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  • image/svg+xml art designer at PLoS, modified by Wikipedia users Nina, Beao, JakobVoss, and AnonMoos Open Access logo, converted into svg, designed by PLoS. This version with transparent background. http://commons.wikimedia.org/wiki/File:Open_Access_logo_PLoS_white.svg art designer at PLoS, modified by Wikipedia users Nina, Beao, JakobVoss, and AnonMoos http://www.plos.org/
    Authors: Tilly, Nora; Hoffmeister, Dirk; Aasen, Helge; Brands, Jonas; +1 Authors

    Research in the field of precision agriculture is becoming increasingly important due to the growing world population whilst area for cultivation remains constant or declines. In this context, methods of monitoring in?season plant development with high resolution and accuracy are necessary. Studies show that terrestrial laser scanning (TLS) can be applied to capture small objects like crops. In this contribution, the results of multi-temporal field campaigns with the terrestrial laser scanner Riegl LMS-Z420i are shown. Four surveys were carried out in the growing period 2012 on a field experiment where various barley varieties were cultivated in small-scale plots. In order to measure the plant height above ground, the TLS-derived point clouds are interpolated to generate Crop Surface Models with a very high resolution of 1 cm. For all campaigns, a common reference surface, representing the Digital Elevation Model was used to monitor plant height in the investigated period. Manual plant height measurements were carried out to verify the results. The very high coefficients of determination (R² = 0.89) between both measurement methods show the applicability of the approach presented. Furthermore, destructive biomass sampling was performed to investigate the relation to plant height. Biomass is an important parameter for evaluating the actual crop status, but non-destructive methods of directly measuring crop biomass do not exist. Hence, other parameters like reflectance are considered. The focus of this study is on non-destructive measurements of plant height. The high coefficients of determination between plant height and fresh as well as dry biomass (R² = 0.80, R² = 0.77) support the usability of plant height as a predictor. The study presented here demonstrates the applicability of TLS in monitoring plant height development with a very high spatial resolution. Proceedings of the Workshop on UAV-based Remote Sensing Methods for Monitoring Vegetation Kölner geographische Arbeiten, 94 ISSN:0454-1294

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    Research Collection
    Conference object . 2014
    License: CC BY
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    Conference object . 2014
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    Other literature type . 2014
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      Conference object . 2014
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  • image/svg+xml art designer at PLoS, modified by Wikipedia users Nina, Beao, JakobVoss, and AnonMoos Open Access logo, converted into svg, designed by PLoS. This version with transparent background. http://commons.wikimedia.org/wiki/File:Open_Access_logo_PLoS_white.svg art designer at PLoS, modified by Wikipedia users Nina, Beao, JakobVoss, and AnonMoos http://www.plos.org/
    Authors: Feurer, Thomas;

    Photovoltaic (PV) energy generation has become one of the key pillars of the shift to a renewable energy future. Current devices, under favorable conditions, can already undercut the price per kWh electricity of other technologies on the market. Further reduction in the cost of installed PV systems and increase in solar module conversion efficiency will improve the affordability even more and will substantially aid in wider market penetration and enhance the volume of PV installations. Currently the PV market is dominated by silicon wafer based solar cells, but alternative technologies offer some distinctive advantages, making them interesting for numerous applications. Thin film technologies, as for example based on Cu(In,Ga)Se2 (CIGS) compound semiconductors with high optical absorption coefficient, are becoming important due to lower material and energy requirements for processing of high conversion efficiency solar cells. Inherent advantages are large area depositions with low production costs, and the possibilities for construction of lightweight, flexible devices with roll-to-roll manufacturing processes. The highest efficiency of single-junction CIGS solar cells is approaching the thermodynamic limit, making the use of alternative concepts such as concentration or multijunction (tandem-) devices the next logical step for further increase in efficiency beyond the Shockley-Queisser limit (S-Q limit). Especially the multi-junction technology, in which the thermodynamic losses are reduced by stacking of solar cells with different band gaps, decreasing thermalization of charge carriers excited with energies above the band gap, is a promising approach for enhanced utilization of the solar spectrum, yielding improved efficiency. Such devices, based on epitaxial layers of III-V compounds have already demonstrated remarkably high efficiencies beyond the S-Q limit. However, these devices grown on rather expensive single crystal wafers and with small size are prohibitively pricey for low cost terrestrial solar electricity generation. On the other hand, multi-junction solar cell technology based on polycrystalline thin films is an attractive option for large area, low cost production, provided adequately high efficiencies are achieved. In this context, two-junction tandem devices, developed by stacking a semitransparent large band gap solar cell of 1.6-1.7 eV on top of a low band gap (~1.0 eV) bottom cell, is a viable option. Earlier attempts in this direction were not so successful, but with the rise of perovskite thin film solar cells as a compatible high efficiency wide band gap (>1.6 eV) top cell and CIGS with a tunable band gap as bottom cell, the prospect for all thin film tandem devices with efficiencies beyond the single-junction limitations has opened. Such all thin film devices hold the potential for the low cost production necessary for large scale terrestrial application. This thesis focuses on the development of high efficiency narrow bandgap (1.0 eV) CIGS solar cells for application in all thin film tandem devices. While for CIGS with band gap of around 1.15 eV efficiencies of over 23 % have been demonstrated, cells with a narrow band gap close to 1.0 eV only reach 15.0 %. The efficiency of these narrow band gap cells are limited by charge carrier recombination, leading to low open circuit voltage (VOC) and reduced fill factor. For solar cell efficiency enhancement it is necessary to investigate the underlying reasons contributing to the deficits in PV parameters and develop processes to overcome the limiting factors. An option to reduce recombination within the solar cell is the implementation of a band gap grading as discussed in Chapter 3. The increase of the band gap at the location of highest recombination leads to a reduction in diode current, and therefore an increase in VOC. To keep the band gap of 1.0 eV a substantial part of the absorber needs to be Ga free. As the primary source of recombination is not obvious, different gradings (realized by a change in the Ga to In ratio) are implemented and compared. A single grading with increased band gap (higher Ga/In ratio) towards the front of the absorber shows no significant improvement on photovoltaic parameters. Any gain in VOC is offset by losses in current due to reduced charge collection, mainly visible for long wavelength photons and probably a result of the upwards bending in the conduction band. A single backgrading (higher Ga/In ratio towards the back electric contact) on the other hand leads to substantial improvements in performance ( from 12.0 % to 16.1 %). It is shown that the collection of photo-generated charge carriers improves and recombination is reduced. Measurements of the effective lifetime by time resolved photo-luminescence are carried out, showing an increase from approximately 20 ns to 100 ns when comparing ungraded with back-graded absorbers. By selectively changing the recombination speed at the back contact, strong differences in the behavior of cells with and without a band gap widening towards the back are observed. The results support that considerable recombination at the back contact is present in pure CIS solar cells, and that the single Ga back-grading approach is effective at suppressing this loss channel. In Chapter 4 the alkali treatment of CIS based solar cells is investigated. Alkali elements are known to strongly influence doping and passivation in CIGS solar cells. It is shown that the amount of sodium necessary to reach sufficient doping levels for high performance CIS solar cells is not achieved using the processes developed for CIGS. This may be based on insufficient Na diffusion into the grain, as those cells generally show larger grains than their CIGS counter parts, and since alkali migration energies in CIS are reported to be higher compared to those in CGS. If CIS cells are grown on soda lime glass without any diffusion barrier and additionally receive post deposition treatment (PDT) with NaF they still show low apparent doping concentration and poor PV performance ( = 10.9 %). However, additional annealing at ~ 370 C substrate temperature after PDT is shown to solve this problem, leading to an increase in apparent doping levels close to 1016 cm−3 and cell efficiency of 15.0 %. The application of an additional heavy alkali PDT, specifically RbF, is shown to lead to further improvements in cell efficiency. Changes at the front interface due to the PDT allow a decrease of buffer layer thickness, leading to a higher photo current (approximately + 1.0 mAcm−2). In addition, reduced recombination and the resulting increase in lifetime leads to additional gains in VOC, resulting in considerably improved device performance, up to an efficiency of 18.0 %. Further efficiency improvement is achieved by investigating the effect of close to stoichiometric compositions of Cu to group III elements as described in Chapter 5. The sub-stoichiometric Cu composition of state-of-the-art CIGS absorbers leads to a high concentration of detrimental defects. The defect density within the absorbers is reduced by approaching a stoichiometric Cu composition. Improvements in the defect density are identified by the decrease of Urbach energy from 20 to 16 mV and an increase in doping is observed for cells with almost stoichiometric Cu content. Cells with high, and especially stoichiometric Cu composition tend to be limited by recombination at the front interface, leading to a decrease of VOC of about 20 mV. Using the modified absorber surface after heavy alkali PDT, these losses are suppressed. Based on these improvements, a narrow band gap cell with record breaking 19.2 % efficiency and an open circuit voltage of 609 mV is achieved. Throughout the whole thesis the suitability of these cells for tandem devices with semitransparent perovskite top cells is investigated by 4-terminal tandem measurements. The improvements achieved in this work led to CIS based solar cells that not only show outstanding single cell performance, but also enable highly efficient tandem devices up to 25.0 %. They outperform state-of-the-art single junction CIGS and perovskite cells while showing prospects for further efficiency improvement. Due to the low band gap of the CIS absorber the current density from the bottom cell is high enough to produce current matched tandem devices with high efficient perovskite top cells (19.2 to 18.6 mAcm−2 in 4-terminal configuration), and also monolithic two-terminal configurations are feasible in the future.

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    Doctoral thesis . 2019
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    Doctoral thesis . 2019
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      Doctoral thesis . 2019
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      Doctoral thesis . 2019
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  • image/svg+xml art designer at PLoS, modified by Wikipedia users Nina, Beao, JakobVoss, and AnonMoos Open Access logo, converted into svg, designed by PLoS. This version with transparent background. http://commons.wikimedia.org/wiki/File:Open_Access_logo_PLoS_white.svg art designer at PLoS, modified by Wikipedia users Nina, Beao, JakobVoss, and AnonMoos http://www.plos.org/
    Authors: Trivella, Alessio; id_orcid0000-0002-2614-5051; Corman, Francesco; id_orcid0000-0002-6036-5832;

    Abstract Book: 10th Symposium of the European Association for Research in Transport (hEART 2022)

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    Conference object . 2022
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    Authors: Scheidegger, Florian;

    ISBN:978-3-86628-689-4

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    Doctoral thesis . 2020
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    Doctoral thesis . 2020
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      Doctoral thesis . 2020
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    Authors: Avendaño Valencia, Luis David; id_orcid0000-0001-6889-9110; Abdallah, Imad; id_orcid0000-0001-8678-0965; Chatzi, Eleni; id_orcid0000-0002-6870-240X;

    Proceedings of the Joint ICVRAM ISUMA UNCERTAINTIES Conference ISBN:978-85-60064-77-9

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    Conference object . 2018
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  • Authors: Bataillard, Maxime;

    The rapid growth of clean technologies to address climate change has emphasized the increasing complexity of materials, some of which face criticality and potential supply disruptions. Inte- grated assessment models (IAMs) used for designing illustrative mitigation pathways (IMPs) lack comprehensive information on material annual demand projection. This study focuses on the demand for the rare earth element neodymium (Nd) until 2050 in wind power and transporta- tion sectors. The assessment is based on the three most ambitious IMPs, namely “Low Energy Demand” (LD), “Sustainability Pathways” (SP), and “Rapid Technology Change” (Ren), from the Intergovernmental Panel on Climate Change’s (IPCC) Assessment Report 6 (AR6). The results show that Nd demand steadily increases in all scenarios, but the magnitude and growth rates vary. The LD scenario exhibits the lowest material needs in passenger transport due to shared road transport and rail preferences, consequence of a focus on final energy use changes, while the SP scenario presents the highest growth in material demand. The Ren scenario, char- acterized by fast electrification and energy intensity improvements, represents a middle-ground scenario for material demand with good opportunities for recycling. This study underscores the significance of considering material demand in scenario design and highlights the importance of better assessing crucial external factors used for material stock determination in the future. The findings contribute to improving scenario design precision and the understanding of material use implications, providing valuable insights for climate policies and resource management strategies.

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    Authors: Marten, Ruby;

    Aerosols are an important part of the atmosphere, they are defined as liquid or solid particles suspended in air, ranging from one nanometer to tens of micrometers in diameter. Aerosols affect the climate directly, via aerosol radiation interactions, and indirectly, via aerosol-cloud interactions. While pollution in cities does not have the largest impact on global climate, it does affect local climate and weather. Aerosols can also be deadly; in 2019 lower respiratory infections were reported as the third leading cause of death globally, which are largely caused by aerosols. Since around 55% of the world’s population live in cities, it is important to understand the key drivers of urban aerosol formation and growth. Ammonium nitrate is an important component of aerosols, but not much is known about its contribution to aerosol formation and early growth. In this thesis, we aim to understand how nitric acid (HNO3) and ammonia (NH3) can impact aerosol formation in urban environments. Previous understanding of urban air conditions led to a puzzle of competing growth rates and loss rates, where it appeared that measured growth rates in cities were not high enough to explain the persistence of particle number concentrations in the face of high loss rates from coagulation with pre-existing large particles. Results from the CLOUD chamber at CERN presented in this thesis show a newly discovered mechanism of rapid growth by formation of ammonium nitrate onto pre-existing particles. We find that in situations of excess NH3 and HNO3, with respect to ammonium nitrate saturation ratios, particles can grow orders of magnitude faster than previously measured in ambient environments. Since this mechanism is consistent with the nano-Köhler theory, there is an activation diameter above which ammonium nitrate can form on the particles, and particles as small as a few nanometers can be affected. Furthermore, this mechanism was found to have a strong temperature dependence where at lower temperatures the same gas phase concentrations result in higher growth rates. At temperatures as low as −25°C, ammonia and nitric acid were found to be able to nucleate even in the absence of sulfuric acid or other known nucleating species. In order to determine whether these rapid growth rates are in fact high enough to overcome high coagulation loss rates, further experiments were undertaken at the CLOUD chamber at CERN at 5°C in the presence of a high condensation sink, analogous to haze. Experimental results showed that in experiments with higher NH3 and HNO3 concentrations, particle number concentrations were sustained with a steady formation of 2.5 nm particles. Newly formed particles are found to be effectively lost to the condensation sink, thus confirming that loss rates have not been over-estimated, and high growth rates are more likely to be the explanation for particle survival in haze conditions. Alongside experimental results, a kinetic model was developed which is capable of quantitatively reproducing growth from ammonium nitrate formation. We used this model to predict particle survival over a wide range of NH3 and HNO3 concentrations and condensation sinks. Results showed that survival of newly formed particles was drastically increased in the presence of supersaturated conditions of NH3 and HNO3.

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    Doctoral thesis . 2022
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      Doctoral thesis . 2022
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    Authors: Bader, Cédric;

    Organic soils develop under waterlogged conditions, leading to a reduced decomposition of biomass. Over the last millennia this led to the development of a large carbon (C) pool in the global C cycle. Drainage, necessary for agriculture and forestry, triggers rapid decomposition of soil organic matter (SOM). While undisturbed organic soils are C-sinks, drainage transforms them into C-sources. Climate, drainage depth and land-use are considered the main factors controlling SOM decomposition. However, there is still a large variation in decomposition rates among organic soils, even when climate, drainage and land-use conditions are similar. This thesis investigates the role of SOM composition on peat decomposability in a variety of differently managed drained organic soils. Peat samples from 21 organic soils managed as cropland, grassland and forest soils situated in Switzerland were incubated at 10 and 20 °C for more than 6 months. During incubation, we monitored CO2 emissions and related them to soil characteristics, including bulk density, soil pH, soil organic carbon (SOC) content, and elemental ratios (C/N, H/C and O/C). The incubated samples lost between 0.6 to 1.9% of their SOC at 10 °C and between 1.2 to 42% at 20 °C over the course of 10,000 h (>1 yr). This huge variation occurring under controlled conditions suggests that, besides drainage depth, climate and management, SOM composition is an underestimated factor that determines CO2 fluxes measured in field experiments. In contrast, correlations between the investigated soil characteristics and CO2 emissions were weak. Furthermore, there were no land-use effects. Such effects were expected based on the measured SOM characteristics and IPCC data. Temperature sensitivity of decomposition decreased with depth, indicating an enrichment of recalcitrant SOM in topsoils. This finding stands in contrast to findings in studies of undisturbed organic soils and Further it suggests that future C loss from agriculturally managed organic soils will be similar considering warmer climate conditions. Cultivation of organic soils is accompanied by inputs of young organic carbon (YOC) from plant residues. The amount of YOC inputs, their potential to compensate for oxidative peat loss as well as their lability are unknown. Studying the δ13C signatures in the topsoil of a managed organic soil revealed that at least 19 ± 2.4% of the SOC originate from YOC being accumulated recently. Yet, the accumulation rates are substantially smaller than average peat loss rates on the studied soils. Remarkably, the percentage of YOC in decomposing SOC was 53 ± 0.1%, indicating that YOC is more labile than bulk SOC. These findings are supported by the 14C age of emitted CO2 being younger than that of SOC. Inputs of fresh organic matter (FOM) to soil are known to induce priming effects, i.e. an altered decomposition of resident SOM. The effect of FOM addition on peat decomposition of agriculturally used organic soils has seldom been quantified experimentally. Therefore, we incubated soil samples from managed organic soils over three weeks with and without adding corn straw as FOM. The 13C and 14C signatures of SOC and emitted CO2 enabled us to apportion the amount of decomposed corn, as well as to estimate relative effects of corn addition on the decomposition of SOC from old peat and from YOC. FOM addition induced negative, positive and neutral priming of SOC decomposition. Further, the relative contribution of peat SOC to the overall CO2 release consistently decreased after FOM addition, suggesting that young and old C pools in managed organic soils respond differently to the addition of fresh plant residues. A combination of those two findings indicates that FOM addition can effectively reduce the decomposition of old peat. The results of this thesis suggest that agricultural use of organic soils has a tremendous effect on the composition and decomposability of SOC in organic soils. Furthermore, they show that also crop species known for their carbon sequestration potential are not likely to counteract peat losses caused by drainage. Therefore, agricultural management of organic soils without the risk of losing vast amounts of SOC seems unrealistic and thus, CO2 emissions from organic soils are not likely to decrease in the future. This means that they remain a big issue of concern for future generations in order to counteract climate change.

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    Doctoral thesis . 2017
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    Doctoral thesis . 2017
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      Doctoral thesis . 2017
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    Authors: Bianchi, Eva;

    Tree mortality is a key factor for understanding forest dynamics. So far, however, only few studies have focused on the mortality of tree regeneration. Thus, more research is needed in this context to better understand the underlying ecological processes and predict more reliably how forest ecosystems will respond to ongoing climate change. As the current and future changes are expected to either favor or impair the growth and survival of large trees, it is pivotal to investigate the effects on the next generation, i.e. young and small trees. A better understanding of tree regeneration allows to extend or adapt the findings from the already well-studied adult, large trees to small-sized trees, for which sparse empirical data are available. Particularly relevant questions relate to the drivers of survival probabilities and of horizontal spatial patterns (i.e. the distribution in space) of tree regeneration. The aims of this PhD thesis therefore were (i) to improve the understanding of natural mortality processes of tree regeneration at different developmental stages and spatio-temporal scales, (ii) to investigate the effect of various abiotic and biotic factors on the mortality of tree regeneration, and (iii) to study the relationship between mortality, growth and site conditions. For this purpose, I assessed 1) the effect of emergence time, height and number of leaves of seedlings, light availability, temperature, precipitation, seedbed and microsite conditions on the survival time of seedlings; 2) the effect of light availability on the growth of saplings and its relationship with mortality; and 3) the effect of topography and of large neighboring trees on the spatial pattern of living and dead small trees. These effects were investigated for small-sized trees (diameter at breast height < 10 cm) of both conifer and deciduous species at several study sites in Switzerland across elevational gradients that represent distinct climate regimes and growth conditions. In Chapter 1, I studied the effects of emergence time on the mortality of seedlings. The underlying rationale was that global warming is expected to advance the timing of germination, leading the seedlings to potentially experience more severe damage and mortality due to late frost events in spring. Thus, I monitored the emergence, characteristics, and survival of seedlings across ten tree species in temperate mixed deciduous forests around Zurich (Switzerland) over one and a half years. For each seedling, I recorded characteristics such as height, number of cotyledons and euphylls, cause and severity of possible damages, and extent of missing foliar tissue due to herbivory. Moreover, I documented the seedbed type of each seedling and that of the microsite at the plot level. For each plot, I also determined light availability using hemispherical canopy photographs, logged the temperature curve, and measured soil moisture. Based on the empirical data, I conducted a survival analysis using the Kaplan-Meier method to estimate survival curves and Cox’s proportional hazards model to assess the effects of the explanatory variables on survival time. I tested whether the timing of emergence represents a trade‐off for seedling survival between minimizing frost risk and maximizing the length of the growing period. Seedlings that emerged early faced a severe late frost event. Nevertheless, they benefited from the overall longer growing period, resulting in increased overall survival. Larger seedling height and higher number of leaves positively influenced survival. Seedlings growing on moss had higher survival compared to those growing on mineral soil, litter, or in herbaceous vegetation. Since almost two‐thirds of the monitored seedlings died during the first growing season and early-emerging seedlings were more likely to survive, this chapter highlights how the first months of life together with an early emergence time of seedlings are decisive for successful tree regeneration, which will ultimately have an impact on the future development of forest stands. In Chapter 2, I investigated whether radial and vertical growth rates are suitable indicators of impending mortality in young trees, as previous research on adult, large trees had suggested, and whether light availability and tree size have an influence on mortality probability. Thus, I sampled an equal number of living and dead saplings of four conifer species (Swiss stone pine, European larch, Norway spruce and silver fir) in nine mountain forests along an elevational gradient of the Swiss Alps. I performed a tree-ring analysis, calculated both radial and vertical growth rates and compared them between living and dead saplings based on tree-ring widths reconstructed from stem disks at multiple tree heights. I observed a divergent pattern in radial growth of living and dead saplings, with reduced growth of dead saplings starting several years prior to death, which emphasizes the importance of long-term predisposing factors for tree mortality. Then, I quantified the combined effects of light availability, growth and tree size on mortality, using species- and site-specific conditional logistic regression models, by previously matching living and dead saplings of similar ages. Light availability influenced positively the survival probabilities of conifer saplings in mountain forests, although the positive effect decreased with increasing elevation. Recent radial growth rate and diameter had only minor effects on sapling mortality. By highlighting the importance of long-term predisposing factors for the mortality of conifer saplings in mountain forests, this chapter extends well-established findings of the adult stage to the so far little investigated sapling stage. In Chapter 3, I analyzed the horizontal spatial patterns of small living and dead Norway spruce trees in two subalpine forest reserves of Switzerland, Scatlè and Bödmerenwald, by nearest neighbor-based and distance-based analyses. I accounted for spatial inhomogeneity by investigating how the local densities of living and dead small trees depend on environmental covariates. I found that the local density of living and dead small trees is influenced by latitude, elevation and aspect. Yet, the influence of these covariates varied between the two forest reserves due to their different topography and peculiar site conditions. Then, I considered neighborhood interactions between trees based on the vicinity and size of trees, by analyzing how small trees are influenced by large neighboring trees over a range of spatial scales. Both tree vicinity and size were important for the spatial patterns of small trees in both reserves. Small living trees showed a random pattern around large dead trees over a range of distances and, at certain distances in one reserve, even dispersion. Small living trees further showed clustering around large living trees at short distances and dispersion at large distances. Small dead trees featured mainly a random pattern, even though with a tendency to cluster at short distances around large neighbors, irrespective of whether these were living or dead. Yet, the fading of clustering with increasing distance indicates that the influence of large trees on small trees varies with the distance and thus that the neighborhood interactions between trees are scale-dependent. I further found that the influence of large neighboring trees on small trees varied with topography, revealing a relationship between spatial inhomogeneity and neighborhood interactions, as I expected due to the strongly different tree sizes and environmental gradients in mountain forests. Overall, this chapter emphasizes the importance of considering both spatial inhomogeneity and neighborhood interactions when investigating the spatial ecology of mortality of small-sized trees in uneven-aged and unmanaged mountain forests. Throughout this PhD thesis, I extended well-established ecological findings from the adult, large trees to the regeneration stage of trees, which is an important bottleneck of forest dynamics. The empirical findings of my PhD thesis represent a considerable contribution towards a better understanding of the temporal and spatial patterns of mortality in tree regeneration as well as of the relationship between mortality, growth and site conditions.

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    Doctoral thesis . 2020
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  • Authors: Dennis Eberli;

    Aimed at deepening the understanding of the effects of climate variability on cocoa pro-duction in West Africa, conditions between 1959 and 2015 are analyzed based on new data sets of meteorological records, soil water content and evapotranspiration. Comparing the relationship of actual and potential evapotranspiration across the region, differences be-tween cocoa producing countries are found and discussed, affirming that cocoa producing regions in Ghana and Nigeria are the most restricted by water availability. Further, us-ing a machine learning approach (Maxent) the optimal climatic conditions for successful cultivation are determined and used in a model to assess climatic suitability. It is shown, that the precipitation during the driest month of the year is the most specific predictor of production suitability. The model overall predicts the area suitable for cocoa production with high accuracy (AUC = 0.983). Applying the model to climatic data from past years the average suitability is calculated for every county and year. Comparing its yearly vari-ability with reported yield commonalities are observed, but farming practices are found to affect the recorded yield more significantly. Further, the suitability time series shows large areas in Nigeria, Liberia and along the northern borders of the cocoa producing area being vulnerable to prolonged poor weather conditions. These areas are expected to profit most from measures aimed at increasing climate resilience.

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    Authors: Tilly, Nora; Hoffmeister, Dirk; Aasen, Helge; Brands, Jonas; +1 Authors

    Research in the field of precision agriculture is becoming increasingly important due to the growing world population whilst area for cultivation remains constant or declines. In this context, methods of monitoring in?season plant development with high resolution and accuracy are necessary. Studies show that terrestrial laser scanning (TLS) can be applied to capture small objects like crops. In this contribution, the results of multi-temporal field campaigns with the terrestrial laser scanner Riegl LMS-Z420i are shown. Four surveys were carried out in the growing period 2012 on a field experiment where various barley varieties were cultivated in small-scale plots. In order to measure the plant height above ground, the TLS-derived point clouds are interpolated to generate Crop Surface Models with a very high resolution of 1 cm. For all campaigns, a common reference surface, representing the Digital Elevation Model was used to monitor plant height in the investigated period. Manual plant height measurements were carried out to verify the results. The very high coefficients of determination (R² = 0.89) between both measurement methods show the applicability of the approach presented. Furthermore, destructive biomass sampling was performed to investigate the relation to plant height. Biomass is an important parameter for evaluating the actual crop status, but non-destructive methods of directly measuring crop biomass do not exist. Hence, other parameters like reflectance are considered. The focus of this study is on non-destructive measurements of plant height. The high coefficients of determination between plant height and fresh as well as dry biomass (R² = 0.80, R² = 0.77) support the usability of plant height as a predictor. The study presented here demonstrates the applicability of TLS in monitoring plant height development with a very high spatial resolution. Proceedings of the Workshop on UAV-based Remote Sensing Methods for Monitoring Vegetation Kölner geographische Arbeiten, 94 ISSN:0454-1294

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    Conference object . 2014
    License: CC BY
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    Conference object . 2014
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    Other literature type . 2014
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      Other literature type . 2014
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  • image/svg+xml art designer at PLoS, modified by Wikipedia users Nina, Beao, JakobVoss, and AnonMoos Open Access logo, converted into svg, designed by PLoS. This version with transparent background. http://commons.wikimedia.org/wiki/File:Open_Access_logo_PLoS_white.svg art designer at PLoS, modified by Wikipedia users Nina, Beao, JakobVoss, and AnonMoos http://www.plos.org/
    Authors: Feurer, Thomas;

    Photovoltaic (PV) energy generation has become one of the key pillars of the shift to a renewable energy future. Current devices, under favorable conditions, can already undercut the price per kWh electricity of other technologies on the market. Further reduction in the cost of installed PV systems and increase in solar module conversion efficiency will improve the affordability even more and will substantially aid in wider market penetration and enhance the volume of PV installations. Currently the PV market is dominated by silicon wafer based solar cells, but alternative technologies offer some distinctive advantages, making them interesting for numerous applications. Thin film technologies, as for example based on Cu(In,Ga)Se2 (CIGS) compound semiconductors with high optical absorption coefficient, are becoming important due to lower material and energy requirements for processing of high conversion efficiency solar cells. Inherent advantages are large area depositions with low production costs, and the possibilities for construction of lightweight, flexible devices with roll-to-roll manufacturing processes. The highest efficiency of single-junction CIGS solar cells is approaching the thermodynamic limit, making the use of alternative concepts such as concentration or multijunction (tandem-) devices the next logical step for further increase in efficiency beyond the Shockley-Queisser limit (S-Q limit). Especially the multi-junction technology, in which the thermodynamic losses are reduced by stacking of solar cells with different band gaps, decreasing thermalization of charge carriers excited with energies above the band gap, is a promising approach for enhanced utilization of the solar spectrum, yielding improved efficiency. Such devices, based on epitaxial layers of III-V compounds have already demonstrated remarkably high efficiencies beyond the S-Q limit. However, these devices grown on rather expensive single crystal wafers and with small size are prohibitively pricey for low cost terrestrial solar electricity generation. On the other hand, multi-junction solar cell technology based on polycrystalline thin films is an attractive option for large area, low cost production, provided adequately high efficiencies are achieved. In this context, two-junction tandem devices, developed by stacking a semitransparent large band gap solar cell of 1.6-1.7 eV on top of a low band gap (~1.0 eV) bottom cell, is a viable option. Earlier attempts in this direction were not so successful, but with the rise of perovskite thin film solar cells as a compatible high efficiency wide band gap (>1.6 eV) top cell and CIGS with a tunable band gap as bottom cell, the prospect for all thin film tandem devices with efficiencies beyond the single-junction limitations has opened. Such all thin film devices hold the potential for the low cost production necessary for large scale terrestrial application. This thesis focuses on the development of high efficiency narrow bandgap (1.0 eV) CIGS solar cells for application in all thin film tandem devices. While for CIGS with band gap of around 1.15 eV efficiencies of over 23 % have been demonstrated, cells with a narrow band gap close to 1.0 eV only reach 15.0 %. The efficiency of these narrow band gap cells are limited by charge carrier recombination, leading to low open circuit voltage (VOC) and reduced fill factor. For solar cell efficiency enhancement it is necessary to investigate the underlying reasons contributing to the deficits in PV parameters and develop processes to overcome the limiting factors. An option to reduce recombination within the solar cell is the implementation of a band gap grading as discussed in Chapter 3. The increase of the band gap at the location of highest recombination leads to a reduction in diode current, and therefore an increase in VOC. To keep the band gap of 1.0 eV a substantial part of the absorber needs to be Ga free. As the primary source of recombination is not obvious, different gradings (realized by a change in the Ga to In ratio) are implemented and compared. A single grading with increased band gap (higher Ga/In ratio) towards the front of the absorber shows no significant improvement on photovoltaic parameters. Any gain in VOC is offset by losses in current due to reduced charge collection, mainly visible for long wavelength photons and probably a result of the upwards bending in the conduction band. A single backgrading (higher Ga/In ratio towards the back electric contact) on the other hand leads to substantial improvements in performance ( from 12.0 % to 16.1 %). It is shown that the collection of photo-generated charge carriers improves and recombination is reduced. Measurements of the effective lifetime by time resolved photo-luminescence are carried out, showing an increase from approximately 20 ns to 100 ns when comparing ungraded with back-graded absorbers. By selectively changing the recombination speed at the back contact, strong differences in the behavior of cells with and without a band gap widening towards the back are observed. The results support that considerable recombination at the back contact is present in pure CIS solar cells, and that the single Ga back-grading approach is effective at suppressing this loss channel. In Chapter 4 the alkali treatment of CIS based solar cells is investigated. Alkali elements are known to strongly influence doping and passivation in CIGS solar cells. It is shown that the amount of sodium necessary to reach sufficient doping levels for high performance CIS solar cells is not achieved using the processes developed for CIGS. This may be based on insufficient Na diffusion into the grain, as those cells generally show larger grains than their CIGS counter parts, and since alkali migration energies in CIS are reported to be higher compared to those in CGS. If CIS cells are grown on soda lime glass without any diffusion barrier and additionally receive post deposition treatment (PDT) with NaF they still show low apparent doping concentration and poor PV performance ( = 10.9 %). However, additional annealing at ~ 370 C substrate temperature after PDT is shown to solve this problem, leading to an increase in apparent doping levels close to 1016 cm−3 and cell efficiency of 15.0 %. The application of an additional heavy alkali PDT, specifically RbF, is shown to lead to further improvements in cell efficiency. Changes at the front interface due to the PDT allow a decrease of buffer layer thickness, leading to a higher photo current (approximately + 1.0 mAcm−2). In addition, reduced recombination and the resulting increase in lifetime leads to additional gains in VOC, resulting in considerably improved device performance, up to an efficiency of 18.0 %. Further efficiency improvement is achieved by investigating the effect of close to stoichiometric compositions of Cu to group III elements as described in Chapter 5. The sub-stoichiometric Cu composition of state-of-the-art CIGS absorbers leads to a high concentration of detrimental defects. The defect density within the absorbers is reduced by approaching a stoichiometric Cu composition. Improvements in the defect density are identified by the decrease of Urbach energy from 20 to 16 mV and an increase in doping is observed for cells with almost stoichiometric Cu content. Cells with high, and especially stoichiometric Cu composition tend to be limited by recombination at the front interface, leading to a decrease of VOC of about 20 mV. Using the modified absorber surface after heavy alkali PDT, these losses are suppressed. Based on these improvements, a narrow band gap cell with record breaking 19.2 % efficiency and an open circuit voltage of 609 mV is achieved. Throughout the whole thesis the suitability of these cells for tandem devices with semitransparent perovskite top cells is investigated by 4-terminal tandem measurements. The improvements achieved in this work led to CIS based solar cells that not only show outstanding single cell performance, but also enable highly efficient tandem devices up to 25.0 %. They outperform state-of-the-art single junction CIGS and perovskite cells while showing prospects for further efficiency improvement. Due to the low band gap of the CIS absorber the current density from the bottom cell is high enough to produce current matched tandem devices with high efficient perovskite top cells (19.2 to 18.6 mAcm−2 in 4-terminal configuration), and also monolithic two-terminal configurations are feasible in the future.

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    Authors: Trivella, Alessio; id_orcid0000-0002-2614-5051; Corman, Francesco; id_orcid0000-0002-6036-5832;

    Abstract Book: 10th Symposium of the European Association for Research in Transport (hEART 2022)

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    Authors: Scheidegger, Florian;

    ISBN:978-3-86628-689-4

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    Authors: Avendaño Valencia, Luis David; id_orcid0000-0001-6889-9110; Abdallah, Imad; id_orcid0000-0001-8678-0965; Chatzi, Eleni; id_orcid0000-0002-6870-240X;

    Proceedings of the Joint ICVRAM ISUMA UNCERTAINTIES Conference ISBN:978-85-60064-77-9

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  • Authors: Bataillard, Maxime;

    The rapid growth of clean technologies to address climate change has emphasized the increasing complexity of materials, some of which face criticality and potential supply disruptions. Inte- grated assessment models (IAMs) used for designing illustrative mitigation pathways (IMPs) lack comprehensive information on material annual demand projection. This study focuses on the demand for the rare earth element neodymium (Nd) until 2050 in wind power and transporta- tion sectors. The assessment is based on the three most ambitious IMPs, namely “Low Energy Demand” (LD), “Sustainability Pathways” (SP), and “Rapid Technology Change” (Ren), from the Intergovernmental Panel on Climate Change’s (IPCC) Assessment Report 6 (AR6). The results show that Nd demand steadily increases in all scenarios, but the magnitude and growth rates vary. The LD scenario exhibits the lowest material needs in passenger transport due to shared road transport and rail preferences, consequence of a focus on final energy use changes, while the SP scenario presents the highest growth in material demand. The Ren scenario, char- acterized by fast electrification and energy intensity improvements, represents a middle-ground scenario for material demand with good opportunities for recycling. This study underscores the significance of considering material demand in scenario design and highlights the importance of better assessing crucial external factors used for material stock determination in the future. The findings contribute to improving scenario design precision and the understanding of material use implications, providing valuable insights for climate policies and resource management strategies.

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    Authors: Marten, Ruby;

    Aerosols are an important part of the atmosphere, they are defined as liquid or solid particles suspended in air, ranging from one nanometer to tens of micrometers in diameter. Aerosols affect the climate directly, via aerosol radiation interactions, and indirectly, via aerosol-cloud interactions. While pollution in cities does not have the largest impact on global climate, it does affect local climate and weather. Aerosols can also be deadly; in 2019 lower respiratory infections were reported as the third leading cause of death globally, which are largely caused by aerosols. Since around 55% of the world’s population live in cities, it is important to understand the key drivers of urban aerosol formation and growth. Ammonium nitrate is an important component of aerosols, but not much is known about its contribution to aerosol formation and early growth. In this thesis, we aim to understand how nitric acid (HNO3) and ammonia (NH3) can impact aerosol formation in urban environments. Previous understanding of urban air conditions led to a puzzle of competing growth rates and loss rates, where it appeared that measured growth rates in cities were not high enough to explain the persistence of particle number concentrations in the face of high loss rates from coagulation with pre-existing large particles. Results from the CLOUD chamber at CERN presented in this thesis show a newly discovered mechanism of rapid growth by formation of ammonium nitrate onto pre-existing particles. We find that in situations of excess NH3 and HNO3, with respect to ammonium nitrate saturation ratios, particles can grow orders of magnitude faster than previously measured in ambient environments. Since this mechanism is consistent with the nano-Köhler theory, there is an activation diameter above which ammonium nitrate can form on the particles, and particles as small as a few nanometers can be affected. Furthermore, this mechanism was found to have a strong temperature dependence where at lower temperatures the same gas phase concentrations result in higher growth rates. At temperatures as low as −25°C, ammonia and nitric acid were found to be able to nucleate even in the absence of sulfuric acid or other known nucleating species. In order to determine whether these rapid growth rates are in fact high enough to overcome high coagulation loss rates, further experiments were undertaken at the CLOUD chamber at CERN at 5°C in the presence of a high condensation sink, analogous to haze. Experimental results showed that in experiments with higher NH3 and HNO3 concentrations, particle number concentrations were sustained with a steady formation of 2.5 nm particles. Newly formed particles are found to be effectively lost to the condensation sink, thus confirming that loss rates have not been over-estimated, and high growth rates are more likely to be the explanation for particle survival in haze conditions. Alongside experimental results, a kinetic model was developed which is capable of quantitatively reproducing growth from ammonium nitrate formation. We used this model to predict particle survival over a wide range of NH3 and HNO3 concentrations and condensation sinks. Results showed that survival of newly formed particles was drastically increased in the presence of supersaturated conditions of NH3 and HNO3.

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    Authors: Bader, Cédric;

    Organic soils develop under waterlogged conditions, leading to a reduced decomposition of biomass. Over the last millennia this led to the development of a large carbon (C) pool in the global C cycle. Drainage, necessary for agriculture and forestry, triggers rapid decomposition of soil organic matter (SOM). While undisturbed organic soils are C-sinks, drainage transforms them into C-sources. Climate, drainage depth and land-use are considered the main factors controlling SOM decomposition. However, there is still a large variation in decomposition rates among organic soils, even when climate, drainage and land-use conditions are similar. This thesis investigates the role of SOM composition on peat decomposability in a variety of differently managed drained organic soils. Peat samples from 21 organic soils managed as cropland, grassland and forest soils situated in Switzerland were incubated at 10 and 20 °C for more than 6 months. During incubation, we monitored CO2 emissions and related them to soil characteristics, including bulk density, soil pH, soil organic carbon (SOC) content, and elemental ratios (C/N, H/C and O/C). The incubated samples lost between 0.6 to 1.9% of their SOC at 10 °C and between 1.2 to 42% at 20 °C over the course of 10,000 h (>1 yr). This huge variation occurring under controlled conditions suggests that, besides drainage depth, climate and management, SOM composition is an underestimated factor that determines CO2 fluxes measured in field experiments. In contrast, correlations between the investigated soil characteristics and CO2 emissions were weak. Furthermore, there were no land-use effects. Such effects were expected based on the measured SOM characteristics and IPCC data. Temperature sensitivity of decomposition decreased with depth, indicating an enrichment of recalcitrant SOM in topsoils. This finding stands in contrast to findings in studies of undisturbed organic soils and Further it suggests that future C loss from agriculturally managed organic soils will be similar considering warmer climate conditions. Cultivation of organic soils is accompanied by inputs of young organic carbon (YOC) from plant residues. The amount of YOC inputs, their potential to compensate for oxidative peat loss as well as their lability are unknown. Studying the δ13C signatures in the topsoil of a managed organic soil revealed that at least 19 ± 2.4% of the SOC originate from YOC being accumulated recently. Yet, the accumulation rates are substantially smaller than average peat loss rates on the studied soils. Remarkably, the percentage of YOC in decomposing SOC was 53 ± 0.1%, indicating that YOC is more labile than bulk SOC. These findings are supported by the 14C age of emitted CO2 being younger than that of SOC. Inputs of fresh organic matter (FOM) to soil are known to induce priming effects, i.e. an altered decomposition of resident SOM. The effect of FOM addition on peat decomposition of agriculturally used organic soils has seldom been quantified experimentally. Therefore, we incubated soil samples from managed organic soils over three weeks with and without adding corn straw as FOM. The 13C and 14C signatures of SOC and emitted CO2 enabled us to apportion the amount of decomposed corn, as well as to estimate relative effects of corn addition on the decomposition of SOC from old peat and from YOC. FOM addition induced negative, positive and neutral priming of SOC decomposition. Further, the relative contribution of peat SOC to the overall CO2 release consistently decreased after FOM addition, suggesting that young and old C pools in managed organic soils respond differently to the addition of fresh plant residues. A combination of those two findings indicates that FOM addition can effectively reduce the decomposition of old peat. The results of this thesis suggest that agricultural use of organic soils has a tremendous effect on the composition and decomposability of SOC in organic soils. Furthermore, they show that also crop species known for their carbon sequestration potential are not likely to counteract peat losses caused by drainage. Therefore, agricultural management of organic soils without the risk of losing vast amounts of SOC seems unrealistic and thus, CO2 emissions from organic soils are not likely to decrease in the future. This means that they remain a big issue of concern for future generations in order to counteract climate change.

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    Authors: Bianchi, Eva;

    Tree mortality is a key factor for understanding forest dynamics. So far, however, only few studies have focused on the mortality of tree regeneration. Thus, more research is needed in this context to better understand the underlying ecological processes and predict more reliably how forest ecosystems will respond to ongoing climate change. As the current and future changes are expected to either favor or impair the growth and survival of large trees, it is pivotal to investigate the effects on the next generation, i.e. young and small trees. A better understanding of tree regeneration allows to extend or adapt the findings from the already well-studied adult, large trees to small-sized trees, for which sparse empirical data are available. Particularly relevant questions relate to the drivers of survival probabilities and of horizontal spatial patterns (i.e. the distribution in space) of tree regeneration. The aims of this PhD thesis therefore were (i) to improve the understanding of natural mortality processes of tree regeneration at different developmental stages and spatio-temporal scales, (ii) to investigate the effect of various abiotic and biotic factors on the mortality of tree regeneration, and (iii) to study the relationship between mortality, growth and site conditions. For this purpose, I assessed 1) the effect of emergence time, height and number of leaves of seedlings, light availability, temperature, precipitation, seedbed and microsite conditions on the survival time of seedlings; 2) the effect of light availability on the growth of saplings and its relationship with mortality; and 3) the effect of topography and of large neighboring trees on the spatial pattern of living and dead small trees. These effects were investigated for small-sized trees (diameter at breast height < 10 cm) of both conifer and deciduous species at several study sites in Switzerland across elevational gradients that represent distinct climate regimes and growth conditions. In Chapter 1, I studied the effects of emergence time on the mortality of seedlings. The underlying rationale was that global warming is expected to advance the timing of germination, leading the seedlings to potentially experience more severe damage and mortality due to late frost events in spring. Thus, I monitored the emergence, characteristics, and survival of seedlings across ten tree species in temperate mixed deciduous forests around Zurich (Switzerland) over one and a half years. For each seedling, I recorded characteristics such as height, number of cotyledons and euphylls, cause and severity of possible damages, and extent of missing foliar tissue due to herbivory. Moreover, I documented the seedbed type of each seedling and that of the microsite at the plot level. For each plot, I also determined light availability using hemispherical canopy photographs, logged the temperature curve, and measured soil moisture. Based on the empirical data, I conducted a survival analysis using the Kaplan-Meier method to estimate survival curves and Cox’s proportional hazards model to assess the effects of the explanatory variables on survival time. I tested whether the timing of emergence represents a trade‐off for seedling survival between minimizing frost risk and maximizing the length of the growing period. Seedlings that emerged early faced a severe late frost event. Nevertheless, they benefited from the overall longer growing period, resulting in increased overall survival. Larger seedling height and higher number of leaves positively influenced survival. Seedlings growing on moss had higher survival compared to those growing on mineral soil, litter, or in herbaceous vegetation. Since almost two‐thirds of the monitored seedlings died during the first growing season and early-emerging seedlings were more likely to survive, this chapter highlights how the first months of life together with an early emergence time of seedlings are decisive for successful tree regeneration, which will ultimately have an impact on the future development of forest stands. In Chapter 2, I investigated whether radial and vertical growth rates are suitable indicators of impending mortality in young trees, as previous research on adult, large trees had suggested, and whether light availability and tree size have an influence on mortality probability. Thus, I sampled an equal number of living and dead saplings of four conifer species (Swiss stone pine, European larch, Norway spruce and silver fir) in nine mountain forests along an elevational gradient of the Swiss Alps. I performed a tree-ring analysis, calculated both radial and vertical growth rates and compared them between living and dead saplings based on tree-ring widths reconstructed from stem disks at multiple tree heights. I observed a divergent pattern in radial growth of living and dead saplings, with reduced growth of dead saplings starting several years prior to death, which emphasizes the importance of long-term predisposing factors for tree mortality. Then, I quantified the combined effects of light availability, growth and tree size on mortality, using species- and site-specific conditional logistic regression models, by previously matching living and dead saplings of similar ages. Light availability influenced positively the survival probabilities of conifer saplings in mountain forests, although the positive effect decreased with increasing elevation. Recent radial growth rate and diameter had only minor effects on sapling mortality. By highlighting the importance of long-term predisposing factors for the mortality of conifer saplings in mountain forests, this chapter extends well-established findings of the adult stage to the so far little investigated sapling stage. In Chapter 3, I analyzed the horizontal spatial patterns of small living and dead Norway spruce trees in two subalpine forest reserves of Switzerland, Scatlè and Bödmerenwald, by nearest neighbor-based and distance-based analyses. I accounted for spatial inhomogeneity by investigating how the local densities of living and dead small trees depend on environmental covariates. I found that the local density of living and dead small trees is influenced by latitude, elevation and aspect. Yet, the influence of these covariates varied between the two forest reserves due to their different topography and peculiar site conditions. Then, I considered neighborhood interactions between trees based on the vicinity and size of trees, by analyzing how small trees are influenced by large neighboring trees over a range of spatial scales. Both tree vicinity and size were important for the spatial patterns of small trees in both reserves. Small living trees showed a random pattern around large dead trees over a range of distances and, at certain distances in one reserve, even dispersion. Small living trees further showed clustering around large living trees at short distances and dispersion at large distances. Small dead trees featured mainly a random pattern, even though with a tendency to cluster at short distances around large neighbors, irrespective of whether these were living or dead. Yet, the fading of clustering with increasing distance indicates that the influence of large trees on small trees varies with the distance and thus that the neighborhood interactions between trees are scale-dependent. I further found that the influence of large neighboring trees on small trees varied with topography, revealing a relationship between spatial inhomogeneity and neighborhood interactions, as I expected due to the strongly different tree sizes and environmental gradients in mountain forests. Overall, this chapter emphasizes the importance of considering both spatial inhomogeneity and neighborhood interactions when investigating the spatial ecology of mortality of small-sized trees in uneven-aged and unmanaged mountain forests. Throughout this PhD thesis, I extended well-established ecological findings from the adult, large trees to the regeneration stage of trees, which is an important bottleneck of forest dynamics. The empirical findings of my PhD thesis represent a considerable contribution towards a better understanding of the temporal and spatial patterns of mortality in tree regeneration as well as of the relationship between mortality, growth and site conditions.

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  • Authors: Dennis Eberli;

    Aimed at deepening the understanding of the effects of climate variability on cocoa pro-duction in West Africa, conditions between 1959 and 2015 are analyzed based on new data sets of meteorological records, soil water content and evapotranspiration. Comparing the relationship of actual and potential evapotranspiration across the region, differences be-tween cocoa producing countries are found and discussed, affirming that cocoa producing regions in Ghana and Nigeria are the most restricted by water availability. Further, us-ing a machine learning approach (Maxent) the optimal climatic conditions for successful cultivation are determined and used in a model to assess climatic suitability. It is shown, that the precipitation during the driest month of the year is the most specific predictor of production suitability. The model overall predicts the area suitable for cocoa production with high accuracy (AUC = 0.983). Applying the model to climatic data from past years the average suitability is calculated for every county and year. Comparing its yearly vari-ability with reported yield commonalities are observed, but farming practices are found to affect the recorded yield more significantly. Further, the suitability time series shows large areas in Nigeria, Liberia and along the northern borders of the cocoa producing area being vulnerable to prolonged poor weather conditions. These areas are expected to profit most from measures aimed at increasing climate resilience.

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