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

Plant performance in living wall systems in the Scandinavian climate

The concept of green façades is not new (Koehler, 2008), but their reintroduction may offer benefits in the current urban design, which is increasingly focused on urban densification. The benefits of vertical greening include noise abatement (Van Renterghem et al., 2013), filtering of airborne dust and pollutants (Ottele et al., 2010 and Sternberg et al., 2010), and reduction of temperature close to the area of vertical greening (Onishi et al., 2010, Wong et al., 2010 and Perini et al., 2011a). The thermal aspects of vertical greening are, however, still under debate (Hunter et al., 2014). One particular type of green façade is living wall systems, which are vertical greening systems where plants are grown without the need for contact with the ground (Koehler, 2008, Francis and Lorimer, 2011 and Perini et al., 2011b). Living wall systems can be seen as an alternative way of introducing urban greening in dense urban areas in the same way as e.g. green roofs, which have shown to support a high arthropod diversity (Rumble and Gange, 2013 and Madre et al., 2013). Like plants on green roofs (Emilsson and Rolf, 2005 and Emilsson, 2008), plants in living wall systems must be able to cope with extreme conditions, such as high irradiation, considerable differences in temperature and possible water shortage. The main aim of this study was to determine whether it is possible to grow perennial plants in living wall systems in the Scandinavian climate and we hypothesized that perennial plants could survive in, and would be a viable option for, living wall systems in the Scandinavian climate

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

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

Priorities and barriers for urban ecosystem service provision: A comparison of stakeholder perspectives from three cities

Urban Green Infrastructure (UGI) can provide many needed ecosystem services (ES) to help address challenges like biodiversity loss and climate change while contributing to the health and wellbeing of urban inhabitants. In order to optimize UGI for a given city, a first step is to assess the local ES needs and the potential barriers to ES provision. However, it is not known how consistent these needs and barriers are among cities in different settings. To help address this knowledge gap, the aim of this study was to assess ES priorities and existing barriers to ES provision for three cities varying in socioeconomic, cultural and climatic setting: Addis Ababa (Ethiopia), Cincinnati (USA) and Malmö (Sweden). In case studies of each of the three cities, we carried out workshops with key stakeholders and collected their assessments of both current provision of ES from UGI and future priorities. The workshops were followed by expert stakeholder interviews aimed at highlighting existing barriers to ES provision. In spite of the different urban contexts, expressed ES priorities were similar among the cities, with the highest cross-cutting priorities being climate change adaptation, stormwater runoff management and water quality, mental and physical health, biodiversity, and provision of local food. Stakeholder-expressed barriers to ES provision were also broadly similar among cities, falling into three main categories: structural pressures, gaps in governance, and lack of ecological awareness and vision. Our results suggest that certain key ES priorities and barriers may apply broadly to cities regardless of climatic or socio-cultural context. These generic needs can help direct the focus of future studies, and imply a clear benefit to international, even cross-continental study and knowledge-exchange among practitioners and researchers working with UGI

Gröna tak för biologisk mångfald

Gröna tak kan utgöra livsmiljö för många växter och djur om man anlägger taken med detta syfte. I detta Movium Fakta presenteras erfarenheter och resultat från BiodiverCity samt andra relaterade projekt med målsättningen att bidra till ökad kunskap om den potential ett grönt tak kan ha för att främja den biologiska mångfalden

Gröna tak - klimatanpassning för täta städer

Ett förändrat klimat är ett faktum men med gröna ytor i urbana miljöer kan man motverka en del av de negativa konsekvenserna. Problemet för städernas gröna miljöer är att konkurrensen om marken är väldigt hög och att det finns många intressen som strider om samma mark

Extensive vegetated roofs in Sweden

This thesis discusses extensive vegetated roofs, i.e. vegetation systems placed on top of buildings as an aesthetical and/or ecological cover. Specific objectives was to (1) quantify how establishment techniques, substrates and plant mixes influence establishment and development of extensive vegetated roofs, (2) investigate effect of vegetated roofs on stormwater quality, and quantify how maintenance and starting fertilisation influences stormwater quality, and (4) investigate the role of vegetated roofs in planning tools for urban green space. The studies on vegetation establishment and development was carried out at the Augustenborg Botanical Roofgarden, Malmö (55°34’34’’N, 13°1’42’’E), the nutrient runoff was investigated on commercially installed systems in the Malmö-Lund region and in a greenhouse study. The role of vegetated roofs in planning of green areas was performed as a literature study. Vegetation establishment and development was investigated in relation to substrate, species and establishment method. Nutrient runoff was in the greenhouse study investigated in relation to fertiliser type, vegetation type and fertiliser amount. Prefabricated vegetation mats had an advantage in establishment in creating high plant cover during the first year, which can be important on exposed sites. Establishment was similar for plug plants and cuttings. The commercial substrate was beneficial for establishment. The advantage in succulent cover of vegetation mats had disappeared after 3.5 years. All establishment techniques achieve the same long-term succulent cover. Moss cover increased over time and was at the end of the study dominating the system with approx 50-80% cover. Maintenance fertilisation can cause degradation of stormwater quality if conventional fertilisers are used. Conventionally installed vegetated roofs were found to be a source of potassium and phosphorous, and a sink for nitrogen. Vegetated roofs had a minor influence on heavy metal runoff. Spontaneous establishment on extensive vegetated roofs was low, which is beneficial from a maintenance perspective but unfavourable from a biodiversity perspective. The Green Space Factor tool was found to overestimate the environmental functions of thin vegetated roofs