Water level impact on pine seedlings in greenhouse conditions: assessing growth and survival potential in ditched and managed peatlands

Tree establishment on peatlands has various adverse effects on the environment, with one of the most significant being their transformation from carbon sinks to carbon sources. This transformation has largely been instigated by economic-driven ditching initiatives. In this study, 80 peat-rooted pine seedlings were subjected to hydrological scenarios corresponding to natural, ditched, and rewetted conditions to investigate how different management strategies affect tree growth and survival. The study was conducted in a greenhouse where all plants were exposed to identical conditions except for the water level, and focused on factors like stomatal conductance, plant survival, length, biomass, and radial tree growth. Wet conditions, specifically treatments rewetted and natural, resulted in consistently lower stomatal conductance compared to drier treatments. Plant survival was affected, with 15 deaths in the rewetted and 2 in natural groups. Moreover, length, biomass, radial growth, and cell formation were significantly lower for the groups exposed to wet conditions. Rewetting can therefore effectively control tree colonisations, and thereby preventing water consumption, litter fertilisation, and other positive feedback effects for the trees that might be negative for the carbon uptake and biodiversity in peatlands. This study thereby offers valuable insights for rewetting initiatives in tree colonised peatland ecosystems

Urban tree establishment

The aim of this PhD project was to study tree establishment, both how it may be improved in urban areas and how it is measured and defined. The establishment phase of trees is a period of reduced tree vitality, and a successful establishment is crucial for long-term survival and prosperity of newly planted trees. However, failed plantings and poor establishment is a common problem in the often harsh growing conditions present in urban areas. Improving tree establishment is thus important for securing the presence of trees in urban environments. Another important part is to understand how the process of establishment is expressed in trees, so that the needs of the trees can be met. Tree nursery industry has recently developed production systems that aim to produce trees that are better prepared for transplanting. This study set out to investigate the effect nursery production systems might have on tree establishment success, and to examine different ways of assessing establishment, since the term is not consistently defined. Sweet cheery and red oak trees, cultivated as either bare-rooted (BR), balled & burlapped (B&B), root-pruned (RP), air-potted (AP) or fabric container (FC) grown were planted at one urban and one rural site in Southern Sweden. The trees were studied during the final nursery year and the four first post-transplant years. The production systems influenced total root length for both species, providing root systems with large differences in appearance. Shoot growth was restored to pre-transplant values for RP, FC and B&B sweet cherry trees at the rural site, three years after transplanting. Water status was significantly higher for AP trees than BR trees of both species, but only during the first year after transplanting, at the rural site. In general, effects of production system were more pronounced at the rural site with the higher water availability, indicating that none of the studied production systems was superior to use in urban plantings. Visual assessments of the establishment success of the trees were affected by leaf size, colour and shape. Leaf size was related to water status. Water status and shoot growth measurements were not correlated during the first years after transplanting. The term establishment can be used in different ways, and the differences might affect the outcome of an establishment assessment

Experimental evaluation of waterlogging and drought tolerance of essential Prunus species in central Europe

Fruit-bearing and flowering minority tree species, such as many species from the Prunus genus, are essential for multiple ecosystem services in the landscape. Although common, but never dominating, these minority species are often overlooked compared to commercial timber trees in relation to climate change. Induced stress on trees through climate change in central Europe will not only be caused by drought but also by extreme precipitation and pluvial flooding. This study experimentally address this by testing both waterlogging and drought tolerance in three key species of Prunus for central Europe that naturally span a wide variation of habitat conditions. The selected species Prunus mahaleb, Prunus avium and Prunus padus were subjected to both drought and waterlogging in a greenhouse experiment. Plant functionality in the form of midday leaf water potential, stomatal conductance and turgor loss point together with different aspects of biomass allocation and growth was tested. All included species lost their stomatal conductance and leaf water potential within a few days in the waterlogging treatment. Only P. padus had the capacity to recover with new leaves after the waterlogging ended, suggesting that avoidance strategies though leaf shedding can be a complementary mechanism to withstand waterlogging. P. padus kept its stomatal conductance and water potential for the longest time in the drought treatment followed by P. mahaleb and P.avium. This longevity in the drought treatment for P. padus could be explained by both tolerance strategies through lower turgor loss point, but also avoidance strategies with fast changes in growth and higher allocation of biomass to the roots. There is a clear risk that ecosystem service from Prunus species in the landscape can be negatively affected not only by drought but also by increased events of waterlogging. This highlights the need for including minority species and also other climate stressors in addition to drought in the planning and management of multifunctional landscapes

Using stomatal conductance capacity during water stress as a tool for tree species selection for urban stormwater control systems

Improving our understanding of how different tree species function in urban stormwater management systems is important, as tree pits may provide a temporary reservoir for stormwater and as trees have the potential to actively reduce stormwater runoff by transpiration. While urban tree planting pits are increasingly used for shortterm water storage during stormwater runoff events, this storage can have negative effects on both tree vitality and water removal capacity, since stress from waterlogging result in stomatal closure. However, sensitivity to water stress varies by species. It is therefore important to determine which tree species can maintain long-term vitality and continued transpiration even under water stress, and thus are suitable for such locations. Here, we studied how nine different tree species, varying in expected tolerance to water stress, were affected by short-term and seasonal waterlogging, in a greenhouse experiment. The seedlings (Magnolia x loebneri, Tilia tomentosa, and Sorbus torminalis - low water logging tolerance; Cercidiphyllum japonicum, Rhamnus cathartica, and Fraxinus ornus - medium water logging tolerance; Quercus palustris, Acer saccharinum, and Fraxinus pennsylvanica - high water logging tolerance) were exposed to two days, five days and seasonal waterlogging. The treatments reflected best practice (optimal), suboptimal and total lack of tree pit drainage, using Swedish standards. Stomatal conductance and leaf water potential were determined regularly over a period of 71 days, and morphological adjustments were registered. Four of the species were affected already after two days of waterlogging, with reduced stomatal conductance either during the waterlogging or immediately after, and only the most waterlogging tolerant species were unaffected by the five-day treatment. However, all plants survived waterlogging for almost 30 days before the estimated permanent wilting was reached in some plants. We suggest that tree species selection for stormwater management systems should consider the species' capacity to maintain high stomatal conductance during waterlogging, as there were clear differences between species. The effectiveness of the selected species could have an important impact on the stormwater management capacity of cities, as well as on other aspects of ecosystem service delivery from urban trees

Violent radicalization during the COVID-19 pandemic: at the intersection of gender, conspiracy theories and psychological distress

The COVID-19 pandemic continues to pose a threat to health, economic stability and collective functioning. The related upsurge in psychological distress has fuelled the emergence of conspiracy theories regarding the origins of the virus. Worldwide, there is mounting evidence that these narratives have increased stigma and discrimination against diverse ethnic, age and occupational groups. However, the role of gender in the dynamics weaving together psychological distress, conspiracy theories and legitimation of violence toward other groups is still unknown. This paper addresses this knowledge gap, analysing a Canadian interprovincial survey conducted in November 2020. In total, 6003 individuals aged 18-35 years residing in large Canadian cities responded to an online survey administered in English and French between October 16 and November 17, 2020. A total of 4928 individuals with complete data on support for violent radicalization (VR), psychological distress, and endorsement of COVID-19 conspiracy theories were included in the analysis. This study indicates that for young Canadian adults, gender, endorsement of COVID-19 conspiracy theories and psychological distress, as measured by the Hopkins Symptom Checklist-25 (HSCL-25), have an interaction effect on support for VR, as measured by both the Sympathy for Violent Radicalization Scale (SyfoR) and the Radicalism Intention Scale (RIS) (both p-values <.001). While the magnitude of the association between support for VR and endorsement of COVID-19 conspiracy theories is greatest among individuals with scores of psychological distress above the clinical cut-off, there is a significant association between scores on support for VR and endorsement of COVID-19 conspiracy theories in both women and men, both above and below the psychological distress cut-off of the HSCL-25. Effective strategies to mitigate the relationship between violent radicalization and pandemic-related psychological distress must explicitly address gender differences in expression and management of psychological distress

How green is an urban tree? The impact of species selection in reducing the carbon footprint of park trees in Swedish cities

Introduction: Planting trees in urban areas can mitigate some of the emissions generated in cities by carbon sequestration (annual uptake of CO2 through the process of photosynthesis) and carbon storage (amount of carbon stored in the tree's biomass throughout its lifespan). The aim of this study was to calculate the carbon footprint from nursery production to final establishment of different tree species grown for planting in urban parks in a northern European context.Material and methods: The analysis included a cradle-to-gate approach and investigated the amount of carbon the adult trees needed to sequester in order to compensate for initial carbon emissions and which temporal perspectives are of concern. Greenhouse gas emissions were estimated based on an inventory of consumption of fuels, energy, materials and other production inputs during cultivation, delivery, planting and establishment of three different tree species in three different locations in Sweden. The tree species considered in the analysis (Salix alba, Quercus rubra, Pinus sylvestris) were selected due to significant differences in their growth rates. Salix alba is a competitive strategist in resource-rich habitats, and is proficient at converting these resources into vigorous growth. Pinus sylvestris is a pronounced stress strategist with good ability to handle resource-limited habitats, and invests in traits accordingly, resulting in significantly slower development. Quercus rubra has its main distribution in cool and moderately resource-rich habitats, but has relatively high stress tolerance and can be considered intermediate between the other two species in terms of growth rate.Results and discussion: The results showed that within 16 years of planting, all species in all three cities, except Pinus sylvestris planted in Umeå, compensated for initial carbon emissions, i.e. showed net absorption of CO2 after emissions from cultivation, delivery, planting and establishment of the trees had been deducted. There was a clear link between the time by which compensation of initial carbon emissions was achieved and growth rate of the different species, with the fast-growing Salix alba showing the best results. The single largest source of emissions among all activities carried out during cultivation, delivery and planting of all species, regardless of the city in which they were planted, was fuel consumption during tree planting

Violent radicalization during the COVID-19 pandemic: at the intersection of gender, conspiracy theories and psychological distress

The COVID-19 pandemic continues to pose a threat to health, economic stability and collective functioning. The related upsurge in psychological distress has fuelled the emergence of conspiracy theories regarding the origins of the virus. Worldwide, there is mounting evidence that these narratives have increased stigma and discrimination against diverse ethnic, age and occupational groups. However, the role of gender in the dynamics weaving together psychological distress, conspiracy theories and legitimation of violence toward other groups is still unknown. This paper addresses this knowledge gap, analysing a Canadian interprovincial survey conducted in November 2020. In total, 6003 individuals aged 18-35 years residing in large Canadian cities responded to an online survey administered in English and French between October 16 and November 17, 2020. A total of 4928 individuals with complete data on support for violent radicalization (VR), psychological distress, and endorsement of COVID-19 conspiracy theories were included in the analysis. This study indicates that for young Canadian adults, gender, endorsement of COVID-19 conspiracy theories and psychological distress, as measured by the Hopkins Symptom Checklist-25 (HSCL-25), have an interaction effect on support for VR, as measured by both the Sympathy for Violent Radicalization Scale (SyfoR) and the Radicalism Intention Scale (RIS) (both p-values <.001). While the magnitude of the association between support for VR and endorsement of COVID-19 conspiracy theories is greatest among individuals with scores of psychological distress above the clinical cut-off, there is a significant association between scores on support for VR and endorsement of COVID-19 conspiracy theories in both women and men, both above and below the psychological distress cut-off of the HSCL-25. Effective strategies to mitigate the relationship between violent radicalization and pandemic-related psychological distress must explicitly address gender differences in expression and management of psychological distress

Evaluation of Alnus subcordata for urban environments through assessment of drought and flooding tolerance

The urban environment is stressful and trees experience multiple stresses, including drought, flooding, and extreme heat, all of which are likely to increase under future climate warming and increasing urbanisation. In the selection of tree species to maximise ecosystem services, tolerance to site characteristics such as flooding and severe drought is of critical importance. This study evaluated the suitability of a rare species, Mims subcordata C.A. Mey (Caucasian alder) from the Hyrcanian forests of southern Azerbai-jan, for its functionality as an urban tree.A total of 48 pot-grown, two-year-old saplings of A. subcordata were tested in a greenhouse experiment using a complete randomised block design. Each block contained four replicates of three treatments (waterlogging, drought, control), with 16 plants per treatment. Height differences between treatments were measured, and water status was estimated by determination of midday leaf water potential (psi(L)) and stomatal conductance (g(s)). To estimate drought tolerance reaction in the treatments, leaf water potential at turgor loss (psi(P0)) was used together with broken-stick modelling of water status over time.A. subcordata plants showed no height increase, while plants in both the waterlogged and control treatments increased in height during the nine-week experiment. Over 63 days of flooding, plant water status was slightly more negative in the waterlogging treatment, but did not deviate essentially from the control. In the drought treatment, plant water status rapidly deviated from the control. There was a significant difference in psi(P0) between treatments, with drought-treated plants showing the lowest value (-2.31 MPa).This study demonstrated that A. subcordata has limited tolerance to drought and seems to rely more on water loss-avoiding strategies. However, the species may be usable at periodically waterlogged sites, due to its high tolerance to flooding. It could therefore be recommended for wet urban environments and stormwater management facilities, for which reliable guidance on suitable trees is currently lacking

Nulägesanalys trädgård

Rapporten Nulägesanalys - trädgård har genomförts inom ramen för projektgruppen Insatsstyrka trädgård. Syftet med inventeringen har varit att ge svar på vem som jobbar med trädgårdsvetenskap, vilka forskargrupper och med vilka forskningsämnen, samt identifiera framtida arbetsfält inom ämnet trädgårdsvetenskap och därmed ge uppslag för framtida utveckling av forskningsfält, utbildning och samverkan. I detta ingår att kartlägga trädgårdsvetenskaplig forskning, utbildning och samverkan vid SLU. Nulägesanalysen förväntas därmed ge en grund för fortsatt strategiskt arbete med att utveckla ämnet trädgårdsvetenskap (Horticultural Science) utifrån inventerade resurser och förutsättningar