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It is common practice in agriculture to apply high‑carbon amendments, e.g. straw, or nitrification inhibitors (NI) to reduce soil nitrogen (N) losses. However, little is known on the combined effects of straw and NI and how seasonal soil temperature variations further affect N immobilization. We conducted a 113-day mesocosm experiment with different levels of 15N-fertilizer application (N0: control; N1: 125 kg N ha−1; N2: 250 kg N ha−1) in an agricultural soil, amended with either wheat straw, NI or a combination of both in order to investigate N retention and loss from soil after a cooling-warming phase simulating a seasonal temperature shift, i.e., 30 days cooling phase at 7 °C and 10 days warming phase at 21 °C. Subsequently, soils were planted with barley as phytometers to study 15N-transfer to a following crop.Straw addition significantly reduced soil N-losses due to microbial N immobilization. Although carbon added as straw led to increased N2O emissions at high N fertilization, this was partly counterbalanced by NI. Soil cooling-warming strongly increased ammonification (+77 %), while nitrification was suppressed, and straw-induced microbial N immobilization dominated. N immobilized after straw addition was mineralized at the end of the experiment as indicated by structural equation models. Re-mineralization in N2 was sufficient, but still suboptimal in N0 and N1 at critical times of early barley growth. N-use efficiency of the 15N tracer decreased with fertilization intensity from 50 % in N1 to 35 % in N2, and straw amendment reduced NUE to 25 % at both fertilization rates. Straw amendment was most powerful in reducing N-losses (−41 %), in particular under variable soil temperature conditions, but NI enforced its effects by reducing N2O emission (−40 %) in N2 treatment. Sufficient N-fertilization coupled with straw application is required to adjust the timely re-mineralization of N for subsequent crops.

Journal of environmental quality 52(4), 814-828 (2023). doi:10.1002/jeq2.20482, Ecological sanitation combined with thermophilic composting is a viable option to transform human excreta into a stabilized, pathogen-free, and nutrient-rich fertilizer. In combination with suitable bulking materials such as sawdust and straw, and additives such as biochar, this could also be a suitable waste management strategy for reducing greenhouse gas (GHG) emissions. In this study, we conducted a 143-days thermophilic composting of human excreta or cattle manure together with teff straw, organic waste, and biochar to investigate the effect that biochar has on GHG (CO2, N2O, and CH4) and NH3 emissions. The composting was performed in wooden boxes (1.5 × 1.5 × 1.4 m3), GHG were measured by using a portable FTIR gas analyzer and NH3 was sampled as ammonium in an H2SO4 trap. We found that the addition of biochar significantly reduced CH4 emissions by 91% in the cattle manure compost, and N2O emissions by 56%−57% in both humanure and cattle manure composts. Overall, non-CO2 GHG emissions were reduced by 51%−71%. In contrast, we did not observe a significant biochar effect on CO2 and NH3 emissions. Previous data already showed that it is possible to sanitize human fecal material when using this composting method. Our results suggest that thermophilic composting with biochar addition is a safe and cost-effective waste management practice for producing a nutrient-rich fertilizer from human excreta, while reducing GHG emissions at the same time., Published by Wiley, Hoboken, NJ

11 páginas.- 7 figuras.- 4 tablas.- 46 referencias.- Supplementary data to this article can be found online at https://doi.org/10.1016/j.geoderma.2022.116274, Nitrogen (N) immobilization controls the N availability in soil, however, mechanisms involved in the chemical N fixation into soil organic N (SON) through reactions of reactive N compounds with soil organic matter (SOM) is not clear. Knowledge about the composition and stability of chemically produced SON is limited, which impedes understanding of the interplay of N and carbon (C) cycles at both the local and global scale. Here, we studied the chemical N immobilization of nitrite in soils from grassland, cropland, and forest with 15N labelling technique. And solid state 15N- and 13C NMR spectroscopies were applied to further explore the structure of chemically immobilized SON. We found that the chemical retention rate of nitrite did not differ significantly between land-uses, while the fulvic acid fraction was the SOM component most reactive to nitrite. In contrast to the common assumption that amides are mainly of biological origin and that black N compounds are formed from organic N compounds at high temperature during fires, our study revealed that amides and black N in the form of pyrroles were the main products of chemical reactions of nitrite with SOM. These findings indicate that chemical processes play a key role in biogeochemical N cycling, and provide new insight into the mechanisms of Csingle bondN interactions in soil, This study was supported by Guangdong Major Project of Basic and Applied Basic Research (2020B0301030004), Guangdong Province Key Laboratory for Climate Change and Natural Disaster Studies (Grant 2020B1212060025), the German Federal Ministry of Education and Research (BMBF) in the framework of the BonaRes INPLAMINT project (grant no. 031B0508A), by Innovation Group Project of Southern Marine Science and Engineering Guangdong Laboratory (Zhuhai) (No. 311021009), and the Chinese Scholarship Council (scholarship no. 201406890023)

Predicting the impact of land use and climate change on the Earth system hinges on credible representation of soil hydrological processes (SHP), adequate availability of parameters and hydrological states and inclusion of key soil properties. There is increasing evidence that extreme events such as droughts and high intensity precipitation, and land use changes, affect fundamental hydrological processes such as infiltration and runoff generation. In this review, we analyse the influence of soil structure on SHP, critically evaluate the parameterization of soil hydrologic properties and their importance in representing the terrestrial water cycle and highlight the key role of soil hydrology in the functioning of carbon-rich soils and in linking the water and carbon cycles. It emerges that linking soil hydrology and pedology will lead to better understanding critical zone processes, especially in tropical regions. Further, we discuss the role of local scale hydrological processes in understanding root water uptake, vegetation and groundwater dynamics and feedbacks. These processes control and modulate the impact of extreme events such as droughts, floods and heatwaves and they are essential to assess drought and flooding. Finally, new emerging technologies such as wireless and automated sensing approaches, soil moisture observation through novel synthetic aperture radars satellites, big data analysis and machine learning approaches offer unique opportunities to advance soil hydrology.

The CloudRoots field experiment was designed to obtain a comprehensive observational dataset that includes soil, plant, and atmospheric variables to investigate the interaction between a heterogeneous land surface and its overlying atmospheric boundary layer at the sub-hourly and sub-kilometre scale. Our findings demonstrate the need to include measurements at leaf level to better understand the relations between stomatal aperture and evapotranspiration (ET) during the growing season at the diurnal scale. Based on these observations, we obtain accurate parameters for the mechanistic representation of photosynthesis and stomatal aperture. Once the new parameters are implemented, the model reproduces the stomatal leaf conductance and the leaf-level photosynthesis satisfactorily. At the canopy scale, we find a consistent diurnal pattern on the contributions of plant transpiration and soil evaporation using different measurement techniques. From highly resolved vertical profile measurements of carbon dioxide (

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Increasing evidence has been found that chemical reactions affect significantly the terrestrial nitrogen (N) cycle, which was previously assumed to be mainly dominated by biological processes. Due to the limitation of knowledge and analytical techniques, it is currently challenging to discern the contribution of biotic and abiotic processes to the terrestrial N cycle for geobiologists and biogeochemists alike. To better understand the role of abiotic reactions in the terrestrial N cycle, it is necessary to comprehend the chemical controls on nitrogenous trace gas emissions and N retention in soil under various environmental conditions. In this manuscript, we assess the role of abiotic reactions in nitrous oxide (N2O) and nitric oxide (NO) emissions as well as N retention through a meta-analysis using all related peer-reviewed publications before August 2020. Results show that abiotic reactions contributed 29.3–37.7% and 44.0–57.0% to the total N2O emission and N retention, representing 3.7–4.7 and 4.0–6.0 Tg year−1 of global terrestrial N2O emission and N retention, respectively. Much higher NO production was observed in sterilized soils than that in unsterilized treatments indicating the major contribution of chemical reactions to NO emission and rapid microbial reduction of NO to N2O and N2. Chemical hydroxylamine oxidation accounts for the largest abiotic contribution to N2O emission, while chemical nitrite reduction and fixation represent for the largest contribution to abiotic NO production and soil N retention, respectively. Factors influencing the abiotic processes include pH, total organic carbon (TOC), total nitrogen (TN), the ratio of carbon to nitrogen (C/N), and transition metals. These results broadened our knowledge about the mechanisms involved in chemical N reactions and provided a simplified estimation about their contribution to nitrogenous trace gas emission and N retention, which is meaningful to further study interactions of biologically and chemically mediated reactions in biogeochemical N cycle.

Microbial-Induced Calcite Precipitation (MICP) stimulates soil microbiota to induce a cementation of the soil matrix. Urea, calcium and simple carbon nutrients are supplied to produce carbonates via urea hydrolysis and induce the precipitation of the mineral calcite. Calcium chloride (CaCl2) is typically used as a source for calcium, but basic silicate rocks and other materials have been investigated as alternatives. Weathering of calcium-rich silicate rocks (e.g., basalt and dolerite) releases calcium, magnesium and iron; this process is associated with sequestration of atmospheric CO2 and formation of pedogenic carbonates. We investigated atmospheric carbon fluxes of a MICP treated sandy soil using CaCl2 and dolerite fines applied on the soil surface as sources for calcium. Soil-atmosphere carbon fluxes were monitored over 2 months and determined with an infrared gas analyser connected to a soil chamber. Soil inorganic carbon content and isotopic composition were determined with isotope-ratio mass spectrometry. In addition, soil-atmosphere CO2 fluxes during chemical weathering of dolerite fines were investigated in incubation experiments with gas chromatography. Larger CO2 emissions resulted from the application of dolerite fines (116 g CO2-C m–2) compared to CaCl2 (79 g CO2-C m–2) but larger inorganic carbon precipitation also occurred (172.8 and 76.9 g C m–2, respectively). Normalising to the emitted carbon to precipitated carbon, the environmental carbon cost was reduced with dolerite fines (0.67) compared to the traditional MICP treatment (1.01). The carbon isotopic signature indicated pedogenic carbonates (δ13Cav = −8.2 ± 5.0‰) formed when dolerite was applied and carbon originating from urea (δ13Cav = −46.4 ± 1.0‰) precipitated when CaCl2 was used. Dolerite fines had a large but short-lived (

International audience; Differentiating the contributions of photosynthesis and respiration to the global carbon cycle is critical for improving predictive climate models. Carbonic anhydrase (CA) activity in leaves is responsible for the largest biosphere-atmosphere trace gas fluxes of carbonyl sulfide (COS) and the oxygen-18 isotopologue of carbon dioxide (CO18O) that both reflect gross photosynthetic rates. However, CA activity also occurs in soils and will be a source of uncertainty in the use of COS and CO18O as carbon cycle tracers until process-based constraints are improved. In this study, we measured COS and CO18O exchange rates and estimated the corresponding CA activity in soils from a range of biomes and land use types. Soil CA activity was not uniform for COS and CO2, and patterns of divergence were related to microbial community composition and CA gene expression patterns. In some cases, the same microbial taxa and CA classes catalyzed both COS and CO2 reactions in soil, but in other cases the specificity towards the two substrates differed markedly. CA activity for COS was related to fungal taxa and β-D-CA expression, whereas CA activity for CO2 was related to algal and bacterial taxa and α-CA expression. This study integrates gas exchange measurements, enzyme activity models, and characterization of soil taxonomic and genetic diversity to build connections between CA activity and the soil microbiome. Importantly, our results identify kinetic parameters to represent soil CA activity during application of COS and CO18O as carbon cycle tracers.

Nitrous oxide (N2O) emission is a negative side effect of modern agriculture and a serious issue for global climate change. The combined application of nitrogen (N) fertilizer and high organic carbon soil amendments (HCA) has been regarded as an alternative to promote fertilizer-related N immobilization and enhance nitrogen use efficiency. The effect of HCA on N2O emission and N immobilization highly depends on its chemical composition, as it controls carbon (C) supply to soil microbes and reactivity of lignin-derived phenols to fertilizer-derived N species. Here we present a 127-d laboratory incubation study to explore the N2O emission and N immobilization after combined application of N fertilizer and HCA (wheat straw, spruce sawdust, and commercial alkali lignin) differing in their chemical composition. The 15N labeling technique was used to trace the transformation of fertilizer-N in ammonium (NH4+), nitrate (NO3–), soil organic nitrogen (SON), and N2O. The amendment of wheat straw and spruce sawdust greatly promoted N immobilization and N2O emission, while lignin amendment enhanced the immobilization of fertilizer N. The chemical composition of HCA explained 26% of the total variance of fertilizer-derived N2O emission and N retention via soil microbial biomass, composition of lignin-derived phenols, and nitrification. The holocellulose/lignin ratio of HCA could be used as an indicator for predicting HCA decomposition, microbial N immobilization and N2O emission. In addition, the composition of lignin-derived phenols was affected by HCA amendment and significantly related to N2O emission and N retention. The varying chemical composition of HCA could thus be a promising tool for controlling N2O emission and N immobilization in environment-friendly and climate-smart agriculture.

For an assessment of the roles of soil and vegetation in the climate system, a further understanding of the flux components of H 2 O and CO 2 (e.g., transpiration, soil respiration) and their interaction with physical conditions and physiological functioning of plants and ecosystems is necessary. To obtain magnitudes of these flux components, we applied source partitioning approaches after Scanlon and Kustas (2010; SK10) and after Thomas et al. (2008; TH08) to high-frequency eddy covariance measurements of 12 study sites covering different ecosystems (croplands, grasslands, and forests) in different climatic regions. Both partitioning methods are based on higher-order statistics of the H 2 O and CO 2 fluctuations, but proceed differently to estimate transpiration, evaporation, net primary production, and soil respiration. We compared and evaluated the partitioning results obtained with SK10 and TH08, including slight modifications of both approaches. Further, we analyzed the interrelations among the performance of the partitioning methods, turbulence characteristics, and site characteristics (such as plant cover type, canopy height, canopy density, and measurement height). We were able to identify characteristics of a data set that are prerequisites for adequate performance of the partitioning methods. SK10 had the tendency to overestimate and TH08 to underestimate soil flux components. For both methods, the partitioning of CO 2 fluxes was less robust than for H 2 O fluxes. Results derived with SK10 showed relatively large dependencies on estimated water use efficiency (WUE) at the leaf level, which is a required input. Measurements of outgoing longwave radiation used for the estimation of foliage temperature (used in WUE) could slightly increase the quality of the partitioning results. A modification of the TH08 approach, by applying a cluster analysis for the conditional sampling of respiration-evaporation events, performed satisfactorily, but did not result in significant advantages compared to the original method versions developed by Thomas et al. (2008). The performance of each partitioning approach was dependent on meteorological conditions, plant development, canopy height, canopy density, and measurement height. Foremost, the performance of SK10 correlated page1112 negatively with the ratio between measurement height and canopy height. The performance of TH08 was more dependent on canopy height and leaf area index. In general, all site characteristics that increase dissimilarities between scalars appeared to enhance partitioning performance for SK10 and TH08.

For an assessment of the roles of soil and vegetation in the climate system, a further understanding of the flux components of H2O and CO2 (e.g., transpiration, soil respiration) and their interaction with physical conditions and physiological functioning of plants and ecosystems is necessary. To obtain magnitudes of these flux components, we applied source partitioning approaches after Scanlon and Kustas (2010; SK10) and after Thomas et al. (2008; TH08) to high-frequency eddy covariance measurements of 12 study sites covering different ecosystems (croplands, grasslands, and forests) in different climatic regions. Both partitioning methods are based on higher-order statistics of the H2O and CO2 fluctuations, but proceed differently to estimate transpiration, evaporation, net primary production, and soil respiration. We compared and evaluated the partitioning results obtained with SK10 and TH08, including slight modifications of both approaches. Further, we analyzed the interrelations among the performance of the partitioning methods, turbulence characteristics, and site characteristics (such as plant cover type, canopy height, canopy density, and measurement height). We were able to identify characteristics of a data set that are prerequisites for adequate performance of the partitioning methods. SK10 had the tendency to overestimate and TH08 to underestimate soil flux components. For both methods, the partitioning of CO2 fluxes was less robust than for H2O fluxes. Results derived with SK10 showed relatively large dependencies on estimated water use efficiency (WUE) at the leaf level, which is a required input. Measurements of outgoing longwave radiation used for the estimation of foliage temperature (used in WUE) could slightly increase the quality of the partitioning results. A modification of the TH08 approach, by applying a cluster analysis for the conditional sampling of respiration–evaporation events, performed satisfactorily, but did not result in significant advantages compared to the original method versions developed by Thomas et al. (2008). The performance of each partitioning approach was dependent on meteorological conditions, plant development, canopy height, canopy density, and measurement height. Foremost, the performance of SK10 correlated negatively with the ratio between measurement height and canopy height. The performance of TH08 was more dependent on canopy height and leaf area index. In general, all site characteristics that increase dissimilarities between scalars appeared to enhance partitioning performance for SK10 and TH08.

Soil greenhouse gas (GHG) emissions contribute to global warming. To support mitigation measures against global warming, it is important to understand the controlling processes of GHG emissions. Previous studies focusing mainly on paddy rice fields or wetlands showed a strong relationship between soil redox potential and GHG emission (e.g., N2O). However, the interpretation of redox potentials for the understanding of the controlling factors of GHG emission is limited due to the low number of continuous redox measurements in most ecosystems. Recent sensor developments open the possibility for the long-term monitoring of field-scale soil redox potential changes. We performed laboratory lysimeter experiments to investigate how changes in the redox potential, induced by changes in the water level, affect GHG emissions from agricultural soil. Under our experimental conditions, we found that N2O emissions followed closely the changes in redox potential. The dynamics of redox potential were induced by changing the water-table depth in a laboratory lysimeter. Before fertilization during saturated conditions, we found a clear negative correlation between redox potentials and N2O emission rates. After switching from saturated to unsaturated conditions, N2O emission quickly decreased, indicating denitrification as the main source of N2O. In contrast, the emissions of CO2 increased with increasing soil redox potentials. After fertilization, N2O emission peaked at high redox potential, suggesting nitrification as the main production pathway, which was confirmed by isotope analysis of N2O. We propose that redox potential measurements are a viable method for better understanding of the controlling factors of GHG emissions, for the differentiation between different source processes, and for the improvement of process-based GHG models.

Root water uptake plays a crucial role in the water cycle, as it is the largest flux on land surfaces returning water to the atmosphere. Its complex dynamics and ecosystem feedbacks are however still not well understood and can therefore not be adequately accounted for in models simulating water transport in the soil-plant-atmosphere interface. Especially on short time scales, high uncertainty exists with regards to the plasticity of water uptake and its associated driving forces. In view of an increase in hydrological extremes and a changing climate, a more mechanistic understanding is however crucial.For five decades, water stable isotopes substantially improved our knowledge about this hard to observe belowground process. However, monitoring short-term variations was restricted, due to the necessity for destructive sampling and laborious sample analysis. Recent methodological advances now offer new possibilities to overcome these constraints and triggered the development of new approaches, which enable an in-situ monitoring of water stable isotopes in soil water and water taken up by plants. First combined in-situ measurements were already conducted in trees, but have not yet been applied to the examination of root water uptake in herbaceous species.In the presented work, a new method is tested that allows for long-term in-situ sampling of water stable isotopes across a soil column and in plant transpiration under controlled conditions in the laboratory, using Cavity Ring-Down Spectroscopy.For this purpose, an existing soil column setup is further developed and expanded by a plant component. Dual isotope data in daily and sub-daily temporal resolution is collected across soil isotopic profiles and transpiration of Centaurea jacea, respectively. It will be shown that measured transpiration values reflect a mixture of soil water differing in its isotopic composition across the profile throughout a period of six weeks, despite pronounced dynamic changes in both systems. Derived measurement precision is comparable to that of established and also other newly developed in-situ methods. The setup proved to be an adequate tool for capturing short-term variations in root water uptake in response to differences of water availability in daily resolution. To visualize water uptake profiles, data sets of the isotopic composition in plant transpiration and soil profiles are combined in a statistical multi-source mixing model. Observed trends can logically be interpreted with existing knowledge on water uptake dynamics and plasticity, while highlighting knowledge gaps in the mechanistic understanding of contributions of underlying processes. Prospectively, the implementation of data sets, obtained with the tested method, in mechanistic state-of-the-art models could help to further disentangle complex interactions between soils and root systems. On the other hand modeling approaches across scales that now more commonly include water stable isotopes, will potentially benefit from recorded time series. Therefore temporally highly resolved data sets should be collected for a rangeof plant species, soil types and scenarios in the future.

Due to their high-quality routine measurement programme, ICOS sites lend themselves as anchors for additional experiments. As an example, we describe the CloudRoots campaign near the agricultural site Selhausen (DE-RuS) in spring 2018.Little is known about the two-way feedback between stomatal control (controlling the partitioning of energy into sensible and latent heat) and cloud development (affecting potential evapotranspiration). Coupled models of the soil-vegetation-boundary layer continuum have the potential to explain this, but their calculations are only as robust as the data used to parameterize or validate the model. For observations and modelling, the challenge is in interconnecting processes at leaf level to the physics of turbulence and clouds.We temporarily amend the existing radiation, flux and soil dynamics/respiration measurements of the ICOS site by scintillometry, sap-flow and leaf-level flux measurements, vertical profiles and isotope measurements. Scintillometers provide minute-scale turbulent fluxes enabling to connect stomatal responses to the energy, moisture and CO2 fluxes at this timescale [1]. Sap-flow [2], leaf-level chamber, canopy-resolving profile [3] and isotope measurements have the potential to distinguish stomatal CO2 and H2O fluxes from the eddy-covariance based net fluxes. Relating the leaf and canopy level measurements to cloud development and potential cross-scale feedbacks are integrated and explored with the CLASS model ([4], https://classmodel.github.io).The campaign is partnering with two complementary test campaigns for the FLEX mission (https://earth.esa.int/web/guest/missions/esa-future-missions/flex) and the MOSES project (https://moses.eskp.de/home/), taking place, among others, in the same region in spring and summer 2018. The poster will show first results and method intercomparisons from the CloudRoots field campaign.[1] van Kesteren et al. 2013, Agric. For. Meteorol. 178-179:75-105[2] Langensiepen et al. 2014, Agric. For. Meteorol. 186:34[3] Ney and Graf 2018, Bound.-Layer Meteorol. 166:449[4] Vilà-Guerau de Arellano et al. 2015, Atmospheric Boundary Layer: Integrating air chemistry and land interactions. Cambridge University Press.

Abiotic conversion of the reactive nitrification intermediate hydroxylamine (NH2OH) to nitrous oxide (N2O) is a possible mechanism of N2O formation during nitrification. Previous research has demonstrated that manganese dioxide (MnO2) and organic matter (OM) content of soil as well as soil pH are important control variables of N2O formation in the soil. But until now, their combined effect on abiotic N2O formation from NH2OH has not been quantified. Here, we present results from a full-factorial experiment with artificial soil mixtures at five different levels of pH, MnO2 and OM, respectively, and quantified the interactive effects of the three variables on the NH2OH-to-N2O conversion ratio (RNH2OH-to-N2O). Furthermore, the effect of OM quality on RNH2OH-to-N2O was determined by the addition of four different organic materials with different C/N ratios to the artificial soil mixtures. The experiments revealed a strong interactive effect of soil pH, MnO2 and OM on RNH2OH-to-N2O. In general, increasing MnO2 and decreasing pH increased RNH2OH-to-N2O, while increasing OM content was associated with a decrease in RNH2OH-to-N2O. Organic matter quality also affected RNH2OH-to-N2O. However, this effect was not a function of C/N ratio, but was rather related to differences in the dominating functional groups between the different organic materials.

A process-based understanding of the water cycle in the atmosphere is important for improving meteorological and hydrological forecasting models. Usually only net fluxes of evapotranspiration – ET are measured, while land-surface models compute their raw components evaporation –E and transpiration –T. Isotopologues can be used as tracers to partition ET, but this requires knowledge of isotopic kinetic effects which impact the stable isotopic composition of water pools (e.g., soil, plant, surface waters) during phase change and vapor transport by soil evaporation and plant transpiration. Craig and Gordon (1965) introduced the kinetic fractionation in their model. It’s defined as the ratio of the transport resistances in air of the isotopologue to the most abundant isotopologue. Previous studies conducted laboratory experiments for free evaporating water (Merlivat, 1978. Cappa et al. 2003) or bare soil evaporation (Braud et al. 2009) with only a low temporal resolution. The goal of this study is to provide estimates of this factor at higher temporal resolution. We performed a soil evaporation laboratory experiment to determine the kinetic fractionation factor by applying the Craig and Gordon model. A 0.7 m high column (0.48 m i.d.) was filled with silt loam (20.1 % sand, 14.9 % loam, 65 % silt) and saturated with water of known isotopic composition. Soil volumetric water content, temperature and the isotopic composition of the soil water vapor were measured at six different depths. At each depth microporous polypropylene tubing allowed the sampling of soil water vapor and the measurement of its isotopic composition in a non-destructive manner with high precision and accuracy as detailed in Rothfuss et al. (2013). In addition, atmospheric water vapor was sampled at seven different heights up to one meter above the surface. Finally, air relative humidity and temperature were monitored at one meter height. Results showed that soil and atmospheric isotopic composition profiles could be monitored at high temporal and vertical resolutions during the course of the experiment. The kinetic fractionation factor could be calculated by using an inverse Graig and Gordon model and the Keeling plot method at high temporal resolution over a long period. We observed an increasing isotopic composition in the evaporating water vapor due to more enriched surface water. This leads to a higher transport resistances and an increasing kinetic fractionation factor.

A complex simulation model of a heavy duty truck, including an Organic Rankine Cycle (ORC) based waste heat recovery system and a vehicle cooling system, was applied to determine the system fuel economy potential in a typical drive cycle. Measures to increase the system performance were investigated and a comparison between two different cooling system designs was derived. The base design, which was realized on a Mercedes-Benz Actros vehicle revealed a fuel efficiency benefit of 2.6%, while a more complicated design would generate 3.1%. Furthermore, fully transient simulation results were performed and are compared to steady state simulation results. It is shown that steady state simulation can produce comparable results if averaged road data are used as boundary conditions.

Wie reagiert die Biosphäre auf den Globalen Wandel und die lokale Landbewirtschaftung, und wie wirkt sie sich wiederum auf den Klimawandel aus? Die Landoberfläche kann zum jetzigen Zeitpunkt ca. 33 % (±17 %) des Kohlenstoffdioxids (CO2) aus der Verbrennung fossiler Brennstoffe aufnehmen. Dem gegenüber steht allerdings eine zusätzliche CO2-Abgabe von 14 % (±10 %) aus Landnutzungsänderungen (IPCC 2013). Photosynthetische CO2-Aufnahme und respiratorische CO2-Abgabe werden unterschiedlich von Umweltfaktoren wie Temperatur, CO2-Konzentration, und Wasserverfügbarkeit beeinflusst. Diese Faktoren sind wiederum dem globalen Wandel unterworfen. Um diese Wechselwirkungen analysieren zu können, müssen Nettoflüsse von Treibhausgasen, wie sie beispielsweise mit der Eddy-Kovarianz-Methode gemessen werden können, in ihre Einzelbeiträge zerlegt werden. Derartige Versuche, den CO2-Fluss in Photosynthese und Respiration oder den latenten Wärmefluss in Evaporation und Transpiration aufzuschlüsseln, werden unter dem Begriff “Source Partitioning” zusammengefasst.Das BMBF-geförderte Forschungsprojekt IDAS-GHG (Instrumental and Data-driven Approaches to Source-Partitioning of Greenhouse Gas Fluxes: Comparison, Combination, Advancement) hat die Zielsetzung, existierende Ansätze zum Source-Partitioning von Treibhausgasflüssen systematisch miteinander zu vergleichen und zu verbessern. Diese lassen sich in zwei Gruppen gliedern: Datenbasierte Ansätze nutzen bestehende (Roh)daten aus der Eddy-Kovarianz-Messung. Instrumentelle Ansätze hingegen beinhalten die Durchführung zusätzlicher Messungen, wie z. B. Kammer- und Profilmessungen, oder die Verwendung von Tracern (z. B. stabile Isotope), die Auskunft über die Herkunft der Gasmoleküle geben können.In unserer Präsentation werden einige dieser Methoden am Beispiel des Messstandorts Selhausen beschrieben. Der Standort befindet sich im TERENO-Observatorium Eifel/Niederrheinische Bucht in der intensiv landwirtschaftlich genutzten niederrheinischen Bördelandschaft. Der Untersuchungszeitraum erstreckt sich über die Vegetationsperiode eines Winterweizenfeldes von der Aussaat im Oktober 2014 über die Ernte hinaus bis Ende September 2015. Im Messfeld installiert ist eine dauerhafte Eddy-Kovarianz-Station und ein automatisches Bodenrespirations-Kammersystem mit bis zu vier Langzeitkammern. Zusätzlich wurden stichprobenartig Profilmessungen der CO2- und H2O-Konzentrationen mit einem eigens gebauten Liftsystem durchgeführt.Mithilfe der gemessenen Eddy-Kovarianz-Daten zeigen wir einen Vergleich bestehender Ansätze zum Source-Partitioning des Netto-Ökosystem-Austauschs in Bruttoprimärproduktion (Photosynthese) und Ökosystematmung (Respiration). Unter Verwendung von Kammermessungen wird dieser um die Terme Nettoprimärproduktion und Bodenrespiration erweitert.Das Profilsystem misst Änderungen der Konzentration von CO2 und H2O mit einer hohen vertikalen und zeitlichen Auflösung zwischen Bodenoberfläche, Pflanzenbestand und Atmosphäre. Die Profile im Halbstundenmittel bilden den Effekt der photosynthetischen Kohlenstoff-Assimilation und Bodenatmung deutlich ab und geben somit qualitative Informationen über Quell- und Senkbereiche. Im nächsten Schritt wird versucht, diese zu quantifizieren und mit den bereits beschriebenen Ansätzen zu vergleichen.

The remarkable complexity of soil and its importance to a wide range of ecosystem services presents major challenges to the modeling of soil processes. Although major progress in soil models has occurred in the last decades, models of soil processes remain disjointed between disciplines or ecosystem services, with considerable uncertainty remaining in the quality of predictions and several challenges that remain yet to be addressed. First, there is a need to improve exchange of knowledge and experience among the different disciplines in soil science and to reach out to other Earth science communities. Second, the community needs to develop a new generation of soil models based on a systemic approach comprising relevant physical, chemical, and biological processes to address critical knowledge gaps in our understanding of soil processes and their interactions. Overcoming these challenges will facilitate exchanges between soil modeling and climate, plant, and social science modeling communities. It will allow us to contribute to preserve and improve our assessment of ecosystem services and advance our understanding of climate-change feedback mechanisms, among others, thereby facilitating and strengthening communication among scientific disciplines and society. We review the role of modeling soil processes in quantifying key soil processes that shape ecosystem services, with a focus on provisioning and regulating services. We then identify key challenges in modeling soil processes, including the systematic incorporation of heterogeneity and uncertainty, the integration of data and models, and strategies for effective integration of knowledge on physical, chemical, and biological soil processes. We discuss how the soil modeling community could best interface with modern modeling activities in other disciplines, such as climate, ecology, and plant research, and how to weave novel observation and measurement techniques into soil models. We propose the establishment of an international soil modeling consortium to coherently advance soil modeling activities and foster communication with other Earth science disciplines. Such a consortium should promote soil modeling platforms and data repository for model development, calibration and intercomparison essential for addressing contemporary challenges., Vadose Zone Journal, 15 (5), ISSN:1539-1663

To explore effective ways to decrease soil CO2 emission and increase grain yield, field experiments were conducted on two upland rice soils (Lixisols and Gleyic Luvisols) in northern Benin in West Africa. The treatments were two tillage systems (no-tillage, and manual tillage), two rice straw managements (no rice straw, and rice straw mulch at 3 Mg ha-1) and three nitrogen fertilizers levels (no nitrogen, recommended level of nitrogen: 60 kg ha-1, and high level of nitrogen: 120 kg ha-1). Potassium and phosphorus fertilizers were applied to be non-limiting at 40 kg K2O ha-1 and 40 kg P2O5 ha-1. Four replications of the twelve treatment combinations were arranged in a randomized complete block design. Soil CO2 emission, soil moisture and soil temperature were measured at 5 cm depth in 6 to 10 days intervals during the rainy season and every two weeks during the dry season. Soil moisture was the main factor explaining the seasonal variability of soil CO2 emission. Much larger soil CO2 emissions were found in rainy than dry season. No-tillage planting significantly reduced soil CO2 emissions compared with manual tillage. Higher soil CO2 emissions were recorded in the mulched treatments. Soil CO2 emissions were higher in fertilized treatments compared with non fertilized treatments. Rice biomass and yield were not significantly different as a function of tillage systems. On the contrary, rice biomass and yield significantly increased with application of rice straw mulch and nitrogen fertilizer. The highest response of rice yield to nitrogen fertilizer addition was obtained for 60 kg N ha-1 in combination with 3 Mg ha-1 of rice straw for the two tillage systems. Soil CO2 emission per unit grain yield was lower under no-tillage, rice straw mulch and nitrogen fertilizer treatments. No-tillage combined with rice straw mulch and 60 kg N ha-1 could be used by smallholder farmers to achieve higher grain yield and lower soil CO2 emission in upland rice fields in northern Benin.

Auf dem Poster werden Ziele und erste Ergebnisse des kürzlich gestarteten BMBF-Projekts „IDAS-GHG“ vorgestellt, dessen Gegenstand in-situ-Messungen des Austauschs klimarelevanter Spurengase (CO2, H2O, N2O) über unterschiedlich (z.B. landwirtschaftlich) genutzten Vegetationsflächen sind.Insbesondere während der ersten Projektjahre stehen methodische Fragen zum sogenannten „Source Partitioning“ (Quellenzuordnung oder Komponentenentmischung) im Vordergrund. Damit werden verschiedene bestehende und in Entwicklung befindliche Methoden bezeichnet, Messungen des Netto-Austauschs zwischen Biosphäre und Atmosphäre (z.B. mit der Eddy-Kovarianz-Methode) hinsichtlich der beteiligten Quellen- und Senken aufzuschlüsseln, etwa Respiration und Photosynthese bzw. Evaporation und Transpiration.Sollen Messungen zur Parametrisierung des Verhaltens von Pflanzenbeständen und Böden in gekoppelten Klimamodellen genutzt werden, so kann eine erfolgreiche Quellenzuordnung in den Messdaten die Unsicherheit bei der Ermittlung der Modellparameter verringern. Auch direkt aus Messungen gewonnen Aussagen zum Mitigationspotential von Landnutzungsstrategien können besser erklärt, auf Plausibilität überprüft und auf ähnliche Fälle übertragen werden, wenn beispielsweise bekannt ist, aus welcher der möglichen Kombinationen von (Boden-)Respiration und (Netto-)Primärproduktion ein bestimmter gemessener Netto-CO2-Fluss resultiert. Derartige Bewertungsmöglichkeiten sollen im weiteren Verlauf des Projekts an Beispielen wie Gründüngung in der Landwirtschaft, Waldumbau und Dachbegrünung getestet werden.Unter den untersuchten, zu vergleichenden und weiterzuentwickelnden Methoden der Quellenzuordnung befinden sich sowohl solche, die auf bereits vorhandene Messdaten bestehender Eddy-Kovarianz-Standorte angewendet werden können, als auch Zusatzmessungen. Als Beispiel für letztere wird auf erste Ergebnisse vertikal hochauflösender Profilmessungen in niedrigen Pflanzenbeständen wie Grünland oder Weizen eingegangen.

absent

Journal für Kulturpflanzen 66(7) 2014, Groß angelegte und langfristig etablierte Feldversuche sind ein zentrales Element der standortbezogenen Agrarwissenschaften. Die Erarbeitung des Grundlagenwissens zu standortangepassten bzw. regional spezifischen Produktivitätspotentialen von Pflanzenbeständen sowie die Entwicklung von ökologisch vertretbaren, innovativen Produktionssystemen mit hoher Produktivität und Resi­lienz erfordern leistungsfähige Forschungsinfrastrukturen, die relevante Gradienten an Klima- und Bodenfaktoren abdecken und den interdisziplinären Dialog fördern. Das Positionspapier der Senatskommission für Agrar­öko­systemforschung der Deutschen Forschungsgemeinschaft stellt den Status quo und die zukünftigen Anforderungen an Feldversuchseinrichtungen dar. Zur Optimierung des agrarwissenschaftlichen Feldversuchswesens wird angeregt, in einem Netzwerk aus Versuchseinrichtungen Landschaftsfunktionen prototypisch abzubilden, um in einem interdisziplinären Ansatz Flächenproduktivität, Resilienz und Ressourceneffizienz landschaftsspezifisch untersuchen zu können. Des Weiteren ist es erforderlich, der wissenschaftlichen Community standardisierte Daten in Datenrepositorienzur Verfügung zu stellen.

Journal für Kulturpflanzen 66(7) 2014, Mit dem vorliegenden Grundsatzpapier zeigt die Senatskommission für Agrarökosystemforschung Perspektiven für die Grundlagenforschung zur nachhaltigen Erhöhung der Kulturpflanzenproduktion auf. Agrarsysteme stehen im Spannungsfeld zwischen steigendem Bedarf an landwirtschaftlichen Produkten, der Verknappung der Ressourcen, dem Verlust der Biodiversität und dem Klimawandel. Die für das Jahr 2050 prognostizierte notwendige Ertragssteigerung zur Sicherstellung des Bedarfs an Nahrungsmitteln kann, ohne die Belastbarkeitsgrenzen ökologischer Systeme zu überschreiten,nur durch wissenschaftlichen Fortschritt bewältigt werden (Abb. 1), der eine nachhaltige und ressourcen­effiziente Steigerung der Agrarproduktion ermöglicht (FAO,2011;Dobermann und Nelson,2013). Die nachhaltige Intensivierung stellt die Agrarwissenschaften vor neue Aufgaben, die weit über ihre klassischen Grenzen hinausgehen. Die Senatskommission plädiert daher für eine Erweiterung der agrarwissenschaftlichen Perspektive. Die meist auf einzelne Feldfrüchte bezogene Bewertung der Rela­tion zwischen Input und Ertrag muss ergänzt werden um die Optionen, die sich aus der räumlichen und zeitlichen Diversifikation der Produktionssysteme unter Einbeziehung der standörtlichen Eigenschaften, des Landschaftskontextes sowie des Klimawandels ergeben. Um Ökosystemleistungen einzubeziehen, müssen Produktionsstrategien entwickelt werden, die sich auf ganze Landschaften und Regionen richten und auch entsprechende sozio­öko­no­mische und agrarpolitische Rahmenbedingungen berücksichtigen. Vor diesem Hintergrund schlägt die Senatskommission drei interdisziplinäre Forschungsschwerpunkte zur ressourceneffizienten Erhöhung der Flächenproduktivität vor: (1) Ausnutzung des Potentials von Kulturpflanzen zur umweltschonenden Ertragssteigerung im Kontext öko­systemarer Bedingungen. (2) Nachhaltige Steigerung der Pflanzenproduktion im Landschaftskontext. (3) Ökonomische, gesellschaftliche und politische Dimensionen der Ertragssteigerung von Kulturpflanzen.

ISSN:1810-6277 ISSN:1810-6285

International audience; NO soil emissions are directly influenced by soil environmental (temperature, humidity), chemical (pH, N content, C content...) and physical (soil content, texture) variables. All these parameters exert linear or non linear influences that fluctuate in threshold and intensity between sites. Because of the lack of field experiments and to the high variability in time (diurnal and seasonal cycle) and space (regions, soil and vegetation type) of the environmental parameters influencing NO emissions, estimates of NO emissions worldwide still remain highly uncertain. In this study we developed nonlinear regressions to describe NO flux emission from soil in dependency with relevant environmental parameters for a forest site in a temperate region (Höglwald, South Germany, 1994–1997) using an Artificial Neural Network (ANN). The resulting algorithm links NO fluxes with air, surface and depth temperatures, surface WFPS (Water Field Pore Space) and humus pH. All these parameters were evaluated and selected as relevant and non redundant. Network performances are evaluated for different numbers of hidden neurons. Resulting equations linking NO fluxes from soils and variables are obtained, and show to perform well with measurements (R2 = 0.81). Average NO fluxes values of 14.6 gN ha−1 d−1 are obtained for calculated and measured fluxes. In a second part, 2002–2003 NO soil fluxes are estimated from the ANN equation obtained from 1994–1997 flux measurements performed at the same site. Overall, simulated results give a good estimation of NO fluxes, with a mean value of 15.3 gN ha d−1 close to the 21.7 gN ha d−1 measured mean for the 2002–2003 period. ANN algorithm gives also a good representation of low frequency (seasonal) variations. On the basis of our results, we suggest that ANN is a good alternative between detailed biogeochemical models and large scale models, and may be the appropriate tool for estimating NO emissions at a regional scale.

Data processing methods; Energy balance closure; Intra-annual temporal dynamics of ET; Tables S1-S2; Figures S1-S2

Data processing methods; Energy balance closure; Intra-annual temporal dynamics of ET; Tables S1-S2; Figures S1-S2

Philosophical Transactions of the Royal Society B: Biological Sciences, 375 (1810), ISSN:0962-8436, ISSN:1471-2970, ISSN:0080-4622

Biogeosciences Discussions, 8 (2), ISSN:1810-6277, ISSN:1810-6285