Mechanisms of Soil Erosion in Subtropical Chinese Forests - Effects of Species Diversity, Species Identity, Functional Traits and Soil Fauna on Sediment Discharge

Soil erosion is a serious environmental problem in many parts of the world, especially in ecosystems with high anthropogenic influences. It is also a serious challenge in subtropical China, but forest stands mitigate soil loss rates in this area. Forests provide a multi-storey canopy layer which largely influences rain throughfall patterns as well as a leaf litter layer on the forest floor which protects the soil against direct raindrop impact and modifies the water flow and storage capacities. Nevertheless, only little research has been conducted on biodiversity and species effects on soil erosion control under forest stands. Furthermore, the processes within a protective leaf litter cover as well as the impact of soil mesofauna and macrofauna are not yet clear. This thesis investigated the effects of species diversity, species identity, functional traits and soil fauna on soil erosion in subtropical forest ecosystems. It focused on interrill soil erosion rates determined by micro-scale ROPs under natural and simulated rainfall. Additionally, investigations with splash cups were carried out on changes in throughfall kinetic energy during the canopy passage of raindrops. Measurements took place in a forest biodiversity and ecosystem functioning experiment in the PR China (BEF China). Results showed that tree species richness did not affect sediment discharge, runoff and TKE, although a negative trend was visible. This could be attributed to an absence of species richness effects on canopy characteristics in early successional forest stands. Nevertheless, stands with multiple species seemed to ensure a more balanced and homogenous soil cover. Furthermore, results showed that leaf litter species diversity did not influence the litter cover and thus soil erosion rates. Nonetheless, we could show that species identity influenced initial soil erosion processes under forest. That also applied to the leaf litter cover, where single leaf species showed significantly different influences on sediment discharge. Therefore, the appropriate choice of tree species during the establishment of plantations plays a major role in erosion control, even in young forest stages. Moreover, species-specific functional traits affected soil erosion rates. High crown cover and leaf area index reduced soil erosion, whereas it was slightly increased by increasing tree height. Investigations on the kinetic energy of raindrops showed that low LAI, low tree height, simple pinnate leaves, dentate leaf margins, a high number of branches and a low crown base height effectively minimized TKE. At last, the presence of soil mesofauna and macrofauna increased soil erosion and thus effects of this fauna group on sediment discharge have to be considered in soil erosion experiments.Die Bodenerosion stellt eines der weltweit bedeutendsten Umweltprobleme dar und tritt vor allem in Ökosystemen unter starker anthropogener Nutzung auf. Ein wesentlicher Einflussfaktor auf den Bodenabtrag ist hierbei die überdeckende Vegetation und insbesondere Waldökosysteme gelten als erosionsmindernd. Baumkronen beeinflussen die durch das Blätterdach fallenden Regentropfen und Laubstreu auf dem Boden schützt die Oberfläche gegen Abtrag. Biodiversitäts- und Arteffekte in der Baum- als auch in der bodenbedeckenden Laubschicht können hierbei eine Rolle spielen, wurden in der Forschung bislang aber wenig berücksichtigt. Diese Dissertation liefert einen Beitrag zur Erforschung von Diversitäts-, Art- und Bodenfauna-Effekten auf initiale Bodenerosion in subtropischen Waldökosystemen. Hierzu wurden experimentelle Messungen mit kleinräumlichen Erosionsmessrinnen und Splash Cups durchgeführt. Neben der Nutzung des natürlichen Regenfalls erfolgte eine künstliche Beregnung mit einem mobilen Regensimulator. Die Messungen fanden in einem waldbaulichen Biodiversitätsexperiment in der Volksrepublik China (BEF China) statt. In den Experimenten konnte ein deutlicher Einfluss einzelner Baum- und Blattarten auf den Bodenabtrag, aber kein Einfluss der Baum- und Blattdiversität festgestellt werden. Bei steigendem Diversitätsniveau war ein negativer Trend im Sedimentaustrag, im Oberflächenabfluss und der kinetischen Energie der Regentropfen zu verzeichnen. Es lag allerdings keine signifikante Einflussnahme vor, was mit dem frühen Sukzessionsstadium des untersuchten Waldökosystems begründet wird. Höher diverse Baumbestände zeigten eine ausgeglichenere und homogenere Bodenbedeckung als Monokulturen. Unterschiedliche Monokulturen und Blattarten unterschieden sich teilweise sehr deutlich in ihren Abtragsraten. Diese Unterschiede sind bei der Auswahl von Bäumen für Aufforstungen zu berücksichtigen und zeigen bereits in sehr jungen Sukzessionsstadien Wirkung. Weiterhin beeinflussten verschiedene funktionelle Gruppen der einzelnen Baumarten die Bodenerosion. Eine hohe Kronenüberdeckung und ein hoher Blattflächenindex führten zu geringeren Erosionsraten, während steigende Baumhöhen diese erhöhten. Die kinetische Energie der Regentropfen wurde von einem geringen Blattflächenindex, niedriger Baumhöhe, einfach gefiederten Blättern, gezähnten Blatträndern, einer hohen Anzahl an Ästen und geringer Kronenhöhe negativ beeinflusst. Außerdem führte das Auftreten von Bodenfauna in der Laubschicht zu einem erhöhten Sedimentabtrag. untranslate

Identifying Anode and Cathode Contributions in Li-Ion Full-Cell Impedance Spectra

Measured impedance spectra of Li-ion battery cells are often reproduced with equivalent circuits or physical models to determine losses due to charge transfer processes at the electrodes. The identified model parameters can usually not readily or unambiguously be assigned to the anode and the cathode. A new measurement method is presented that enables the assignment of features of impedance spectra of full cells to single electrodes. To this end, temperature gradients are imprinted perpendicular to the electrode layers of a single-layered Li-ion battery cell while impedance spectra are measured. The method exploits different dependences of the charge transfer processes at the electrodes on temperature. An equivalent circuit model of RC-elements and the effect of temperature on the related electrode properties is discussed to demonstrate the feasibility of the method. A reliable assignment of the change of impedance spectra to the electrode processes is shown to be possible. The assignment can be used to identify if changes in an impedance spectrum originate from the anode or the cathode

Generalizable Classification of UHF Partial Discharge Signals in Gas-Insulated HVDC Systems Using Neural Networks

Undetected partial discharges (PDs) are a safety critical issue in high voltage (HV) gas insulated systems (GIS). While the diagnosis of PDs under AC voltage is well-established, the analysis of PDs under DC voltage remains an active research field. A key focus of these investigations is the classification of different PD sources to enable subsequent sophisticated analysis. In this paper, we propose and analyze a neural network-based approach for classifying PD signals caused by metallic protrusions and conductive particles on the insulator of HVDC GIS, without relying on pulse sequence analysis features. In contrast to previous approaches, our proposed model can discriminate the studied PD signals obtained at negative and positive potentials, while also generalizing to unseen operating voltage multiples. Additionally, we compare the performance of time- and frequency-domain input signals and explore the impact of different normalization schemes to mitigate the influence of free-space path loss between the sensor and defect location.Comment: 8 pages, submitted to IEEE Transactions on Power Deliver

Metrological Traceability Concept for Electrolytic Conductivity and pH

The metrological traceability concept links measurement results by a chain of calibrations to the quantity values of primary standards, which are realised by primary measurement procedures. These procedures undergo periodical international comparison measurements, in order to guarantee worldwide comparability of measurement results. In this article we demonstrate how the metrological traceability concept applies to electrolytic conductivity and pH measurements. Furthermore we will outline promising activities in current metrological research to extend traceability of electrolytic conductivity measurements down to the low ?S cm?1 level

Ice wedge polygon stability on steep slopes in West Greenland related to temperature and moisture dynamics of the active layer

Ice wedge polygons on steep slopes have generally been described as being covered by periglacial sediments and, typically, the active layer on slopes becomes mobile during thaw periods, which can lead to solifluction. In West Greenland close to the ice margin, however, the active layer and ice wedge polygons are stable despite their occurrence on steep slopes with inclinations of ≥30°. We conducted a soil survey (including sampling for soil analyses and radiocarbon dating) in the Umimmalissuaq valley and installed a field station ~4 km east of the current ice margin to monitor soil temperature and water tension at depths of 10, 20 and 35 cm of the active layer on a steep, north-facing slope in the middle of an ice wedge polygon from 2009 to 2015. Thawing and freezing periods lasted between 2 and 3 months and the active layer was usually completely frozen from November to April. We observed simultaneous and complete water saturation at all three depths of the active layer in one summer for 1 day. The amount of water in the active layer apparently was not enough to trigger solifluction during the summer thaw, even at slope inclinations above 30°. In addition, the dense shrub tundra absorbs most of the water during periods between thawing and freezing, which further stabilizes the slope. This process, together with the dry and continental climate caused by katabatic winds combined with no or limited frost heave, plays a crucial role in determining the stability of these slopes and can explain the presence of large-scale stable ice wedge polygon networks in organic matter-rich permafrost, which is about 5,000 years old. This study underlines the importance of soil hydrodynamics and local climate regime for landscape stability and differing intensities of solifluction processes in areas with strong geomorphological gradients and rising air temperatures

SalaciaML: A Deep Learning Approach for Supporting Ocean Data Quality Control

We present a skillful deep learning algorithm for supporting quality control of ocean temperature measurements, which we name SalaciaML according to Salacia the roman goddess of sea waters. Classical attempts to algorithmically support and partly automate the quality control of ocean data profiles are especially helpful for the gross errors in the data. Range filters, spike detection, and data distribution checks remove reliably the outliers and errors in the data, still wrong classifications occur. Various automated quality control procedures have been successfully implemented within the main international and EU marine data infrastructures (WOD, CMEMS, IQuOD, SDN) but their resulting data products are still containing data anomalies, bad data flagged as good and vice-versa. They also include visual inspection of suspicious measurements, which is a time consuming activity, especially if the number of suspicious data detected is large. A deep learning approach could highly improve our capabilities to quality assess big data collections and contemporary reducing the human effort. Our algorithm SalaciaML is meant to complement classical automated quality control procedures in supporting the time consuming visually inspection of data anomalies by quality control experts. As a first approach we applied the algorithm to a large dataset from the Mediterranean Sea. SalaciaML has been able to detect correctly more than 90% of all good and/or bad data in 11 out of 16 Mediterranean regions

A new method to prevent carry-over contaminations in two-step PCR NGS library preparations

Two-step PCR procedures are an efficient and well established way to generate amplicon libraries for NGS sequencing. However, there is a high risk of cross- contamination by carry-over of amplicons from first to second amplification rounds, potentially leading to severe misinterpretation of results. Here we describe a new method able to prevent and/or to identify carry-over contaminations by introducing the K-box, a series of three synergistically acting short sequence elements. Our K-boxes are composed of (i) K1 sequences for suppression of contaminations, (ii) K2 sequences for detection of possible residual contaminations and (iii) S sequences acting as separators to avoid amplification bias. In order to demonstrate the effectiveness of our method we analyzed two-step PCR NGS libraries derived from a multiplex PCR system for detection of T-cell receptor beta gene rearrangements. We used this system since it is of high clinical relevance and may be affected by very low amounts of contaminations. Spike-in contaminations are effectively blocked by the K-box even at high rates as demonstrated by ultra-deep sequencing of the amplicons. Thus, we recommend implementation of the K-box in two-step PCR- based NGS systems for research and diagnostic applications demanding high sensitivity and accuracy

Do humans and Convolutional Neural Networks attend to similar areas during scene classification: Effects of task and image type

Deep Learning models like Convolutional Neural Networks (CNN) are powerful image classifiers, but what factors determine whether they attend to similar image areas as humans do? While previous studies have focused on technological factors, little is known about the role of factors that affect human attention. In the present study, we investigated how the tasks used to elicit human attention maps interact with image characteristics in modulating the similarity between humans and CNN. We varied the intentionality of human tasks, ranging from spontaneous gaze during categorization over intentional gaze-pointing up to manual area selection. Moreover, we varied the type of image to be categorized, using either singular, salient objects, indoor scenes consisting of object arrangements, or landscapes without distinct objects defining the category. The human attention maps generated in this way were compared to the CNN attention maps revealed by explainable artificial intelligence (Grad-CAM). The influence of human tasks strongly depended on image type: For objects, human manual selection produced maps that were most similar to CNN, while the specific eye movement task has little impact. For indoor scenes, spontaneous gaze produced the least similarity, while for landscapes, similarity was equally low across all human tasks. To better understand these results, we also compared the different human attention maps to each other. Our results highlight the importance of taking human factors into account when comparing the attention of humans and CNN

The Addressee Types of the Internet Open Letters

The author considers open letters on Internet sites as a variation of an epistolary genre. A novel type of an open letter, a letter to the future is described. Computer mediated communication as a form of public discourse increases the number of recipients of the letters, introducing changes to the conventional model of a letter addressee. It is concluded that messages on the open letters sites, high in personalization (i.e. private) and low in exclusivity (i.e. public), allow bridging the gap between mass and personal communication, thus remediating an epistolary genre