1,720,958 research outputs found
A New Approach to Address Soil Heterogeneity as a Source of Uncertainty in the Flux‐Gradient Method: CO 2 Case Studies
No full textABSTRACT The flux‐gradient method (FGM) is an important tool to study soil‐atmosphere and subsurface gas fluxes. The simplicity of the approach can lead to an uncritical application. Typical uncertainty found in the input parameters is not considered in most cases. Their potential effect on the flux estimations might be negligible, but could also result in a relevant uncertainty or even bias. In this study, we investigated how measurement uncertainty and soil heterogeneity may affect the application of the FGM. We introduce a new analysis approach that allows to include (a) additional chamber measurements and (b) known parameter ranges/distribution of soil physical properties for model calibration and (c) to quantify the uncertainty in the flux estimate. The new Robust Calibrated Inverse FGM (RCI‐FGM) approach is an extension of the FGM and shared within the new R‐package ConFluxPro. In two soil CO 2 data studies, we demonstrate how soil heterogeneity affects gas flux estimations calculated with the FGM, and how RCI‐FGM helps to derive more robust flux estimates. In study 1, we found that scattering (due to measurement uncertainty and soil heterogeneity) found typically in the total porosity of soils can drastically change the vertical concentration profile of soil CO 2 . Assuming mean porosity in the FGM led to a significant bias in the estimated flux rates. The new RCI‐FGM approach successfully reduced this bias by incorporating reference flux measurements for calibration. In study 2, we applied the RCI‐FGM approach to a previously published dataset of forest soil CO 2 fluxes. RCI‐FGM improved the fit to reference chamber measurements and the plausibility of the vertical partitioning of the flux rates. The application of the RCI‐FGM approach in future studies was demonstrated for CO 2 fluxes but can be used for CH 4 and O 2 uptake in well‐aerated soils. For soils and processes dominated by hot spots or hot moments, such as N 2 O formation from denitrification, additional consideration may need to be taken. Our approach can help in future studies to address the uncertainty in the FGM method, improve the robustness of the estimated flux rates, and increase the comparability of studies.Fachagentur Nachwachsende Rohstoffe https://doi.org/10.13039/501100010812Waldklimafonds https://doi.org/10.13039/501100010297Bundesministerium für Ernährung und Landwirtschaft https://doi.org/10.13039/501100005908Bundesministerium für Umwelt, Naturschutz, nukleare Sicherheit und Verbraucherschutz https://doi.org/10.13039/50110001354
Trend analysis of methane uptake in 13 forest soils based on up to 24 years of field measurements in south-west Germany
No full textLong Term Soil Gas Monitoring as Tool to Understand Soil Processes
No full textSoils provide many functions as they represent a habitat for flora and fauna, supply water, nutrient, and anchorage for plant growth and more. They can also be considered as large bioreactors in which many processes occur that involve the consumption and production of different gas species. Soils can be a source and sink for greenhouse gases. During the last decades this topic attracted special attention. Most studies on soil-atmosphere gas fluxes used chamber methods or micro-meteorological methods. Soil gas fluxes can also be calculated from vertical soil gas profiles which can provide additional insights into the underlying processes. We present a design for sampling and measuring soil gas concentration profiles that was developed to facilitate long term monitoring. Long term monitoring requires minimization of the impact of repeated measurements on the plot and also minimization of the routine workload while the quality of the measurement needs to be maintained continuously high. We used permanently installed gas wells that allowed passive gas sampling at different depths. Soil gas monitoring set ups were installed on 13 plots at 6 forest sites in South West Germany between 1998 and 2010. Until now, soil gas was sampled monthly and analysed for CO2, N2O, CH4, O2, N2, Ar, and C2H4 using gas chromatography. We present typical time series and profiles of soil gas concentrations and fluxes of a selected site as an example. We discuss the effect of different calculation approaches and conclude that flux estimates of O2, CO2 and CH4 can be considered as highly reliable, whereas N2O flux estimates include a higher uncertainty. We point out the potential of the data and suggest ideas for future research questions for which soil gas monitoring would provide the ideal data basis. Combining and linking the soil gas data with additional environmental data promises new insights and understanding of soil processes
High throughput femtosecond laser processing for new generation battery
Get PDFUse of Ultra-Short Pulse lasers (UPLs) represent an advantageous technological choice on one hand to texture electrode collectors (CC, both Cu and Al) and on the other hand to structure the electrode active layer (EAL) of both anode and cathode. Whilst the first could enhance the electro-mechanical bonding of the EAL coated on CCs the second enables a faster battery recharging and the increase of electrode capacity. We present the results obtained from extending the aforementioned processes to Gen 3b batteries, utilizing water-based material formulations to eliminate NMP and other toxic solvents. Three different kind of surface structures (LIPSS, micro-Grooves and DLIP) have been generated over CC and characterised via SEM and electrochemically, showing an improvement of the anode performances by 15%. Interestingly, Post-mortem analysis shows the possibility to prevent delamination phenomena observed on pristine CC after repeated cycling. High throughput processing is reported by using a 300 Watt UPL. Also reported results obtained on structuring of EAL by means of micrometric holes. A 100 W femtosecond laser with POD capabilities has been used. The beam has been split in a matrix of identical sub-beams by a DOE, a fast galvo-scanner (20 m/s) has been utilised to increase the throughput and a surface as large as 10cm×10cm has been processed. Finally, a comprehensive morphological (SEM) and electrochemical characterisation of laser structured electrodes are reported. We believe our results demonstrate that UPL represent an effective fabrication tool for enhancing the performance of next-generation battery technologies
Dynamics of Soil CO2 Efflux and Vertical CO2 Production in a European Beech and a Scots Pine Forest
Get PDFThe conversion of coniferous forest to deciduous forest is accompanied by changes in the vertical distribution of fine roots and soil organic carbon (SOC) content. It is unclear how these changes affect soil CO2 efflux and vertical soil CO2 production, considering changing climate. Here, we present the results of a 6-year study on CO2 efflux, covering relatively warm-dry and cool-wet years. A combination of the flux-gradient method and closed chamber measurements was used to study the CO2 efflux and the vertical distribution of soil CO2 production in a beech (Fagus sylvatica L.) and a pine (Pinus sylvestris L.) forest in northeast Germany. We observed, on average, similar CO2 efflux with 517 (±126) and 559 (±78) g C m–2 a–1 for the beech site and the pine site, respectively. CO2 efflux at the beech site exceeded that at the pine site during the wet year 2017, whereas in dry years, the opposite was the case. Water availability as indicated by precipitation was the primary determining long-term factor of CO2 efflux, whereas seasonal variation was mainly affected by soil temperature, and—in the case of beech—additionally by soil water content. CO2 efflux decreased more dramatically (-43%) at the beech site than at the pine site (-22%) during the warm-dry year 2018 compared to the cool-wet year 2017. We assumed that drought reduces heterotrophic respiration (Rh) at both sites, but additionally decreases autotrophic respiration (Ra) at the beech stand. Soil CO2 production at the beech site ranged over a greater soil depth than at the pine site, attributed to different fine root distribution. The organic layer and the A horizon contributed 47 and 68% of total CO2 efflux at the beech site and the pine site, respectively. The seasonal patterns of different CO2 efflux between both sites were assumed to relate to different phases of tree physiological activity of deciduous compared to evergreen tree species
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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