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Laggner A.,Thunen Institute For Agrarklimaschutz
ZFV - Zeitschrift fur Geodasie, Geoinformation und Landmanagement

The Basis-DLM is a digital landscape model delivered as a feature type structured, topographic vector dataset. It is part of ATKIS. ATKIS is the landscape specifying Geographical Information System (GIS) of the German national survey and represents the «Authoritative topographic cartographic information System». This paper introduces two use cases for the Basis-DLM in the context of the German Greenhouse Gas Inventory contributed by the Thünen Institute of Climate-Smart Agriculture. The basis for the German Greenhouse Gas Inventory includes a consistent time series of annual area sums for land use and land use change in Germany from 1990 to the present. As from the year 2000 the Basis-DLM is the most important dataset for this time series. The second example presents the large-scale regionalization of water table depth in German peatlands (Bechtold et al. 2014, HESS). These results rely on the Basis-DLM as well. Source

Loick N.,Rothamsted Research | Dixon E.R.,Rothamsted Research | Abalos D.,Technical University of Madrid | Vallejo A.,Technical University of Madrid | And 6 more authors.
Soil Biology and Biochemistry

Agricultural soils are a major source of nitric oxide (NO) and nitrous oxide (N2O), which are produced and consumed by biotic and abiotic soil processes. The dominant sources of NO and N2O are microbial nitrification and denitrification. While N2O emissions have been attributed to both processes, depending on the environmental conditions such as substrate availability, pH and water filled pore space (WFPS), NO emissions are thought to predominantly derive from nitrification. Although attributing gaseous emissions to specific processes is still difficult, recent findings challenge the latter of those assumptions. Using the gas-flow-soil-core method, i.e soil cores incubated under a He/O2 atmosphere at constant surface gas flow, combined with 15N labelled isotopic techniques, the present study investigated the role of denitrification on NO, N2O and N2 emissions in a UK grassland soil under high soil moisture and an aerobic headspace atmosphere. With the application of KNO3 and glucose to support denitrification, denitrification was the source of N loss of between 0.61 and 0.67% of the added N via NO emissions, 1.60-1.68% via N2O and 0.03-0.05% via N2 emissions. Overall, our study showed that denitrification has been overlooked as a source of NO emissions. © 2016. Source

Lebegue B.,French Climate and Environment Sciences Laboratory | Schmidt M.,University of Heidelberg | Ramonet M.,French Climate and Environment Sciences Laboratory | Wastine B.,French Climate and Environment Sciences Laboratory | And 7 more authors.
Atmospheric Measurement Techniques

Over the last few decades, in situ measurements of atmospheric N2O mole fractions have been performed using gas chromatographs (GCs) equipped with electron capture detectors. This technique, however, becomes very challenging when trying to detect the small variations of N2O as the detectors are highly nonlinear and the GCs at remote stations require a considerable amount of maintenance by qualified technicians to maintain good short-term and long-term repeatability. With new robust optical spectrometers now available for N2O measurements, we aim to identify a robust and stable analyzer that can be integrated into atmospheric monitoring networks, such as the Integrated Carbon Observation System (ICOS). In this study, we present the most complete comparison of N2O analyzers, with seven analyzers that were developed and commercialized by five different companies. Each instrument was characterized during a time period of approximately 8 weeks. The test protocols included the characterization of the short-term and long-term repeatability, drift, temperature dependence, linearity and sensitivity to water vapor. During the test period, ambient air measurements were compared under field conditions at the Gif-sur-Yvette station. All of the analyzers showed a standard deviation better than 0.1ppb for the 10min averages. Some analyzers would benefit from improvements in temperature stability to reduce the instrument drift, which could then help in reducing the frequency of calibrations. For most instruments, the water vapor correction algorithms applied by companies are not sufficient for high-precision atmospheric measurements, which results in the need to dry the ambient air prior to analysis. © Author(s) 2016. Source

Helfrich M.,Thunen Institute For Agrarklimaschutz | Ludwig B.,University of Kassel | Thoms C.,Nordwestdeutsche Forstliche Versuchsanstalt | Gleixner G.,Max Planck Institute For Biogeochemie | Flessa H.,Thunen Institute For Agrarklimaschutz
Applied Soil Ecology

Although microbial-derived carbon (C) inputs to soil are increasingly acknowledged as an important source of soil organic matter (SOM), the contribution of different microbial compounds to soil C transformation and their role in aggregation remain poorly understood. This study assessed the contribution of soil fungi and bacteria to the decomposition of maize residues by means of extracted phospholipid fatty acids (PLFAs) and 13C in specific PLFAs and investigated the importance of soil fungi in the formation of macroaggregates. Sieved soil (<250μm) was incubated for 28 days with and without addition of maize residues and fungicide. Our results show a significant relation between the amount of fungal PLFA 18:2ω6 and the amount of macroaggregates. Further, the amount of macroaggregates was higher in the treatment with the higher amount of maize-derived C in fungal PLFA, suggesting that fungal activity is important for macroaggregate formation. Based on an increased incorporation of maize-derived C into actinomycetes in fungicide treatments, we suggest that actinomycetes may take over the role of soil fungi in the decomposition of SOM. Our study underpins the important role of soil fungi in the decomposition of organic matter and structure formation in the soil, and shows that during inhibition of soil fungi other soil microorganisms are promoted and adopt their function in the soil food web. © 2015 Elsevier B.V. Source

Eibisch N.,Thunen Institute For Agrarklimaschutz | Helfrich M.,Thunen Institute For Agrarklimaschutz | Don A.,Thunen Institute For Agrarklimaschutz | Mikutta R.,Leibniz University of Hanover | And 4 more authors.
Journal of Environmental Quality

Biomass carbonized via hydrothermal carbonization (HTC) yields a liquid and a carbon (C)-rich solid called hydrochar. In soil, hydrochars may act as fertilizers and promote C sequestration. We assumed that the chemical composition of the raw material (woodchips, straw, grass cuttings, or digestate) determines the properties of the liquid and solid HTC products, including their degradability. Additionally, we investigated whether easily mineralizable organic components adsorbed on the hydrochar surface influence the degradability of the hydrochars and could be removed by repetitive washing. Carbon mineralization was measured as CO2 production over 30 d in aerobic incubation experiments with loamy sand. Chemical analysis revealed that most nutrients were preferably enriched in the liquid phase. The C mineralization of hydrochars from woodchips (2% of total C added), straw (3%), grass (6%), and digestate (14%) were dependent on the raw material carbonized and were significantly lower (by 60-92%; p < 0.05) than the mineralization of the corresponding raw materials. Washing of the hydrochars significantly decreased mineralization of digestate-hydrochar (up to 40%) but had no effect on mineralization rates of the other three hydrochars. Variations in C mineralization between different hydrochars could be explained by multiple factors, including differences in the O/C-H/C ratios, C/N ratios, lignin content, amount of oxygen-containing functional groups, and pH. In contrast to the solids, the liquid products were highly degradable, with 61 to 89% of their dissolved organic C being mineralized within 30 d. The liquids may be treated aerobically. © American Society of Agronomy, Crop Science Society of America, and Soil Science Society of America. Source

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