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, 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 - 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 - 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 - 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 - 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 - 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 - 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 - 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 - 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 - 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 - 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 - 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 - 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 - 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 - 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 - 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 - 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 - 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 - 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 -