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The aim of our work was to investigate the habitat preferences of, and specific management measures for, the endangered spider species Eresus kollari Rossi 1846 and the eurytopic species Trochosa terricola Thorell 1856. For this purpose extensive field study data were collected for both spider species in the area of the nature reserve Lueneburg Heath. The ecological niches of the two spider species were also compared. The specific habitat preference of E. kollari was clarified and described in the course of the present studies. Heathland management measures that result in a thin organic layer on the ground, a high temperature at the depth of the spiders’ burrows (10 cm below ground level), and at the same time a relatively high heath cover satisfy the habitat requirements of E. kollari. Comparing the ecological niche of the stenotopic species E. kollari with that of the eurytopic species T. terricola in terms of habitat parameters demonstrated that the two species only differ in the following three factors: ‘tree cover’, ‘thickness of organic layer’ and ‘grass cover’. The reaction scheme of E. kollari appears as a subset of that of T. terricola. In this respect, E. kollari could serve not only as a characteristic species but also as an umbrella species in the Lueneburg Heath region. Against the background of the findings of the habitat modeling, management measures such as prescribed burning and choppering - carried out variably in space and time – seem to be particularly appropriate for maintaining E. kollari’s (but also T. terricola’s) microhabitat requirements in the long term. Due to the poor dispersal power of E. kollari some suitable habitats will probably not be re-colonized by the species. However, long-term monitoring as well as a recolonization experiment for this species should be carried out in the near future in areas providing suitable conditions for lasting conservation of E. kollari in this region of northwest Germany.
Not only time has influence on the formation of societies, but also space. People do not only write history, they also produce spaces. And just like history retroacts on social development processes, space forms society. A socially segregated society is controlled through space. The place of residence of a person already determines a big part of its fixed opportunities and conditions. Also, the living location is already suggested by the social class of a person within a capitalist structured society. Those socio-spatial structures lead to an unjust distribution of all kinds of goods, such as the access to basic living conditions, public services, infrastructure, education and work, and psychologically or socially defined restricted spaces. Injustices therefore can only be cured by changing their spatial manifestations. As Brazil is one of the economically uprising and promising BRIC countries, its development involves chances and risks. If unjust conditions remain, its long-term advancement is rather unlikely. The changes within the country are especially visible and present in its principal metropolis: São Paulo.
The dissertation deals with the impact of nitrogen deposition on the functioning of heathland ecosystems. Special interests were the displacement of heather (Calluna vulgaris) by the purple moor-grass (Molinia caerulea) as well as the fate of nitrogen loads in dry heathland ecosystems. The results of the studies undertaken in the field and in the greenhouse are presented as five individual journal articles. The nature of nutrient limitation was studied by means of fertilisation experiments with nitrogen (N) and phosphorus for heather and purple moor-grass (Articles I and II). The impact of nitrogen deposition on the outcome of competition between these two species was analysed during a competition experiment in the greenhouse (Article III). The aim of a 15N tracer experiment was to determine the fate of nitrogen deposition as well as allocation patterns (Article IV). In addition, the response of purple moor-grass to the combined effects of nitrogen deposition and summer droughts was investigated in a second greenhouse experiment (Article V). The fertilisation experiments showed that the growth of heather as well as of purple moor-grass is predominantly limited by N (Articles I and II). However, the results of the competition experiment demonstrated that only purple moor-grass has the ability to benefit from additional N loads, which in turn gives the grass the opportunity to displace heather (Article III). Drought treatment resulted in strikingly reduced biomass production of purple moor-grass in N-fertilised pots, mainly as a result of dying aboveground biomass during dry periods (Article V). This striking susceptibility of purple moor-grass to the combination of nitrogen deposition and drought must be taken into account, when predicting future developments of dry heathlands. The results of the 15N tracer experiment showed that the investigated heath is still in an early stage of N saturation, as indicated by a high immobilisation capacity and negligible leaching losses of 15N (Article IV). The findings of the dissertation contribute to a better understanding of the processes underlying the encroachment of purple moor-grass in dry heathlands and can enhance heathland management. The results can also be used to to evaluate the current and future status of this ecosystem particularly with regard to the various stages of N saturation as well as in the determination of “Critical Loads”.
In my dissertation I explore conceptual and economic aspects of resilience, i.e. a system’s ability to maintain its basic functions and controls under disturbances. I provide methodological considerations on the conceptual level and general insights derived from stylized ecological-economic models. In doing so, I demonstrate how to frame resilience so as to economically evaluate and investigate it as an important property of ecological-economic systems. Is conceptual vagueness an asset or a liability? In chapter 1 I address this question by weighing arguments from philosophy of science and applying them to the concept of resilience. I first sketch the wide spectrum of resilience concepts that ranges from concise concepts to the vague perspective of “resilience thinking”. Subsequently, I set out the methodological arguments in favor and against conceptual vagueness. While traditional philosophy of science emphasizes precision and conceptual clarity as precondition for empirical science, alternative views highlight vagueness as fuel for creative and pragmatic problem-solving. Reviewing this discussion, I argue that a trade-off between vagueness and precision exists, which is to be solved differently depending on the research context. In some contexts research benefits from conceptual vagueness while in others it depends on precision. Assessing the specific example of “resilience thinking” in detail, I propose a restructuring of the conceptual framework which explicitly distinguishes descriptive and normative knowledge. Chapter 2 investigates the common assumption that the optimization problem within a simple selfprotection problem (spp) is convex. It is shown that the condition given in the literature to legitimate this assumption may have implausible consequences. Via a simple functional specification we analyze the (non-)convexity of the spp more thoroughly and find that for reasonable parameter values strict convexity may not be justified. In particular, we demonstrate numerically that full self-protection is often optimal. Neglecting these boundary solutions and analyzing only the comparative statics of interior maxima may entail misleading policy implications such as underinvestment in self-protection. Thus, we highlight the relevance of full self-protection as a policy option even for non-extreme losses. Chapter 3 starts from the observation that ecosystem resilience is often interpreted as insurance: by decreasing the probability of future drops in the provision of ecosystem services, resilience insures risk-averse ecosystem users against potential welfare losses. Using a general and stringent definition of “insurance” and a simple ecological-economic model, we derive the economic insurance value of ecosystem resilience and study how it depends on ecosystem properties, economic context, and the ecosystem user’s risk preferences. We show that (i) the insurance value of resilience is negative (positive) for low (high) levels of resilience, (ii) it increases with the level of resilience, and (iii) it is one additive component of the total economic value of resilience. Chapter 4 performs a model analysis to study the origins of limited resilience in coupled ecologicaleconomic systems. We demonstrate that under open access to ecosystems for profit-maximizing harvesting forms, the resilience properties of the system are essentially determined by consumer preferences for ecosystem services. In particular, we show that complementarity and relative importance of ecosystem services in consumption may significantly decrease the resilience of (almost) any given state of the system. We conclude that the role of consumer preferences and management institutions is not just to facilitate adaptation to, or transformation of, some natural dynamics of ecosystems. Rather, consumer preferences and management institutions are themselves important determinants of the fundamental dynamic characteristics of coupled ecological-economic systems, such as limited resilience. Chapter 5 describes how real option techniques and resilience thinking can be integrated to better understand and inform decision making around environmental risks within complex systems. Resilience thinking offers a promising framework for framing environmental risks posed through the non-linear responses of complex systems to natural and human-induced disturbance pressures. Real options techniques offer the potential to directly model such systems including consideration of the prospect that the passage of time opens new options while closing others. Examples are provided which illustrate the potential for integrated resilience and real options approaches to contribute to understanding and managing environmental risk.
Both practitioners and researchers alike assign considerable importance to innovation. However, the process of how innovation unfolds over time is still not well understood. It is the aim of this dissertation to introduce an elaborated picture of innovation processes over time and to discuss the implications of the dynamics of the innovation process for individuals working in innovative contexts, that is, leaders and team members of innovative teams. The first paper of lays the theoretical and empirical groundwork of my dissertation in demonstrating that within the boundaries of the gradual development of innovation activities over time innovation processes are recursive and highly dynamic. These dynamics make the innovation process a challenge for everyone involved in it. In the second and third paper of my dissertation, I discuss this challenge in greater detail for leaders and team members of innovative work teams. Thus, with this dissertation I do not only to give a more elaborate picture of how innovation projects unfold over time, but also describe the challenges attached to the innovation process and give first answers to the question of how individuals involved in this process may be able to master these challenges.
Air quality models are important tools which are utilized for a large field of application. When combined with data from observations, models can be employed to create a comprehensive estimation of the past and current distribution of pollutants in the atmosphere. Moreover, projections of future concentration changes due to changing emissions serve as an important decision basis for policymakers. For the determination of atmospheric concentrations of air pollutants by means of numerical modelling it is essential to possess a model which is able to create anthropogenic and biogenic emissions with a temporally and spatially high resolution. The emission data is needed as input for a chemistry transport model which calculates transport, deposition, and degradation of air pollutants. To evaluate the impact of changing emissions on the environment a flexible emission model with the capability to create diverse emission scenarios is needed. Further, it is important to always take into account a variety of different species to properly represent the major chemical reactions in the atmosphere (e.g. ozone chemistry, aerosol formation). Currently there are only a few high resolution emission datasets available for Europe. The amount of substances included in these datasets, however, is limited. Moreover, they can not be used as basis for the creation of new emission scenarios. To enable the creation of emission scenarios in the course of this doctoral thesis the American emission model SMOKE was adopted and modified. On the basis of a multitude of different georeferenced datasets, official statistics, and further model results the newly created emission model “SMOKE for Europe” is capable of creating hourly emission data for the European continent with a spatial resolution of up to 5x5km2. In order to demonstrate the universal applicability of the emission model the carcinogenic species benzo[a]pyrene (BaP) was exemplarily implemented into the model. BaP belongs to the group of polycyclic aromatic hydrocarbons. Because of its high toxicity the European Union introduced an annual target value of 1 ng/m3 in January 2010. SMOKE for Europe was used to create a variety of emission scenarios for the years 1980, 2000, and 2020. These emission scenarios were then used to determine the impact of emission changes on atmospheric concentrations of BaP and to identify regions which exceed the European target value. Additionally the impact of different legislation and fuel use scenarios on the projected atmospheric concentrations in 2020 was investigated. Furthermore, additional use cases for a flexible emission model are pointed out. The SMOKE for Europe model was used to simulate the transport of volcanic ash after the eruption of the Icelandic volcano Eyjafjallajokull in March 2010. By comparison of modelled concentrations for different emission scenarios with observations from remote sensing and air plane flights distribution and concentration of the volcanic ash over Europe was estimated. The results of this thesis have been presented in four scientific papers published in international peerreviewed journals. The papers are reprinted at the end of this thesis.
Against the backdrop of aging populations, labor shortages, and a longer healthy life expectancy, there has recently been considerable discussion of the great potential that post-retirement activities hold for individuals, organizations, and society alike. This dissertation consists of three empirical papers investigating the life reality of active retirees in Germany. In addition, framework conditions and motivational structures that need to be considered in creating jobs for this group of workers are examined. The first paper identifies the prerequisites for productivity after retirement age and describes the changed nature of modern-day retirement. Current levels of post-retirement work are quantified by reference to German Microcensus data. The data show that adults continue to engage in paid employment beyond the applicable retirement age, with self-employment and unpaid work in family businesses making up the greatest share of post-retirement activities. Qualitative data collected from 146 active retirees (mean age = 67 years, standard deviation = 4) showed that the changes entailed in retirement include more flexible structures in everyday life. Content analysis revealed that reasons for taking up post-retirement activities were the desire to help, pass on knowledge, or remain active; personal development and contact with others; and a desire for appreciation and recognition. In addition, flexible working hours and the freedom to make decisions are evidently important aspects that need to be taken into account in creating employment activities for silver workers. The second paper extends the findings of the first paper by investigating the differences that respondents experienced between their former career job and their post-retirement activities, drawing on an additional quantitative sample of active retirees (N = 618, mean age = 69 years, standard deviation = 4). Factor analysis revealed differences in four areas: First, differences were identified in person-related variables, such as work ability. Second, differences were perceived in the scope of the job itself with regard to workers’ tasks, skills, or job function. Third, the perceived freedom of time allocation and flexibility in job practice distinguished between the silver job and the former career job. Fourth, differences were noted in perceived responsibility and in the significance of the activity. The third paper further examined how relevant personal motivational goals (achievement, appreciation, autonomy, contact, and generativity) as well as corresponding occupational characteristics of the silver job were related to life and work satisfaction in the quantitative sample (N = 661, mean age = 69 years, standard deviation = 4). Hierarchical regression analyses showed that the motivational goals of achievement, appreciation, autonomy, contact, and generativity significantly predicted life satisfaction, whereas only generativity predicted work satisfaction. With respect to the occupational characteristics, none of the situational predictors influenced life satisfaction, but opportunities to fulfill one’s achievement goals, to pass on knowledge, and to experience appreciation and autonomy predicted work satisfaction. The results suggest that post-retirement workers seem to differentiate between perceived life satisfaction and work satisfaction as two independent constructs. In conclusion, key motives for taking up post-retirement activities were generativity (the wish to help and pass on knowledge), but also personal development, appreciation, autonomy, and contact. The findings indicate that organizations should introduce flexible working hours, and offer silver workers advisory and freelance work. Providing freedom to make decisions and ensuring due appreciation of the contribution made by silver workers will lead to a fruitful interplay of silver workers and organizations. Future research should build on these findings by applying longitudinal designs and drawing on samples of retirees with more diverse educational and financial backgrounds. The papers of this dissertation echo the call for a new, more positive way of looking at the capacities of active retirees.