In the Arctic tundra, wood ants play an important ecological role in aerating the soil, cycling nutrients, for seed dispersal and, as biological control by preying on forest pest insects during outbreaks. The increase in temperature, caused by climate change, is positively associated with ant abundance.  This could accelerate the wood ants’ effects on the ecosystem, with potentially dramatic consequences for associated taxa. It is, however, still unclear to what extent the ants influence the vegetation and arthropod community. The aim of this study is to investigate the effects ants have on the Arctic tundra ecosystem and how climate change may modify these effects. The study was conducted in Abisko national park, north Sweden, were two study sites were selected: one at low altitude and one at high altitude. I found that wood ants had a substantial effect on the vegetation community close to the mound, with a positive effect on different kind of vascular plant species, and a negative effect on rushes, mosses, and lichens. All the arthropods taxonomic orders and most of the families were positively affected by the presence of ant mounds. Ant mound abundance and volume were positively related with annual insolation and GPP, which indicates that climate change will increase ant abundance in the Arctic tundra. Thus, my results suggest that future climate change will have significant effects on Arctic tundra vegetation and arthropod communities, via positive effects on ant abundance.

Tools that highlight the human impact on ecosystems and the accelerating depletion of natural resources are essential in the strife towards a more sustainable way of living. Emergy analysis is a scientific and robust method to assess the degree of sustainability of human as well as natural systems. Despite the advantages of the method, its public breakthrough has been slow. One reason could be that the results of an emergy analysis are difficult to grasp. In contrast, ecological footprint is a concept that has a widespread impact, much due to its pedagogical disposition. Ecological footprint made use of the vision to develop a method to well communicate the magnitude of human effect on nature. Another more recently created method suitable in this context is ecosystem services. Ecosystem services as a concept is not yet so well developed methodologically, but its use of mainstream concepts point toward a promising application. The main purpose of this study is to make the emergy analysis and ecosystem services methods more accessible and also to facilitate effective communication of the results from these methods. The second part of the study aims to assess the degree of sustainability ofan agricultural system in central Sweden by means of emergy analysis and ecosystems services. By demonstrating the results of the emergy analysis as a foot- and fingerprint, a better understanding of the outcome may be achieved. The footprint, here called emergy-based footprint, visualizes all resources used in the production system. An emergy-based fingerprint identifies the resources of the most important items in the system. Furthermore, ecosystem services are evaluated from a data matrix and presented by means of a radar diagram. Alternative scenarios for the agricultural system were created in the study, each presented as an emergy-based foot- and fingerprint, as well as by means of a radar diagram to visualize the values of the ecosystem services. Together, these methods demonstrate the sustainability characteristics of the different production systems. Results from this study suggest the agricultural system analysed, as well as the developed scenarios, not to be sustainable. The use of emergy analysis combined with ecosystem services and the visualization methods developed in this study, serve to provide accessible and effective communication methods when aiming to transform agricultural systems towards sustainability. The communication methods developed in this study are alsoapplicable in systems other than agriculture.

Ecological opportunity—the availability of open niche space to an evolving lineage—has long been thought to modulate the extent of adaptive diversification. Many microbial evolution experiments have confirmed that ecological opportunity drives diversification of initially homogeneous populations into communities of ecologically distinct sub-lineages (ecotypes). Interactions among ecotypes are crucial for both community function and the maintenance of the ecological diversity produced during adaptive diversification, however the factors influencing the evolution of these interactions remain unexplored. We assessed the influence of ecological opportunity on this process by studying communities of the bacterium Pseudomonas aeruginosa that were evolved in either nutritionally complex (COM) or simple (SIM) environments. We measured the net ecological interactions in these communities by comparing the cellular productivity and competitive fitness of whole communities from each environment to that of their component isolates in both complex and simple media. On average, COM communities had both higher productivity and fitness than their component isolates in complex media, indicating that the components of these communities share net positive interactions. The same was not true of SIM communities, which did not differ in either measure from their component isolates. Follow-up experiments revealed that high fitness in two COM communities was driven by rare variants (frequency < 0.1%) that secrete compounds during growth which inhibit PA14, the strain used as a common competitor for fitness assays. Taken together, our results suggest that environments with high levels of ecological opportunity drive diversification into ecotypes that share net positive ecological interactions. The strong effect of diversity on productivity and fitness we found in newly diversified communities has a number of implications for evolutionary ecology as well as the treatment of P. aeruginosa infections.

京都大学 / 0048 / 新制・課程博士 / 博士(経済学) / 甲第18760号 / 経博第511号 / 新制||経||273(附属図書館) / 31711 / 京都大学大学院経済学研究科経済学専攻 / (主査)教授 椙山 泰生, 教授 日置 弘一郎, 教授 武石 彰 / 学位規則第4条第1項該当 / Doctor of Economics / Kyoto University / DGAM

京都大学 / 0048 / 新制・課程博士 / 博士(工学) / 甲第20689号 / 工博第4386号 / 新制||工||1682(附属図書館) / 京都大学大学院工学研究科都市環境工学専攻 / (主査)教授 清水 芳久, 教授 田中 宏明, 教授 米田 稔 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DFAM

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