The variability in Salix BVOC emissions and possible consequences for managed SRC plantations

Willow (Salix spp.) trees have been used commercially since the 1980s to produce renewable energy. Some benefits with these trees are that they can clean soil from heavy metals, reduce the risk of nutrient leakage and eutrophication. They could be an alternative to reduce carbon dioxide emissions from fossil fuel, but they are known to emit high rates of biogenic volatile organic compounds (BVOCs). Many thousands of different compounds are included in this group and they can be divided into terpenes, alcohols, alkanes and esters, to mention a few. These compounds are important. For instance, BVOCs help plants to attract pollinators. They serve as a protection to different kinds of stress, e.g., herbivores, heat and pollutions. Once they are released into the atmosphere, they will be involved in many chemical processes. Hydroxyl radicals, which are known to clean the air from pollutions, are depleted by BVOCs leading to increased lifetime of methane. Emissions of BVOCs could also act as precursors for aerosol formation, which in turn might lead to changes in cloud properties and radiative forcing. Photochemical smog like ozone (O3) is another result of the reactions in the atmosphere where BVOCs are involved, which impairs regional air quality. The reported range of emission rates from Salix is wide. Details about age, canopy position of leaves and how commercially used Salix varieties differ in their emission potentials are lacking, which lead to large errors if modelled emissions are based on too simple assumptions. Therefore, the aim of the work in this thesis was to investigate how the emissions vary with height, age, variety and during the growing season to get more reliable emission rates that can be used in models to better assess the impacts on the regional air quality. Measurements of aerosol formation were conducted to be able to determine the potential particle production near the Salix site. The outcome from the Salix measurements was then combined with BVOC measurements on spruce to assess how an expansion of Salix plantations could affect the regional air quality if a conversion of the land was shifted into these plantations, e.g., by using more arable and forest land. The study between 2015 and 2016, and the measurements in 2017, showed that Salix mainly emitted isoprene, which peaked during summer. Emissions of monoterpenes (MTs) showed a decreasing trend through the growing season. The BVOC emission rates differed depending on if the leaves were acclimatized to sunlit or shaded conditions, where the sun-adapted leaves emitted twice as much isoprene as the shaded. There was also a significant difference among the studied varieties, where Wilhelm emitted approx. three times more isoprene than Tora. Age influenced the emission rates. The emissions of non-terpenes from younger trees were substantially higher than from the older trees. Emissions of MTs were higher from younger trees compared to older as well. When comparing isoprene emissions, the emission rates from the older trees were almost five times larger than from the younger. Induced emissions of stress-related compounds like hexanal was observed due to an outbreak of Melampsora in 2015. Together with some other compounds, these emissions increased several times. All these results highlight the complexity of BVOC emissions and existing models need to be improved by including parameters like season, age, microclimate adaption and stress to better predict and estimate BVOC emissions. No particle enhancement could be observed from the Salix plantation near the site in 2015. The explanation for this result was the lack of precursors, e.g., MTs. However, spruce trees emitted higher rates of MTs and are probably more prone to generate particles compared to Salix trees. The high isoprene emissions from Salix is more likely to produce O3 if sources of anthropogenic NOx are sufficiently close. An expansion of Salix plantations where spruce forest and traditional agriculture are converted into willow fields would lead to considerably more regional isoprene in the atmosphere. Thus, plantations of Salix should be strategically located to avoid prerequisites to form O3, and preferably the variety Tora should be chosen since it emitted the lowest rates of isoprene

Strategies for creating new venture legitimacy

New ventures, being heavily subjected to liabilities of newness, are seen to engage in legitimacy strategies to overcome these liabilities. Building on an adapted theoretical framework of organizational legitimacy, self-reported weekly diaries of twelve entrepreneurs were analysed to identify strategies used by new ventures to create legitimacy. New ventures appear to prefer pragmatically related strategies over moral and cognitive ones, and adopt malleability with respect to moral strategies. The novelty of the venture technology increases the focus on conformity strategies, whereas more established technologies use manipulative strategies to gain legitimacy. New ventures also appear to engage strongly in moral selection strategies in terms of goal formulation

Variability of BVOC Emissions from Commercially Used willow (<i>Salix</i> spp.) Varieties

Willow (Salix spp.) trees are commonly used in short rotation coppices (SRC) to produce renewable energy. However, these plants are also known to emit high concentrations of biogenic volatile organic compounds (BVOCs), which have a large influence on air quality. Many different clones of commercially used Salix varieties exist today, but only a few studies have focused on BVOC emissions from these newer varieties. In this study, four varieties commercially propagated for biofuel production have been studied on a leaf-scale in the southern part of Sweden. The trees had either their first or second growing season, and measurements on BVOC emissions were done during the growing season in 2017 from the end of May to the beginning of September. Isoprene was the dominant emitted compound for all varieties but the average emission amongst varieties varied from 4.00 to 12.66 µg gdw−1 h−1. Average monoterpene (MT) (0.78–1.87 µg gdw−1 h−1) and sesquiterpene (SQT) emission rates (0.22–0.57 µg gdw−1 h−1) differed as well among the varieties. Besides isoprene, other compounds like ocimene, linalool and caryophyllene also showed a response to light but not for all varieties. Younger plants had several times higher emissions of non-isoprenoids (other VOCs) than the corresponding 1-year-old trees. The conclusions from this study show that the choice of variety can have a large impact on the regional BVOC emission budget. Genetics, together with stand age, should be taken into account when modelling BVOC emissions on a regional scale, for example, for air quality assessments

Birch establishes anywhere! So, what is there to know about natural regeneration and direct seeding of birch?

We tested three soil scarification approaches of varying intensity (intensive preparation exposing bare mineral soil, medium intensity with a mixture of organic material and mineral soil, and control without site preparation) on six clear-felled sites in two localities in northern and central Sweden between 2018 and 2021. The effect of soil scarification intensity and soil moisture on the occurrence of naturally regenerated birch seedlings was tested one, two and three years after soil scarification, and the density of direct-seeded birch seedlings one year after seeding. In addition, we tested the effect of the annual seed rain, and differences between the two birch species, on the density of direct-seeded seedlings. Soil scarification and its interaction with soil moisture had a significant positive effect on both the occurrence of naturally regenerated birch seedlings and the density of direct-seeded birch seedlings. There was no significant effect of neither annual natural seed rain nor species choice on direct-seeded seedling density. Time since soil scarification had a significant effect on the occurrence of naturally regenerated birch seedlings. In moist soils with high volumetric water content (>= 28%), birch seeds germinate at high rates and seedlings survive without soil scarification. In mesic soils, birch seeds germinate with higher rates after soil scarification. In dry soils, birch seeds rarely germinate regardless of any disturbance of the humus layer

On the magnetic characteristics of magnetic holes in the solar wind between Mercury and Venus

The occurrence rate of linear and pseudo magnetic holes has been determined during MESSENGER&#39;s cruise phase starting from Venus (2007) and arriving at Mercury (2011). It is shown that the occurrence rate of linear magnetic holes, defined as a maximum of 10∘ rotation of the magnetic field over the hole, slowly decreases from Mercury to Venus. The pseudo magnetic holes, defined as a rotation between 10 and 45∘ over the hole, have mostly a constant occurrence rate

La fin des nouvelles classes : couches moyennes éclatées et société d’appareils

Le gonflement des effectifs des diplômés de l'enseignement supérieur, l'utilisation massive des savoirs scientifiques, techniques et sociaux dans le monde de la production, la croissance des grandes organisations et la multiplication de leurs niveaux hiérarchiques intermédiaires, autant d'éléments qui permettent d'expliquer le développement des couches moyennes salariées. Mais que signifie sociologiquement la croissance de ce groupe médian ? Est-elle compatible avec la représentation d'une société déchirée par le conflit de deux classes antagonistes ? Est-elle l'un des nombreux signes d'une transformation qualitative des sociétés industrielles ou plutôt le produit d'un travail idéologique et socio-politique visant à modifier le système des représentations et à occulter le conflit Capital -Travail ? Ces couches constituent-elles des fractions de la classe ouvrière et/ou de la classe dirigeante, ou fondent-elles au contraire une « nouvelle classe » qui se singulariserait non seulement par son mode de consommation, ses orientations culturelles et ses projets politiques, mais aussi par ses relations aux autres classes ? [Premier paragraphe