Grading of parameters for urban tree inventories by city officials, arborists and academics using the Delphi method

Tree inventories are expensive to conduct and update, so every inventory carried out must be maximized. However, increasing the number of constituent parameters increases the cost of performing and updating the inventory, illustrating the need for careful parameter selection. This paper reports the results of a systematic expert rating of tree inventories aiming to quantify the relative importance of each parameter. Using the Delphi method, panels comprising city officials, arborists and academics rated a total of 148 parameters. In order of total mean score, the top ranking parameters, which can serve as a guide for decision-making at practical level and for standardization of tree inventories, were: Scientific name of the tree species and genera, Vitality, Coordinates, Hazard class and Identification number. The study also examined whether the different responsibilities and usage of urban tree databases among organizations and people engaged in urban tree inventories affected their prioritization. The results revealed noticeable dissimilarities in the ranking of parameters between the panels, underlining the need for collaboration between the research community and those commissioning, administrating and conducting inventories. Only by applying such a transdisciplinary approach to parameter selection can urban tree inventories be strengthened and made more relevant

Skiktning och strukturell utveckling i unga naturlika skogsplanteringar

Multilayered woodland types are an important part of the urban forest. The knowledge how to establish and maintain such plantations are not as deep as other knowledge fields concerning forestry. Therefore this study has looked upon how to achieve multilayered structures in young nature-like woodland plantations. As a theoretical base for the study three different major knowledge culture have been studied that concerns the subject, ecology, forestry and landscape management/design. This three theoretical framework concludes that many natural processes strive in the opposite direction of multilayered structures in their youth. At the same time this different theories give us a understanding who and why we could manipulate this stand through planting composition and management towards more stratified structures. To deepen the practical experiences and knowledge about these questions, a field study project was designed. All together twelve different stands that had been planted mainly during the 1980-s where chosen and studied in the Öresund region focusing on their vegetation structure and canopy stratification. Crown height and tree height together with crown projections where the main parameters used to evaluate the structure of the stands. The data was analyzed using a wide range of scientifically approaches including, the quantity stratification models LMS and TSTRAT. The results show that a three layered structure can be achieved within thirty years after plantation. The key element for achieving a multilayered structure where found to be a combination of both species mixture and management. A species mixture with oak and not to many other tree species together with some middle layer species and the low growing shade tolerant bush species like Alpine Currant Ribes alpinum proved to be one good alternative. Depending on the species mixture and the management goal, two different management tactics could be used for the thinning of the stand. One where the tree layer was favoured and one where the middle layer was favoured giving rise to different kind of multilayered forest structures.del av den urbana skogen men kunskapen kring hur man kan anlägga och sköta sådana planteringar är tämligen liten. Kunskapsbilden som finns i dagsläget kring rikt skiktade bestånd, berör främst skiktning i äldre kulturskogar och merparten av kunskapen kring hur man planterar och sköter skog är inriktad på enskiktade monokulturer. Målet med detta arbete har därför varit att försöka utvidga den praktiska och teoretiska kunskapen kring rikt skiktade unga planterade bestånd. Som en grund för detta undersöktes tre kunskapskulturer som berör ämnet, den ekologiska, den skogliga och den landskapliga. Utifrån dessa teoretiska ramverk kan man förstå att många processer verkar mot att flerskiktade struktur utbildas under ett planterat bestånds ungdom. Samtidigt ger de olika ramverken en förståelse varför och hur man kan påverka de olika processerna så att en flerskiktad struktur lättare kan utvecklas. För att fördjupa den praktiska och teoretiska kunskapsbilden har en undersökande studie av naturlika skogsplanteringar utformats. Studien omfattar 12 bestånd i Öresund regionen och dessa har analyserats utifrån dess skiktning med hjälp av bland annat höjd, kronhöjd och kronprojektioner. Skiktningen har främst analyserats med hjälp av de kvantitativa skiktningsmodellerna LMS och TSTRAT. Resultatet visar att upp till tre tydliga skikt kan uppnås i en naturlik skogsplantering inom en 30 års period i Öresund regionen med rätt kombination av artblandning och skötsel. Avgörande för ett lyckat resultat verkar vara en artblandning med ek och endast några få andra arter i trädskiktet kombinerat med några robusta buskträdarter samt skuggtåliga låga buskar såsom måbär. Skötselmässigt finns sedan två huvudalternativ beroende på målsättning och artblandningen. Antigen lägger man fokus på att trädskiktet ska separeras ifrån mellanskiktet så fort som möjligt genom att man eftersträvar att kronorna lyfts högt eller så hugger man tidigare i trädskiktet och gynnar mellanskiktet med buskträdarterna istället. Kombinationen av olika artblandningar och skötselstrategier ger sedan olika strukturella typer

Forest edge development

This thesis investigates design guidelines and management systems for the development of stationary forest edges with a graded profile in infrastructure and urban environments. The spatial restriction for the edge to move forward caused by human land use counteracts the natural dynamics and development patterns of graded forest edges. However graded forest edges with successively increasing height from the periphery to the interior of the forest edge are often seen as ideal as they supports important multiple functions while at the same time keeping hazardous trees away from tracks, roads, power lines and houses. This calls for suitable management systems and design guidelines. This thesis focuses on the woody species assemblies and vegetation structures. Two starting points of forest edge development was investigated in Southern Sweden; 1) Planted designed forest edges in the Landscape Laboratory of Alnarp, and 2) Natural regenerated forest edges, after clearing along a 610 km railway line between Malmö and Stockholm. Based on the studies it is proposed that the planning of active forest edge development should depart from basic abiotic gradients and it is important to incorporate vegetation structure at site and landscape level into the long-term planning. The management and design actions taken in relation to this should acknowledge the importance of controlling tree dominance. Traits and species strategies relating to tolerance of shade, drought, waterlogging, browsing as well as dispersal mode and growth form can be used as interpretive framework for forest edges assembly and to guide management actions. When assembling species in relation to these traits, placement along the cross section of the forest edge should be a central aspect of the planting design. Based on the findings two management systems were conceptualized; Zoned Selective Coppice that departs from threshold heights and spatial zonation, respectively Functional Species Control that focus on control of dominating tree species. Further a guideline for planting principle was conceptualized. Three long term experimental trials have been developed and established to enable controlled evaluation of these management systems and design guidelines

Perceived personal safety in relation to urban woodland vegetation – A review

Urban woodland vegetation provides people with many aesthetic, ecological and psychological benefits, but can also generate problems concerning people’s perception of safety. This paper reviews existing knowledge about perceived personal safety in relation to vegetation, particularly woodland vegetation, in urban green spaces such as parks and residential areas. Individual and social factors, but also vegetation character, maintenance and design, proved to be important for perceived personal safety. Vegetation-related aspects identified as being of particular importance include landscape design, possibilities for overview and control, vegetation density, and vegetation character and maintenance. Vegetation of an open character with low density undergrowth might have positive effects on perceived personal safety without reducing other benefits. Issues for future research include context-based studies to consider several aspects of vegetation and their interactions

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

Datarapport för 2021 års SLU-enkät om kommunal skötsel av grönområden och träd

Denna datarapport sammanställer och redovisar enkätdata från ”SLU:s enkät för kommunal skötsel av grönområden och träd” som syftar till att ge en översikt över kommunernas gröna resurs och dess förvaltning. Enkäten är en del av Sveriges lantbruksuniversitets (SLU) långsiktiga arbete kring urbana utemiljöer. Enkäten har vänt sig till alla kommuner i Sverige vid två tillfällen med fem års mellanrum och behandlar frågor som rör den kommunala förvaltningen av grönområden, träd och skog utifrån sex delområden; A) Budget och Finansiering, B) Drift och underhåll för parker, grönområden och träd, C) Policy, planer och strategier, D) Kvalitet, E) Träd och trädinventeringar, F) Icke planlagd skogsmark

Residential urban trees – socio-ecological factors affecting tree and shrub abundance in the city of Malmö, Sweden

Trees and large shrubs in urban environments provide a wide array of ecosystem services, enhancing the well-being of urban residents. Public trees in Sweden are managed by local governments, but private-owned urban trees, which represent a large proportion of the total urban tree population, are managed by residential property owners. Residential urban trees are generally not included in urban forest management plans at local government level. This study examined property-level characteristics that could lead to better management decisions by property owners on residential trees in Malmö, Sweden. Using spatial sampling, 99 properties were inventoried to determine tree basal area (m2/ha), as a measure of woody plant abundance. In parallel, residents were surveyed about their attitudes to trees, and information on background variables on their properties was collected using through publicly available spatial data. Statistical modelling was used to determine relationships between key socio-ecological variables and tree abundance as well as reasons for planting and removal of trees. The results showed that positively perceived benefits of trees to property owners did not necessarily result in greater tree and shrub abundance on individual properties. Instead, house age and potential plantable space were the variables positively correlated with tree and shrub abundance. Years of residence had a negative correlation with probability of planting. The primary reason for tree removal was improper growing site, which indicates that providing practical information on appropriate site/species selection could reduce the risk of healthy urban tree removal