More than a canopy cover metric: Influence of canopy quality, water-use strategies and site climate on urban forest cooling potential

11 Pág.The authors would like to thank the Australia–Germany Joint Research Cooperation Scheme by the Universities Australia and the German Academic Exchange Service (DAAD) (Project-ID: 57601120) for funding several trips of MAR, EF, TR, SL and PT to initiate the research collaboration on this article. Thanks also to the German Science Foundation (Deutsche Forschungsgemeinschaft) for providing funds for the projects PR 292/21-1 and PA 2626/3-1 ‘Impact of trees on the urban microclimate under climate change: Mechanisms and ecosystem services of urban tree species in temperate, Mediterranean and arid major cities’. Additionally, the authors want thank student assistant A. Islam for his support during the data analyses.Peer reviewe

<i>Cenostigma pluviosum</i> Tree Stem Growth and Carbon Storage in a Subtropical Urban Environment: A Case Study in Sao Paulo City

Our aim is to contribute to understanding the role of subtropical trees on carbon storage and CO2 removal in the city of Sao Paulo/Brazil, besides highlighting the surrounding environment implications to sibipiruna trees (Cenostigma pluviosum)’s performance. The case study was conducted with three trees, one planted on a sidewalk in Pinheiros neighborhood, a highly sealed area, and two in a green area, the Ibirapuera Park. To define the stem basal area growth and its pattern, local measurements were taken over a year and a segmented linear regression model was adjusted. The stem growth dependency on microclimate was tested by a Spearman Correlation. The trees’ active stem growth presented a similar pattern. The soil volumetric water content and soil temperatures were the variables with more impact. The total mean radial stem growth for the IBIRA1 and IBIRA2 trees was 1.2 mm year−1 and 3 mm year−1, while at PIN1 it was 1.3 mm year−1. The total biomass increment in IBIRA1 and IBIRA2 was 4.2 kg C year−1 and 12.8 kg C year−1, while in PIN it was 4.9 kg C year−1 and the removal was 15.3 C year−1, 47.1 kg CO2 year−1 and 17.9 kg CO2 year−1, respectively. The results indicated that the land cover difference implies a significant interference with the promotion of carbon fixation and CO2 removal, demonstrating that planting urban trees in soils with better water storage conditions is more efficient

Effects of Climate and Drought on Stem Diameter Growth of Urban Tree Species

Urbanization and climate change are two inevitable megatrends of this century. Knowledge about the growth responses of urban trees to climate is of utmost importance towards future management of green infrastructure with the aim of a sustainable provision of the environmental ecosystem services. Using tree-ring records, this study analyzed growth response to climate by stem diameter at breast height (DBH) of 1178 trees in seven large cities worldwide, including Aesculus hippocastanum L. in Munich; Platanus × hispanica Münchh. in Paris; Quercus nigra L. in Houston; Quercus robur L. in Cape Town; Robinia pseudoacacia L. in Santiago de Chile, Munich, and Würzburg; and Tilia cordata Mill. in Berlin, Munich, and Würzburg. Climate was characterized following the de Martonne aridity index (DMI). Overall, trees showed an 8.3% lower DBH under arid than humid climate at the age of 100. Drought-tolerant tree species were overall not affected by climate. However, R. pseudoacacia showed a lower diameter when growing in semi-dry than humid climate. In contrast, drought-sensitive tree species were negatively affected by arid climate. Moreover, the effect of drought years on annual diameter increment was assessed. P. × hispanica and R. pseudoacacia appeared as the most drought-resistant species. The highest sensitivity to drought was detected in T. cordata and Q. robur. A. hippocastanum and Q. nigra showed a lower diameter growth during drought events, followed by a fast recovery. This study’s findings may contribute to a better understanding of urban tree growth reactions to climate, aiming for sustainable planning and management of urban trees

Crown Shapes of Urban Trees-Their Dependences on Tree Species, Tree Age and Local Environment, and Effects on Ecosystem Services

Crown shapes of common European urban tree species differ from tree species to tree species and are modified by the age of a tree and its local environment. A tree&rsquo;s crown shape has a great influence on the crown volume and thus on the ecosystem service provision of a tree such as the shade area or the shade density. We used the data of 3852 tree individuals from eight German cities and the crown shape data of 528 trees for the species Acer platanoides, Acer pseudoplatanus, Aesculus hippocastanum, Fraxinus excelsior, Platanus &times; acerifolia, Robinia pseudoacacia and Tilia cordata to analyze tree structural dimensions and the crown volume and shade dependency on a tree&rsquo;s crown shapes. Ovoid (57% of all tree individuals) and spherical (24%) crown shapes were mostly observed. However, columnar shape was observed for light-demanding R. pseudoacacia in close proximity of objects. The greatest shade areas were measured for spherical shape and the highest shade density for ovoid shape. Logistic regression analysis showed significant effects of age and distance to objects on crown shapes. Significant probability of crown shapes was found for different tree species, e.g., A. hippocastanum strongly showed half-ellipsoid crown shapes

Crown Shapes of Urban Trees-Their Dependences on Tree Species, Tree Age and Local Environment, and Effects on Ecosystem Services

Crown shapes of common European urban tree species differ from tree species to tree species and are modified by the age of a tree and its local environment. A tree’s crown shape has a great influence on the crown volume and thus on the ecosystem service provision of a tree such as the shade area or the shade density. We used the data of 3852 tree individuals from eight German cities and the crown shape data of 528 trees for the species Acer platanoides, Acer pseudoplatanus, Aesculus hippocastanum, Fraxinus excelsior, Platanus × acerifolia, Robinia pseudoacacia and Tilia cordata to analyze tree structural dimensions and the crown volume and shade dependency on a tree’s crown shapes. Ovoid (57% of all tree individuals) and spherical (24%) crown shapes were mostly observed. However, columnar shape was observed for light-demanding R. pseudoacacia in close proximity of objects. The greatest shade areas were measured for spherical shape and the highest shade density for ovoid shape. Logistic regression analysis showed significant effects of age and distance to objects on crown shapes. Significant probability of crown shapes was found for different tree species, e.g., A. hippocastanum strongly showed half-ellipsoid crown shapes

Effects of the urban heat island and climate change on the growth of Khaya senegalensis in Hanoi, Vietnam

Abstract Background Recent projections expect that Vietnam will be affected most severely by climate change with higher temperatures, more precipitation and rising sea levels. Especially increased temperatures will worsen the situations in cities, amplifying the urban heat island effect. Green infrastructures, i.e. urban trees are a common tool to improve the urban micro-climate for humans. Vital and well growing trees provide greatest benefits such as evaporative cooling, shading, air filtering and carbon storage. However, urban tree growth is often negatively affected by urban growing conditions such as high soil sealing with compacted tree pits providing small growing spaces with limited water, nutrient and oxygen supply, further warm temperatures and high pollution emissions. This study analyzed the growth of urban and rural African mahogany (Khaya senegalensis (Desr.) A. Juss.) trees in the city of Hanoi, Vietnam and the effects of the surrounding climate conditions on tree growth. Results The results showed that rural African mahogany trees grew better than trees situated in the city center, which is contrary to other results on tree growth of temperate and subtropical cities worldwide. Moreover tree growth was similar regardless of the time of growth. Other results regarding stem growth of African mahogany located in different areas of Hanoi (east, west, north, city center) revealed a better growth in the northern and western outskirts of the city compared to the growth of trees in the city center. Conclusion African mahogany trees in the urban centers of Hanoi showed a decreased growth compared to rural trees, which was likely induced by a low ground-water level and high pollution rates. In view of climate change and global warming, the decreased tree growth in the city center may also affect tree service provision such as shading and cooling. Those climate mitigation solutions are strongly needed in areas severely affected by climate change and global warming such as Vietnam

Growth and cooling potential of urban trees across different levels of imperviousness

12 Pág.[EN] City centers experience higher temperatures than surrounding suburban and rural areas due to the urban heat island effect (UHI) (Oke, 1988). Previous studies have observed localized hot and cool spots, large intra-urban temperature differences, and variations of UHI intensity within the city's boundaries (Buyantuyev and Wu, 2010; Heusinkveld et al., 2014). These variations are directly linked to various urban factors, such as land cover, surface characteristics, building size and shape, material properties, anthropogenic heat generated from vehicles, building systems, and industrial activities (Smithers et al., 2018). The primary cause of UHI is the modification in the surface energy balance due to changes in land cover types in urban areas (Oke, 1973). Coupled with climate change, UHI poses a serious threat to the quality of life of the population in urban areas (Iungman et al., 2023). Thus, implementing effective urban heat mitigation strategies is essential for to promote the adaptive capacity of our cities (Pauleit et al., 2020).We thank the Deutsche Forschungsgemeinschaft (DFG) for funding the project “Impact of trees on the urban microclimate under climate change: Mechanisms and ecosystem services of urban tree species in temperate, Mediterranean and arid major cities” (grant number PR 292/21–1 and PA 2626/3–1). We also thank Ms. Alejandra Zelada, Mr. Amjad Hijazin and Mr. Alaa Amer for their help in the field work. We thank the municipality of Munich for the permission to measure the trees and extract tree cores.Peer reviewe

Smart Urban Forestry: Is It the Future?

The urban forest, i.e. the stock of urban trees, is a major component of urban green spaces. It can make significant contributions to urban sustainability and climate change adaptation. Urban forest governance and management play a key role in the extent to which these contributions are realized for good. This chapter presents a selection of promising new technologies in support of urban forestry. Techniques and applications are introduced in the domains of remote sensing, modeling and citizen science. These technology-driven developments offer new potentials for ‘smart’ urban forestry but may also create new risks of a shift towards techno-managerialism as opposed to more open and democratic processes

The footprint of heat waves and dry spells in the urban climate of Würzburg, Germany, deduced from a continuous measurement campaign during the anomalously warm years 2018–2020

The present study contributes to the issue of the urban heat island (UHI) effect with its possibly associated thermal stress for city dwellers and its potential mitigation during heat waves and dry spells in Central Europe. It is based on meteorological measurements along an urban transect in the city of Würzburg, Germany. Due to its topographic and structural situation, Würzburg is prone to an intense urban heat island (UHI). The measurements have started in 2018 and, hence, cover a period that was characterized by record high temperatures and long dry spells in Central Europe. Particularly on days with a maximum air temperature of more than 25 °C, an intense UHI was observed with the highest amplitude in the afternoon and, even more, during the evening hours. The highest measured difference between the densely built inner city and the outskirts was 8.2 °C. The UHI during summer is noticeably more pronounced, especially during the evening hours, when the regional background climate is anomalously warm and dry. This can be ascribed to anticyclonic weather types that prevailed over Central Europe during summertime between 2018 and 2020. The cooling effect of urban trees, in this case Tilia cordata, on near-surface air temperature amounts to partly more than 2 °C and, hence, mitigates the UHI locally, especially at noon and in the early afternoon. However, the cooling rate is only half as much when the trees suffer from water stress. Thus, an appropriate management of city's green infrastructure represents a useful strategy to mitigate the strength of the UHI and the heat stress in Central Europe