Urban Forest Area Research Articles

Developing an integrative management plan for urban and peri-urban forests: A case study of Ljubljana, Slovenia

Many cities worldwide have adopted management strategies for urban forests, typically focusing on forest parks, street trees and park trees. However, planning that concentrates on natural urban forest areas remains scarce. This study introduces an advanced planning framework for the integrative management of natural urban forests and applies it to Ljubljana's urban forests (2151 ha). The framework consists of an initiation phase and a six-step planning procedure. Through a comprehensive process lasting 20 months, with strong stakeholder involvement and political support, we developed a strategic plan for Ljubljana’s entire urban forest area and an operational plan for a specific block within this area. The approach employs the integrative management of forest stands within or near the city, incorporating harmonised activities in silviculture, recreation, protection, harvesting and communication. This planning method aims to bridge the gap between traditional forest management planning and urban green infrastructure planning.

Forecasting urban forest recreation areas in Turkey using machine learning methods

Recreation is the process of revitalizing and renewing human existence through optional activities, serving as a broad description. It has prominently arisen as a reaction to personal requirements for stress reduction, especially in developed urban areas. Engaging in this recreational activity provides a way to utilize one's spare time, providing refreshment for both the physical and mental aspects, whether done alone or with others, in countryside or city environments. Urban forests are important leisure places within city environments. An expanded presence of urban forest places can greatly enhance the general well-being of society. The estimation of urban forest areas in the future may receive increased attention, leading to measures to extend current areas or prepare for future activities and services. We utilized official statistics from the years 2013 to 2021, sourced from the Republic of Turkey official website. Ministry of Agriculture and Forestry's General Directorate of Forestry. We used statistics that contained information about urban forests, classified as Type D recreational areas, to create a dataset. We performed provincial-level area projections for the year 2021. Using the KNIME platform, we used three different analysis techniques: linear regression analysis, gradient-boosted regression trees and artificial neural networks. It is seen that the results of linear regression and artificial neural networks are close to each other and give good results. The peak performance was attained using artificial neural networks, resulting in an R2 score of 0.99. This study differs from other similar projects by concentrating on calculating urban forest recreational spaces per province throughout Turkey, using data provided by government agencies. The accomplishments highlight the ability to make reliable predictions about future forest resources by using analogous forecasts in the upcoming years.

Bioluminescence Inhibition Bioassay for Estimation of Snow Cover in Urbanised Areas within Boreal Forests of Krasnoyarsk City

It has been proposed that the level of air pollution in a city should be estimated based on the accumulation of pollutants in the snow cover of urban forests. This study presents a bioluminescence method for estimating the extent of snow cover pollution in the urbanised areas of boreal forests in Krasnoyarsk city. A bioluminescent assay involving NAD(P)H:FMN oxidoreductase (Red) and luciferase with luminous bacteria (BLuc) was employed to measure the concentrations of six heavy metals (As, Cd, Zn, Co, Hg, and Pb) in the snow cover. The tested snow samples demonstrated a correlation between the reduced activity of the enzyme system and variations in Cd concentration. Furthermore, the research indicated that the period of unfavourable meteorological conditions in Krasnoyarsk city resulted in a notable decline in the activity of the BLuc–Red enzyme system, which may be associated with elevated air pollution levels. This study underscores the potential of the bioluminescence method for monitoring environmental pollution in urban forested areas.

Mercury distribution and transfer in mangrove forests in urban areas under simulated rising sea levels

Mercury distribution and transfer in mangrove forests in urban areas under simulated rising sea levels

The Development of Flora and Fauna Conservation Area Through Signage and Digital Map: Study on Srengseng Urban Forest, West Jakarta

This research aims to identify and analyze the development of flora and fauna conservation areas through signage and digital maps in Srengseng Urban Forest, West Jakarta. The research method used is a qualitative method described by descriptive analysis conducted through in-depth interviews and documentation. This research concludes that Srengseng Urban Forest has proven unable to develop thoroughly in terms of signposting facilities. The obstacles, such as the lack of directions and the absence of a map of the location, affect the comfort of visitors and safety and hygiene issues. Suggestions that can be given to improve the development of conservation areas in Srengseng Urban Forest are that Srengseng Urban Forest should have multifunctional signage, such as directional signs that include several directions from facilities and attractions in the urban forest with signage placement in strategic locations, such as at the roundabout around the main entrance of the Srengseng Urban Forest. In addition to creating multifunctional signage, Srengseng Urban Forest also needs to have a digital map type map that visitors can access by scanning a QR Code to show an overall picture of the Srengseng Urban Forest area.

First Report of Anthracnose Caused by Colletotrichum siamense on Machilus thunbergii Siebold & Zucc. in South Korea.

Machilus thunbergii Siebold & Zucc., known as Japanese bay tree, is an evergreen tree distributed widely in East Asia, including South Korea, where the species is of ecological importance. Machilus thunbergii provides habitat for wildlife species and is a common urban tree. In September 2022, anthracnose symptoms on leaves were observed in Jeju (33°26'02.4"N, 126°19'48.8"E) and Tongyeong (34°49'27.1"N, 128°24'01.8"E) in South Korea. Disease incidence on leaves of each affected tree, naturally growing in an urban forest area covering approximately 0.5 ha was approximately ~ 70 % in each study area. Anthracnose symptoms that were observed on 70 to 80% leaves per tree in each study area included orbicular or irregular, whitish-grey spots on leaves that were 1.5 to 3.0 cm in diam. In some cases where leaves were severely affected, larger blotches were formed, leading to bleaching symptoms and eventually defoliation. For pathogen isolation, two or three leaves showing anthracnose symptoms from each of the 15 trees were randomly selected and brought to the laboratory. Fungal isolations were then directly made by transferring spores from acervuli that developed on diseased leaves onto potato dextrose agar (PDA) media. Cushion shaped acervuli filled with salmon to orange-colored conidial masses were produced on media approximately two weeks after the incubation at 25 ± 1°C with a photoperiod of 12 h. Conidia were single celled, hyaline, cylindrical with rounded ends, smooth walls, 13.7 to 18.1 μm long and 3.1 to 4.5 μm wide (n=30). Among 15 cultures that were successfully isolated, 10 isolates were retained based on culture characteristics, and two randomly selected monoconidial cultures were deposited in the culture collection (CDH) of the Chungnam National University, Republic of Korea (Accession No. CDH057-58). Two isolates selected, CDH057 and CDH058, were subjected to identification, and this was achieved based on multiplesequence comparisons using on internal transcribed spacer regions of rDNA (ITS1 and ITS2), partial sequences of actin (ACT) and β-tubulin (TUB2) gene regions amplified using ITS1F / ITS4, ACT-512F / ACT-783R and T1 / Bt2b, respectively (Weir et al. 2012). The representative sequence data were deposited in GenBank under the accession numbers OR473277 and OR473278 for the ITS, OR480772 and OR480773 for ACT, and OR480774 and OR480775 for TUB2. The resulting sequences were further used for a phylogenetic analysis based on the maximum likelihood method using a concatenated dataset of the ITS, ACT and TUB2 gene sequences for Colletotrichum species in the C. gloeosporioides clade. The results showed that the pathogen isolated in this study clustered with Colletotrichum siamense (Vouchered specimens: MFLU 090230, COUFPI291, and COUFPI294) (Prihastuti et al. 2009). Sequence comparisons revealed that the isolates obtained in this study differed from the type species of C. siamense (MFLU 090230; FJ972613 for ITS, FJ 907423 for ACT, FJ907438 for TUB2) at 2 of 258 bp (∼0.8%) and 6 of 387 bp (∼1.6%) in the ACT and TUB2 sequences, respectively, while the ITS was identical to the type species. For pathogenicity tests, a total of ten three-year-old seedlings of M. thunbergii were used. The leaves of each tree were sprayed with 5 ml of conidial suspension (105 conidia/ml, isolate CDH057). Three control plants were sprayed with sterile water. After being sprayed, treated areas were sealed with a plastic bag for 24 hours to preserve humidity. Anthracnose symptoms, identical to those observed in the field, appeared five to seven days after the inoculations, while no symptoms were observed on control plants. The isolates used in the pathogenicity test were reisolated from 90% of lesions, and their identity was confirmed based on sequence comparisons, thus fulfilling Koch's postulates. Species of the C. gloeosporioides species complex include important plant pathogens, particularly C. siamense, which cause significant losses of economic and ecological relevance on a wide range of hosts (~ 100 hosts) (Talhinhas and Baroncelli 2021). Although C. fioriniae in the C. acutatum species complex, was found on M. thunbergii in South Korea (Thao et al. 2023), anthracnose associated with C. siamense on M. thunbergii has not been reported in the country. In this regard, this is the first report of anthracnose caused by C. siamense on M. thunbergii in South Korea. To effectively control the disease, more attention should be paid on the host range of the pathogen and other regions where the disease caused by the pathogen might occur in the country.

Impact of Urban Forest and Park on Air Quality and the Microclimate in Jinan, Northern China

Though the impact of urban vegetation on air quality and the microclimate has attracted increasing attention, there have been few studies quantitatively assessing this impact in North China, where air pollution is severe. In this study, we investigated the impact of urban forests and urban parks on air quality and the microclimate in Jinan, northern China. Six sites were chosen to represent urban forest, urban park, and downtown areas, respectively. The results indicate that urban forest can effectively reduce PM2.5 and ozone (O3) concentrations in the warm season, when temperatures are higher and plants are lush. The PM2.5 and O3 concentrations in the urban forest areas were 6.3–6.5 μg m−3 and 21–23 μg m−3 lower than those in downtown areas during the period of 10:00–15:00. In contrast, urban park areas can reduce PM2.5 concentrations but have little impact on gaseous pollutants such as nitrogen dioxide and O3. Furthermore, both urban forest and urban park areas reduced temperatures, by approximately 4.1–6.8 °C and 1.36 °C, respectively, and increased relative humidity, by about 13.4–12.9% and 0.9%, promoting a more comfortable thermal environment for residents. Therefore, this study highlights the crucial role of urban vegetation in improving air quality and creating a comfortable environment for residents.

Ecological Risk Assessment, Distribution and Source of Polycyclic Aromatic Hydrocarbons in the Soil of Urban and Suburban Forest Areas of Southern Poland

Polycyclic aromatic hydrocarbons (PAHs) are widespread environmental pollutants that can pose a risk to people living near contaminated soils. The role of forest ecosystems around urban agglomerations as a draw to urban dwellers has been highlighted by the COVID-19 pandemic. The pandemic led us to focus this study on the soils beneath forested areas around urban agglomerations, with the aim of assessing the sources and ecological risk of PAHs in the soils. For the study, a 150 km transect was delineated by six sampling sites, located in urban and commercial forests, which were characterised by the same species composition. Samples were taken from the 0–10 cm depth horizon, after removal of the organic layer. The content of 16 PAHs was determined, from which the potential source of contamination, the toxic equivalent quotient (TEQ), the potential ecological risk quotient (RQ) and the incremental lifetime cancer risk quotient (ILCR) were calculated. The mean sums of the PAHs ranged from 12.41 to 52.76 μg·kg−1. Our analysis indicated that the share of pollutants in the soils had resulted from industrial combustion, biomass and coal combustion, and traffic. The RQ of the PAHs in the soils of the Upper Silesian Industrial Region, or within its impact range, were found to be low to moderate. High ILCR ratios for children (1.9 × 10−4) and adults (8.38 × 10−5) were recorded in soils related to a refinery. Our findings confirm that forests around urban areas are vulnerable to pollution. People living in cities should consider spending their leisure time in forest areas at a distance from their homes. Systematic and continuous monitoring of PAHs is necessary to ensure that human safety is guaranteed.

Urban–Rural Comparisons of Biogenic Volatile Organic Compounds and Ground-Level Ozone in Beijing

Ground-level ozone (O3) pollution has been a severe environmental and health problem for decades. The importance of biogenic volatile organic compounds (BVOCs) in the formation of tropospheric photochemistry O3 has been highlighted, especially in areas of rapid urbanization. We conducted simultaneous measurements of trace gases, including NO, NOX, O3, and BVOCs (i.e., isoprene and α-pinene), in the urban and rural forest areas of Beijing to determine the relationships between them. The results highlight the differences between the urban and rural forest areas of Beijing in terms of ambient air concentrations of BVOCs and O3, and the interrelationships between BVOCs, NOX, and ozone were quantified. Moreover, the isoprene concentration was found to be higher in the atmosphere of the urban site than of the rural site, which had higher α-pinene concentrations and higher O3 concentrations. The NOX concentration was higher at the urban site than at the rural site, and there was a significant exponential relationship between NOX and O3 at the urban site, indicating that the impact of NOx on O3 at the urban site was greater than that at the rural site. The O3 concentration increased with rising isoprene and α-pinene in both sites. In the case of substantially increased BVOC concentrations, declining NOX concentrations strongly promote the formation of O3. Consideration should be given to planting tree species with low-BVOC emissions, as they are crucial for mitigating O3 pollution in urban areas. Additionally, the relationships between BVOCs, NOX, and O3 should be considered in policymaking related to O3 control.

Effect of urbanization and urban forests on water quality improvement in the Yangtze River Delta: A case study in Hangzhou, China

In the context of rapid global urbanization, the sustainable development of ecosystems should be considered. Accordingly, the Planetary Boundaries theory posits that reducing the amount of nitrogen and phosphorus pollutants entering bodies of water is necessary as excess levels may harm the aquatic environment and reduce in water quality. Thus, based on the long-term monitoring data of representative urban rivers in the Yangtze River Delta region, we evaluated the nitrogen and phosphorus pollution of water bodies in different urbanization stages and further quantified the effect of urban forests on water quality improvement. The results showed that, with the continuous progression of urbanization, the proportion of impervious surface area increased, along with the levels of nitrogen and phosphorus pollution in water bodies. The critical period of water quality deterioration in urban rivers occurred during the medium urbanization level when the proportion of impervious surface area reached 55–65 %, and the probability of an abrupt increase in total nitrogen (TN) and total phosphorus (TP) concentration exceeded 95 %. However, increasing the area of urban forests during this period reduced TN pollution by 36.64 % and TP pollution by 49.03 %. The results of this study support the expansion of urban forests during the medium urbanization stage to improve water quality. Furthermore, our results provide a reference and theoretical basis for urban forest construction as a key aspect of the sustainable development of the urban ecosystem in the Yangtze River Delta and similar regions around world.

Does nationality affect landscape perceptions of urban sacred forests? A Japan–China cross‐cultural comparison

AbstractThis study explores the cultural ecosystem services of sacred forests in urban areas, focusing on the Meiji‐Jingu Shrine's forest in Japan. We assessed the forest's sublimity and landscape perceptions among Japanese and Chinese visitors using a mixed‐method approach. Data were gathered from 359 geotagged photographs and a questionnaire completed by 30 participants, evaluating sublimity and psychological aspects. GIS analysis identified scenic hotspots, and statistical methods compared landscape perceptions between the two visitor groups. Text mining analyzed differences in their forest evaluation. Key findings include (1) Cultural differences in perceiving landscape hotspots, (2) insights into the sublime nature of Meiji‐Jingu Shrine's forest, and (3) varied perceptions of forest sublimity between Japanese and Chinese visitors. This cross‐cultural study provides valuable insights for sacred forest conservation.

KEANEKARAGAMAN FITOPLANKTON DI DANAU KENANGA UNIVERSITAS INDONESIA, JAWA BARAT

In addition to urban forest area at the University of Indonesia, Depok Campus, West Java, there are lakes that functions as water reservoir area. University of Indonesia is eager to create green and beautiful campus environment with one of its efforts is to care for the lake ecosystem in the campus. This study was conducted to analyze the diversity of phytoplankton in the lake. Sampling was carried out by determining 3 location points with 3 times repetitions conducted on different days. The water samples taken were then identified at the Biology Laboratory FMIPA UNJ. The mean values of water quality parameters obtained were pH 10, TDS 90 ppm, temperature 30°C, and water clarity 46 cm. The results showed that 14 genera and 20 species have been found, they are Chlorophyta, Chroococcus, Coelosphaerium, Crucigeniella, Euglena, Gloeocapsa, Merismopedia, Pediastrum (3 species), Peridinium, Scenedesmus (4 species), Tablelaria, Tetrastrum, Volvox, and Westella (2 species). The Diversity Index Shannon-Wiener during the observation was 2.9, which means that the condition of water at the University of Indonesia Lake was very good and not polluted. The availability of phytoplankton in the area was generally sufficient which can be utilized by other organisms as food source.

Active recreational and silvicultural co-use of forested areas: an innovative forest management study

Abstract Issue Forests are crucial in the sustainability transition to a biobased modern society. However, forests may also be recreational sites, and positively affect human health and well-being. Modern silvicultural harvesting practices alters the landscape overnight, and hence may affect the recreational and public health promoting use of it. Description of the problem Municipalities, as owners of urban forest areas, may actively support inhabitants’ recreational use of near-by forested areas by 1) allocate resources to local voluntary organizations who facilitate for recreational users and 2) actively facilitate for continuous recreational use while practicing modern silviculture. In 2020-2022, an innovative integrative forest management approach was tested in a municipality in mid-Norway. This study explores how the local forests are used for recreational purposes, and how potential conflicts in land use can be mitigated or prevented. Results The forest areas are mostly used for health-promoting activities like exercise, walking, general recreation, and seasonal harvesting of wild berries and mushrooms. Half of the users get to the forest by foot or bicycle. Easy access, closeness to home, free parking arrangements and access to maps of the areas is important to users. Most users were well-informed about local forest-based businesses and carbon sequestration in wood and held that forests should be harvested and regenerated. They showed a high tolerance for forestry if the footpaths were cleared immediately. However, three out of four users want to be informed before harvesting. A small share of users wants educational posters about forest ecosystems. Lessons A pre-existing low conflict level between modern forestry and recreational forest use may be maintained by quite simple and modest means. In this municipality information posters were placed by the footpaths and an arena for discussions, information and co-creation of recreational facilitation was established in 2022. Key messages • Near-urban forests are frequently used for exercise and recreational activities, especially if easily accessible. • Harmonious co-use of forest areas, even in times of timber harvesting, is supported by rapidly recovering the footpaths and by notifying inhabitants in advance.

How Should Soundscape Optimization from Perceived Soundscape Elements in Urban Forests by the Riverside Be Performed?

Urban forests by the riverside are important habitats for various animals and contribute various soundscapes for citizens. Unfortunately, urban forests are exposed to the influence of riverside traffic noises from freeways. This study aims to explore the spatial and temporal variation of soundscape, conduct soundscape optimization for multiple parameters, and find a balance and its interval of soundscape elements through optimizing a soundscape map. Questionnaires and measuring equipment were used to gather soundscape information in an urban forested area in Fuzhou, China. Diurnal variations and soundscape mapping were used to analyze spatial and psychophysical relationships between soundscape drivers. We then conducted optimization for a soundscape map, which included normalization, critical value determination, target interval of optimal SPL determination, and modification of SPL and mapping. Our findings suggest that biological activities and natural phenomena are potential drivers for diurnal variation of soundscapes, especially tidal phenomena contributing water and shipping soundscapes. Our results also suggest that all the high values of perceived soundscapes were found at the southwest corner of the study area, which includes both riverside and urban forest elements. Furthermore, we suggest combining both optimal soundscape and SPL correction maps to aid in sustainable design in urban forests. This can contribute to the understanding and methodology of soundscape map optimization in urban forests when proposing suitable design plans and conservation of territorial sound.

Developing a mapping procedure for urban forests using online map services and Sentinel-2A images

Accurate area statistics at the local government level are important for the scientific management of urban forests. A more consistent and robust mapping of urban forests can enable a comparison of the size and quality management guidelines at major cities in Asia. However, few administrative statistics have employed these scientific techniques. Therefore, a cover map of urban forests focusing on their types is needed for the quantitative and qualitative estimation and evaluation of urban forests. This study presents an approach for mapping urban forest cover for 2021 using Sentinel remote sensing images and aerial photographs from commercial maps. Cover maps of urban forests at a city scale were developed for three pilot study areas in Korea’s capital area. Labeling was performed for deciduous forests, coniferous forests, grasslands, wetlands, bare land, croplands, urban areas, and water bodies. The land cover classification was performed using machine learning models, including random forest (RF), support vector machines (SVM), and gradient tree boost classifier (GBT), and a comparison was made among them. All three methods performed well in the three study areas; the RF model was simple to use, and the SVM was better at detecting forest connections. The proposed mapping method, which focuses on forest types in cities, can be used to compare the area and connection of urban forests in cities.

Effects of Climate Change and Urbanization on Vegetation Phenology in the Bucharest Metropolitan Area

Being an essential issue in global warming, the response of urban vegetation to climate change and urbanization has become an increasing concern at both the local and global levels. This study aims to investigate the effect of the urban environment on vegetation phenology for the Bucharest metropolitan area in Romania and to identify the potential climate drivers that influence key phenology in the urban environment. In this study, we comprehensively analyzed the response of urban vegetation phenology shifts due to climate variability and urbanization in the Bucharest metropolitan area from a spatiotemporal perspective during the 2002- 2022 period. Through synergy use of time series of the main climate variables, Air temperature -AT, land surface temperature (LST), and biophysical variables derived from MODIS Terra/Aqua satellite and in-situ data, this study developed a complex statistical and spatial regression analysis. Green space was measured with satellite-derived vegetation indicators Normalized Vegetation Index (NDVI), and Enhanced Vegetation Index (EVI), Net Primary Production (NPP) data, which captures the combined availability of urban parks, street trees, forest, and periurban agricultural areas. Leaf Area Index (LAI) and Photosynthetically active radiation (FPAR) indicators have been used to characterize the effects of meteorological parameters and urbanization impacts on vegetation phenology and their changes. The results show that the response of vegetation phenology to urbanization level and climate parameters variability has a distinct spatiotemporal difference across the urban/periurban gradient. The findings of this study show that the land surface temperature anomalies associated with urbanization-induced climate warming, especially during strong summer heat waves and under urban heat islands alter urban vegetation biophysical properties, directly impacting its phenology shifts. At the metropolitan scale, the urban thermal environment directly impacts vegetation phenology patterns. The quantitative findings of this study are of great importance for understanding the complex impacts of urbanization and climate changes on vegetation phenology and for developing models to predict vegetation phenological changes under future urbanization.

Identifying Suitable Variables for Visual Aesthetic Quality Assessment of Permanent Forest Reserves in the Klang Valley Urban Area, Malaysia

Permanent forest reserves (PFR) in urban areas are an integral aspect of the urban forest concept and the basis of a city’s green infrastructure. The preservation of natural forests in urban areas has become a widely researched topic due to the environmental, social, and economic benefits provided by it. Although several studies have shown that visual aesthetics play a role in preserving natural forests in urban areas, visual aesthetic value is typically not prioritized in preservation plans since it varies based on the physical characteristics of natural forests in urban areas, making it difficult to measure universally. Therefore, this research aims to identify the suitable variables for assessing the visual aesthetic quality of permanent forest reserves within urban areas in Malaysia. This study selected two permanent forest reserves based on four criteria. Data were collected via participant-generated images taken along selected forest trails based on participant visual aesthetic preferences. Researchers and experts analyzed and classified the data according to content to identify suitable visual aesthetic quality variables. This research identified 14 suitable variables for assessing the visual aesthetics of PFRs in urban areas, with a dominant preference for information-processing theory variables. Mystery was the most present variable for the visual aesthetic quality assessment of PFRs. Furthermore, participants’ educational and emotional backgrounds, categorized as design, environmental, social, and technical, impacted their visual aesthetic preferences. Our findings serve as a foundation for assessing the visual aesthetic quality of natural forests within urban areas in Malaysia.

Combination of multiple stable isotope and elemental analyses in urban trees reveals air pollution and climate change effects in Central Mongolia

The Ulaanbaatar area in Mongolia has become one of the most polluted regions worldwide due to the rapid increase in urbanization, industrial activity and traffic. However, we critically lack knowledge on the impacts of air pollution on surrounding forest ecosystems that may be further amplified by the ongoing climate change. Here, we apply a novel combination of multiple stable isotope analyses (nitrogen: δ15N, carbon: δ13C, oxygen: δ18O, hydrogen: δ2H) in foliar and tree-ring samples from different tree species, including deciduous, broadleaf species (poplar and birch), a deciduous conifer (larch) and needle evergreen species (spruce and Scots pine). This was complemented by trace element analysis, to study the influence of air pollution and climate on urban, suburban and more remote forests in and around Ulaanbaatar. We found indications of pollution effects in urban and suburban sites in foliar material, particularly in δ15N, with unusually high values of > 10‰, that could be related to tree uptake of NOx. Results were similar for all species, but with a smaller effect for Scots pine. The tree-ring δ15N values were found to be clearly enriched in recent years compared to 50 years ago at the urban sites, consistent with a pollution signal. Leaves and needles at suburban and urban sites had accumulated higher concentrations of various trace elements including Al, B, Ba, Ca, Cr, Cu, Fe, Mg, Na, S and Zn compared to the more distant sites, confirmed by Principal Component Analysis. Our data on δ13C, δ18O and δ2H enabled us to infer possible physiological effects induced by air pollution. Consistently increasing tree-ring δ13C values over recent decades for all investigated species indicated increasing plant stress, like hampered stomatal conductance and photosynthesis, but this was found for all sites, suggesting climate change rather than air pollution effects. In summary, we show that our multi-isotope and -element approach provides new insights into the threats to forests in urban areas, where the occurrence of more frequent droughts acts together with air pollution.

The effects of intensive eradication efforts for Asian longhorned beetle on understory plant communities, tree regeneration, and forest structure in southern New England hardwood forests

The United States has been experiencing an influx of nonnative pests due to increased globalization, and these pests have the potential to permanently alter the composition, structure, and function of forests. Asian longhorned beetle (ALB) is an invasive pest detected in Worcester, MA in 2008, where it invaded both urban and natural forested areas. As a part of the eradication measures (full host removals, herbicide treatments, and stump grinding), all host tree species, primarily Acer spp. were removed to prevent the spread of ALB. While these eradication measures successfully eliminate ALB, little is known about their effects on forest structural and compositional conditions and recovery over time. To address this, we examined forest compositional and structural development following eradication treatments and in adjacent unimpacted forested areas. Overall, our results indicated forest recovery followed similar pathways documented after natural disturbances in southern New England forests. There was little difference among eradication treatments in terms of the resultant forest composition and structure. Overall, forest types shifted to primarily oak-hickory or pine dominance following the removal of all Acer spp. Notably, maple species were present in high numbers in the regeneration layer regardless of treatment, followed by other early colonizing species. Red maple (Acer rubrum) was the most abundant sapling and seedling species and stump sprouting occurred at 60% of sites but was absent in untreated areas. These results suggest that ALB management does not drastically alter forest compositional dynamics in these mixed species forests in the short term, despite significant reductions in the abundance of mature host species through eradication treatments.

Evaluation of urban forest spatial distribution characteristics in Guangdong - Hong Kong - Macao Greater Bay Area

To understand the health and ecological benefits of scenic recreational forests, we elucidated their spatial distribution characteristics, which can be used to create guidelines and reveal strategic issues regarding the spatial distribution of tree species. We randomly set up 900 m2 quadrats in scenic recreational forest communities in Guangzhou, Foshan, and Zhuhai, and surveyed each tree using LiDAR. We then calculated the living vegetation volume (LVV) and amount of recreational space on the forest floor (RSFF), and analyzed the differences in spatial distribution characteristics across cities, locations, and forest types. The spatial distribution characteristics of trees differed between different cities, but were similar among different locations and forest types. Urban scenic recreational forest areas are thus configured based on aesthetics, recreational functions, and the spatial distribution characteristics of different tree species. Additionally, the relationship between the tree crown LVV and the RSFF was generally synergistic, yet contradictory. Although an increase in LVV can effectively improve ecological benefits, it may also reduce RSFF and other benefits provided by tree crowns to urban residents.