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Institut
In recent years, both scientists and practitioners have become interested in the affectivemotivational concept of work engagement and research on work engagement has strongly accumulated. Engaged people invest physical, affective, and cognitive resources in their work tasks and activities (Sonnentag, Dormann, & Demerouti, 2010) and high levels of work engagement involve positive consequences both for the individual and the organization (Rich, Lepine, & Crawford, 2010). The objective of this dissertation is twofold. The first and second empirical studies help to advance knowledge on antecedents of work engagement and to extend theoretical models in which work engagement is embedded. The third study aims at expanding present knowledge of the role of specific work events as proximal antecedents of distinct affective states and as distal antecedents of job attitudes and affective consequences such as work engagement by developing a taxonomy of work events. This dissertation suggests ideas for future research and provides practical implications regarding work design and human resource practices that are based on the empirical findings reported. Study 1 investigates the cognitive-motivational concept of focus on opportunities (i.e. the number of goals, plans, and possibilities employees believe themselves to have in their future) as a predictor of work engagement and a personal resource that buffers for low levels in employee’s job control. By using a cross-sectional survey study based on a sample of bluecollar workers (N = 174), and a daily diary study based on a sample of administrative employees (N = 64), this study revealed that job control was less strongly related to work engagement when people’s focus on opportunities was reported to be high. Employees with a high focus on opportunities compensated for low job control. This finding refines theoretical models of antecedents of work engagement by supporting the role of focus on opportunities as a motivational resource. The goal of Study 2 was to examine self-efficacy regarding a person‘s work role as a personal resource that helps employees to effectively regulate affective states in a way to show high levels of work engagement. The study was conducted based on a sample of 111 full-time employees who completed daily online questionnaires on affective experiences and work engagement twice a day over ten working days. Results of multilevel linear regression analysis showed that self-efficacy acted as a moderator on the relationship between daily negative affect and daily work engagement. Self-efficacy enabled people to show high levels of work engagement on days when they experience negative affective states. Moreover, the relationship between self-efficacy and work engagement was mediated by an increase of positive affect during the day. Through the mechanism of up-regulating positive affect, people high in self-efficacy succeed in maintaining daily work engagement. These results extend existing theoretical frameworks of work engagement by indicating that self-efficacy is an important personal resource that enables people to effectively regulate affective states and show high levels of work engagement. Study 3 addresses the development of a comprehensive taxonomy of daily work events that provides a frame of reference for future studies to more systematically test propositions of Affective events theory (AET) (Weiss & Cropanzano, 1996). AET provides a theoretical framework that emphasizes the role of work events as proximal antecedents of affect but does not formulate specific propositions about which kind of work events elicit distinct affective states. Based on 559 positive and 383 negative work events mentioned in three daily diary studies by an overall of 218 employees, the qualitative concept mapping methodology was used to establish the taxonomy on work events. Explorative statistical analyses resulted in four positive and seven negative work events clusters. The study provides evidence for the validity of the taxonomy by testing the relationships of the events clusters with distinct positive and negative activating and deactivating affective states.
Algae-bacteria-based biotechnology has received more and more attention in recent years, especially in the subtropical and tropical regions, as an alternative method of conventional multistep wastewater treatment processes. Moreover, the algal biomass generated during wastewater treatment is regarded as a sustainable bioresource which could be used for producing biofuel, agricultural fertilizers or animal feeds. Although this technology is attractive, a number of obstacles need to be solved before large-scale applications. The main purposes of this work are to find more effective biomass harvesting strategies and develop high-effective algal-bacterial systems to improve wastewater treatment performance, biomass generation rate and biomass settleability. A wastewater-borne algal-bacterial culture, cultivated and trained through alternate mixing and non-mixing strategy, was used to treat pretreated municipal wastewater. After one month cultivation and training, the acclimatized algal-bacterial system showed high carbon and nutrient removal capacity and good settleability within 20 minutes of sedimentation. Algal biomass uptake was the main removal mechanism of nitrogen and phosphorus. The biomass productivity, nitrogen and phosphorus accumulation in biomass during the wastewater treatment process were investigated. The characterization of the microbial consortium composition in the enriched algal-bacterial system provided new insights in this research field. Aerobic activated sludge which already showed good settleability was used as bacterial inoculum to enhance the wastewater treatment performance and biomass settleability of algal-bacterial culture. The influence of different algae and sludge inoculum ratios on the treatment efficiency and biomass settleability was investigated. There was no significant effect of the inoculation ratios on the chemical oxygen demand (COD) removal. But algae/sludge inoculum ratio of 5 showed the best nitrogen and phosphorus removal efficiencies (91.0 ± 7.0% and 93.5 ± 2.5%, respectively) within 10 days. Furthermore, 16S rDNA gene analysis showed that the bacterial communities were varying with different algae and sludge inoculation ratios and some specific bacteria species were enriched during the operation. Four commonly used and high-potential microalgae species including one cyanobacteria (Phormidium sp.) and three green microalgae species (Chlamydomonas reinhardtii, Chlorella vulgaris and Scenedesmus rubescens) were cultivated and trained through alternate mixing and non-mixing strategy for tertiary municipal wastewater treatment. After one month of cultivation, the four microalgae species were compared in terms of biomass settleability, nutrient removal rates and biomass productivity. The three green microalgae showed good settleability within 1 h sedimentation and had higher biomass generation rates (above 6 g/m2/d). The nutrient removal efficiencies were 99% for the four selected microalgae species but within different retention time, resulting in 3.66 ± 0.17, 6.39 ± 0.20, 4.39 ± 0.06 and 4.31 ± 0.18 mg N/l/d (N removal rate) and 0.56 ± 0.07, 0.89 ± 0.05, 0.76 ± 0.09 and 0.60 ± 0.05 mg P/l/d (P removal rate) for Phormidium sp., Chlamydomonas reinhardtii, Chlorella vulgaris and Scenedesmus rubescens, respectively. A mixed algal culture composed of three selected high-effective green microalgae (Chlamydomonas reinhardtii, Chlorella vulgaris and Scenedesmus rubescens) was used for tertiary municipal wastewater treatment. The key biotic factor (algal inoculum concentration) and abiotic factors such as illumination cycle, mixing velocity and nutrient strength were studied. Based on the nitrogen and phosphorus balance, it was found that assimilation into algal biomass was the main removal mechanism.
The challenges of sustainable development have spurred the complexity of management reality, unveiling considerable risks and opportunities for companies. The past twenty years of development in management science and practice have refined the understanding of the linkages between corporate success and sustainability aspects of business. Nevertheless, numerous management tools and concepts have been criticised for failing to contribute to improved sustainability performance. Management accounting is an indispensable system for generating, preparing and providing information for recognising decision situations and informing decisions. Building on the relevance of information, sustainability accounting has received considerable attention in the past decade. Related research has emphasised the contribution of sustainability accounting to tackling sustainability challenges in specific settings. A systematic investigation of the role of sustainability accounting is virtually non-existent to date. To overcome this limitation and provide an insight into the practice of sustainability accounting and its role in sustainability management and ultimately in corporate success, this doctoral thesis approaches the question How does sustainability accounting contribute to improved information management and management control? The direct contribution is two-fold. First, a number of decision situations are explicated. Examples for such decision situations include utilising certain types of information for specific decisions, engaging various functions in different ways, etc. Making a decision within these decision situations was observed to contribute to achieving corporate goals. Second, the overarching view on the results reveals an interesting pattern. It is the existence of this pattern that supports the view that sustainability accounting can help companies in the pursuit of improved sustainability performance and (thereby) corporate success. The findings enable both practitioners and researchers gain an insight into how sustainability accounting can be deployed so that the company’s limited resources are focused on the crucial decisions in information management and management control. Subsequent recommendations are supported by up-to-date examples. The nature and the scope of the research constituting this doctoral thesis also highlight the path for future research to expand and refine the propositions made herein.
Entrepreneurs and entrepreneurial firms are a frequent research topic in psychological research. However, the focus of this research has largely been on the entrepreneur as a person and on the entrepreneurs’ strategy for the business. By contrast, the entrepreneur as a leader and the entrepreneurial firm as a work environment for employees have received little attention. Therefore, this dissertation aims to integrate theoretic thoughts from organizational behavior research into entrepreneurship research. Specifically, I will focus on novelty creation within entrepreneurial firms and organizational phenomena which provide a context for employees in novelty creating activities. This dissertation adds to the literature as it provides insight in the effects of work environment facets on employees’ engagement in novelty creating activities in entrepreneurial businesses. In three empirical chapters, I will focus first on the effects of entrepreneurial orientation on efficiency of employee work in innovation projects. Second, I will look at a facet of organizational culture, the error management culture, and its effects on individual learning of employees. Last, I will focus on occupational roles of employees within small businesses and effects of these roles on responses to a questionnaire and on work in innovation projects. In all three empirical chapters I test my hypotheses in a sample of N = 40 entrepreneurial businesses and employees within these businesses. For my chapter on occupational roles this sample is complemented by two additional samples of college students. In sum, results indicate that the entrepreneurial business in all three chapters exerts significant influences on employee work. Furthermore, I show that employee participation in novel activities is positive for entrepreneurial businesses (Chapter 2: Correlation between employees’ and entrepreneurs’ evaluation of innovation project effectiveness: r = .44; p < .01; Chapter 3: Correlation between organizational level leaning and organizational growth in sales: r = .35; p < .01). Therefore, I suggest that research on the entrepreneurial firm as a context for work may contribute to our knowledge on success factors in entrepreneurship, and may therefore be a relevant direction of future research. Especially, it may be fruitful to investigate aspects of work in which entrepreneurial firms may differ from other, less entrepreneurial organizations.
The role of tree diversity for individual tree growth, crown architecture and branch demography
(2012)
In the light of the concurrent loss of biodiversity, biodiversity and ecosystem functioning (BEF) research attracted a great deal of attention and emerged as one of the important fields of research in ecology. Since important ecological interactions such as competition occur between individuals, the understanding of individual tree growth was considered to be fundamental for forest related BEF research. Individual tree growth is determined by the above- and belowground interactions of a tree individual with its local neighbourhood. To obtain a deeper understanding of BEF relationships, I broadened the focus from individual tree growth (usually measured as diameter or biomass increment) to the arrangement and dynamics of the above-ground modules of trees in dependence of their local neighbourhood. More precisely, the main objective of the present thesis was to analyse the impact of tree diversity on individual tree growth, crown architectural and branch demographic variables. Thereby I considered crown architectural variables as important indicators of the competition for light. In addition, crown architectural variables impacted ecosystem services such as erosion control. Furthermore, the results of the present thesis contributed to the current discussion on species coexistence theories, which may be differentiated by two opposing views: one that relies on neutral processes and one that implicates a role for meaningful differences in the ecological strategy (niche) of co-occurring species. The studied forest ecosystems were the subtropical broad-leaved evergreen forests of southeast China, which have been under high human pressure due to a long history of intensive land-use. The area is of particular interest for BEF research due to the high species richness of woody plants, including many, yet poorly studied species, and due to the rough terrain with steep slopes, which cause severe soil erosion. The present thesis combines three observational with two experimental studies, applying the local neighbourhood approach along an age gradient from tree saplings to mature trees. In the Gutianshan National Nature Reserve (GNNR), I conducted two observational studies on permanent plots which were chosen according to a space-for-time substitution design. The aim of the first study was to reveal the effects of diversity (species richness, functional diversity) together with other biotic and abiotic variables on morphological growth parameters (crown area, crown displacement and stem inclination) of target trees of four tree species (Castanea henryi, Castanopsis eyrei, Quercus serrata and Schima superba). In the second study, the same target trees together with their neighbours were used to analyse the relation between stand related functional diversity and the horizontal and vertical structure of the canopy. The third study was conducted in a young secondary broad-leaved evergreen forest. Using two target species (Castanopsis fargesii and Quercus fabri), the role of diversity, intra- vs. inter-specific competition and the mode of competition (symmetric vs. asymmetric) on the target individuals was tested by analysing five-year radial growth increments. The two other studies were carried out in an experimentally established plantation, using saplings of four tree species (C. henryi, Elaeocarpus decipiens, Q. serrata and S. superba), which were planted in monoculture, twoand four-species combinations and in three densities. The fourth study focused on mechanisms of coexistence and the role of species richness, species composition, species identity and density on sapling growth. The fifth study tested the effect of sapling density and identity on the througfall kinetic energy, which represents a measure for the erosive power of rain. It was found that functional diversity does affect crown architectural and canopy related parameters of forests in the GNNR. However, no effects of species richness on radial-growth were detected in the younger forest. Since I also did not find strong effects of species richness on saplings in the experimental plantation, diversity effects may evolve at a later age stage. The importance of the diversity effect may be related reversely to that of species identity in an age gradient of forest stands. The findings suggest that different mechanisms of coexistence operate simultaneously but that their relative importance may shift through the life stages of trees. During the sapling stage, species-specific differences in growth and architectural traits support niche theory. In older forest stands, no species-specific differences in growth parameters could be detected. However, I did find effects of functional diversity on horizontal canopy structure. I conclude that mechanisms of coexistence may not only change with forest stand age, but may also differ for distinct traits. The present thesis, being the first to apply the local neighbourhood approach with regard to crown architecture and branch demography within the BEF field of research, stresses the importance of this individual based approach. Although the observed forest systems are very complex, crown architectural and canopy structural variables were found to be affected by diversity. The finding that the degree of erosive power of rain could be elucidated by crown architectural variables, encourages further studies to reveal possible relations between biodiversity and other ecosystem functions or services, which might be mediated by crown architectural and canopy structural variables.