| 1. |
- Acosta Navarro, Juan Camilo, 1983-
(författare)
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Anthropogenic influence on climate through changes in aerosol emissions from air pollution and land use change
- 2017
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Particulate matter suspended in air (i.e. aerosol particles) exerts a substantial influence on the climate of our planet and is responsible for causing severe public health problems in many regions across the globe. Human activities have altered the natural and anthropogenic emissions of aerosol particles through direct emissions or indirectly by modifying natural sources. The climate effects of the latter have been largely overlooked. Humans have dramatically altered the land surface of the planet causing changes in natural aerosol emissions from vegetated areas. Regulation on anthropogenic and natural aerosol emissions have the potential to affect the climate on regional to global scales. Furthermore, the regional climate effects of aerosol particles could potentially be very different than the ones caused by other climate forcers (e.g. well mixed greenhouse gases). The main objective of this work was to investigate the climatic effects of land use and air pollution via aerosol changes.Using numerical model simulations it was found that land use changes in the past millennium have likely caused a positive radiative forcing via aerosol climate interactions. The forcing is an order of magnitude smaller and has an opposite sign than the radiative forcing caused by direct aerosol emissions changes from other human activities. The results also indicate that future reductions of fossil fuel aerosols via air quality regulations may lead to an additional warming of the planet by mid-21st century and could also cause an important Arctic amplification of the warming. In addition, the mean position of the intertropical convergence zone and the Asian monsoon appear to be sensitive to aerosol emission reductions from air quality regulations. For these reasons, climate mitigation policies should take into consideration aerosol air pollution, which has not received sufficient attention in the past.
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| 2. |
- Barrientos, Natalia, 1985-
(författare)
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Arctic Ocean benthic foraminifera preservation and Mg/Ca ratios : Implications for bottom water palaeothermometry
- 2018
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Reconstructions of Arctic Ocean palaeotemperatures are needed to disentangle natural variability from anthropogenic changes and understand the role of ocean heat transport in forcing or providing feedbacks on Arctic climate change. Despite known complications with calcareous microfossil preservation in Arctic Ocean sediments, calcareous benthic foraminifera can be common in interglacial sequences. However, thus far they have been underutilized in palaeoceanographic studies. This thesis explores the application of the Mg/Ca palaeothermometry proxy for reconstructing bottom water temperatures (BWT) in the Arctic Ocean during the late Quaternary. This method, which is supported by previous empirical studies demonstrating a strong temperature control on trace Mg inclusion into foraminiferal shell calcite, has been applied in many ocean regions and time intervals. Until now its application in the Arctic Ocean has been sparingly explored.The results of this doctoral thesis are based on benthic foraminifera retrieved from marine sediment cores covering a wide geographical Arctic Ocean area including both the shallow and vast continental shelves and slopes to the intermediate-to-deep waters of the Lomonosov Ridge and Morris Jesup Rise. These provide the first benthic foraminifera Mg/Ca ratios from the central Arctic Ocean region. In the first study, mechanisms that could affect Mg incorporation in Arctic benthic foraminifera are investigated using oceanographic field data and six 'live' modern Arctic species (Elphidium clavatum, Nonionella labradorica, Cassidulina neoteretis, Oridorsalis tener, Cibicidoides wuellerstorfi and Quinqueloculina arctica). The result is new species-specific Mg/Ca–BWT field calibrations that provide important constraints at the cold end of the BWT spectrum (-2 to 1°C) (Paper I). Using the new Mg/Ca–BWT equation for E. clavatum, a palaeotemperature record was generated for the late Holocene (past ca. 4100 yr) from the western Chukchi Sea. The data showed BWT fluctuations from -2 to 1°C that are interpreted as showing pulses of warmer Pacific water inflow at 500–1000 yr periods, thus revealing multi-centennial variability in heat transport into the Arctic Ocean driven by low latitude forcings (Paper II). Complications with foraminiferal calcite preservation that limit Mg/Ca palaeothermometry in the Arctic were discovered and these are tackled in two additional papers. Anomalously high Mg content in benthic foraminifera from the central Arctic Ocean is linked to diagenetic contamination as a result of the unique oceanographic, sedimentary and geochemical environment (Paper III). Lastly, the dramatic post-recovery dissolution of foraminifera from a Chukchi Shelf sediment core during core storage is investigated and attributed to acidification driven by sulphide oxidation in this organic rich and calcite poor shelf setting (Paper IV).The findings of this thesis demonstrate that benthic foraminiferal Mg/Ca-palaeothermometry can be applied in the Arctic Ocean and capture small BWT change (on the order of -2 to 2°C) even at low temperatures. In practice, preservational complexities can be limiting and require special sample handling or analysis due to the high potential for diagenetic contamination in the central Arctic Ocean and rapid post coring calcite dissolution in the seasonally productive shelf seas. This Ph.D. project is a component of the multidisciplinary SWERUS-C3 (Swedish-Russian-US Arctic Ocean Climate-Cryosphere- Carbon Interactions) project that included an expedition with Swedish icebreaker Oden to the East Siberian Arctic Ocean.
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| 3. |
- Bryngelsson, David, 1981
(författare)
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Land-use competition and agricultural greenhouse gas emissions in a climate change mitigation perspective
- 2015
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Productive land for food production, bioenergy, or preservation of nature is a limited resource. Climate change mitigation puts additional pressure on land via higher demand for bioenergy to replace fossil fuels and via restrictions on deforestation—two processes that limit the availability of land for food produc- tion, and may thus also raise food prices. Methane and nitrous oxide emis- sions from agriculture may also need to be reduced to efficiently mitigate climate change. This thesis deals with this in three ways.In papers I–II, we estimate greenhouse gas emissions from food production for current diets and expected future developments, together with alternative di- etary developments and potential technical improvements in the agricultural sec- tor. Costs and possibilities for reaching climate goals are analyzed for the differ- ent diets. The results indicate that a phase out of ruminant products would cut mitigation cost in half, for staying below a 2◦C limit, and it may be necessary if the climate sensitivity is high.In papers III–IV, a conceptual and transparent partial equilibrium model of global land-use competition is developed, analyzed and applied. The model is to a large degree analytically explored and price differentials between crops are derived. The model is subjected to a detailed characterization of its mechanisms and parameters that are critical to the results. We conclude that the total amount of productive agricultural area and bioenergy yields are of crucial importance to the price impacts from large-scale introduction of bioenergy. We also show how limiting bioenergy production to marginal land could be difficult to implement in practice.In paper V, we use two established indicators for poverty and sensitivity to food-price changes to capture peoples’ vulnerability to rising food-prices in four Sub-Sahara African countries/regions. In contrast to previous studies, we include all food products instead of just one or a few main staples. We found that the vast majority of people are net consumers of food and that the inclusion of more than main staples increases their net position as consumers and thus vulnerability to high food prices.
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| 4. |
- Klint, Erik, 1989
(författare)
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Washing with (con)science — Combining psychology and life cycle assessment to better understand the environmental impacts from domestic laundering
- 2024
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Technological aids often allow us to trade resources for time. Having taken away the tedious work of laundering clothes by hand, the washing machine has allowed people to spend more time on increasing household productivity, leisure activities and education. Unfortunately, behaviours are not static. Reduced costs often lead to increased consumption. Today, people in Europe own more clothes and wash them more frequently than at any other time in history. This extensive consumption also means that the environmental impacts from domestic laundering are higher than at any other time in history. One way to estimate these impacts is through life cycle assessment (LCA). The results from such LCAs can help prioritise interventions and policies that aim to reduce pressures on the environment. Unfortunately, many initiatives that have attempted to curb the environmental impacts of laundry have failed again and again. These failures indicate an incomplete understanding of what motivates consumer behaviours and present a challenge regarding how to appropriately address these behaviours in LCAs. This thesis shows what motivates domestic laundering behaviours psychologically speaking, highlights the uncertainties associated with contemporary LCAs of domestic laundering, and presents a way to expand the LCA methodology. The main message is that laundering our clothes is socially motivated. Therefore, a proper assessment of the environmental impacts associated with laundering behaviours must be based on a social perspective rather than a contemporary technical one. Since behaviours are adaptive, they need to be treated as systemic components in LCAs rather than as static values. Failing to do so might otherwise result in compensatory behaviours and burden shifting. By using insights from psychology and sociology as a starting point for the analysis, LCAs can offer a more nuanced assessment of the environmental impacts of consumer products and services. A social perspective also permits a more comprehensive assessment of societal trends, such as the rebound effect. With a more holistic understanding of why people engage in certain behaviours, LCAs can better guide interventions and policies towards targeting motivations rather than focusing on the consequences of behaviours. As such, a social perspective in an LCA is critical for the success of any policy or initiative aimed at reducing environmental impacts where the use phase is a significant contributor.
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| 5. |
- Åström, Stefan, 1977
(författare)
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Research and reflections on European air pollution policy support models
- 2019
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- European emissions to air of SO2, NOx, PM2.5, NH3 and NMVOC still today cause harm to human health and the environment. These pollutants are associated with the premature death of ~400 000 people annually in the EU (25 000 perished in traffic accidents 2017). Improvements are expected but problems will persist. To abate these effects European countries are engaged in several international agreements, all dependent on interaction between science and policy. For some 15 years scientific decision support to policy-makers was based on integrated assessment models (IAM) combined with quantification of economic benefits in cost-benefit analysis (CBA) of proposed policies. However, in 2013 the European Commission changed approach and used CBA to model socio-economic optimal emission levels and used these levels as basis for a policy proposal. This new approach puts higher demand on model coverage and reliability. It can also be methodologically controversial. This thesis presents research and reflections on the robustness of air pollution policy support models used by the European Commission, with focus on IAM and CBA. Robustness over climate metrics is analysed with cost-effectiveness analysis of air pollution control options, with sensitivity analysis of metric choice. An SO2 decomposition analysis indicates if consideration of end-of-pipe control options is enough. Robustness of emission control strategies with respect to investment parameters is analysed with IAM, and CBA provides estimates of whether options to reduce emissions from international shipping should be considered in the modelling. Methodological issues are also reviewed. The results indicate that the models are robust with respect to climate metrics used and the focus on end-of-pipe SO2 options. The modelling of emission control can be sensitive to investment parameters and to the current exclusion of control options on ships. The methodological foundation of CBA is criticised but since environmental policies depend on support also from arenas outside science it remains unclear if CBA-shortcomings impairs the air pollution policy process. Regardless, there are arguments for inter alia complementing CBA with analyses based on non-economic decision rationales. Finally, the thesis provides insights and suggestions for air pollution policy modelling and research that should be considered in the future.
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| 6. |
- Wieloch, Thomas, 1979-
(författare)
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Intramolecular isotope analysis reveals plant ecophysiological signals covering multiple timescales
- 2019
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Our societies' wellbeing relies on stable and healthy environments. However, our current lifestyles, growth-oriented economic policies and the population explosion are leading to potentially catastrophic degradation of ecosystems and progressive disruption of food chains. Hopefully, more clarity about what the future holds in store will trigger stronger efforts to find, and adopt, problem-focused coping strategies and encourage environmentally friendly lifestyles.Forecasting environmental change/destruction is complicated (inter alia) by lack of complete understanding of plant-environment interactions, particularly those involved in slow processes such as plant acclimatisation and adaptation. This stems from deficiencies in tools to analyse such slow processes. The present work aims at developing tools that can provide retrospective ecophysiological information covering timescales from days to millennia.Natural archives, such as tree-rings, preserve plant metabolites over long timescales. Analyses of intramolecular isotope abundances in plant metabolites have the potential to provide retrospective information about metabolic processes and underlying environmental controls. Thus, my colleagues and I (hereafter we) analysed intramolecular isotope patterns in tree rings to develop analytical tools that can convey information about clearly-defined plant metabolic processes over multiple timescales. Such tools might help (inter alia) to constrain plants' capacities to sequester excess amounts of anthropogenic CO2; the so-called CO2 fertilisation effect. This, in turn, might shed light on plants' sink strength for the greenhouse gas CO2, and future plant performance and growth under climate change.In the first of three studies, reported in appended papers, we analysed intramolecular 13C/12C ratios in tree-ring glucose. In six angiosperm and six gymnosperm species we found pronounced intramolecular 13C/12C differences, exceeding 10‰. These differences are transmitted into major global C pools, such as soil organic matter. Taking intramolecular 13C/12C differences into account might improve isotopic characterisation of soil metabolic processes and soil CO2 effluxes. In addition, we analysed intramolecular 13C/12C ratios in a Pinus nigra tree-ring archive spanning the period 1961 to 1995. These data revealed new ecophysiological 13C/12C signals, which can facilitate climate reconstructions and assessments of plant-environment interactions at higher resolution; thus providing higher quality information. We proposed that 13C/12C signals at glucose C-1 to C-2 derive from carbon injection into the Calvin-Benson cycle via the oxidative pentose phosphate pathway. We concluded that intramolecular 13C/12C measurements provide valuable new information about long-term metabolic dynamics for application in biogeochemistry, plant physiology, plant breeding, and paleoclimatology.In the second study, we developed a comprehensive theory on the metabolic and ecophysiological origins of 13C/12C signals at tree-ring glucose C-5 and C-6. According to this theory and theoretical implications of the first study on signals at C-1 to C-3, analysis of such intramolecular signals can provide information about several metabolic processes. At C-3, a well-known signal reflecting CO2 uptake is preserved. The glucose-6-phosphate shunt around the Calvin-Benson cycle affects 13C/12C compositions at C-1 and C-2, while the 13C/12C signals at C-5 and C-6 reflect carbon fluxes into downstream metabolism. This theoretical framework enables further experimental studies to be conducted in a hypothesis-driven manner. In conclusion, the intramolecular approach provides information about carbon allocation in plant leaves. Thus, it gives access to long-term information on key ecophysiological processes, which could not be acquired by previous approaches.The abundance of the hydrogen isotope deuterium, δD, is important for linking the water cycle with plant ecophysiology. The main factors affecting δD in plant organic matter are commonly assumed to be the δD in source water and leaf-level evaporative enrichment. Current δD models incorporate biochemical D fractionations as constants. In the third study we showed that biochemical D fractionations respond strongly to low ambient CO2 levels and low light intensity. Thus, models of δD values in plant organic matter should incorporate biochemical fractionations as variables. In addition, we found pronounced leaf-level δD differences between α-cellulose and wax n-alkanes. We explained this by metabolite-specific contributions of distinct hydrogen sources during biosynthesis.Overall, this work advances our understanding of isotope distributions and isotope fractionations in plants. It reveals the immense potential of intramolecular isotope analyses for retrospective assessment of plant metabolism and associated environmental controls.
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| 7. |
- Linkhorst, Annika
(författare)
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Greenhouse gas emission from tropical reservoirs : Spatial and temporal dynamics
- 2019
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The emission of methane (CH4) and carbon dioxide (CO2) from reservoirs has been estimated to make up for about 1.3% of the global anthropogenic greenhouse gas emission. The impoundment of a river leads to the accumulation of sediment that is brought in from inflowing rivers, and the sediment organic matter is degraded to CH4 and CO2. CH4 is of particular concern as its global warming potential is 34 times stronger than that of CO2. In the tropics, high temperatures and high availability of fresh organic matter from high net primary production fuel CH4 and CO2 production. As the construction of hydropower plants is currently undergoing a boom, especially in the tropics, reservoir emission is probably bound to increase.The emission of CH4 and CO2 from reservoir surfaces is, however, highly variable, which makes current estimates uncertain. This thesis is built on the hypothesis that the spatial and temporal variability of greenhouse gas emission in tropical reservoirs, particularly of CH4 ebullition (the emission via gas bubbles), is so large that the sampling strategy affects whole-system estimates of greenhouse gas emission.This thesis shows that greenhouse gas emission from the four studied tropical reservoirs in Brazil varied greatly at different timescales – over 24 hours, between days and between seasons. Seasonal variability was identified as the most important temporal scale to be covered for CH4 ebullition inventories. In addition, the spatial variability of gas emission was large for all pathways. The variability of CH4 ebullition across space, for example, was estimated to be almost as large as its variability between seasons, and patterns of spatial variability in diffusive CH4 and CO2 emission differed between seasons. For both ebullition and diffusion, river inflow areas were prone to elevated greenhouse gas emission.This thesis shows that for retrieving solid emission estimates, there is no alternative to time-consuming measurements in the field. Measurements should be repeated at least once during each hydrological season (i.e. falling and rising water level). The seasonal surveys should cover space at a high resolution, including areas with and without river inflows, and different water column depths. CH4 ebullition made up for 60–99% of the total CO2-equivalent emission from the whole water surface of the studied reservoirs, with the highest contribution in the most productive reservoir. The most variable greenhouse gas emission pathway is therefore the most important one to be measured at appropriate resolution, particularly in productive reservoirs.
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| 8. |
- Steffens, Karin Anna
(författare)
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Modelling climate change impacts on pesticide leaching : uncertainty and scenario analysis at field and regional scales
- 2015
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Climate change projections for Sweden indicate increases in both temperature and precipitation. In a warmer and wetter climate, weed and pest pressures are likely to increase, which might in turn trigger an increased use of pesticides. This thesis analysed potential impacts of climate change on pesticide losses from Swedish arable soils under present (1970-1999) and future (2070-2099) climate conditions. The pesticide fate model MACRO was used to evaluate the direct effects of climate change on pesticide losses to tile-drains at the field scale accounting for uncertainties related to model structure (i.e. the description of temperature dependent processes), parameters and climate input data. At the regional scale, MACRO-SE was used to assess the direct and the indirect effects of climate change (i.e. changes in cropping patterns and herbicide use) on the leaching of herbicides towards groundwater in southern Sweden. At the field scale, the results showed that differences in model structures affected predictions of pesticide losses under climate change, despite large parameter uncertainty. The effect of climate input uncertainty was more important than the effect of parameter uncertainty for predicted changes in pesticide losses between present and future climates, while it was the opposite for simulated absolute pesticide losses. The direction and magnitude of predicted changes in pesticide losses depended on pesticide properties, application season and climate scenario. In the regional scale study, the area at risk of groundwater contamination was only slightly affected by direct effects of climate change, whereas the area at risk doubled due to the indirect effects of climate change that were included in the analysis. The main conclusions are that (1) the relative importance of different sources of uncertainty depends on the pesticide properties, application season and whether the focus is on absolute losses or predicted changes, (2) ensembles of climate scenarios are necessary for robust assessments and (3) indirect effects need to be considered alongside the direct effects as predictions can be significantly affected. Despite large uncertainties, this thesis highlights the need to strengthen policies, to adopt improved mitigation measures and to implement management strategies that will limit pesticide use and minimize the risks of contamination of ground- and surface waters.
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| 9. |
- Ödalen, Malin, 1982-
(författare)
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Model analysis of ocean carbon storage and transport across climate states
- 2019
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The ocean carbon cycle plays a fundamental role in the Earth’s climate system, on decadal to multi-millennial timescales. Of the carbon held in the ocean, the atmosphere, and the terrestrial biosphere combined, more than 90% resides in the ocean. Carbon enters the surface ocean through air-sea gas exchange and from terrestrial sources. It is transported to the deep ocean with the ocean circulation and through the so-called biological pump, where carbon is taken up in the surface ocean by photosynthetic organisms that fall down and decompose at depth. This thesis contributes to the understanding of the processes involved in ocean carbon storage and transport. It examines how these processes respond to model perturbations, and how this response influences our attempts to simulate glacial-interglacial fluctuations in atmospheric carbon dioxide (CO2).The thesis investigates the response of the simulated ocean carbon storage, and distribution of the isotopic tracer δ13C, to changes in physical and biological parameters. In the included studies, we use observational as well as proxy records of oceanic properties to evaluate our model simulations. In addition, we use a climate model to interpret proxy evidence of glacial-interglacial changes in ocean δ13C. By using a separation framework, we identify the origin of the carbon in the model ocean, and attribute observed changes to the processes involved.The results indicate a strong link between ocean carbon storage and the strength of the global ocean overturning circulation. Stronger circulation leads to less carbon storage through a weakening of the biological pump, and through reduced solubility due to an increase in global ocean average temperature.In simulations of glacial climate, we find that biological adaptability to the surrounding nutrient conditions, through a flexible carbon-to-phosphorus ratio (C/P) in ocean photosynthesis, increases the ocean carbon storage compared to simulations where fixed C/P is applied. The biological flexibility improves the model’s ability to reproduce glacial atmospheric CO2. In line with previous research, we find freshwater input to the North Atlantic to be an important factor for reproducing glacial proxy records. The ensemble of simulations that achieve a good representation of glacial-interglacial δ13C indicates a deglacial whole-ocean change in δ13C of 0.28 ± 0.06‰.The thesis underlines the importance of the initial state, and the choice of model parameterisations, for the outcome of model ensemble, and intercomparison studies. Finally, it proposes a new method for estimation of ocean carbon transport, and attribution of this transport to different water masses and carbon system processes.
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| 10. |
- Monteux, Sylvain, 1989-
(författare)
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A song of ice and mud : Interactions of microbes with roots, fauna and carbon in warming permafrost-affected soils
- 2018
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Permafrost-affected soils store a large quantity of soil organic matter (SOM) – ca. half of worldwide soil carbon – and currently undergo rapid and severe warming due to climate change. Increased SOM decomposition by microorganisms and soil fauna due to climate change, poses the risk of a positive climate feedback through the release of greenhouse gases. Direct effects of climate change on SOM decomposition, through such mechanisms as deepening of the seasonally-thawing active layer and increasing soil temperatures, have gathered considerable scientific attention in the last two decades. Yet, indirect effects mediated by changes in plant, microbial, and fauna communities, remain poorly understood. Microbial communities, which may be affected by climate change-induced changes in vegetation composition or rooting patterns, and may in turn affect SOM decomposition, are the primary focus of the work described in this thesis.We used (I) a field-scale permafrost thaw experiment in a palsa peatland, (II) a laboratory incubation of Yedoma permafrost with inoculation by exotic microorganisms, (III) a microcosm experiment with five plant species grown either in Sphagnum peat or in newly-thawed permafrost peat, and (IV) a field-scale cold season warming experiment in cryoturbated tundra to address the indirect effects of climate change on microbial drivers of SOM decomposition. Community composition data for bacteria and fungi were obtained by amplicon sequencing and phospholipid fatty acid extraction, and for collembola by Tullgren extraction, alongside measurements of soil chemistry, CO2 emissions and root density.We showed that in situ thawing of a palsa peatland caused colonization of permafrost soil by overlying soil microbes. Further, we observed that functional limitations of permafrost microbial communities can hamper microbial metabolism in vitro. Relieving these functional limitations in vitro increased cumulative CO2 emissions by 32% over 161 days and introduced nitrification. In addition, we found that different plant species did not harbour different rhizosphere bacterial communities in Sphagnum peat topsoil, but did when grown in newly-thawed permafrost peat. Plant species may thus differ in how they affect functional limitations in thawing permafrost soil. Therefore, climate change-induced changes in vegetation composition might alter functioning in the newly-thawed, subsoil permafrost layer of northern peatlands, but less likely so in the topsoil. Finally, we observed that vegetation encroachment in barren cryoturbated soil, due to reduced cryogenic activity with higher temperatures, change both bacterial and collembola community composition, which may in turn affect soil functioning.This thesis shows that microbial community dynamics and plant-decomposer interactions play an important role in the functioning of warming permafrost-affected soils. More specifically, it demonstrates that the effects of climate change on plants can trickle down on microbial communities, in turn affecting SOM decomposition in thawing permafrost.
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