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- Institut für Ökologie (IE) (7) (entfernen)
Die Kulturlandschaft im Alpenraum war in den letzte Jahrzehnten einem besonders starken Strukturwandel ausgesetzt. Als Region mit einem hohen Anteil an Grenzertragsstandorten lassen sich hier zwei gegenläufige Entwicklungen feststellen: zum einen findet eine Intensivierung der Landnutzung in Bereichen mit guter Zugänglichkeit und maschineller Nutzbarkeit statt, zum anderen kommt es häufig zu einem Rückgang der Nutzungsintensität oder Nutzungsaufgabe in Bereichen, in denen die landwirtschaftliche Bearbeitung schwierig ist. Die Auswirkungen auf die Biodiversität werden bei beiden Entwicklungen kritisch gesehen, allerdings mangelt es an detaillierten Untersuchungen.
Im Rahmen eines sechsjährigen Forschungsvorhabens wurden auf einer Weidefläche in den Allgäuer Alpen Laufkäfer, Spinnen und Vegetation untersucht. Auf der Fläche fand zu Beginn der Untersuchung eine Nutzungsänderung statt: ein großer Teil der vormals intensiv von Schafen beweideten Fläche wurde auf extensive Rinderbeweidung umgestellt, kleine Teilflächen wurden aus der Nutzung genommen.
Der Fokus dieser Dissertation liegt in den Untersuchungen der Laufkäfer. Hier wurde zunächst ein Erfassungsschema für Laufkäfer in schwer erreichbaren Gebieten der Alpen erarbeitet, um intensive und mehrjährige Untersuchungen logistisch durchführen zu können. Dabei wurden die Ergebnisse der Laufkäfererfassung über die gesamte Vegetationsperiode mit den Ergebnissen einer reduzierten Erhebung verglichen. Es konnte gezeigt werden, dass eine Beprobung über jeweils zwei Wochen Anfang Juni und Anfang Juli den gesamten Datensatz hinreichend repräsentiert.
Des weiteren wurde untersucht, ob die Vegetation als Surrogat für die beiden untersuchten Arthropodengruppen (Spinnentiere und Laufkäfer) dienen kann, d.h. die Ergebnisse der Vegetation auf die anderen Artengruppen übertragbar ist. Dies wurde sowohl auf Ebene der Artzusammensetzung als auch des Artenreichtums für die drei Taxa geprüft. Zudem wurde überprüft, ob die unter vegetationskundlichen Aspekten abgegrenzten geschützten Lebensraumtypen auch besonders wertvolle Habitate für die Arthropodengruppen darstellen. Die Ergebnisse der Untersuchung zeigen, dass eine ausreichende Kongruenz nicht gegeben und damit die Übertragbarkeit von Ergebnissen bei der Vegetation auf die untersuchten Arthropodengruppen in den Gebirgslebensräumen nicht gewährleistet ist. Dies hat eine hohe praktische Relevanz, da im Rahmen von Managementplanungen für die FFH-Richtlinie als auch bei der Bayerischen Alpenbiotopkartierung überwiegend ein starker Fokus auf vegetationskundlichen Aspekten liegt und insbesondere artenreiche Arthropodengruppen meist nicht betrachtet werden.
Abschließend wurde mittels gemischter Modelle (mixed effects models) untersucht, welche Veränderungen bei den Laufkäfern nach der Nutzungsänderung im Untersuchugnsgebiet auftraten. Sämtliche errechneten Modelle zeigten Veränderungen der abhängigen Variablen über die Zeit: nach Aufgabe der intensiven Schafbeweidung nahmen die Arten- und Individuenzahlen sowie die Biomasse an Laufkäfern zu. Die Tiere wurden durchschnittlich größer und es traten mehr herbivore Laufkäfer auf. Auch konnten unterschiedliche Entwicklungen zwischen den Standorten beobachtet werden. Die beobachteten Veränderungen werden im Artikel detailliert diskutiert. Die meisten Veränderungen, insbesondere die Zunahme der Artenzahlen sowie der durchschnittlichen Körpergröße, deuten auf eine Erholung der Laufkäferfauna von der intensiven Schafbeweidung hin. Die Nutzungsumstellung und die aktuell praktizierte extensive Rinderbeweidung werden im Gebiet naturschutzfachlich positiv bewertet. Die Arbeit liefert eine gute Vorlage und fundierte Begründung, gerade auch im Alpenraum verstärkt Laufkäfer bei der Beantwortung naturschutzfachlicher Fragestellungen einzubinden.
Climate change and atmospheric deposition of nitrogen affect biodiversity patterns and functions of forest ecosystems worldwide. Many studies have quantified tree growth responses to single global change drivers, but less is known about the interaction effects of these drivers at the plant and ecosystem level. In the present study, we conducted a full-factorial greenhouse experiment to analyse single and combined effects of nitrogen fertilization (N treatment) and drought (D treatment) on 16 morphological and chemical response variables (including tissue δ13C signatures) of one-year-old Fagus sylvatica seedlings originating from eight different seed families from the Cantabrian Mountains (NW Spain). Drought exerted the strongest effect on response variables, reflected by decreasing biomass production and increasing tissue δ13C signatures. However, D and N treatments interacted for some of the response variables, indicating that N fertilization has the potential to strengthen the negative effects of drought (with both antagonistic and amplifying interactions). For example, combined effects of N and D treatments caused a sevenfold increase of necrotic leaf biomass. We hypothesize that increasing drought sensitivity was mainly attributable to a significant reduction of the root biomass in combined N and D treatments, limiting the plants’ capability to satisfy their water demands. Significant seed family effects and interactions of seed family with N and D treatments across response variables suggest a high within-population genetic variability. In conclusion, our findings indicated a high drought sensitivity of Cantabrian beech populations, but also interaction effects of N and D on growth responses of beech seedlings.
We are in a phase of an alarming biodiversity loss, by scientist already referred to as Earth’s sixth mass extinction. According to estimations, the current extinction rates are 100 to 1000 times higher than those predicted from fossil records. To counteract species loss and preserve the remaining biodiversity, with its important ecosystem functioning and services essential to human well-being, there is an urgent need to develop promising and long-term conservation strategies. In order to achieve these goals, extensive research to gain a better understanding of the general mechanisms underlying community diversity is of greatest importance. Especially, the identification of intrinsic ecological and distributional species traits is receiving increased attention in ecology and conservation biology research. Depending on the expression of their traits, species perform particular ecosystem functions and respond in a specific manner to environmental conditions. The identification of the effect of certain traits on community compositions can therefore significantly improve our understanding of species extinction processes and help to develop valuable and appropriate recommendations for conservation management. As trait-based analyses are applicable to different geographical, temporal and taxonomical scales, they may even allow for a broader generalization if similar results are found on different scales, i.e. for local species pools, the complete species pools of different habitat types or the entire species pool across several habitat types including different climatic regions. Although insects make up the largest part of animal diversity and provide essential ecosystem services in form of e.g. pollination, pest control, and decomposition, the majority of studies on extinctions have mainly focused on vertebrates. Among invertebrates either charismatic taxa or those targeted by conservation laws have been investigated until now (e.g. butterflies or saproxylic beetles). Being highly species-rich and trait-diverse, ground beetles (Coleoptera: Carabidae) should be even more suitable for conducting trait-based analyses. Thus, using ground beetles as a model taxon, four case studies focusing on the analyses of traits form the basis of this doctoral thesis. The work of this thesis was conducted with the aim of gaining general insights on the influence of species traits on ground beetle community compositions, such as habitat occupancy and species vulnerability to extinction, for instance. An important aspect when investigating species traits is the consideration of confounding factors which could influence the results, such as dependent relations between the different traits. Compiling a large dataset of 566 Central European species, I identified that dependent relations between the six tested traits of ground beetles (distribution range size, habitat specialization, body size, hind-wing morphology, breeding season and trophic level) are highly common. Across all identified dependent trait relations, the relation between body size and hind wing morphology or range size and hind wing morphology showed the strongest significant dependencies. Since the consideration of trait relations is necessary to provide reliable interpretations, all analyses of this thesis tested several traits simultaneously and considered possible trait interactions. Studies on local communities found specific traits characterizing the local species pools of certain habitat types. Here, the species pools of seven different habitat types (coastal, forest, mountain, open, riparian, wetland and special habitat) were used to determine habitat-specific trait filters. The identified traits, characteristic for certain habitat types, were in most cases in accordance with the previous findings on local communities. Across Germany, the species of frequently disturbed habitat types, namely coastal, riparian and wetland habitats were characterized by small body size, high amount of macroptery, intermediate to high habitat specialization, spring breeding, and predatory feeding behavior. The species of stable habitat types (forest, mountain, and open habitats), however, were found to be generally larger in body size and more frequently breeding in autumn, further displaying greater variations in the other traits. The gained knowledge on the habitat-specific filtering of traits improve our understanding of the organization and assembly of communities, and can thereby help to detect alterations in the habitat-specific species pool due to natural or human-induced environmental changes. Furthermore, traits can provide evidence on species occurrences and vulnerability to extinction. Three case studies of this thesis aimed to gain new insights on this topic, through the investigations on the following research questions; I. Which traits drive species extinction risks of Central European ground beetle species, II. How traits influence the species occurrences of 28 forest species within a large area in Central Europe, and III. Whether certain traits are related to long-term population trends of the species pool from an ancient forest in northern Germany. The results indicated, that depending on the habitat type and tested species pool, different traits prove to be good predictors for the vulnerability of species. Nevertheless, across different geographical and taxonomical scales, especially species with small range sizes and high habitat specialization faced a greater risk of extinction. Therefore, the two traits distributional range size and habitat specialization emerge as reliable predictors of ground beetles vulnerability to extinction. Interestingly, body size did not display a consistent response; while increasing body size led to higher extinction risk in riparian, wetland and open habitats and large macropterous species showed higher extinction risks across the entire species pool, smaller species showed long-term population declines in an ancient forest. To summarize, this thesis presents a comprehensive picture of ground beetle species traits, providing valuable insights and a better understanding of the mechanisms driving changes in ground beetle diversity. On the basis of the results presented in this work, the efficiency of biodiversity protection can be increased by developing appropriate management and recovery plans, especially targeting species of threatened habitat types or ‘functional groups’ of species, exhibiting trait values strongly associated with a greater vulnerability to extinction.
Forest ecosystems significantly contribute to global carbon (C) sequestration and therefore play a crucial role for climate change mitigation. At the same time, forests were and are subjected to past and current environmental changes with consequences for the functioning of forest ecosystems and their associated ecosystem services. Forests in Central Europe are highly influenced by former settlement activities and land-use changes, as well as silvicultural management measures. Until the beginning of the 19th century anthropogenic activities caused a tremendous decline of the forest area. The resulting timber shortage led to large scale afforestations on previously agriculturally used land (e.g. heathlands, grasslands and croplands) during the 19th and 20th century. Widespread afforestation programs created recent forest ecosystems (i.e. young forest systems in terms of their development history). Despite the positive effect of increasing the forest area of Central Europe, the ecological effects of these land-use changes on forest ecosystems remain poorly understood. In addition, most forests in Central Europe are under silvicultural management, while the knowledge about the consequences of management measures on forest ecosystem functioning, particularly in the face of ongoing global environmental changes, is also still limited. In order to increase the understanding of ecosystem processes in forests, an assessment of conceivable shifts in ecosystem functions caused by former land-use changes and forest management is required. By analysing aboveground growth rates of European beech (Fagus sylvatica L.) in response to environmental change drivers, such as climate extremes and nitrogen (N) deposition, the presented thesis aims to assess the role of land-use and management legacies in modulating present responses to drivers of environmental change. To this end, annual radial growth rates of individual trees were measured in mature beech stands. The investigated stands differed either in their land-use history (i.e. ancient forest sites with a forest continuity > 230 years versus recent forests afforested on former arable land ~ 100 years ago) or their forest management history (i.e. managed forest sites versus short-term and long-term unmanaged forest sites). Measurements of radial growth rates were complemented by analyses of the fine root systems, soil chemical properties and crown projection areas to gain insights into the mechanisms underlying alterations in tree growth. Within the projects of the presented thesis, shifts in the climate-growth relationships driven by land-use and management legacies were analysed. In addition, land-use legacy mediated differences in the climate-nitrogen-growth relationships were assessed. The key findings are: (I) Soil legacy driven alterations in the fine root systems cause a higher sensitivity of radial increment rates to water deficits in summer for trees growing on recent forest sites than for trees growing on ancient forest sites. (II) Management legacies (in terms of tree release) enhance the sensitivity of beech’s radial growth to water deficits in spring through changes in crown sizes. (III) Interacting effects of spring water deficits and co-occurring high deposition of reactive N compounds lead to stronger radial growth declines in trees growing in ancient forests. This is likely caused by resource allocation processes towards seed production, which is, in turn, mirrored by decreasing radial growth rates. In this context, high N deposition likely boosts mass fructification in beech trees. Overall, it has been demonstrated that the ecological continuity plays a crucial role in modulating both climate sensitivity and the growth response to interacting effects of water deficits and nitrogen deposition in beech trees. The presented thesis identified a trade-off between the climate sensitivity and maximised growth rates within beech trees, depending on forest history. The results show that the growth of beech in ancient, unmanaged beech forests is less sensitive to water deficits than in recent and managed beech forests. Additionally, interacting effects of spring water deficits and N deposition likely increase the reproductive effort of beech trees, particularly in ancient forests. Thus, the results of this thesis once again underpin the uniqueness of ancient, unmanaged beech forests, whose importance for the conservation of biodiversity has been widely acknowledged. In summary, the presented thesis highlights the need to consider the ‘ecological memory’ of forest ecosystems when predicting responses to current and future environmental changes.
Through the expansion of human activities, humanity has evolved to become a driving force of global environmental change and influences a substantial and growing part of natural ecosystem trophic interactions and energy flows. However, by constructing and building its own niche, human distance from nature increased remarkably during the last decades due to processes of globalization and urbanization. This increasing disconnect has both material and immaterial consequences for how humans interact and connect with nature. Indeed, many regions across the world have disconnected themselves from the productivity of their regional environment by: (1) accessing biological products from distant places through international trade, and (2) using non-renewable resources from outside the biosphere to boost the productivity of their natural environment. Both mechanisms allow for greater resource use then would be possible otherwise, but also involve complex sustainability challenges and lead to fundamentally different feedbacks between humans and the environment. This dissertation empirically investigates the sustainability of biophysical human-nature connections and disconnections from a social-ecological systems perspective. The results provide new insights and concrete knowledge about biophysical human-nature disconnections and its sustainability implications, including pervasive issues of injustice. Through international trade and reliance on non-renewables, particularly higher-income regions appropriate an unproportional large share of global resources. Moreover, by enabling seemingly unconstrained consumption of resources and simultaneous conservation of regional ecosystems, increasing regional disconnectedness stimulates the misconception of decoupling. Whereas, in fact, the biophysically most disconnected regions exhibit the highest resource footprints and are, therefore, responsible for the largest environmental damages. The increasing biophysical disconnect between humans and nature effectively works to circumvent limitations and self-constraining feedbacks of natural cycles. The circumvention of environmental constraints is a crucial feature of niche construction. Human niche construction refers to the process of modifying natural environments to make them more useful for society. To ease integration of the chapters in this thesis, the framework paper uses human niche construction theory to understand the mechanisms and drivers behind increasing biophysical disconnections. The theory is employed to explain causal relationships and unsustainable trajectories from a holistic perspective. Moreover, as a process-oriented approach, it allows connecting the empirically assessed states of disconnectedness with insights about interventions and change for sustainability. For a sustainability transformation already entered paths of disconnectedness must be reversed to enable a genuine reconnection of human activities to the biosphere and its natural cycles. This thesis highlights the unsustainability of disconnectedness and opens up debate about how knowledge around sustainable human niche construction can be leveraged for a reconnection of humans to nature.
The smallholder-dominated landscapes of southwestern Ethiopia support a unique biodiversity with great importance to local livelihoods and high global conservation value. These landscapes, however, are severely threatened by deforestation, forest degradation and the adverse effects of farmland management regimes. These changes have fundamentally altered the structure of the landscapes and threaten their biodiversity and ecosystem services. Managing biodiversity and related services in such rapidly changing landscapes requires a thorough understanding of the effects of land use change and the reliance of local communities on biodiversity. This dissertation examines woody plant biodiversity patterns and services and presents several recommendations regarding biodiversity and multiple ecosystem services in smallholder-dominated landscapes of southwestern Ethiopia. Using a social-ecological systems approach, I conducted four studies on the complex interactions of local people and woody plant diversity. First, I investigated the effects of human-induced forest degradation on woody plant species. My results suggest that forest biodiversity has been affected by the combined effects of coffee management intensity, landscape context and history at the local and landscape level. Specifically, richness of forest specialist species significantly has decreased with coffee management intensity and in secondary compared to old growth forests, but increased with current distance from forest edge in both primary and secondary forests. These findings highlight the need to maintain undisturbed forest sites to conserve forest biodiversity. Second, I examined legacy effects of past agricultural land use on woody plant biodiversity. My results show that historical distance seems to be the most important variable affecting woody plant composition and distribution in farmland sections of the landscapes. I found evidence for immigration credits for generalist and pioneer species but not for extinction debts for forest specialist species which might be rapidly paid off in farmland. The results suggest not only an unrecognized conservation value of old farmland but also a disturbing loss of forest specialist species. To slow this trend, it is necessary to shift to a cultural landscape development approach and to restore forest specialist species in the landscapes. Third, I evaluated the supply of potential multiple ecosystem services and the relationships between the diversity of woody plant and ecosystem service in the three major land use types, namely forests with and without coffee management and farmland. The results revealed a high multifunctionality of landscapes and showed that ecosystem services significantly increase with woody plant diversity in all types of land use. These findings suggest that the woody plant diversity and multifunctionality in southwestern Ethiopian landscapes has to be maintained. Fourth, I explored farmers’ woody plant use to assess their dependency on and maintenance of woody plants and also considered the influence of property rights and management in this context. I found that local farmers used 95 species for eleven major purposes from all major land uses across the landscapes. I also found that most of the widely used tree species regenerated successfully throughout the landscapes, including in farmland. Local people felt, however, that their property and tree use rights were limited, especially in forests, and that some of the most widely used plant species, including important timber species, appeared to have been overharvested in forests. The results suggest that many species are important for local livelihoods, but a perceived low sense of property rights also seems to adversely affect the management of woody plants, particularly in forests. By focusing on woody plants and their ecosystem services to local people, this dissertation documents a dramatic loss of native forest biodiversity and rapid changes in the cultural landscapes of southwestern Ethiopia. This study also reveals low levels of perceived property and tree use rights by local people, particularly when it comes to forests, and the present overharvesting of important tree species in forests in particular. This dissertation also highlights current value of the multifunctionality of the landscapes examined here, the increase in ecosystem services diversity with increasing woody plant biodiversity and the importance of woody plant species for local livelihoods. Overall, my findings suggest the need for preservation of intact forest sites and for cultural landscapes development to safeguard biodiversity and multifunctionality of the landscapes in the future. This, in turn, requires holistic and integrated approaches that involve local people and recognize their basic needs of woody plants and their property rights to foster the management of biodiversity and ecosystem services. Maintaining primary forests in and using cultural landscape approaches to the rapidly changing rural setting of southwestern Ethiopia would also contribute to the global effort to halt biodiversity loss.
Ensuring food security and halting biodiversity loss are two of the most pressing global sustainability challenges. Traditionally food security and biodiversity conservation were treated as mutually exclusive goals, and as a result, discourses and approaches were developed separately around each of these goals. Recently, however, sustainability science increasingly recognizes the close interdependence of food security and biodiversity and hence, pays greater emphasis to the need for integration of the two goals. Navigating pathways to ensure the successful integration of the two goals is, therefore, an important requirement. Attempts to identify pathways toward such integration have been dominated with a biophysical-technical focus that provides technical solutions to the integration of food security and biodiversity conservation. To this end, different food production techniques, and agricultural land use strategies have been widely considered as a solution to the food security-biodiversity nexus. While much scholarly attention has been given to the biophysical-technical dimensions, the social-political dimension, including equity, governance, and empowerment received little to no attention. By focusing on the poorly investigated social-political dimension, this dissertation aimed to identify governance properties that facilitate and impede the integration of food security and biodiversity conservation through an empirical case study conducted in a multi-level governance setting of southwestern Ethiopia. To address the overarching goal of this dissertation, first I examined how the existing widely discussed food security approaches and agricultural land use framework, land sparing versus land sharing unfold in the local context of southwestern Ethiopia. The finding in this dissertation indicated that the existing global framing of food security approaches as well as frameworks around agricultural land use has limited applicability in on-the-ground realities mainly because landscapes are complex systems that consist of stakeholders with multiple and (often) conflicting interests. This was evident from the finding that, unlike the binary framing of agricultural land use as land sparing and land sharing, local land use preference was not a matter of ‘either/or’, but instead involved mixed features exhibiting properties of both land sparing and land sharing. Moreover, in addition to the biophysical factors embedded in the existing food security approaches and land use frameworks, stakeholders preference involved social factors such as the compatibility of land use strategy with local values and traditions, which are mainly unaccounted in the existing global frameworks. Findings in his dissertation revealed that the existing reductionist analytical framings to the issues of food security and biodiversity conservation seldom address the complexity inherent within and between food security and biodiversity conservation sectors. Second, this dissertation identified governance structural and process related challenges that influence individual as well as integrated achievements of food security and biodiversity conservation goals. The result of the study showed that the governance of food security and biodiversity conservation was characterized by a strongly hierarchical system with mainly linear vertical linkages, lacking horizontal linkages between stakeholders that would transcend administrative boundaries. This type of governance structure, where stakeholders interaction is restricted to administrative boundaries could not fit with the nature of food security and biodiversity conservation because the two goals are complex in their own involving sub-systems transcending different policy sectors and administrative boundaries. Furthermore, with regard to the governance process, three key and interdependent categories of governance process challenges namely, institutional misfit, the problem of interplay, and policy incoherence influenced the achievement of individual and integrated goals of food security and were identified. Given the interdependence of these governance challenges, coupled with the complexity inherent in the food security and biodiversity conservation, attempts to achieve the dual goals thus needs an integrative, flexible and adaptive governance system Third, to understand how food security and biodiversity conservation unfold in the future, I explored future development trajectories for southwestern Ethiopia. Iterative scenario planning process produced four plausible future scenarios that distinctly differed with regard to dominating land use strategies and crops grown, actor constellations and governance mechanisms, and outcomes for food security and biodiversity conservation. Three out of the four scenarios focused on increasing economic gains through intensive and commercial agricultural production. The agricultural intensification and commercialization may increase food availability and income gains, but negatively affect food security through neglecting other dimensions such as dietary diversity, social justice and stability of supply. It also affects biodiversity conservation by causing habitat loss, land degradation, and water pollution, biodiversity loss. In contrast, one scenario involved features that are widely considered as beneficial to food security and biodiversity conservation, such as agroecological production, diversification practices, and increased social-ecological resilience. In smallholder landscapes such as the one studied here, such a pathway that promises benefits for both food security and biodiversity conservation may need to be given greater emphasis. In order to ensure the integration of food security and biodiversity conservation, recognizing their interdependence and addressing the challenges in a way that fits with the local dynamics is essential. In addition, addressing the food security-biodiversity nexus requires a holistic analytical lens that enables proper identification of system properties that benefit food security and biodiversity conservation. Moreover, this dissertation indicated that there is a clear need to pay attention to the governance structure that accommodates the diversity of perspectives, enable participation and strong coordination across geographical boundaries, policy domains and governance levels. Finally, this dissertation revealed opportunities to integrate food security and biodiversity through the pro-active management of social-ecological interactions that produce a win-win outcome. The win-win outcome could be achieved in a system that involve properties such as diversification and modern agroecological techniques, smallholders empowerment, emphasize adaptive governance of social-ecological systems, value local knowledge, culture and traditions, and ensure smallholders participation. While such diversification and agroecological practices may lack the rapid economic development that is inherent to the conventional intensification, it essentially create a system that is more resilient to environmental and economic shocks, thereby providing a more sustainable long-term benefit.