The aim of this studv is to investigate interrelationships betweenbedrock relief and geological material. The area of investigation covers ca 350 km and is located in the Precambrian bedrock in the central part of Umeå commune, in northern Norrland. The boundary between two morphologically different types of landscape, the coastal plain (kustslätten) and the Norrland terrain (Norrlandsterrängen), crosses this area in a north-westerly direction.The study area's Precambrian bedrock has been mapped in detail by the author and the results are presented in a map at the scale of 1:50,000 together with a description. The occurring rock types have been studied with regard to their resistance against physical and chemical weathering. By relating recent research experience concerning Fennoscandia's palaeogeography, palaeoclimatology and isostasy, an appreciation is given of the character and strength of the forces of disintegration. Accordingly, it seems probable that chemical weathering was the dominant phenomenon during Silurian, Devonian, and even Carboniferous and Permian, whereas when the climate worsened significantly after the Tertiary period Fennoscandia's landscape was resculptured by glacial forces.During Tertiary and Quarternary times, Pennoscandia was twice uplifted and once loweredStatistical correlations between landscape relief, bedrock structure and rock variations, show that the highest sections of the landscape are dominated by resistant older granitoids, granitic mobilizate and veined gneisses, whereas the low-lying valleys and plains are characterized by the easily weathered biotite-plagioclase schists. Much suggests that the distinctive morphology of the coastal plain and Norrland terrain was initiated by bedrock structure and rock variations. As in some earlier works on Fennoscandia, this study attributes great importance to selective weathering in shaping the landscape. / digitalisering@umu

During the late or post Weichselian glacial periods, about 9500 years ago, several faulting associated with large scale earthquakes were triggered in northern Fennoscandia. The end- or post-glacial scarps have a range of the lengths c. 3 to 155 km and the heights 0 to 30 m while most of them are reverse faults trending NE-SW with SE dips. In this literature study, I try to compile the estimated history and cause of seismicity in northern Sweden, and predict the future activity. The result indicates that although the timing of these faulting might not be in the same phase of deglaciation, the upheaval induced by glacial retreating is considered as the major factor of these paleoseismicity. Since the strain from glaciers has been mostly released, the main cause of recent earthquakes in this region is tectonic stress accumulation. Accompanied by the progress of observing techniques such as drilling and grand penetrating radar detection especially in this decade, the geometry of these glacially induced faults and recent micro-seismicity in the vicinity of these scarps have been detected better and better. According to the results, the recorded epicenters form clusters in the east side of the faults’ zone. It implies the correlation between recent seismicity and end- or post-glacial faults. However, there is still insufficient data of the faults’ structure and previous seismicity in order to clarify the faults’ geometry, the age of main movements and estimate their future activity. More investigations are expected to take place in this region.

Recent studies applying innovative technologies, such as genetic analysis and carbon dating, contradict the palynological based assumption that Scots pine (Pinus sylvestris) and Norway spruce (Picea abies) vanished from Fennoscandia during the Last Glacial Maximum (c. 20.000 yrs BP) and re-colonized after the cold Younger Dryas (c. 12.000 yrs BP). Instead, those studies indicate glacial survival of boreal trees in ‘cryptic’ refugia within Scandinavia, which is still heavily debated. In this report, I try to get a better grip on the discussion if Norway spruce and Scots pine survived Weichselian glacial periods in isolated ‘cryptic’ refugia within Scandinavia, or either re-colonized Fennoscandia by post-glacial migration from eastern areas such as Russia. To this aim, climatic settings are described and an overview is given on what is already known on the distribution of boreal trees during the Weichselian glaciations and the post-glacial landscape. Several records are important to detect ancient boreal trees: pollen, macrofossils and currently DNA. Macrofossils indicate early post-glacial tree growth in the central Scandes just after the Younger Dryas, aDNA indicates the existence of a ‘cryptic’ refugium on Andøya during the Last Glacial Maximum and modern DNA analysis possibly indicates isolation of spruce in western Norway, which are all contradicted by the current interpretation of low pollen percentages. Altogether, alternative hypotheses supporting glacial survival of plants might have been overlooked and pollen interpretations need revision, which could turn the exclusion from the past into supporting evidence for the glacial survival of P. abies and P. sylvestris in Scandinavia.

This thesis presents results from several studies that have focused on the carbon and nutrient dynamics in soils at the forest – tundra ecotone in Fennoscandia. The main objectives of the study were: (i) to investigate the links between the physical environment, above-ground vegetation communities, soil carbon storage, nutrient status and the chemical composition of the soil organic matter (SOM), and (ii) to quantify trace gas fluxes (methane and carbon dioxide) between mesic soils and the atmosphere. Four main field areas spanning an 8 degree latitudinal gradient were established at the ecotone in 1998 and studied for four years. In addition to the natural gradients we also established a warming treatment. Decomposition rates (i.e. carbon dioxide efflux and litter decomposition) were higher at our forest sites. This was linked principally to the more favourable physical environment at the forest sites, rather than to SOM quality, despite some indications of higher SOM quality at forest sites based upon conventional chemical analysis and 13C NMR techniques. Tundra soils stored large amounts of potentially labile carbon that could readily be accessed by microorganisms when transferred to a forest environment. The interrelation between increased soil temperature and reduced soil moisture content is likely to moderate the response of decomposition rates to increased temperatures. Generally, these mesic soils showed net methane uptake from the atmosphere, which was enhanced by the warming treatment. No differences between forest or tundra soils could be detected. The major conclusions presented here are that (1) soil carbon storage is likely to be reduced if mountain birch forest replaces tundra heath and (2), methane uptake in mesic soils in the Fennoscandian mountains represents a negative feedback to further environmental change in a warmer climate.

Minimum blue intensity is a reflected light imaging technique that provides an inexpensive, robust and reliable surrogate for maximum latewood density. In this application it was found that temperature reconstructions from resin-extracted samples of Pinus sylvestris (L.) from Fennoscandia provide results equivalent to conventional x-ray densitometry. This paper describes the implementation of the blue intensity method using commercially available software and a flat-bed scanner. A calibration procedure is presented that permits results obtained by different laboratories, or using different scanners, to be compared. In addition, the use of carefully prepared and chemically treated 10-mm-diameter cores are explored; suggesting that it may not be necessary to produce thin laths with the rings aligned exactly perpendicular to the measurement surface.

<p>This thesis presents results from several studies that have focused on the carbon and nutrient dynamics in soils at the forest – tundra ecotone in Fennoscandia. The main objectives of the study were: (i) to investigate the links between the physical environment, above-ground vegetation communities, soil carbon storage, nutrient status and the chemical composition of the soil organic matter (SOM), and (ii) to quantify trace gas fluxes (methane and carbon dioxide) between mesic soils and the atmosphere. Four main field areas spanning an 8 degree latitudinal gradient were established at the ecotone in 1998 and studied for four years. In addition to the natural gradients we also established a warming treatment. Decomposition rates (i.e. carbon dioxide efflux and litter decomposition) were higher at our forest sites. This was linked principally to the more favourable physical environment at the forest sites, rather than to SOM quality, despite some indications of higher SOM quality at forest sites based upon conventional chemical analysis and ¹³C NMR techniques. Tundra soils stored large amounts of potentially labile carbon that could readily be accessed by microorganisms when transferred to a forest environment. The interrelation between increased soil temperature and reduced soil moisture content is likely to moderate the response of decomposition rates to increased temperatures. Generally, these mesic soils showed net methane uptake from the atmosphere, which was enhanced by the warming treatment. No differences between forest or tundra soils could be detected.</p><p>The major conclusions presented here are that (1) soil carbon storage is likely to be reduced if mountain birch forest replaces tundra heath and (2), methane uptake in mesic soils in the Fennoscandian mountains represents a negative feedback to further environmental change in a warmer climate.</p>

This thesis presents results from several studies that have focused on the carbon and nutrient dynamics in soils at the forest – tundra ecotone in Fennoscandia. The main objectives of the study were: (i) to investigate the links between the physical environment, above-ground vegetation communities, soil carbon storage, nutrient status and the chemical composition of the soil organic matter (SOM), and (ii) to quantify trace gas fluxes (methane and carbon dioxide) between mesic soils and the atmosphere. Four main field areas spanning an 8 degree latitudinal gradient were established at the ecotone in 1998 and studied for four years. In addition to the natural gradients we also established a warming treatment. Decomposition rates (i.e. carbon dioxide efflux and litter decomposition) were higher at our forest sites. This was linked principally to the more favourable physical environment at the forest sites, rather than to SOM quality, despite some indications of higher SOM quality at forest sites based upon conventional chemical analysis and 13C NMR techniques. Tundra soils stored large amounts of potentially labile carbon that could readily be accessed by microorganisms when transferred to a forest environment. The interrelation between increased soil temperature and reduced soil moisture content is likely to moderate the response of decomposition rates to increased temperatures. Generally, these mesic soils showed net methane uptake from the atmosphere, which was enhanced by the warming treatment. No differences between forest or tundra soils could be detected. The major conclusions presented here are that (1) soil carbon storage is likely to be reduced if mountain birch forest replaces tundra heath and (2), methane uptake in mesic soils in the Fennoscandian mountains represents a negative feedback to further environmental change in a warmer climate.

Målet med denna uppsats var att undersöka de nomadiska folkets användning av trä i norra Fennoskandien, samt möjliga analytiska metoder att studera arkeologiskt trämaterial. Detta möjliggjordes genom relevanta etnografiska, historiska och arkeologiska studier och en genomgång av analytiska metoder. De nomadiska folken använde trämaterial i en stor del av deras vardag så som mat i form av den näringsrika inner barken, ved för eldning, till både temporära och permanenta kåtor, förvarning samt jakt. De analytiska metoder som presenteras var träidentifikation, dendrokronologi och 14C-metoden. Träidentifikation möjliggör de två senare metoderna som kan förse tillförlitlig datering beroende på trämaterialets struktur samt tafonomiska processer / The aim of this thesis was to investigate the nomadic people’s wood usage in northern Fennoscandia, as well as possible analytical methods of investigating wooden remains. This was achieved through relevant ethnographic, historical and archaeological studies and a review of analytical methods. Wooden material played a big role in the life of the nomadic people in the shape of food, firewood, storage, construction material for both temporary and permanent huts, and for hunting. The analytical methods presented are species identification, dendrochronology and 14C-method. Species identification enables the latter methods of which provides reliable dating of wood, depending on the structure and taphonomic processes.

This thesis investigates how variations in the oxygen isotopic composition of lake waters in northern Fennoscandia are recorded in lake sediment archives, especially diatoms, and how these variations can be used to infer past changes in climate and atmospheric circulation. Results from analyses of the oxygen isotopic composition of lake water samples (δ18Olakew) collected between 2001 and 2006 show that δ18O of northern Fennoscandian lakes is mainly controlled by the isotopic composition of the precipitation (δ18Op). Changes in local δ18Op depend on variations in ambient air temperature and changes in atmospheric circulation that lead to changes in moisture source, vapour transport efficiency, or winter to summer precipitation distribution. This study demonstrates that the amount of isotopic variation in lake water δ18O is determined by a combination of the original δ18Olakew, the amount and timing of the snowmelt, the amount of seasonally specific precipitation and groundwater, any evaporation effects, and lake water residence time. The fact that the same isotope shifts have been detected in various δ18Olakew proxies, derived from hydrologically different lakes, suggests that these records reflect regional atmospheric circulation changes. The results indicate that diatom biogenic silica isotope (δ18Odiatom) records can provide important information about changes in atmospheric circulation that can help explain temperature and precipitation changes during the Holocene. The reconstructed long-term Holocene decreasing δ18Op trend was likely forced by a shift from strong zonal westerly airflow (relatively high δ18Op) in the early Holocene to a more meridional flow pattern (relatively low δ18Op). The large δ18Olakew depletion recorded in the δ18O records around ca. 500 cal yr BP (AD 1450) may be due to a shift to more intense meridional airflow over northern Fennoscandia resulting in an increasing proportion of winter precipitation from the north or southeast. This climate shift probably marks the onset of the so-called Little Ice Age in this region. / At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 1: In press. Paper 2: Submitted. Paper 5: In progress.

Abstract The crustal and upper mantle structures of the Shield on the regional scale were investigated using the data of the POLENET/LAPNET passive seismic array and the previously published models of active and passive seismic experiments in the study area. This area is centred in northern Finland and it extends to surrounding areas in Sweden, Norway and northwestern Russia. The bedrock there is mostly of the Archaean origin and the lithosphere of the region was reworked by two orogenies during Palaeoproterozoic. One of the results of the thesis was a new map of the Moho depth of the study area, for which new estimates of the crustal thickness were obtained using receiver function method and complemented by published results of receiver function studies and controlled source seismic profiles. The map differs from the previously published maps in two locations, where we found significant deepening of the Moho. The 3D structure of the upper mantle was studied using teleseismic traveltime tomography method. The resulting model shows high seismic velocities below three cratonic units of the study area, which may correspond to non-reworked fragments of cratonic lithosphere and a low velocity anomaly separating these cratonic units from each other. The regional scale studies were complemented by two smaller scale studies in upper crust level using combined interpretation of seismic profiling and gravity data. These studies were centred on Archaean Kuhmo Greenstone Belt in eastern Finland and central Lapland in northern Finland located in the crust reworked during Palaeoproterozoic. Both areas are considered as prospective ones for mineral exploration. Both studies demonstrate the advantage of gravity data inversion in studying 3D density structure of geologically interesting formations, when the Bouguer anomaly data is combined with a priori information from petrophysical and seismic datasets.