Urban forest structure and land cover composition effects on land surface temperature in a semi-arid suburban area

Using multispectral imagery and LiDAR data, we developed a high-resolution land cover dataset for a semi-arid, Colorado (USA) suburb. These data were used to evaluate patterns of land cover composition and vertical structure in relation to land use and age of development. Landsat 5 TM thermal band data for six separate dates were used to compare land surface temperature (LST) in urbanized and remnant shortgrass steppe reference areas. We used 2010 census blocks to extract LST and various explanatory variables for use in Random Forest models evaluating the relative importance of land cover composition, LiDAR-derived vertical structure variables, and the Normalized Difference Vegetation Index (NDVI) on LST patterns.We found that land cover, vertical structure, and LST varied between areas with different land use and neighborhood age. Older neighborhoods supported significantly higher tree cover and mean tree height, but differences in LST were inconsistent between Landsat image dates. NDVI had the highest variable importance in Random Forests models, followed by tree height and the mean height difference between trees and buildings. Models incorporating NDVI, vertical structure, and land cover had the highest predictive accuracy but did not perform significantly better than models using just vertical structure and NDVI. Developed areas were cooler on average than shortgrass steppe reference areas, likely due to the influence of supplemental irrigation in urbanized areas. Patterns of LST were spatially variable, highlighting the complex ways land cover composition and vertical structure can affect urban temperature.     

Anomalies in Australian municipal tree managers’ street-tree planting and species selection principles

There is scant research on Australian municipal tree managers’ motivations for street tree planting and the rationales for street tree species selections. Tree managers from 129 city councils across Australia were surveyed to address this knowledge gap. This paper presents the findings from 115 (89%) usable survey responses. Tree managers reported four primary motives for street tree planting: visual and aesthetic (97%), environmental (92%), socio-cultural and community (87%), and health (70%). In contrast, tree species characteristics (97%), management and maintenance issues (92%), visual and aesthetic benefits (89%), site environmental factors (80%) and problems caused by different species (70%) were reported to govern street tree species selection. In spite being the primary motives for planting, considerations for socio-cultural and community benefits (61%) and environmental benefits/ecosystem services (61%) had minor influence on street tree species selection. In absence of established research, Australian city councils’ institutional culture is biased by personal opinions on potential threats to city’s vital infrastructure posed by street tree, resulting in the mismatch between planting and species selection principles. Future research correlating species characteristics to specific ecosystem services/disservices might help Australian city councils to adopt an ecosystem services based approach to street tree planting and species selection.     

In situ emission of BVOCs by three urban woody species

Controlling and monitoring air quality in cities requires understanding anthropogenic sources, but also natural sources must be considered. This is because beneficial Biogenic Volatile Organic Compounds (BVOCs) can exacerbate air pollution by reacting with anthropogenic pollutants. Although these compounds help trees survive, they may have negative effect on human life in polluted cities. In this study we measured terpenoid emissions of urban trees early and late in the growing season, using Solid Phase Micro-extraction (SPME) in a branch enclosure system. Results showed that Robinia pseudoacacia and Platanus orientalis emitted significant amounts of isoprene throughout the season. Isoprene emission early in the season was roughly the same for both species. Late in the season, the standardized emission rate increased to 17.8 and 45 μg g⁻¹ dw h⁻¹ for R. pseudoacacia and P. orientalis, respectively. Furthermore, all trees emitted significant amounts of 2-ethylhexanol late in the season (7.3, 7.9, and 9.2 μg g⁻¹ dw h⁻¹ for Fraxinus rotundifolia, R. pseudoacacia, and P. orientalis, respectively). In conclusion, trees that are typically planted in urban Tehran, emit significant amounts of isoprene. Planting more F. rotundifolia and fewer P. orientalis trees would help improve air quality in Tehran and the cities like Tehran.     

Linking demand and supply factors in identifying cultural ecosystem services of urban green infrastructures: A review of European studies

Urban green infrastructure provides a number of cultural ecosystem services that are greatly appreciated by the public. In order to benefit from these services, actual contact with the respective ecosystem is often required. Furthermore, the type of services offered depend on the physical characteristics of the ecosystem. We conducted a review of publications dealing with demand or social factors such as user needs, preferences and values as well as spatially explicit supply or physical factors such as amount of green space, (bio)diversity, recreational infrastructure, etc. and linking demand and supply factors together. The aim was to provide an overview of this highly interdisciplinary research, to describe how these linkages are being made and to identify which factors significantly influence dependent variables such as levels of use, activities or health and well-being benefits. Commonly used methods were the combination of questionnaires with either on-site visual recording of elements or GIS data. Links between social and physical data were usually established either by using statistical tools or by overlaying different thematic maps. Compared to the large number of variables assessed in most studies, the significant effects in the end were relatively few, not consistent across the studies and largely dependent on the context they were seen in. Studies focused on aesthetic and recreational services, while spiritual, educational and inspirational services were not considered when creating links to spatially explicit ecological structures. We conclude that an improvement and harmonization of methodologies, cross-country studies and an expansion of this line of research to a wider range of services and more user groups could help clarify relationships and thereby increase applicability for urban management and planning.     

Socioecological features of plant diversity in domestic gardens in the city of Bogotá, Colombia

Domestic gardens contribute substantially to green spaces in cities, where urbanization removes and fragments natural landscapes, causing the loss of biodiversity and the homogenization of biota. We analyzed the diversity and composition of the flora of 70 domestic gardens in seven localities in Bogotá, Colombia, which represent different periods of expansion of the city. Floristic composition and diversity were related to the origin and use of plants, the urbanization history, and the income of owners. We recorded 4110 individuals belonging to 238 species. The mean species richness per garden was 15.4, with older localities having significantly higher species richness. The similarity among the localities, which evaluated the distinctness of assemblages, ranged from 0.42 to 0.50. Plants from the Neotropical region and exotic plants were the most abundant in all gardens. The most common use was ornamental, and use depended on the socioeconomic status of the owner. The lower-income homes cultivated larger proportions of edible and medicinal plants. Gardens at the oldest localities, with the largest number of native species, contribute to the conservation of flora because they contain the largest number of native species. Furthermore, domestic gardens are good sources of employment for gardeners and are useful places to keep senior citizens active, helping these citizens relieve stress, maintain good health and teach young people the cultural uses of plants. The receptivity of the homeowners to the study opens the door to future research and conservation programs in the city.     

Effectiveness of corridor vegetation depends on urbanization tolerance of forest birds in central Tokyo,Japan

Vegetation corridors, such as street trees in urban areas, which connect patchy woodland and mitigate habitat isolation, are expected to enhance the persistence of birds in urban landscapes. However, the effectiveness of urban corridors on birds remains equivocal because vegetation corridor is often managed for human use with little consideration of wildlife. Here we compared the effects of three major corridors of varying vegetation structures (trees with a dense understory, trees with a sparse understory, and grassy areas with sparse trees) on the species richness and abundance of birds in 21 wooded patches in the center of Tokyo, Japan, during wintering and breeding seasons. Using generalized linear models and Akaike’s information criterion, we found that the effectiveness of corridors depended on the tolerance of birds to urbanization. Urban avoider species, having low tolerance to urbanization, demonstrated lower species richness and abundance in patches close to the corridor with a sparsely vegetated understory as compared with patches close to the understory-richer corridors during winter, although such an effect disappeared during the breeding season. The corridors did not have a significant effect on suburban adapter species with a high tolerance to urbanization. Our results suggest that corridors with scarce understory vegetation may limit the persistence of birds avoiding urban areas.     

The impact of greenspace size on the extent of local nocturnal air temperature cooling in London

Urban greenspaces can provide a significant cooling service, which extends beyond the greenspace boundaries. Consequently, greenspaces are recognised for their ability to locally reduce the urban heat island, a phenomenon that has negative implications for the thermal comfort and health of urban citizens. However, the amount of cooling provided by a greenspace and the distance over which that cooling extends depend on factors such as greenspace size and characteristics. Based on data collected in and around eight London greenspaces, with areas ranging from 0.2 to 12.1 ha, this work models the distance and magnitude of cooling provided by each greenspace and defines the relationships between cooling extent and the size of greenspace or the areas of tree canopy and grass. Such data, illustrating the value of expanding the area of urban greenspaces and explaining how cooling relates to greenspace size/coverage characteristics, will be of use to urban planners and climatologists concerned with finding solutions to the urban heat island. Modelling was statistically valid on calm warm nights (with mean air temperatures ≥10 °C and wind speed ≤3 m s⁻¹). On those nights, cooling distance increased linearly with increasing area of greenspace, tree canopy and grass, but the relationship between those factors and the amount of cooling was non-linear. Cooling distance was most strongly related with tree canopy whereas the amount of cooling was most strongly linked to the grass coverage. Our results suggest that a comprehensive cooling service on calm warm nights within cities with similar climate/characteristics to London may come from greenspaces with 3–5 ha, situated 100–150 m apart.     

Environmental inequities in terms of different types of urban greenery in Hartford,Connecticut

Urban greenery has long been recognized as an important component of urban ecosystem and provides many benefits to urban residents. However, different types of urban greenery provide different kinds of natural experiences to people. In this study, green metrics calculated based on multisource spatial datasets were used to quantify the spatial distribution of different types of urban greenery in Hartford, Connecticut. Geo-tagged Google Street View images, which capture the profile view of cityscape, were used to quantify street greenery by considering the time information. Land cover map and urban parks map were used to measure residential yard greenery and proximity to urban parks, respectively. We analyzed the associations of the calculated green metrics with socio-economic variables derived from census data. Statistical results show that: (1) people with higher income tend to live in neighborhoods with more street greenery; (2) census block groups with a higher proportion of owner-occupied units tend to have more yard vegetation and yard tree/shrub coverage; (3) Hispanics tend to live in block groups that have less yard vegetation but African Americans mostly live in block groups with more yard greenery; and (4) there are no significant environmental disparities among racial/ethnic groups in terms of proximity to urban parks. In general, this study provides an insight into the environments of urban residents in terms of urban greenery, and a valuable reference data for urban planning.     

Linking forest naturalness and human wellbeing—A study on public's experiential connection to remnant forests within a highly urbanized region in Malaysia

Being the country's major economic propellers, Klang Valley region in Malaysia has been experiencing decades of extensive development. Consequently, the lowland dipterocarp forest – which was once the dominant natural ecosystem in this region – has degraded into fragmented remnants, surrounded by urbanized areas. As a degraded natural ecosystem, however, these remnants are still a key ingredient for the city's livability and urban dwellers’ quality of life, by counter-balancing the adverse impacts caused by various urban activities. While these remnants generally fulfilled various physical, mental, and social functions, exposure to different degree of development pressure and human intrusion have caused them to act differently in the way contributing to these functions. This paper presents results of a study conducted in Klang Valley region, with the general goal to contribute to the empirical rationale for linking forest naturalness with human wellbeing. Three remnants, each with different degree of naturalness, were selected as study sites and were hypothesized to contribute to the urban dwellers’ overall wellbeing by enhancing people's physical health, mental health, and social interaction, through fulfilling the motives of visiting the nature. Information on key variables was collected by surveying forest visitors and data were analyzed using path analysis, to depict the causal relationships between forest naturalness and human wellbeing. The study successfully gives the observational support to the potential relation that links together naturalness, experiential connection to nature, and human wellbeing. The study also contributes to the understanding on the meanings of remnant urban nature, which would in turn provide planners a tool to match the urban natural resource management with the needs of the residents.     

Bioculturally valuable but not necessarily worth the price: Integrating different dimensions of value of urban green spaces

The social processes that took place in the past left a mark not only on cultural heritage but also on ecosystems and biodiversity, which is now depicted in the concept of biocultural diversity. The related “biocultural value” represents yet another dimension of the value of urban green spaces which we attempt to integrate into monetary valuation with the use of hedonic pricing. We compare the impacts of different green spaces on property prices in Łódź, Poland, differentiating green spaces based on their biocultural value. Furthermore, we use quantile regression and analyze the heterogeneity of estimates according to the price of the apartment. Our study indicates that while there is a general desire to live close to the green space, biocultural value does not translate into any positive impact on property prices.