Nowadays global companies view the world as a single entity, sourcing materials fromanywhere and performing operations to create the optimal supply chain for their products.This leads to an increasing complexity which is driving supply management to becomea core capability of businesses. As supply chains are inherently vulnerable to disturbances,supply management will have to play a key role in the field of risk analysisand risk management. An increased awareness of sources of disturbances is essential tocreate significant improvements in the handling and prevention of disturbances.The purpose of this thesis is to identify and classify sources of disturbance which canhave a negative influence on a company’s supply management. This is achieved by theinvestigation of theories available in literature, as well as identifying and analyzing thedisturbances in the supply management of an international manufacturing company.Additionally, the theories on disturbance management are reviewed to create a foundationfor managerial implications.The company studied is Husqvarna, which currently is in a situation with several disturbancesin its supply management. The performed case study aims at both, describingthese phenomena, as well as testing of the theories. The chosen qualitative approachmakes it possible to gain in-depth knowledge and investigate different aspects ofsources of disturbances in this case study. The interviews performed are standardizedopen ended questionnaires in order to get in-depth knowledge of the situation.The empirical findings are then analyzed in regard to the purpose of the thesis. The goalof this analysis is to compare the sources of disturbances of the classification schemecreated in the literature review to the respondents’ answers from the interviews. Moreover,inputs and opinions from the respondents on how to manage disturbances are connectedwith the theories provided in the literature review within this field.Various sources of disturbance with a negative influence on the supply management ofcompanies are identified. It was also possible to compare the classification schemewhich was created based on the theoretical findings with the finding of the case study ofHusqvarna. Consequently a holistic overview of potential and actual sources of disturbancein supply management has been created. Furthermore, it is possible to contribute tothe body of knowledge on how to manage disturbances in supply management. Theprovided insights highlight implications that can help companies to successfully managedisturbances and hence improve their performance.

In this study, I attempted to evaluate the impact of two forest disturbances on the soil temperature and humidity in spruce forest. The spruce forests were attacked by bark beetle in the Březník area 17 years ago. Two types of management were applied after the bark beetle attack. The first approach was clear cutting and removing dead trees. The second approach was non-interventional and this zone was left to natural succession. This study compares differences in daily temperature amplitude and volumetric soil humidity between both types of management. I tried to evaluate whether the soil temperature and humidity conditions are explained more by influence of the management or by vegetation cover. Results showed significant difference in daily temperature amplitudes. Temperature amplitudes are about 49 % higher in clear cut areas than in areas with natural succession. Differences are insignificant in soil humidity conditions. The influence of the vegetation on soil temperature and humidity is insignificant. I, too, compared soil temperature and humidity from Březník areas (17 years after disturbance) and Prameny Vltavy areas where the spruce forest decayed recently.

Numerous studies have focused on the drivers of diversity and stability of communities, especially under global change. However, multi-dimensionality of ecosystems due to biotic components (e.g predation, competition and adaptive dynamics) and abiotic factors (e.g. disturbances, resource dynamics and their distinct attributes) cause context-dependent outcomes and challenge the predictions. There are still controversies around complex community dynamics under varying regimes, however, finding mechanistical explanations will illuminate the fate of multispecies assemblages. Using model microbial communities, consisting of bacterial prey and protist predator, combined with simulation modelling and advanced statistics, this thesis investigated the impact of imposed disturbances (i.e. increased dilution rates that simulate density-independent mortality as press or pulse disturbances) (i) on transient recovery dynamics of a simple microbial food web, and (ii) on bacterial abundance, diversity and community structure in the absence or presence of a protist predator. In addition, this thesis questioned the impacts of species interactions and rapid trait shifts, as a response to predation and competition, on the community dynamics and stability. Our results revealed that the predator suffered more from disturbances over longer time periods. Reduced predation pressure caused a transient phase of prey release during and even after disturbances. Recovery time depended on the strength and duration of disturbances, however, coupling to an alternative resource increased the chance of fast recovery and stabilized the communities. In multi-species prey communities, bacterial abundance, diversity, and community composition were more affected by predation than by the disturbances and resource dynamics. Predator abundance, on the other hand, was strongly affected by the type of disturbance imposed. Importantly, community attributes had differential sensitivities, as reflected by their different response and recovery dynamics. Prey community dynamics varied more temporally andwere less stable under predation stress, while prey diversity increased significantly. Predation rapidly induced anti-predation traits, which altered population dynamics of both prey and predator. More importantly, predator and the resistant prey, in turn, elevated the number of direct cause-effect relationships between the community members. Our findings are not limited to the studied system and can be used to understand the dynamic response and recovery potential of many natural predator-prey or host-pathogen systems. They can be used as a base for future studies to illuminate the debates on the future communities.:Summary Zusammenfassung 1 Scope and Outline 2 General Introduction 2.1 Context dependency of community dynamics 2.2 Ecological disturbances 2.2.1 Transient dynamics and stability 2.2.2 Catastrophic shifts 2.3 Species interactions and evolutionary dynamics under environmental change 2.3.1 Species interactions and coexistence 2.4 Eco-evolutionary dynamics 2.5 Community assembly mechanisms 2.6 Dealing with complexities 2.6.1 Microbial model systems as a tool in ecology 2.6.2 Correlation, causation and the future of predictions 2.7 Aims of this study 3 Community Dynamics under Disturbances 3.1 Transient recovery dynamics of a predator-prey system 4 Interactions of Community Drivers 4.1 Interactions between predation and disturbances shape prey communities 5 Species Interactions and Evolutionary Dynamics Shaping Communities 5.1 Summary 5.2 Introduction 5.2.1 Predator-Prey Dynamics and Community Stability 5.2.2 Causal inferences 5.3 Aim of the study 5.4 Methods 5.4.1 Organisms 5.4.2 Microcosm experiments and estimation of species abundances 5.4.3 Statistical analysis 5.5 Results 5.5.1 Community dynamics 5.5.2 Dynamics of prey diversity and community stability 5.5.3 Causal links between the species dynamics 5.6 Discussion 5.7 Synopsis 6 General Discussion 6.1 Communities under disturbances: Predator{ prey dynamics 6.2 Temporal species dynamics and community assembly Synthesis and Outlook 7.1 Increasing complexity of species interactions 7.2 Going further from causal links 7.3 Metacommunities References 8 Appendix 8.1 Declaration of the authorship 8.2 Author contributions of published articles 8.3 List of publications and conference contributions 8.4 Acknowledgments 8.5 Supplementary material for Chapter 3 8.6 Supplementary material for Chapter 4 8.7 Supplementary material for Chapter 5

Disturbance is fundamental to forest ecosystem function and overall health, but climate change is likely to increase both disturbance frequency and intensity in the future. Forests subject to increasingly frequent and intense disturbances are more likely to experience compounding disturbance effects. Compounding disturbances may exert unpredicted, non-additive stresses on ecosystems, leading to novel conditions that may exceed the capacity for local species to survive and regenerate. I further hypothesize that compounding disturbances could create conditions misaligned with species’ adaptations by altering physical and chemical growing conditions in forest soils, affecting forest composition, structure, and, subsequently, function for many years following disturbance. A better understanding of these remnant effects will be essential to managing and conserving coast redwood forests, which are projected to see increased frequency of fire under future climate scenarios. My objectives in this study were to quantify the effects of time-since-fire and single vs. compounding disturbances on coast redwood forest structure, composition, and regeneration dynamics and to evaluate the effects of abiotic soil qualities on post-fire regeneration. I mapped and sampled coast redwood forests burned in 1985, both 1985 and 1999, 2008, and 2013; modeled regeneration as a function of burn history, understory light, and post-fire nutrient levels; and tested redwood seed regeneration in post-fire soils in a greenhouse experiment. Forest structure, composition, and regeneration following compounding disturbance were most similar to the homogenous, redwood-dominated forest of the recent 2013 burn. There were no unique effects of compounding disturbance on soil nutrient levels, although variations in nutrient levels generally followed patterns seen in previous studies. Soil nitrate was positively associated with coast redwood regeneration levels, showing that soil nutrients may be influential in regeneration processes following disturbance. Time since burn and single burn histories were negatively associated with regeneration levels in the field, and there were no differences in seed germination in the greenhouse between soils from different fire histories. Increases in coast redwood forest dominance accompanied declines in bay laurel and tanoak presence, indicating a shift in post-fire forest structure and composition resulting from compounding disturbance. These results illustrate a complex relationship between regeneration dynamics, post-fire soil quality, and disturbance histories. Forest homogenization from compounding disturbances may have negative implications for ecosystem services and overall function if compounding disturbances are more frequent as predicted under future climate conditions.

The spatial and population dynamics of avian scavengers are poorly understood. This information is key for management and conservation interventions that guarantee long-term species conservation. My goal in this dissertation is to fill information gaps on the movement ecology of New World vultures using the Turkey Vulture (Cathartes aura) as a model species. I used a continental-wide satellite telemetry dataset to study the migration ecology, space-use, and demography of the three North American breeding populations of Turkey Vultures wintering in the Neotropics during a 17-year period. I found that primary productivity, but not weather, triggered Turkey Vulture migratory behavior, migration initiated when primary productivity dropped at the end of the breeding and non-breeding season. Migratory connectivity was high at the species level (0.85, 95% CI: 0.74–0.94). However, I found evidence of intrapopulation segregation during the non-breeding season demonstrated by lower values of migratory connectivity in each population. I investigated how seasonality interacted with human disturbance, landscape composition and configuration to mediate patterns of geographic and environmental space-use, and annual and seasonal survival probabilities. Environmental space-use was best explained by landscape configuration. Geographic space-use exhibited a quadratic response to landscape configuration metrics, suggesting that Turkey Vultures maximize space-use in landscape with intermediate disturbance. Human disturbance, but not but not landscape composition and configuration, influenced survival rates in space and time. Overall annual survival averaged 0.87 (95% CI = 0.74 – 0.98). Mortality risk was low in western and central populations but was 3.7 times greater for vultures in the eastern population. Risk of mortality for all vulture populations increased with road density, and this was greater during the non-breeding and return migration seasons. My results suggest that spatial and population dynamics are affected at a continental scale by the energy landscape, intermediate disturbance and human disturbance. My dissertation emphasizes the importance of an integrative empirical-modeling approach to address questions on effects of resources availability and search efficiency in the spatial and population dynamics of avian scavengers.

This thesis introduces the Deterministic Disturbance Generator (DDG) and its development process. The DDG performs two motions and five pitch rates. The flap motion, which rotates the airfoil from 0◦ to 20◦ and back, and the ramp motion, which rotates it from 0◦ to 20◦ with a dwell of 1s before returning to 0◦. To determine the angle of attack, a Matlab function converted thrust rod displacement into the assumed angle, validated against true angle of attack measurements on the DDG. Mean angular displacements were plotted, and standard deviations of the 95% confidence intervals were calculated within ±1.3◦ for all motions. The mechanical force on the actuator was computed to be 77N. Aerodynamic forces on the DDG were determined to be 15N and 19N for flap and ramp motions respectively. The total force on the system did not exceed 100N in any case, staying below the peak force capacity, while acceleration reached its limit. Flow velocimetry in the Virginia Tech Stability Wind Tunnel (VTSWT) employed a time-resolved Particle Image Velocimetry (PIV) to study the effects of 20◦ flap and ramp motions, with mean actuation times of 63ms and 37ms. Flap motion showed a significant deficit in mean streamwise velocities, and the ramp motion exhibited similar behavior until its dwell position, generating a large wake region due to airfoil stall after its peak. Comparison of data from the Goodwin Hall Subsonic Tunnel (GHST) with VTSWT data for overlapping domains revealed similar flow field features when normalized based on the boundary layer velocity (43mm plane from wall) of the latter. Considering actuation time differences, the freestream normalized GHST data was combined with VTSWT data. The cohesive PIV domain offered a broader perspective on the missing flow features. / Master of Science / A Deterministic Disturbance Generator (DDG) was designed to generate consistent largescale transversal transient disturbances in the wall boundary layer of the Virginia Tech Stability Wind Tunnel. It comprises an airfoil connected to an actuator through a rotating mechanism. The rotating mechanism can be controlled by manipulating the actuator to induce motion. The rotational speed of the airfoil is regulated by a program provided to the actuator. The DDG motions were validated to achieve nearly identical motion profiles to ensure it produced consistent turbulence wakes. The linear displacement of the actuator and airfoil was measured using a laser sensor, and a code was developed to convert this data into the observed angle of attack. Tests were conducted to verify repeatability and fine-tune the system's motions. A comprehensive description of the fabrication process, hardware and software setup, and calibration procedures involved in developing the DDG are provided. Using aerodynamic models, a computational study is performed to determine the forces associated with the airfoil and actuator. Subsequently, the DDG was subjected to testing in two wind tunnels: the Goodwin Hall Subsonic Tunnel for preliminary characterization and error mitigation and the Virginia Tech Stability Wind Tunnel for final assessment of the DDG's performance. Flow velocimetry data obtained from both tests are analyzed, revealing similarities in the induced motions. Mean flow fields and turbulence values are determined, and the effects of different pitch rates are also assessed. Finally, the mean flow fields corresponding to identical motion types from both datasets were integrated into a cohesive plot. This resulted in a comprehensive understanding of the flow field.

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Impulsivity and sleep and circadian rhythm disturbance are two core features of bipolar disorder that are elevated antecedents to bipolar disorder onset and persist even between mood episodes; their pervasive presence in bipolar disorder suggests that they may be particularly relevant to better understanding bipolar disorder etiology, onset, and course. Given considerable research demonstrating bidirectional associations between sleep and circadian rhythm disturbance and impulsivity in healthy individuals, it is surprising that little research has examined how these core features interact to impact bipolar disorder symptomatology, onset, and course. In a sample of late adolescents and young adults (N = 150) at low or high risk for developing bipolar disorder, we employed a naturalistic experiment in the context of an ecological momentary assessment (EMA) design to examine relationships between impulsivity, sleep and circadian rhythm alterations, and mood symptoms in everyday life. Furthermore, we sought to understand how the relationships between sleep and circadian rhythm alterations and mood fluctuation, collected during the EMA study, prospectively predicted mood symptom severity and mood episode onset at a 6-month follow-up. Linear regression, logistic regression, and multi-level modeling (MLM) revealed that higher impulsivity predicted increased mood symptoms during the EMA study, and less total sleep time (measured by actigraphy) predicted increased next-day EMA-assessed mood symptoms. Interaction analyses suggested that dim light melatonin onset time, total sleep time, and sleep onset latency moderated the relationship between impulsivity and mood symptoms (both next-day and at 6-month follow-up). Results are discussed in terms of their contribution to the existing literature. Findings highlight the necessity of multi-method, nuanced examination of the dynamic relationships between impulsivity and sleep and circadian disturbance within bipolar disorder. / Psychology

Thesis {\clqq} Behavioural disturbance in adolescence.`` Author: Vlasta Houserová Thesis 2008 Summary: The topic of my thesis reflects the current problem in our society. It deals with a presence of disturbing behaviour among teenagers. The theoretical part not only handles particular behavioural disorders and their symptoms but also reveals causes of such behaviour; conditions, which have the effect on existing disorder, and elements, which determine their origin. Lately, the thesis introduces several ways of re-education, change in disturbing behaviour and ways of prevention. In the practical part there is a research on specific types of disorders. One of the aims is also to compare occurrence of such behaviour in cities and towns. The research was based on a questionnaire and interviews with pedagogical counsellors at particular schools.

Semi-arid forests are in a period of rapid transition as a result of unprecedented landscape scale fires, insect outbreaks, drought, and anthropogenic land use practices. Understanding how historically episodic disturbances led to coherent forest structural and spatial patterns that promoted resilience and resistance is a critical part of addressing change. Here my coauthors and I apply metabolic scaling theory (MST) to examine scaling behavior and structural patterns of semi-arid conifer forests in Arizona and New Mexico. We conceptualize a linkage to mechanistic drivers of forest assembly that incorporates the effects of low-intensity disturbance, and physiologic and resource limitations as an extension of MST. We use both aerial LiDAR data and field observations to quantify changes in forest structure from the sub-meter to landscape scales. We found: (1) semi-arid forest structure exhibits MST-predicted behaviors regardless of disturbance and that MST can help to quantitatively measure the level of disturbance intensity in a forest, (2) the application of a power law to a forest overstory frequency distribution can help predict understory presence/absence, (3) local indicators of spatial association can help to define first order effects (e.g. topographic changes) and map where recent disturbances (e.g. logging and fire) have altered forest structure. Lastly, we produced a comprehensive set of above-ground biomass and carbon models for five distinct forest types and ten common species of the southwestern US that are meant for use in aerial LiDAR forest inventory projects. This dissertation presents both a conceptual framework and applications for investigating local scales (stands of trees) up to entire ecosystems for diagnosis of current carbon balances, levels of departure from historical norms, and ecological stability. These tools and models will become more important as we prepare our ecosystems for a future characterized by increased climatic variability with an associated increase in frequency and severity of ecological disturbances.