to the fact that silicon (Si) increases the resistance of plants against diverse abiotic and biotic stresses, Si nowadays is categorized as beneficial substance for plants. However, humans directly influence Si cycling on a global scale. Intensified agriculture and corresponding harvest-related Si exports lead to Si losses in agricultural soils. This anthropogenic desilication might be a big challenge for modern agriculture. However, there is still only little knowledge about Si cycling in agricultural systems of the temperate zone, because most studies focus on rice and sugarcane production in (sub)tropical areas. Furthermore, many studies are performed for a short term only, and thus do not provide the opportunity to analyze slow changes in soil-plant systems (e.g., desilication) over long periods. We analyzed soil and plant samples from an ongoing long-term field experiment (established 1963) in the temperate zone (NE Germany) to evaluate the effects of different nitrogen-phosphoruspotassium (NPK) fertilization rates and crop straw recycling (i.e., straw incorporation) on anthropogenic desilication in the long term. Our results clearly show that crop straw recycling not only prevents anthropogenic desilication (about 43-60% of Si exports can be saved by crop straw recycling in the long term), but also replenishes plant available Si stocks of agricultural soil-plant systems. Furthermore, we found that a reduction of N fertilization rates of about 69% is possible without considerable biomass losses. This economy of the need for N fertilizers potentially can be combined with the benefits of crop straw recycling, i.e., enhancement of carbon sequestration via straw inputs and prevention of anthropogenic desilication of agricultural soil-plant systems. Thus crop straw recycling might have the potential to act as key management practice in sustainable, low fertilization agriculture in the temperate zone in the future. KW - Sustainable crop production KW - Straw incorporation KW - Phytoliths KW - Silicon exports KW - Plant available Si Y1 - 2021 U6 - https://doi.org/10.1016/j.geoderma.2021.115187 SN - 0016-7061 SN - 1872-6259 VL - 403 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Heinrich, Ingo A1 - Balanzategui, Daniel A1 - Bens, Oliver A1 - Blasch, Gerald A1 - Blume, Theresa A1 - Boettcher, Falk A1 - Borg, Erik A1 - Brademann, Brian A1 - Brauer, Achim A1 - Conrad, Christopher A1 - Dietze, Elisabeth A1 - Dräger, Nadine A1 - Fiener, Peter A1 - Gerke, Horst H. A1 - Güntner, Andreas A1 - Heine, Iris A1 - Helle, Gerhard A1 - Herbrich, Marcus A1 - Harfenmeister, Katharina A1 - Heussner, Karl-Uwe A1 - Hohmann, Christian A1 - Itzerott, Sibylle A1 - Jurasinski, Gerald A1 - Kaiser, Knut A1 - Kappler, Christoph A1 - Koebsch, Franziska A1 - Liebner, Susanne A1 - Lischeid, Gunnar A1 - Merz, Bruno A1 - Missling, Klaus Dieter A1 - Morgner, Markus A1 - Pinkerneil, Sylvia A1 - Plessen, Birgit A1 - Raab, Thomas A1 - Ruhtz, Thomas A1 - Sachs, Torsten A1 - Sommer, Michael A1 - Spengler, Daniel A1 - Stender, Vivien A1 - Stüve, Peter A1 - Wilken, Florian T1 - Interdisciplinary Geo-ecological Research across Time Scales in the Northeast German Lowland Observatory (TERENO-NE) JF - Vadose zone journal N2 - The Northeast German Lowland Observatory (TERENO-NE) was established to investigate the regional impact of climate and land use change. TERENO-NE focuses on the Northeast German lowlands, for which a high vulnerability has been determined due to increasing temperatures and decreasing amounts of precipitation projected for the coming decades. To facilitate in-depth evaluations of the effects of climate and land use changes and to separate the effects of natural and anthropogenic drivers in the region, six sites were chosen for comprehensive monitoring. In addition, at selected sites, geoarchives were used to substantially extend the instrumental records back in time. It is this combination of diverse disciplines working across different time scales that makes the observatory TERENO-NE a unique observation platform. We provide information about the general characteristics of the observatory and its six monitoring sites and present examples of interdisciplinary research activities at some of these sites. We also illustrate how monitoring improves process understanding, how remote sensing techniques are fine-tuned by the most comprehensive ground-truthing site DEMMIN, how soil erosion dynamics have evolved, how greenhouse gas monitoring of rewetted peatlands can reveal unexpected mechanisms, and how proxy data provides a long-term perspective of current ongoing changes. Y1 - 2018 U6 - https://doi.org/10.2136/vzj2018.06.0116 SN - 1539-1663 VL - 17 IS - 1 PB - Soil Science Society of America CY - Madison ER - TY - JOUR A1 - Sommer, Michael A1 - Jochheim, H. A1 - Höhn, Axel A1 - Breuer, Jörn A1 - Zagorski, Z. A1 - Busse, J. A1 - Barkusky, Dietmar A1 - Meier, K. A1 - Puppe, D. A1 - Wanner, Manfred A1 - Kaczorek, Danuta T1 - Si cycling in a forest biogeosystem - the importance of transient state biogenic Si pools JF - Biogeosciences N2 - The relevance of biological Si cycling for dissolved silica (DSi) export from terrestrial biogeosystems is still in debate. Even in systems showing a high content of weatherable minerals, like Cambisols on volcanic tuff, biogenic Si (BSi) might contribute > 50% to DSi (Gerard et al., 2008). However, the number of biogeosystem studies is rather limited for generalized conclusions. To cover one end of controlling factors on DSi, i.e., weatherable minerals content, we studied a forested site with absolute quartz dominance (> 95 %). Here we hypothesise minimal effects of chemical weathering of silicates on DSi. During a four year observation period (05/2007-04/2011), we quantified (i) internal and external Si fluxes of a temperate-humid biogeosystem (beech, 120 yr) by BIOME-BGC (version ZALF), (ii) related Si budgets, and (iii) Si pools in soil and beech, chemically as well as by SEM-EDX. For the first time two compartments of biogenic Si in soils were analysed, i.e., phytogenic and zoogenic Si pool (testate amoebae). We quantified an average Si plant uptake of 35 kg Si ha(-1) yr(-1) - most of which is recycled to the soil by litterfall - and calculated an annual biosilicification from idiosomic testate amoebae of 17 kg Si ha(-1). The comparatively high DSi concentrations (6 mg L-1) and DSi exports (12 kg Si ha(-1) yr(-1)) could not be explained by chemical weathering of feldspars or quartz dissolution. Instead, dissolution of a relictic, phytogenic Si pool seems to be the main process for the DSi observed. We identified canopy closure accompanied by a disappearance of grasses as well as the selective extraction of pine trees 30 yr ago as the most probable control for the phenomena observed. From our results we concluded the biogeosystem to be in a transient state in terms of Si cycling. Y1 - 2013 U6 - https://doi.org/10.5194/bg-10-4991-2013 SN - 1726-4170 VL - 10 IS - 7 SP - 4991 EP - 5007 PB - Copernicus CY - Göttingen ER - TY - JOUR A1 - Schaller, Jörg A1 - Scherwietes, Eric A1 - Gerber, Lukas A1 - Vaidya, Shrijana A1 - Kaczorek, Danuta A1 - Pausch, Johanna A1 - Barkusky, Dietmar A1 - Sommer, Michael A1 - Hoffmann, Mathias T1 - Silica fertilization improved wheat performance and increased phosphorus concentrations during drought at the field scale JF - Scientific reports N2 - Drought and the availability of mineable phosphorus minerals used for fertilization are two of the important issues agriculture is facing in the future. High phosphorus availability in soils is necessary to maintain high agricultural yields. Drought is one of the major threats for terrestrial ecosystem performance and crop production in future. Among the measures proposed to cope with the upcoming challenges of intensifying drought stress and to decrease the need for phosphorus fertilizer application is the fertilization with silica (Si). Here we tested the importance of soil Si fertilization on wheat phosphorus concentration as well as wheat performance during drought at the field scale. Our data clearly showed a higher soil moisture for the Si fertilized plots. This higher soil moisture contributes to a better plant performance in terms of higher photosynthetic activity and later senescence as well as faster stomata responses ensuring higher productivity during drought periods. The plant phosphorus concentration was also higher in Si fertilized compared to control plots. Overall, Si fertilization or management of the soil Si pools seem to be a promising tool to maintain crop production under predicted longer and more serve droughts in the future and reduces phosphorus fertilizer requirements. Y1 - 2021 U6 - https://doi.org/10.1038/s41598-021-00464-7 SN - 2045-2322 VL - 11 IS - 1 PB - Macmillan Publishers Limited, part of Springer Nature CY - [London] ER -