Liquid transportation and distribution during (re)wetting : impact on coated papers in printing

In many industrial applications, such as the printing and coatings industry, wetting of porous materials by liquids includes not only imbibition and permeation into the bulk but also surface spreading and evaporation. By understanding these phenomena, valuable information can be obtained for improved process control, runnability and printability, in which liquid penetration and subsequent drying play important quality and economic roles. Knowledge of the position of the wetting front and the distribution/degree of pore filling within the structure is crucial in describing the transport phenomena involved. Although exemplifying paper as a porous medium in this work, the generalisation to dynamic liquid transfer onto a surface, including permeation and imbibition into porous media, is of importance to many industrial and naturally occurring environmental processes. This thesis explains the phenomena in the field of heatset web offset printing but the content and the analyses are applicable in many other printing methods and also other technologies where water/moisture monitoring is crucial in order to have a stable process and achieve high quality end products. The use of near-infrared technology to study the water and moisture response of porous pigmented structures is presented. The use of sensitive surface chemical and structural analysis, as well as the internal structure investigation of a porous structure, to inspect liquid wetting and distribution, complements the information obtained by spectroscopic techniques. Strong emphasis has been put on the scale of measurement, to filter irrelevant information and to understand the relationship between interactions involved. The near-infrared spectroscopic technique, presented here, samples directly the changes in signal absorbance and its variation in the process at multiple locations in a print production line. The in-line non-contact measurements are facilitated by using several diffuse reflectance probes, giving the absolute water/moisture content from a defined position in the dynamic process in real-time. The nearinfrared measurement data illustrate the changes in moisture content as the paper is passing through the printing nips and dryer, respectively, and the analysis of the mechanisms involved highlight the roles of the contacting surfaces and the relative liquid carrier properties of both non-image and printed image areas. The thesis includes laboratory studies on wetting of porous media in the form of coated paper and compressed pigment tablets by mono-, dual-, and multi-component liquids, and paper water/moisture content analysis in both offline and online conditions, thus also enabling direct sampling of temporal water/moisture profiles from multiple locations. One main focus in this thesis was to establish a measurement system which is able to monitor rapid changes in moisture content of paper. The study suggests that near-infrared diffuse reflectance spectroscopy can be used as a moisture sensitive system and to provide accurate online qualitative indicators, but, also, when accurately calibrated, can provide quantification of water/moisture levels, its distribution and dynamic liquid transfer. Due to the high sensitivity, samples can be measured with excellent reproducibility and good signal to noise ratio. Another focus of this thesis was on the evolution of the moisture content, i.e. changes in moisture content referred to (re)wetting, and liquid distribution during printing of coated paper. The study confirmed different wetting phases together with the factors affecting each phase both for a single droplet and a liquid film applied on a porous substrate. For a single droplet, initial capillary driven imbibition is followed by equilibrium pore filling and liquid retreat by evaporation. In the case of a liquid film applied on paper, the controlling factors defining the transportation were concluded to be the applied liquid volume in relation to surface roughness, capillarity and permeability of the coating giving the liquid uptake capacity. The printing trials confirmed moisture gradients in the printed sheet depending on process parameters such as speed, fountain solution dosage and drying conditions as well as the printed layout itself. Uneven moisture distribution in the printed sheet was identified to be one of the sources for waving appearance and the magnitude of waving was influenced by the drying conditions.

Evolutionary Ecology of Mountain Birch in Subarctic Stress Gradients: Interplay of Biotic and Abiotic Factors in Plant-Plant Interactions and Evolutionary Processes

In nature, variation for example in herbivory, wind exposure, moisture and pollution impact often creates variation in physiological stress and plant productivity. This variation is seldom clear-cut, but rather results in clines of decreasing growth and productivity towards the high-stress end. These clines of unidirectionally changing stress are generally known as ‘stress gradients’. Through its effect on plant performance, stress has the capacity to fundamentally alter the ecological relationships between individuals, and through variation in survival and reproduction it also causes evolutionary change, i.e. local adaptations to stress and eventually speciation. In certain conditions local adaptations to environmental stress have been documented in a matter of just a few generations. In plant-plant interactions, intensities of both negative interactions (competition) and positive ones (facilitation) are expected to vary along stress gradients. The stress-gradient hypothesis (SGH) suggests that net facilitation will be strongest in conditions of high biotic and abiotic stress, while a more recent ‘humpback’ model predicts strongest net facilitation at intermediate levels of stress. Plant interactions on stress gradients, however, are affected by a multitude of confounding factors, making studies of facilitation-related theories challenging. Among these factors are plant ontogeny, spatial scale, and local adaptation to stress. The last of these has very rarely been included in facilitation studies, despite the potential co-occurrence of local adaptations and changes in net facilitation in stress gradients. Current theory would predict both competitive effects and facilitative responses to be weakest in populations locally adapted to withstand high abiotic stress. This thesis is based on six experiments, conducted both in greenhouses and in the field in Russia, Norway and Finland, with mountain birch (Betula pubescens subsp. czerepanovii) as the model species. The aims were to study potential local adaptations in multiple stress gradients (both natural and anthropogenic), changes in plant-plant interactions under conditions of varying stress (as predicted by SGH), potential mechanisms behind intraspecific facilitation, and factors confounding plant-plant facilitation, such as spatiotemporal, ontogenetic, and genetic differences. I found rapid evolutionary adaptations (occurring within a time-span of 60 to 70 years) towards heavy-metal resistance around two copper-nickel smelters, a phenomenon that has resulted in a trade-off of decreased performance in pristine conditions. Heavy-metal-adapted individuals had lowered nickel uptake, indicating a possible mechanism behind the detected resistance. Seedlings adapted to heavy-metal toxicity were not co-resistant to others forms of abiotic stress, but showed co-resistance to biotic stress by being consumed to a lesser extent by insect herbivores. Conversely, populations from conditions of high natural stress (wind, drought etc.) showed no local adaptations, despite much longer evolutionary time scales. Due to decreasing emissions, I was unable to test SGH in the pollution gradients. In natural stress gradients, however, plant performance was in accordance with SGH, with the strongest host-seedling facilitation found at the high-stress sites in two different stress gradients. Factors confounding this pattern included (1) plant size / ontogenetic status, with seedling-seedling interactions being competition dominated and host-seedling interactions potentially switching towards competition with seedling growth, and (2) spatial distance, with competition dominating at very short planting distances, and facilitation being strongest at a distance of circa ¼ benefactor height. I found no evidence for changes in facilitation with respect to the evolutionary histories of plant populations. Despite the support for SGH, it may be that the ‘humpback’ model is more relevant when the main stressor is resource-related, while what I studied were the effects of ‘non-resource’ stressors (i.e. heavy-metal pollution and wind). The results have potential practical applications: the utilisation of locally adapted seedlings and plant facilitation may increase the success of future restoration efforts in industrial barrens as well as in other wind-exposed sites. The findings also have implications with regard to the effects of global change in subarctic environments: the documented potential by mountain birch for rapid evolutionary change, together with the general lack of evolutionary ‘dead ends’, due to not (over)specialising to current natural conditions, increase the chances of this crucial forest-forming tree persisting even under the anticipated climate change.

Calibration of time domain reflectometry (DTR) for soil moisture measurements in cultivated peat soils

Tiivistelmä: TDR-mittausten kalibrointi viljeltyjen turvemaiden kosteuden mittaamiseen

Equilibrium moisture content of flax/linseed and fibre hemp straw fractions

Selostus: Pellavan ja kuituhampun korren jakeiden tasapainokosteus

Macroalgae across environmental gradients : tools for managing rocky coastal areas of the northern Baltic Sea

Macroalgae are the main primary producers of the temperate rocky shores providing a three-dimensional habitat, food and nursery grounds for many other species. During the past decades, the state of the coastal waters has deteriorated due to increasing human pressures, resulting in dramatic changes in coastal ecosystems, including macroalgal communities. To reverse the deterioration of the European seas, the EU has adopted the Water Framework Directive (WFD) and the Marine Strategy Framework Directive (MSFD), aiming at improved status of the coastal waters and the marine environment. Further, the Habitats Directive (HD) calls for the protection of important habitats and species (many of which are marine) and the Maritime Spatial Planning Directive for sustainability in the use of resources and human activities at sea and by the coasts. To efficiently protect important marine habitats and communities, we need knowledge on their spatial distribution. Ecological knowledge is also needed to assess the status of the marine areas by involving biological indicators, as required by the WFD and the MSFD; knowledge on how biota changes with human-induced pressures is essential, but to reliably assess change, we need also to know how biotic communities vary over natural environmental gradients. This is especially important in sea areas such as the Baltic Sea, where the natural environmental gradients create substantial differences in biota between areas. In this thesis, I studied the variation occurring in macroalgal communities across the environmental gradients of the northern Baltic Sea, including eutrophication induced changes. The aim was to produce knowledge to support the reliable use of macroalgae as indicators of ecological status of the marine areas and to test practical metrics that could potentially be used in status assessments. Further, the aim was to develop a methodology for mapping the HD Annex I habitat reefs, using the best available data on geology and bathymetry. The results showed that the large-scale variation in the macroalgal community composition of the northern Baltic Sea is largely driven by salinity and exposure. Exposure is important also on smaller spatial scales, affecting species occurrence, community structure and depth penetration of algae. Consequently, the natural variability complicates the use of macroalgae as indicators of human-induced changes. Of the studied indicators, the number of perennial algal species, the perennial cover, the fraction of annual algae, and the lower limit of occurrence of red and brown perennial algae showed potential as usable indicators of ecological status. However, the cumulated cover of algae, commonly used as an indicator in the fully marine environments, showed low responses to eutrophication in the area. Although the mere occurrence of perennial algae did not show clear indicator potential, a distinct discrepancy in the occurrence of bladderwrack, Fucus vesiculosus, was found between two areas with differing eutrophication history, the Bothnian Sea and the Archipelago Sea. The absence of Fucus from many potential sites in the outer Archipelago Sea is likely due to its inability to recover from its disappearance from the area 30-40 years ago, highlighting the importance of past events in macroalgal occurrence. The methodology presented for mapping the potential distribution and the ecological value of reefs showed, that relatively high accuracy in mapping can be achieved by combining existing available data, and the maps produced serve as valuable background information for more detailed surveys. Taken together, the results of the theses contribute significantly to the knowledge on macroalgal communities of the northern Baltic Sea that can be directly applied in various management contexts.