Assessing the impacts of urbanization-associated green space on urban land surface temperature: A case study of Dalian,China

Taking Dalian City as the study area, the spatial distribution of urban green space and land surface temperature (LST), as well as their evolution in 1999, 2007 and 2013, were obtained through remote sensing (RS) interpretation and inversion. Landsat ETM and SPOT data were used for this purpose. By combining the temperature and vegetation index models (TVX), the effects of urban green space reduction on the thermal environment during city development were evaluated. The results show the following. (1) During 1999–2013, 88.1 km² of urban green space was converted to other land uses, accounting for a 29.4% reduction in urban green space in the study area. (2) During the study period, the LST in this area increased by +8.455 K. The evolution of the regional thermal landscape can be characterized by increases in the LST, greater complexity of the thermal landscape structure, increase and aggregation of high-temperature areas, and reduction and fragmentation of low-temperature areas. (3) During the process of urbanization, urban green space with low land-surface temperature was converted to other land use types with high land-surface temperature. When development occurred at the price of urban green space, negative effects on the regional thermal environment were observed.     

Urban-rural and temporal differences of woody plants and bird species in Harbin city,northeastern China

Urbanization has been greatly accelerated by the economic growth in China, while its possible effects on woody plants, bird species and their associations are not well defined yet. Here, we analyzed urban-rural gradients (landscape level: urban-farmland-forest-natural reserves; city level: ring road and urban build-up history) and temporal data (1955–1980–2014 for woody plants; 1980s–2010 s for birds) in Harbin city, China, to investigate the changes in the composition and diversity of woody plants and birds during urbanization. Both landscape gradient and temporal data confirmed that urbanization had the function of species conservations with sharp increases of alien species and tropical type plants. In the case woody species, 60-yr urbanization in Harbin had induced increases of 9 families and 17 genera, and there were 7–20 more families, 12–35 more genera, 1.6–2.6 higher Margalef richness in urban areas than those in nature reserves and local forest farms; Increases in alien species (4-fold in 60-yr urbanization; 21% in urban area vs <2% for non-urban region) and tropical type plants (1.6-fold in 60-yr urbanization; temperate/tropical ratio at 1.2 in urban area vs >1.6 in non-urban area) were mainly responsible for these compositional changes, which can be proved by their significant correlations. Moreover, moderate disturbance had peak values in alien species, tropical type plants, Shannon-wiener diversity, Margalef richness index and Pielou evenness index, and both ring road- and buildup history gradients showed the similar tendency. Compared with those in 1980s, forest- and eurytopic-habitats birds increased 9–11 species (23–39%), and omnivorous, insect-eating, and phytophagous bird increased 5–9 species (14.1–29.4%) in those in 2010s, indicating that bird temporal changes were closely related with the changes in urban forests owing to food supply and habitat provision. Our findings could provide data for biodiversity evaluation of urbanization effects, and is also useful for ecological re-construction of local cities in China.     

Contributions of landscape trees in public housing estates to urban biodiversity in Hong Kong

Public housing estates (PHEs) in Hong Kong, accommodating 3.3 million of the 7-million population, have generous landscape planting in their grounds. The independent tree management regime generates a tree stock that deviates from the general urban-tree population. This study evaluated species composition, floristic diversity, importance value, and spatial distribution of trees in 102 PHEs (half of the total) occupying 8.31 km² (territory land area of 1104 km²), assessed their contribution to urban biodiversity, and developed a species selection strategy to enrich urban biodiversity. 48,823 trees belonged to 232 species, 151 genera and 59 families. Natives contributed 69 species and 10,837 trees. Species profile was skewed toward exotic species and trees. The species were divided into six frequency groups. The signature group had 45 species each with >200 trees. The dominant, common and occasional groups had 20, 26 and 48 species, respectively. 59 species in the rare group and 34 in the solitary group denoted changing and diverse species selections, respectively. Nonmetric Multidimensional Scaling (NMDS) found that species distribution in PHEs was strongly associated with species diversity, estate area and estate age. However, district and region were not correlated with NMDS. Some 98 species were significantly correlated (Spearman) with one or both NMDS axes. Species groups were analyzed to inform a species selection strategy to improve future planting program and enrich urban biodiversity. The methods and findings could be applied to south-China and other cities to rationalize urban-forest programs with the help of objective research data.     

Ozone forming potential of tropical plant species of the Vidarbha region of Maharashtra state of India

Volatile organic compounds (VOC) are emitted by many plants. In this study, sixty common plant species of the Vidarbha region of Maharashtra, India were examined for VOC (isoprene and monoterpene) emissions. Plant species VOC emission rates ranged from undetectable to 75.2 μg g^?1 h^?1. Dalbergia sissoo exhibited a maximum VOC emission rate of 75.2 μg g^?1 h^?1. Ozone forming potentials (OFP) of the sixty plant species were also estimated using the method of Benjamin and Winer (1998). Maximum ozone forming potential of 77 g O₃ (tree)^?1 d^?1 was observed in the case of Mangifera indica. Out of 60 species, 26 species (43.3%) had low OFP (less than 1 g O₃ (tree)^?1 d^?1), 18 species (30%) had medium OFP (less than 1–10 g O₃ (tree)^?1 d^?1) and 16 species (26.7%) had high OFP (more than 10 g O₃ (tree)^?1 d^?1).     

Variations of urban greenness across urban structural units in Beijing,China

Urban structural units (USUs) are work (or similar) units in urbanized areas. In this study, USUs based on urban land use and land cover were used to explain and compare urban ecological conditions within Beijing. This study focused on the spatial pattern of land use for different USUs in urban areas. The results showed that 453 USUs belong to 12 primary USUs and to 38 different secondary USUs. The percentage of built-up area was highest in those regions with hotels, and lowest in areas with cemeteries. The percentage of woodland area was highest in primary and middle schools, and the lowest in entertainment plazas. The percentage of grassland area was highest in farmland or orchards, and lowest in Siheyuan (courtyards). The percentage of green space is highest in lands dedicated to middle and primary schools, and lowest in areas with museums. There is no significant linear relationship between construction period and green space percentage in Colleges/Universities (R = 0.045, p = 0.806 > 0.05) and Parks (R = 0.13, p = 0.43 > 0.05). However, there was an inverted-U curve relationship with the relevant housing price in the residential area, a relationship that can be described by the equation: f = 17736.45 + 348.21x ? 4.15 x², p = 0.0022 < 0.05. This relationship implied that the socio-economic factors like housing prices may be a factor in determining the green space pattern of urban ecosystems in Beijing.     

Quantifying green cover change for sustainable urban planning: A case of Kuala Lumpur,Malaysia

Despite the numerous benefits of urban green cover, urban land development has led to its destruction and degradation, including in Malaysia. In this study, time series Landsat satellite imagery were used to monitor green cover changes in Kuala Lumpur (KL), the largest and capital city of Malaysia. An advanced satellite image processing technique that considers the mixed-pixel problem was employed to determine the fraction of green cover in each Landsat pixel. Results show that the total green coverage in Kuala Lumpur decreased by 3% over the first study period, from 6564 ha in 2001–5,891 ha in 2013. However, it increased by 4% in the second, from 6215 ha in 2014–7,310 ha in 2016, and now green cover is 30% of the total land area of KL. These periods were selected to observe the changes in green cover before and after implementation of the “Greening KL” program, which was aimed to plant 100,000 trees in KL by year 2020. Most of the increase in green cover was contributed by trees planted along streets and in recreational parks. Other findings include a loss of ∼9% of green cover in two public parks compared to their total gazetted area, and a loss of green area in other forested parts of KL. Focus group discussions and structured interviews with public, private and non-governmental organizations indicate that green-cover losses can be partly attributed to weak regulations and their poor enforcement. Opportunities to protect and increase green cover in KL are also explored in this study. Such approaches are urgently needed before most of the green areas disappear from the landscape of KL, exacerbating the existing environmental problems in the city.     

Enhancing plant diversity and mitigating BVOC emissions of urban green spaces through the introduction of ornamental tree species

Promoting the plant diversity of urban green spaces is crucial to increase ecosystem services in urban areas. While introducing ornamental plants can enhance the biodiversity of green spaces it risks environmental impacts such as increasing emissions of biogenic volatile organic compounds (BVOCs) that are harmful to air quality and human health. The present study, taking Qingdao City as a case study, evaluated the plant diversity and BVOC emissions of urban green spaces and tried to find out a solution to increase biodiversity while reducing BVOC emissions. Results showed that: (1) the species diversity and phylogenetic diversity of trees in urban green spaces were 22% and 16% lower than rural forest of this region; (2) urban areas had higher BVOC emission intensity (2.6 g C m⁻² yr⁻¹) than their rural surroundings (2.1 g C m⁻² yr⁻¹); (3) introducing the selected 11 tree species will increase 15% and 11% of species diversity and phylogenetic diversity, respectively; and (4) the BVOC emissions from green spaces will more than triple by 2050, but a moderate introduction of the selected low-emitting trees species could reduce 34% of these emissions. The scheme of introducing low-emitting ornamental species leads to a win–win situation and also has implications for the sustainable green space management of other cities.     

Variations in land surface temperature and cooling efficiency of green space in rapid urbanization: The case of Fuzhou city,China

Rapid urbanization has caused significant land cover change (LCC) as well as changes in the land surface temperature (LST). However, the crucial land dynamic process, which could significantly contribute to the increase in LST and aggravation of the urban heat island (UHI) effect, remains poorly understood. Additionally, a strategy to optimize the most significant decreased land cover type in order to maximize the cooling effect is still lacking. Therefore, in this study, we selected the rapidly urbanizing and ‘hottest’ city in China, Fuzhou, as a case study. Two algorithms were selected to compare and obtain reliable LST data. A land use transfer matrix was used to detect critical contributions leading to the LST variations. The concept of cooling efficiency (CE) and the threshold value of efficiency (TVoE) are also proposed, defined, and calculated. The results show that LST values increased with increasing proportion of built-up land and sharply decreasing proportion of green space. Areas where LST differences exceed 4 °C cover 93% of the areas where green spaces decreased. Additionally, the LST variation is not only associated with the dominant land cover types but is also affected by the land cover transfer pattern and dynamics. Finally, we have calculated the TVoE of green space in Fuzhou city to be 4.55 ± 0.5 ha. This finding implies that when Fuzhou municipality implements urban/landscape planning, a green space area of 4.55 ± 0.5 ha is the most efficient to reduce the heat effect. This study extends the current understanding of LCC dynamics and LST variation. The concepts of the CE and TVoE are meaningful for landscape planning practice and can be used in other cases.     

Estimating the stormwater attenuation benefits derived from planting four monoculture species of deciduous trees on vacant and underutilized urban land parcels

This paper presents research that was undertaken to determine whether planting deciduous trees, using intensive tree planting schemes, on vacant and underutilized urban land provides significant hydrologic benefits. This work contributes to an ongoing discussion on how to use vacant and underutilized land productively, and may be important to land use decision-makers, whose policies support the use of green infrastructure for stormwater management. Tree growth parameters for four monoculture planting schemes were modeled (all trees had a 50.8 mm caliper at planting) and included (i) 450 Ginkgo biloba, (ii) 92 Platanus × acerifolia, (iii) 120 Acer saccharinum, and (iv) 434 Liquidambar styraciflua, on a 1.6-acre parcel. i-Tree Hydro (formerly UFORE-Hydro) was used to derive a simplified Microsoft Excel-based water balance model to quantify the canopy interception potential and evaporation, based on 7 years (2002–2008) of historical hourly rainfall and mean temperature data in Hamilton, Ontario, Canada. This study revealed that three of the species responded similarly, while one species (L. styraciflua) performed significantly better with respect to total canopy storage potential and evaporation, capturing and evaporating 2.9 m³/tree over the 7 years analyzed, or 1280 m³ for the total tree stand of 434 trees. The analyses presented herein demonstrate that the tree canopy layer was able to intercept and evaporate approximately 6.5%–11% of the total rainfall that falls onto the crown across the 7 years studied, for the G. biloba, P. × acerifolia and A. saccharinum tree stands and 17%–27% for the L. styraciflua tree stand. This study revealed that the rate at which a species grows, the leaf area index of the species as it matures, and the total number of trees to be planted need to be determined to truly understand the behavior and potential benefits of different planting schemes; had the mature leaf area been used as the sole indicator of the stormwater attenuating potential for each species, the A. saccharinum would have been the selected species. Also, had attenuation and evaporation per unit of tree been the only measurement reported, the P. × acerifolia stand would have been deemed the best performing tree, attenuating and evaporating 8.1 m³/tree. While the actual values presented herein may be uncertain because of a lack of locally-derived tree growth models, the approach described warrants further investigation.     

Investigation of plant growth and flower performance on a semi-extensive green roof

Understanding of plant growth and flower performance is crucial for appropriate planting design. This study was aimed to understand characteristics of growth pattern and flower performance in green roof plants and how plant species diversity effect these characteristics. A semi-extensive green roof was installed in 2005 and 54 species plant species were planted in 10 cm and 20 cm of the substrate in Rotherham, UK. Thirty-two quadrats (50 cm × 50 cm) were set up through the combinations of plant species diversity (high and low), planting density (high and low). Percentage of coverage and height of each species were recorded at every month from February to November 2006 in these 32 quadrates. Flowering time of each species was studied every two weeks from February to November 2006. Flowering time was various from plants; some showed a very long flowering time, over five months whereas some finished flowering within two weeks. The growth characteristics of individual plant species over time were categorized into six patterns of coverage and vertical growth pattern. Spread of individual plants was larger in high diversity of plants than those in low diversity of plants. Number of flowering was higher and overall flowering term was longer in the quadrats of higher plant species diversity than those of lower plant diversity. However, these tendencies were affected strongly by the combination of species used. Therefore, it is important to be aware of individual plant growth characteristics such as plant size, growth pattern and flower performance for planting design.     

The impact of photoperiod and irradiance on flowering of several herbaceous ornamentals

Forty-one herbaceous species were grown under short-days (8 h photoperiod, ambient irradiance averaged 12–13.2 and 6.4–8.3 mol m⁻² day⁻¹ for Experiments I and II, respectively) with or without supplemental high-pressure sodium lighting (+50, 100, or 150 μmol m⁻² s⁻¹); or under long-days delivered using natural day lengths and irradiance with night interruption lighting (2200–0200 h at 2 μmol m⁻² s⁻¹ from incandescent lamps) or under ambient daylight plus supplemental irradiance during the day and as a day extension to 18 h (0800–0200 h) with supplemental high pressure sodium lighting (+50, 100, or 150 μmol m⁻² s⁻¹) to identify the impact of photoperiod and irradiance on flowering of each species. Days to first open flower, leaf number below first flower, and mean dry weight gain per day (MDWG) were measured when the first flower opened. Twenty-seven species were photoperiodic with examples of five photoperiodic response groups represented: obligate short-day (2), facultative short-day (5), obligate long-day (16), facultative long-day (4); 13 were day neutral (no photoperiod response in flowering). One species, Salvia sclarea L., did not flower. A facultative irradiance response was observed with 10 species; 28 species were irradiance indifferent; 2 had delayed flowering as irradiance increased. Photoperiod affected MDWG of 30 species. Increasing irradiance affected MDWG with 14 species. Photoperiod interacted with irradiance to affect MDWG of 11 species. Cobaea scandens had the greatest MDWG (0.40 g day⁻¹) while Amaranthus hybridus had the least MDWG (0.01 g day⁻¹) across photoperiod and irradiance levels.     

Fine-scale characterization of bird habitat using airborne LiDAR in an urban park in Japan

Birds are ecosystem service providers and excellent urban ecosystem indicators because they are sensitive to habitat structure. Light detection and ranging (LiDAR) technology is a promising tool in bird habitat characterization because it can directly acquire fine-scale 3-D information over large areas; however, most of past avian ecological studies using LiDAR were conducted in North America and Europe, and there have been no studies in Asia. The robustness of LiDAR data across different habitat types remain problematic. In this study, we set 13 plots having different canopy area percentages in a large-scale urban park in Japan, and examined the usefulness of airborne LiDAR data in modeling richness and diversity of forest bird species and the abundance of Paridae species that play an important role in the urban food web. Bird surveys were conducted eight times at each plot during the birds’ breeding season, and the results were estimated using generalized linear models. In consequence, all of the response variables were explained by one or a few LiDAR variables, and the 1 × 1 × 1-m voxel-based variables were especially robust estimators. When targeting only densely-forested plots having more than 60% canopy area, the LiDAR data efficiency declined in estimation of the richness and diversity of whole forest bird species, whereas a laser penetration rate was efficient for estimating the Paridae species abundance. These results implied that the LiDAR data are useful in habitat characterization of forest birds, and even when targeting only dense forests, some LiDAR variables are effective for habitat estimation of birds preferring specific forest structures. In the future, application of LiDAR across a variety of ecosystems will greatly serve to develop adaptive conservation and management planning for urban forests.     

Private residential urban forest structure and carbon storage in a moderate-sized urban area in the Midwest,United States

In conjunction with urbanization and its importance as a major driver of land-use change, increased efforts have been placed on understanding urban forests and the provisioning of ecosystem services. However, very little research has been conducted on private property and little is known about the structure and function of privately owned urban forests. This research examines the structure of and carbon storage services provided by private residential urban forests in a moderate-sized Midwestern city. The primary research questions are as follows: What is the structure of private urban forests, and how does it vary across parcels? How much carbon is stored in tree and soil pools of private urban forests, and how does carbon vary across parcels? Ecological inventories were conducted on 100 residential parcels within 14 Neighborhood and Homeowners Associations of varying size and development age. Tree species richness, diversity, density, and diameter distribution were determined on a per parcel basis and for the entire tree population sampled. Further, tree and soil carbon storage were determined for each parcel. Results of this research demonstrated large variability in per-parcel tree metrics. Twelve of the parcels sampled had two or fewer trees, while eleven had greater than 50 trees. Further, tree carbon storage ranged from no carbon to 11.22 kg C m^?2. Alternatively, soil carbon storage was less variable and averaged 4.7 kg C m^?2, approximately 1.9 times higher than the average carbon stored in trees (2.5 kg C m^?2). Management efforts aimed at maintaining or enhancing carbon storage and other ecosystem services should focus on both soil protection and maximizing services in living biomass. Our results demonstrate that sustaining tree-produced ecosystem services requires maintenance of large old trees and species diversity, not only in terms of relative abundance, but also relative dominance, and in combination, species–specific size distributions.     

Current and potential carbon stocks of trees in urban parking lots in towns of the Eastern Cape,South Africa

Greening of shopping centre parking lots is a potentially important strategy that can contribute to urban carbon mitigation efforts, improve aesthetics and the shopping experience of consumers, whilst adding to urban biodiversity. Twenty-eight shopping centre parking lots in six Eastern Cape urban centres, South Africa, were sampled to determine tree species composition, density and annual carbon sequestration potential. The best case parking lot found during the study was used as a benchmark to display the difference between current tree density and above-ground carbon stocks relative to the potential optimum. The highest tree density was 66 trees ha^?1, whereas the average density across all sampled parking lots was less than half that (27.2 ± 22.6 trees ha^?1). The average annual carbon sequestration potential per parking lot was 1390 ± 2503 kg ha^?1. Planting density was positively related to annual sequestration rates, whilst parking lot age and the mean annual rainfall of the town had no influence. Mean tree species richness per parking lot was 2.3 ± 1.8 species, with a positive relationship to parking lot size, but not to mean annual rainfall of the site. The majority of trees (62.5%) in parking lots were alien species, although newer parking lots had significantly greater proportions of indigenous species. There was no difference in mean annual carbon sequestration rate per tree between indigenous and alien trees species. Low tree densities and small parking lot areas constrained the potential for earning carbon credits from trees in parking lots. Nonetheless, planners and designers need to be more aware of the potential contribution of trees towards urban sustainability.     

Relationships between bole and crown size for young urban trees in the northeastern USA

Knowledge of allometric equations can enable urban forest managers to meet desired economic, social, and ecological goals. However, there remains limited regional data on young tree growth within the urban landscape. The objective of this study is to address this research gap and examine interactions between age, bole size and crown dimensions of young urban trees in New Haven, CT, USA to identify allometric relationships and generate predictive growth equations useful for the region. This study examines the 10 most common species from a census of 1474 community planted trees (ages 4–16). Regressions were applied to relate diameter at breast height (dbh), age (years since transplanting), tree height, crown diameter and crown volume. Across all ten species each allometric relationship was statistically (p < 0.001) significant at an α-level of 0.05. Consistently, shade trees demonstrated stronger relationships than ornamental trees. Crown diameter and dbh displayed the strongest fit with eight of the ten species having an R² > 0.70. Crown volume exhibited a good fit for each of the shade tree species (R² > 0.85), while the coefficients of determination for the ornamentals varied (0.38 < R² < 0.73). In the model predicting height from dbh, ornamentals displayed the lowest R² (0.33 < R² < 0.55) while shade trees represented a much better fit (R² > 0.66). Allometric relationships can be used to develop spacing guidelines for commonly planted urban trees. These correlations will better equip forest managers to predict the growth of urban trees, thereby improving the management and maintenance of New England's urban forests.     

Effect of urbanization and climate change in the rooting zone on the growth and physiology of Pyrus calleryana

It is well known that trees can reduce the urban heat island and adapt our cities to climate change through evapotranspiration. However, the effects of urbanization and anticipated climate change in the soil–root rhizosphere have not been widely investigated. The current study studied the growth and physiology of the urban tree Pyrus calleryana grown in a factorial experiment with or without urbanization and simulated climate change between April 2010 and December 2012 in the Botanical Grounds of the University of Manchester, UK. The study indicated that urbanization and simulated climate change had small but contrasting effects on tree growth and morphology. Urbanization increased tree growth by 20–30%, but did not affect leaf area index (LAI) and showed reduced peak water loss and hence evapotranspirational cooling. Although soil moisture content in the upper 20 cm was higher in the urbanized plots, urbanization showed reduced sap flux density, reduced chlorophyll a:b and delayed recovery of chlorophyll fluorescence (Fv:Fm) throughout the experimental period. In contrast, simulated climate change had no effect on growth but increased LAI by 10%. Despite being more water stressed, trees grown in simulated climate change plots lost more water both according to porometry and sap flow measurements. Simulated climate change increased peak energy and water loss by around 13%, with trees having an average sap flux density of around 170 g cm^?2 d^?1, 40% higher than trees grown in control plots. Our study suggested that transpirational cooling benefit might be enhanced with a longer growth season and higher soil temperature in places such as Manchester, UK in future, but potentially at the expense of photosynthesis and carbon gain.     

Spatiotemporal dynamics of plant diversity in response to farmers’ evolved settlements in Shanghai

The expansion of the Shanghai metropolitan region has caused a substantial amount of farmland to become urbanized. Most farmers have lost their land and have been relocated from villages to new collective settlements, resulting in dramatic changes in the landscape pattern. This study explores the effects of this transformation on the spatiotemporal dynamics of plant diversity. We randomly sampled 22 plots comprising 294 subplots within two crossed transects that pass through 5 traditional villages and 17 new settlements. The results show that resettlement has exerted significant effects on plant species diversity, both temporally and spatially. Temporally, the Gleason index (GI) of total species over time could be ordered as 1990s > 2000s > 1980s, while Shannon’s diversity index (SHDI) was ordered as 2000s > 1990s > 1980s. Spatially, the GI of total species decreased from the urban center to the exurbs or from the inside to the outside of the built-up areas. SHDI was highest in suburbs or ecotones. Furthermore, the GI of total species had significant correlations with those of indigenous species, exotic species, and planted species (r > 0.90, p < 0.01) as well as with the region and location of settlement (r < −0.48, p < 0.01). Both indigenous and exotic species had significant positive correlations with total species richness at 0.01 levels. Generally, compared with traditional settlements, new settlements displayed greater richness and diversity of plant species, primarily because of the exotic species present in new settlements. The farmers’ socio-economic status was found to be the primary cause of differences in species richness. To protect indigenous and wild species, it is necessary to take into account local knowledge in villages to encourage Chinese farmers to participate actively in community greening. A bridge should be built between traditional villages and modern settlements and between the past and future for farmers.     

Mapping leaf area of urban greenery using aerial LiDAR and ground-based measurements in Gothenburg,Sweden

Leaf area of urban vegetation is an important ecological characteristic, influencing urban climate through shading and transpiration cooling and air quality through air pollutant deposition. Accurate estimates of leaf area over large areas are fundamental to model such processes. The aim of this study was to explore if an aerial LiDAR dataset acquired to create a high resolution digital terrain model could be used to map effective leaf area index (L_e) and to assess the L_e variation in a high latitude urban area, here represented by the city of Gothenburg, Sweden. L_e was estimated from LiDAR data using a Beer-Lambert law based approach and compared to ground-based measurements with hemispherical photography and the Plant Canopy Analyser LAI-2200. Even though the LiDAR dataset was not optimized for L_e mapping, the comparison with hemispherical photography showed good agreement (r² = 0.72, RMSE = 0.97) for urban parks and woodlands. Leaf area density of single trees, estimated from LiDAR and LAI-2200, did not show as good agreement (r² = 0.53, RMSE = 0.49). L_e in 10 m resolution covering most of Gothenburg municipality ranged from 0 to 14 (0.3% of the values >7) with an average L_e of 3.5 in deciduous forests and 1.2 in urban built-up areas. When L_e was averaged over larger scales there was a high correlation with canopy cover (r² = 0.97 in 1 × 1 km² scale) implying that at this scale L_e is rather homogenous. However, when L_e was averaged only over the vegetated parts, differences in L_e became clear. Detailed study of L_e in seven urban green areas with different amount and type of greenery showed a large variation in L_e, ranging from average L_e of 0.9 in a residential area to 4.1 in an urban woodland. The use of LiDAR data has the potential to considerably increase information of forest structure in the urban environment.     

Density,diversity and richness of woody plants in urban green spaces: A case study in Chennai metropolitan city

A tree diversity inventory was carried out in urban green spaces (UGSs) of Chennai metropolitan city, India. This inventory aims to study the diversity, density and richness of trees in UGSs of Chennai. A total of one hundred 10 m × 10 m (total 1 ha) plots were laid to reveal tree diversity and richness of UGSs. Trees with ≥10 cm girths at breast height (gbh) were inventoried. We recorded 45 species in 42 genera and 21 families. Caesalpiniaceae and Fabaceae each with 6 species dominated the study area followed by Arecaceae (3). Density and stand basal area of the present study were 500 stems ha^?1 and 64.16 m², respectively. Most of the inventoried trees were native (31 species) and deciduous (28 species). Fabaceae and Caesalpiniaceae dominated the present study area in terms of stand basal area and density. The Shannon diversity index and evenness of study area were 2.79 and 0.73, respectively. The most important species and families based on species important value index (IVI) and family important value index were Albizia saman, Polyalthia longifolia and Azadirachta indica; Fabaceae, Caesalpiniaceae and Annonaceae respectively. We find Chennai's urban forest is relatively superior to many urban forests of the world in terms of stand basal area and species richness. Results emphasize the importance of enhancement of urban green spaces in Chennai metropolitan city.     

The feasibility of remotely sensed data to estimate urban tree dimensions and biomass

Accurately measuring the biophysical dimensions of urban trees, such as crown diameter, stem diameter, height, and biomass, is essential for quantifying their collective benefits as an urban forest. However, the cost of directly measuring thousands or millions of individual trees through field surveys can be prohibitive. Supplementing field surveys with remotely sensed data can reduce costs if measurements derived from remotely sensed data are accurate. This study identifies and measures the errors incurred in estimating key tree dimensions from two types of remotely sensed data: high-resolution aerial imagery and LiDAR (Light Detection and Ranging). Using Sacramento, CA, as the study site, we obtained field-measured dimensions of 20 predominant species of street trees, including 30–60 randomly selected trees of each species. For each of the 802 trees crown diameter was estimated from the aerial photo and compared with the field-measured crown diameter. Three curve-fitting equations were tested using field measurements to derive diameter at breast height (DBH) (r² = 0.883, RMSE = 10.32 cm) from the crown diameter. The accuracy of tree height extracted from the LiDAR-based surface model was compared with the field-measured height (RMSE = 1.64 m). We found that the DBH and tree height extracted from the remotely sensed data were lower than their respective field-measured values without adjustment. The magnitude of differences in these measures tended to be larger for smaller-stature trees than for larger stature species. Using DBH and tree height calculated from remotely sensed data, aboveground biomass (r² = 0.881, RMSE = 799.2 kg) was calculated for individual tree and compared with results from field-measured DBH and height. We present guidelines for identifying potential errors in each step of data processing. These findings inform the development of procedures for monitoring tree growth with remote sensing and for calculating single tree level carbon storage using DBH from crown diameter and tree height in the urban forest.