The use of decarbonized virgin lime is connected to environmental problems like high CO₂ emissions, high energy utilization and negative impact from open-pit lime mines. Recycling of used lime would reduce many of these problems. The effect of carbon-rich lime slag (CLS) from the metallurgical industry on germination, growth, and elemental content in barley, oilseed radish and sugar beet was investigated on two soils (clay and sand). CLS without and with water (CLSW) were compared to limestone in the sandy soil, primarily used to increase pH, and hydrated lime, primarily used to increase aggregation, in clay soils. CLS addition did not reduce the germination of the seeds as compared to the control. Including fertilization to the CLS treatment reduced the germination up to 23% in oilseed radish after 16 days. The germination of sugar beet seeds was delayed but had recovered after 16 days. Shoot biomass was higher in plants with CLS and CLSW, in both soils without fertilization. Plants grown in the CLS had lower Cd content compared to plants grown with hydrated lime. We can conclude that CLS show a high potential to be used on agricultural land from a crop growth perspective.

The legacy of post-industrial contamination often limits the safe use of urban soils for food production without pre-treatment to reduce metal(loid) solubility and uptake in crops. In this study, a seed residue biochar was applied at two doses (1% and 5%) to six circumneutral urban allotment soils from Denmark and the UK, all exhibiting elevated concentrations of As, Cd, Pb and Zn. Soil pore water was sampled to assess metal(loid) solubility and soil:solution partitioning, and lettuce was grown to determine metal(loid) uptake. Biochar application had varying effects on metal(loid) solubility. For As and Pb, solubility generally increased, particularly at the higher dose. For Zn and Cd, solubility tended to decline. Metal(loid) uptake in lettuce also varied, with no consistent change between control and treatments for As and Pb, despite their increased solubility. However, a clear reduction in Zn and Cd uptake was observed, especially at the 5% application rate. For Cd, this resulted in a marked decrease in the proportion of samples exceeding health-based guideline values, indicating a tangible reduction in dietary risk. These findings show that even in circumneutral soils, biochar can significantly influence metal(loid) behaviour, with the greatest benefit observed for reducing Cd accumulation in edible crops. However, the observed increase in As and Pb solubility underscores the importance of considering potential risks associated with leaching and water contamination.

Nutrient limitation of forest growth, especially nitrogen (N) deficiency, is widespread in the boreal region. N fertilisation has thus become a common silvicultural practice in Fennoscandian Norway spruce stands, but to what extent phosphorus (P) is co-limiting productivity and how initial basal area affects the growth response to N addition remains unresolved. To address these questions, two experiments were established in mid-rotation Norway spruce stands in southern Sweden where decades of high atmospheric N deposition have reduced the severity of N-limitation. In a P experiment initiated in 2011, we tested P addition alone (two applications of 200 kg P ha⁻¹) and in a second study also starting in 2011 (NP experiment), a single dose of N was administered alone (200 kg ha⁻¹ in thinned and unthinned stands, hereafter called N and N-unthinned treatments) and in combination with P (N+P = one-time 200 kg N ha⁻¹, two applications of 200 kg P ha⁻¹ in thinned stands). P addition alone increased PAI (periodic annual increment) significantly by 21 % during the first, moister assessment period up to 2014 and by 18 % in the drier 2015–2019 period, resulting in a 10 % increase in final stem volume yield. In the NP experiment, significant PAI increases under favourable meteorological conditions up to 2014 occurred in all fertilisation treatments. The strongest effects were seen in the N-unthinned treatment while no significant additive effect resulted from the joint addition of N and P (N: +20 %, N-unthinned: +38 %, N+P: +23 %). In the drier 2015–2019 period, only the N+P treatment caused significantly greater PAI (+29 %). Final stem volume yield in the NP experiment significantly increased by 10 %, 39 % and 16 % in the N, N-unthinned and N+P plots, respectively. In both experiments, foliar P and thus P/N rose drastically in response to P addition alone or in combination with N. Minor increases in leaf area index (LAI) only occurred in P-containing treatments. Our findings indicate that Norway spruce productivity in southern Sweden is constrained to a similar extent by both N and P. Sustainable nutrient management in Norway spruce growing regions with high N loading (like southern Sweden) should prioritise P over N supply.

Trees have many positive effects on the urban environment, but they are also exposed to several stress factors. Water deficit is one of these. Irrigation, structural soils or selecting drought tolerant species are different ways to meet this problem. Another way might be choosing individuals that could reduce water loss due to microclimate differences within the crown. The objective of this study is to address whether different crown densities in single trees may influence the water consumption during days with high atmospheric demand. Two pairs of similar Tilia cordata Mill. ‘Green spire’ with different crown densities, one dense and one sparse, were planted in containers and placed on scales at a paved yard in Alnarp, Sweden, during July and August 2009. Daily weight loss was continuously logged, and measurements of stomatal conductance and stem water potential were performed twice a day. Stomatal conductance was approximately 66% higher (3 mm s-1) in the sparse tree of pair S7:D46 and approximately 20% higher (1 mm s-1) in the sparse tree of pair S52:D21. The dense trees and sparse tree S52 used on average 10.2-10.9 kg water day-1 (1.2-1.4 mm day-1). Sparse tree S7 used on average 13.8 kg water day-1 (2.1 mm day-1). This difference might be caused by different microclimates in the crowns of the sparse and dense trees. Other factors were kept as similar as possible within each pair. The difference in water use was, however, more pronounced in one of the pairs. This could be caused by the different ability for water uptake and transport in the two pairs. The pair with the largest difference in water use had the strongest growth. We conclude that crown density affects water use of a tree in an urban environment; sparse linden trees consume more water than dense.

Designing green infrastructure in cities requires vegetation that has multiple outcomes and functions, particularly using plants that have both attractive visual or aesthetic features and high biodiversity values. Plantings that have high visual appeal are more highly valued by people and increase their feeling of wellbeing. Increasing biodiversity in cities is one of the major challenges facing urban planning and design. However, balancing biodiversity and aesthetic outcomes in urban planting design is complex, and to date there are few methods that can be used to guide plant selection. To address this knowledge gap, we investigated the use of a colour theory framework for planting arrangements to see if we could design vegetation that is highly aesthetic and has high biodiversity. We did this by configuring planting combinations for living walls in Malmö, Sweden, using principles based on Johannes Itten’s colour theories. The plant combinations on each wall were graphically arranged using (1) colour analysis of each plant and (2) design of the plant species into two colour schemes: light-dark colour concept and a complementary colour concept. For each species used in the compositions we created a biodiversity classification, based on its pollination value, “nativeness” and conservation value as a cultivar; and a plant visual quality classification, based on the performance from living walls studies. The graphical colour composition and interlinked biodiversity value were then compared to designs created with randomly selected plant species. The results showed that it is possible to design a living wall based on colour theory without compromising with biodiversity outcomes, namely species richness, pollination and the nativeness of the species. The results also indicate the potential application of this design approach to deliver greater aesthetic appreciation and enjoyment from plantings. While more work is needed, this study has shown that a theoretical colour framework can be a useful tool in designing green infrastructure to improve delivery of both cultural and regulatory ecosystem services. Copyright © 2022 Thorpert, Rayner, Haaland, Englund and Fransson.

Installing green roofs and green walls in urban areas is suggested to supply multiple ecosystem services of benefit to human health and well-being. In a three-step literature review, we examined current knowledge on the link between public health and green roofs and green walls. A systematic search identified 69 scientific articles on green roofs/walls with a public health discourse. These articles were categorized according to type of health path covered (reduction of temperature, air pollution, noise or environmental appraisal) and coverage of issues of relevance for strategies on planning, design/construction, and maintenance of green roofs and green walls. Articles identified through the structured search were complemented with reviews (with no explicit public health rationale) covering reduction of noise, temperature, or air pollution and environmental appraisal. Other relevant studies were identified through snowballing. Several of the articles provided guidelines for optimizing the effect of green roofs/walls in supporting ecosystem services and maximizing well-being benefits to support health pathways identified. These included specifications about planning issues, with recommended spatial allocation (locations where people live, sun-exposed for maximum ambient temperature reduction) and with physical access needed for environmental appraisal. Recommendations regarding design parameters covered substrate depth (deeper generally being better), plant choices (more diverse roofs providing more services), and maintenance issues (moist substrate positively correlated with heat reduction).

Using local and recycled materials is a sustainable way to establish a vegetated roof. In order to understand how the roof ecosystem functions and returns ecosystem services, it is important to study vegetation, soil organisms and runoff quality. We established a vegetated roof experiment based on a substrate containing lightweight crushed concrete, an alkaline side product from a concrete factory, mixed with compost. This five-year experiment in southern Finland tested how planting method (pre-grown vegetation mats vs. pot planting), compost content (20% vs. 40%, fresh volume), and substrate depth affect the cover and diversity of plants, the abundance of soil animals and the quality of runoff. Although the substrate had a high pH (7.3–11.8), many vascular plants were able to survive and establish viable populations. The planting method had a strong effect on plant diversity and the cover of individual species because the vegetation mats became dominated by the invasive, non-native Phedimus hybridus. Establishment with pot plants in turn provided bare ground that was colonised by spontaneous non-invasive species. This resulted in higher diversity, and a more even distribution of species. The amount of compost had only a weak impact on vegetation, whereas high pH generally reduced plant abundance and diversity. The concentrations of total phosphorus and total nitrogen in runoff were low as compared to values reported from many other vegetated roofs, were not affected by compost content and decreased over time. In summary, the high-pH substrate based on recycled materials is an environmentally responsible choice, suitable for a wide variety of plants, even rare and endangered species.

There is a growing awareness of the value of trees for climate adaptation, human health, and biodiversity in urban spaces, and methods for identifying and calculating the benefits of trees have been developed. However, tree roots frequently intrude into sewer pipes and storm-water drains, causing costly damage. Identifying the individual trees that cause damage would be helpful but has proved difficult. There is a need for non-destructive identification of root intruding trees, in order to evaluate the cost and benefits of individual trees. The concentrations of eight heavy metals (silver, gold, cadmium, lead, palladium, rubidium, antimony, and zinc) and of potassium were evaluated in 19 pairs of trees/shrubs in Malmö, southern Sweden. It was found that the concentrations of silver were approximately 28% higher in leaves from trees whose roots had entered sewers than in control trees. Trees whose roots intruded storm-water drains had slightly higher leaf potassium levels, while the concentrations of other elements did not differ from those in control trees. Thus, it may be possible to use the silver concentration in tree leaves to identify individuals with roots intruding into sewer systems. However, considerable differences were found between species, so further tests are required before the method can be adopted in practice.

Establishment is a key concept in urban forestry but it is currently inconsistently defined and measured. Thus, several different methods are being used to determine establishment success but their consequences and applications are rarely discussed. With this paper we would like to stimulate an increased discussion regarding these concepts both in relation to a theoretical definition but also to their practical use. The problem was approached through an experiment using sweet cherry (Prunus avium L.) and northern red oak (Quercus rubra L.) trees and the most common methods used for determination of establishment success. The trees were studied during the first three years after transplant and the association between the different measuring methods was examined. A Principal Component Analysis showed that terminal and lateral shoot length were strongly correlated, and that midday- and pre-dawn shoot water potential, and stomatal conductance were strongly correlated. We developed an index for nightly recovery of water status, which showed that terminal shoot growth was not related to nightly recovery until the third year after transplanting. Our results suggest that successful tree establishment is determined differently depending on which method is used for determination but that the differences might decrease with time. The lack of a firm definition of the term establishment may complicate communication, both within the scientific community and in practice.

Assessing the establishment of newly planted urban trees is important to ensure that establishmentmanagement is maintained as long as needed. Such assessment is often based on visual appraisal of the post-transplant vitality two or three years after planting. How visual assessments relate to water status in the trees, or which morphological characteristics that are driving forces in such assessments have received limited attention in past research. In this interdisciplinary study, several leaf characteristics, such as leafshape, size and colour were determined on 50 trees each of sweet cherry (Prunus avium L.) and red oak(Quercus rubra L.), transplanted to two Swedish sites three seasons before the study. In addition, shoot length was measured, and crown density, crownshape and die-back were estimated. Visual establishment assessments were performed by professional evaluators, who also completed a questionnaire on their background knowledge and priorities during assessments. The study investigated which of these leaf and crown characteristics had the greatest impact on the  assessments. In addition, it compared the characteristics and evaluator assessments against the tree water status, determined by pre-dawn shoot water potential measurements.  Visual assessments proved to be unrelated to shoot water potential for both species but, for red oak the assessments were strongly related to leaf colour and leaf shape. Shootwater potential was related to leaf size but not to leaf colour, indicating that one of the most influential parameters for visual assessments of red oak were not well-suited for determining tree establishment success, if defined by water status. The assessments for sweet cherry were best explained by leaf area. Our findings suggest that leaf size is a good indicator of tree establishment and that leaf shape, the character considered least important by tree evaluators, is influential on tree assessments. These findings are important for the development of more accurate tree expert assessments.