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  - 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  - 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  - 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  - 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  - 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  - 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  - 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  - 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  - 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  - 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  - 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  - 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  - 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  - 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  - 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  - 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  - 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  - 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  - 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  -