Factors driving natural regeneration beneath a planted urban forest

Cities around the world are investing in urban forest plantings as a form of green infrastructure. The aim is that these plantations will develop into naturally-regenerating native forest stands. However, woody plant recruitment is often cited as the most limiting factor to creating self-sustaining urban forests. As such, there is interest in site treatments that promote recruitment of native woody species and simultaneously suppress woody non-native recruitment. We tested how three, common site treatments—compost, nurse shrubs, and tree species composition (six-species vs. two-species)—affected woody plant recruitment in 54 experimental plots beneath a large-scale tree planting within a high-traffic urban park. We identified naturally regenerating seedling and sapling species and measured their abundance six-years after the site was planted. This enabled us to examine initial recruitment dynamics (i.e. seedlings) and gain a better understanding of seedling success as they transition to the midstory (i.e. saplings). Seedling and sapling recruitment (native and total) was greater in areas with higher canopy cover. The combination of the nurse shrub treatment with compost and species composition (six-species) treatments increased seedling recruitment by 47% and 156%, respectively; however, the nurse shrub treatment by itself decreased seedling recruitment by 5% and native seedling recruitment by 35%. The compost treatment alone had no effect on the total number of recruits but resulted in 76% more non-native seedlings. The sizes of these treatment effects were strongly dependent on whether the forest plantings were in open areas, versus areas with existing tree canopy, the latter condition facilitating recruitment. Our findings therefore suggest that combinations of site treatments, paired with broad canopy tree species, may be most effective for promoting regeneration of native species resulting in more self-sustaining urban forests.     

Three decades of urban forestry in China

Urban forestry has been formally recognized as a codified academic discipline in China’s higher education since 1992. This short communication attempts to revisit the emergence and development of urban forestry in China over the last three decades. Despite the traditional disciplinary division existing between forestry (which focuses on forested landscapes in non-urbanized regions) and landscape architecture (which concerns about individual and collective plants in urbanized environments), urban forestry offers an interdisciplinary convergence point, drawing upon disciplinarily-specific understanding and expertise of both forestry and landscape architecture, that supersedes the urban-rural distinction and could be translated into flexible, integrative, and transdisciplinary approaches for the effective governance of urban and peri-urban forests. With the enrichment of empirical evidence from China’s unique socioeconomic context and the theoretical advancement of urban forestry, innovative practical initiatives like “National Forest City” successfully transform urban forestry knowledge into on-the-ground practices. While China’s unprecedented urbanization has been accompanied by social and environmental problems calling for solutions wherein urban forestry can contribute, it offers a fertile ground for further advancing the development of urban forestry.     

Pond area and distance from continuous forests affect amphibian egg distributions in urban green spaces: A case study in Sapporo,Japan

We examined factors that affect egg distributions of amphibians, which are currently declining globally, in urban areas. We counted the number of egg masses of two amphibian species (Hynobius retardatus and Rana pirica) in ponds in urban green spaces during two years (2011 and 2012) and investigated the effects of local and landscape factors on them. Forest area in green spaces and pond area had positive effects, and distance from continuous forests in the suburbs and the rate of pond shore protection had negative effects on the number of eggs. Among these factors, distance from continuous forests and pond area had strong effects on egg distributions. These results suggest the importance of water habitat size and the need for colonization by amphibians from surrounding continuous forests. To conserve urban amphibian assemblages, the preservation of ponds with sufficient area and continuous forests close to urban habitats would be important.     

Values and beliefs about urban forests from diverse urban contexts and populations in the Greater Toronto area

Cities around the world are diverse. People’s perceptions of urban forests may vary according to urban contexts and people’s diverse identities. A better understanding of these diverse perceptions is critical to support stewardship initiatives, inform urban tree decisions, and guide community engagement, among other key management and governance processes in urban forestry. This study examines the values and beliefs that diverse people living in a variety of urban contexts associate with urban trees. Using an urban gradient approach, 2009 responses were collected through an online panel survey conducted in the Greater Toronto Area (GTA) to understand variations in values and beliefs of urban forests across municipal types (inner core, suburban, peri-urban, and regional cities). The GTA has an ethnoculturally diverse population, allowing us to also explore perceptions held by people with various identities. The study uses analytical techniques, such as means differences and linear regression models, to segment the diverse meanings people attribute to urban trees by municipal types and people’s identities. The results show that, while people value the urban forest very highly, people’s value orientations vary depending on their context and identities. For example, respondents who speak European or South Asian languages tend to hold value orientations related to cultural, social, and identity issues. Respondents living in inner municipal types tend to hold values related to identity issues, whereas respondents living in outer municipal types and regional cities tend to hold values related to natural issues. The results also show that people’s beliefs about urban forests are primarily positive. Urban forests managers and stewardship initiatives should recognize the diverse set of values and beliefs that people associate with urban forests, incorporating these perceptions into policy and programs. Additionally, since specific value and belief orientations may depend on personal identity and urban contexts, tailored messaging may also help generate support for policy or stewardship initiatives across different communities and in varied urban contexts.     

Urban forest management and governance in Latin America and the Caribbean: A baseline study of stakeholder views

Cities in the Latin America and Caribbean (LAC) region and around the world are setting long-term greening goals that include planting more trees and increasing green cover. Research in LAC cities has mainly focused on biodiversity and vegetation, with little understanding of the mechanisms underlying the decisions through which stakeholders achieve urban greening. Exploring stakeholders’ views about urban forest management and governance can provide us with an opportunity to identify needs and research gaps for urban greening and urban forestry in LAC. To our knowledge, there has never been a region-wide empirical study to capture these stakeholder views. Here we explore how stakeholders working in urban forestry in LAC, including governmental, and non-governmental professionals, define urban forests, and view management and governance issues as well as educational opportunities. We used an online survey based on a combination of open- and closed-ended questions. The survey was delivered to participants at the first two regional conferences on urban forests in LAC organized by the United Nations. We collected 91 responses from stakeholders working in 50 different cities of varying population sizes across 6 LAC bioregions. Most respondents considered parks, planted green corridors, street trees, and remnant forests in urban and peri-urban areas as components of urban forests. Stakeholder views on management and governance were divided in two distinct perspectives, one dominated by public participation issues, and another one related to operational issues. Most respondents considered operational and management tools for urban forests to exist in LAC cities, but they disagreed on the existence of inventories, long-term strategies, and ways for the public to engage in urban forestry. Responses also revealed that some educational opportunities, such as arboricultural certification, are still relatively scarce and in high demand in the region. This study provides a regional baseline and first insights into a more diverse view of urban forestry which could be enriched with more empirical studies in the future.     

Species diversity of urban forests in China

A good knowledge of species diversity is essential for urban forest planning and management. In this study, we analyzed species diversity of urban forests in China using data synthesized through a systematic review. Our analysis showed that 3740 taxa of woody plants at species level and below have been reported in urban forests in 257 cities. Merging to the species level, there were 2640 species, including 1671 trees, 743 shrubs, and 226 lianas. Salix babylonica L. was the most widely distributed urban tree species in China. Overall, native species accounted for 76.02% of the observed species while the rest were exotic species. Inside cities, parks contained more species than other types of land use. Among cities, composition similarity of urban forests decreased as spatial distances among them increased. Besides, there was a latitudinal pattern in compositional similarity of urban forests in China. The relatively low ratio of the number of woody plant species in urban forests to these naturally distributed in China indicates that there is plenty of room for increasing species diversity of urban forests in China. However, cautions must be taken to avoid increasing compositional similarity of urban forests in China at the same time.     

Diversity and structure in California’s urban forest: What over six million data points tell us about one of the world's largest urban forests

Urban street trees provide many benefits to surrounding communities, but our ability to assess such benefits relies on the availability of high-quality urban tree data. While these data are numerous, they are not available in an easily accessible, centralized place. To fill this gap, we aggregated public and private data into a single, comprehensive inventory of urban trees in California called the California Urban Forest (CUF) Inventory. These data are offered to the public (aggregated to ZIP code) via an online data portal, which at the time of publication contained over 6.6 million urban tree records. In this study, we first describe the assembly and utility of the inventory. Then, we conduct the most comprehensive assessment of the diversity and structure of California’s urban forest to date at statewide, regional, and local spatial scales. These analyses demonstrate that California’s urban forests are highly diverse and among the most diverse urban forests in the world. We present a new and intuitive metric of species diversity, the top diversity or TD-50 index, which represents the cumulative number of species accounting for the top 50 % abundance of trees in an urban forest. We used species abundance data from 81 well-inventoried cities to demonstrate that the TD-50 index was a robust metric of diversity and a good predictor of comprehensive metrics like the Shannon Index. We also found that small-statured trees, such as crape myrtles (Lagerstroemia cv.) dominate California’s urban forests. This aggregated inventory of one of the world's largest urban forests provides the data necessary to assess the structure, diversity, and value of California’s urban forests at multiple spatial scales. The inventory’s presentation to the public and the information that can be gained from its analysis can be a model for urban forest management worldwide.     

Adapting silvicultural management systems to urban forests

An important objective of forest science today is to better serve the cultural and recreational needs of a growing urban population. Forests are complex open systems with multiple functions and to maintain credibility among the public, people in charge of the management of urban forests need to draw on the expertise of a variety of scientific disciplines, not only the humanities, but increasingly also the forest engineering and forest biological sciences. The multi-disciplinary character of forest research can be utilized to achieve a more effective interface between science and politics.The objective of the paper is to present a system for silvicultural management of forests within urban landscapes. The system includes three elements:1. Forest Options Planning, using suitable tools for generating and evaluating silvicultural management options;2. Management Demonstration and Referencing, based on a network of managed and unmanaged field plots;3. Silvicultural Event Analysis, involving preventative evaluation of silvicultural activities based on event-oriented resource assessment.It is concluded that, considering their social and cultural importance, the forests within the growing urban landscapes are hardly receiving the scientific attention they deserve.     

Tree species-rich open oak woodlands within scattered urban landscapes promote biodiversity

It is becoming increasingly evident that cities are important places for biodiversity. Biodiverse urban forests are vital green areas within cities and have favorable impacts on the citizens, including their health. We focused on the effect of the urban forest environment on biodiversity in Prague, the capital of the Czech Republic. We used a multi-taxon approach with five taxa of different ecological demands: butterflies, bees and wasps, vascular plants, mosses, and lichens. We modeled their responses to the various urban forest attributes at four hierarchical levels – plot, permeability, forest, and landscape. Our results revealed that temporally continuous forests dominated by native oaks with open canopies, a high number of admixed and interspersed tree species and shrubs, together with scattered trees in the surrounding landscape, were optimal biodiverse forest environments. The most influential parameter that positively influenced bees and wasps, plants, and lichens at the plot level was canopy openness. We found that the permeability was suitable mainly on 20 m surroundings and increasing coverage of native oaks and tree species richness were the most important parameters. Continuity was the only found parameter that influenced mosses at the forest level. Scattered tree vegetation was the most important landscape parameter and positively drove the species richness of bees and wasps. Forest management methods can relatively easily solve the improvement of the scattered light gap structure within urban forests. Applying traditional forest management (pasture management, controlled burning and/or coppicing) is also an option but requires sensitive communication with the public. The canopy cover has been used as an indicator of urban forest health conditions, now indicating that artificial disturbances could be important issues for urban forest management and planning in the future. Therefore, active forest management is an essential method for biodiversity maintenance. We conclude that urban forests have a high potential for increasing native biodiversity. The response of the studied groups in urban forests was complementary. The resulting biodiverse stages of urban forests are akin to the established idea of the open temperate deciduous woodlands.     

Comparison of historical and current forest surveys for detection of homogenization and mesophication of Minnesota forests

Intense harvesting and slash fires during the late 1800s and early 1900s led to homogenization throughout the Great Lakes region via the conversion from tamarack, pine, and spruce forests to aspen forests, which are supported by the forest products industry. Subsequently, mesophication occurred in the eastern United States due to fire suppression, transforming oak woodlands to mixed mesophytic forests. We explored both homogenization and mesophication at a regional scale by quantifying changes in community composition and density between historical General Land Office survey points and current USDA Forest Analysis and Inventory plots for Minnesota??s Laurentian Mixed and Eastern Broadleaf Forest provinces. We used the Morisita plotless density estimator and applied corrections for surveyor bias to estimate density for historical forests and we used known densities of FIA plots to predict current densities with random forests, an ensemble regression tree method, and terrain and soil predictor variables. Of the 43 ecological units used in the analysis, only one current community was similar to its historical counterpart. Within the Laurentian Mixed Forest province, forest density of primarily mature aspen stands is reduced slightly today compared to the tamarack-dominated forests of the past. Conversely, in the Eastern Broadleaf Forest province, forest densities have increased compared to historical pine and oak woodlands, due to increases of densely growing, fire-sensitive species. Ordinations of functional traits and structure showed substantial changes between current and historical communities as well as reduced differentiation among current communities compared to their historical counterparts. Homogenization in the Laurentian Mixed Forest is occurring by transition from early-successional to late-successional species, with associated changes in forest ecosystems, and homogenization and mesophication in the Eastern Broadleaf Forest are occurring by transition from disturbance-stabilized genera of open forest ecosystems to non-disturbance-dependent genera of dense forests. Despite different starting points of historical forest ecosystems in the Laurentian Mixed Forest and Eastern Broadleaf Forest, we found homogenization and mesophication to be interrelated in the convergence of composition and densities along a common trajectory to dense forests composed of late-successional species in Minnesota.     

How many people should be in the urban forest? A comparison of trail preferences of Vienna and Sapporo forest visitor segments

Differences in trail preferences for social conditions of visitors to forests in Vienna and Sapporo were investigated in 2006 using a standardised image-based stated choice approach. On-site visitors to two comparable peri-urban forests – the Lobau Forest in Vienna, Austria (n=373), and the Nopporo Forest in Sapporo, Japan (n=256) – evaluated the same sets of computer manipulated images depicting 128 trail scenarios with different levels of social stimulation. Latent class segmentations, in three sub-segments of similar sizes, differentiated by partly opposite preferences for social conditions, were derived for both samples. A positive contribution of social stimulation to preferences was found for about 17% of Nopporo and 9% of Lobau respondents, while for close to 50% of Lobau respondents and 38% of Nopporo respondents very low levels of social stimulation were preferred. The results indicate that urban forests should be managed for users with a desire for low social densities as well as a denser social setting providing some levels of social stimulation.     

“森林城市”模式与城市绿地园林景观及功能的弱化

“森林城市”的提法导致城市园林绿化建设模式产生一定的偏差,“森林城市”忽视了城市内绿地与城市外绿地功能的诸多差异,甚至导致城市园林绿地丧失其应该体现的园林艺术特征和休闲、游憩、娱乐、健身等综合功能。除生态效益之外,只有强调城市绿地的园林艺术特征和多功能性才能防止城市绿化中过密、过滥的“森林式”的种植模式。正确定位城市中心和城市外围两种不同地域绿地的功能和结构,并以生态的楔形绿地为桥梁是实现城内外绿地相互联系、功能互补的一个有效途径。     

Role of social networks in urban forest management collaboration: A case study in northern Japan

Public participation is crucial for sustainable forest management. In particular, in urban forest areas, it is an important tool for overcoming conflicts among diverse needs regarding the forests through collaboration between citizens and governments. Such collaboration requires social learning. Social learning is dependent upon the presence of social networks that serve as an infrastructure for social capital. This study analyses the role of the social network in a participatory forest management approach of the Nopporo Forest Regeneration Project (NFRP) in the urban Nopporo National Forest in Hokkaido, northern Japan, aimed at restoring a typhoon damaged forest.Within the framework of the participatory approach the project hascreated a network of several citizen organizations for exchanging information. Outside this formal NFRP network several additional citizenorganizations are concerned about the Nopporo Forest management. The article describes the overall social network that has evolved around the Nopporo Forest and compares the attitudes and evaluations of the NFRP network organizations and the not formally NFRP related organizations towards their collaboration with government agencies and other citizen organizations. The overall social network around the Nopporo Forest had a multi-nodal character with the National Forest Agency and Hokkaido Prefectural Government acting as main central nodes. Only a few citizen organizations had direct relations to both central nodes; many organizations had links to either the National Forest Agency or the Prefectural Government. The organizations involved in the formal NFRP network had close ties with the National Forest Agency. This contributed to a positive evaluation of present forest management approach and the collaborative activities of the government agencies. In contrast, the organizations that were not involved in the formal NFRP network were found to have fewer ties with the National Forest Agency. The lack of opportunity to form a direct social learning relation hindered the formation of social capital and resulted in a lower evaluation of the participatory management approach as well as of the collaborative activities. Thus, although the participatory forest management approach of establishing formal social networks enhanced collaboration between the National Forest Agency and several citizen organizations and social learning, it was less successful in encouraging a democratic process involving all interested citizen organizations.     

Carbon storage and sequestration by urban forests in Shenyang,China

Urban forests can play an important role in mitigating the impacts of climate change by reducing atmospheric carbon dioxide (CO₂). Quantification of carbon (C) storage and sequestration by urban forests is critical for the assessment of the actual and potential role of urban forests in reducing atmospheric CO₂. This paper provides a case study of the quantification of C storage and sequestration by urban forests in Shenyang, a heavily industrialized city in northeastern China. The C storage and sequestration were estimated by biomass equations, using field survey data and urban forests data derived from high-resolution QuickBird images. The benefits of C storage and sequestration were estimated by monetary values, as well as the role of urban forests on offsetting C emissions from fossil fuel combustion. The results showed that the urban forests in areas within the third-ring road of Shenyang stored 337,000 t C (RMB92.02 million, or $ 13.88 million), with a C sequestration rate of 29,000 t/yr (RMB7.88 million, or $ 1.19 million). The C stored by urban forests equaled to 3.02% of the annual C emissions from fossil fuel combustion, and C sequestration could offset 0.26% of the annual C emissions in Shenyang. In addition, our results indicated that the C storage and sequestration rate varied among urban forest types with different species composition and age structure. These results can be used to help assess the actual and potential role of urban forests in reducing atmospheric CO₂ in Shenyang. In addition, they provide insights for decision-makers and the public to better understand the role of urban forests, and make better management plans for urban forests.     

Comparison of bird diversity between temperate floodplain forests and urban parks

Biodiversity in urban green areas has been widely explored in several bird studies because birds are known to be important bio-indicators. Many studies have investigated the different responses of bird communities to urbanization and land use changes in urban environments. However, there are still important knowledge gaps related to the impacts of the heterogeneity, spatial structure, and connectivity of green areas on avian diversity. Such information is needed for sustainable urban planning. In this study, we focused on the comparison of bird communities between urban parks in the heritage city of Olomouc and hardwood floodplain forests in the vicinity of the city. The results of the study indicate the high importance of urban parks for the maintenance of bird diversity even though urban parks are man-made habitats. The results highlight the importance of some native vegetation structures in urban parks (old trees, bush ecotones) for maintaining urban bird biodiversity. Some implications of the results can be widely used as a decision support tool for the management of urban green areas and for the planning of ecological networks in urban landscapes.     

Research on spatiotemporal variation characteristics of soundscapes in a newly established suburban forest park

Passive acoustic monitoring has developed rapidly as a tool for ecological assessments, and the use of acoustic indices to assess biodiversity in urban forests promises to be a low-cost and efficient analytical approach. However, the accuracy of using acoustic indices to characterize biodiversity may be compromised by excessive human interference. The acoustic complexity index (ACI) and normalized difference soundscape index (NDSI) were chosen to determine their application value, and explore the spatiotemporal patterns of change in the soundscape of a newly established suburban forest park in China. To understand the influence of drivers such as different sound source types, road distance, and vegetation structure on the soundscape, the Eastern Suburb Forest Park was selected as the study area, and 55 recording points (200 m intervals, 5 × 11 grids) were set up using a systematic grid. Passive acoustic monitoring was performed for four consecutive days in each season, and the spatiotemporal variation of the soundscape was visualized based on indices interpolation. The results showed that when using ACI and NDSI to rapidly assess biodiversity in urban forest environments, attention needs to be paid to the implications of seasonal fluctuations on indices. The temporal variation of the soundscape was closely related to the natural rhythms and vocal activity intensity of organisms. Distance to a nearby main road, distance to water, and structural complexity of vegetation were key factors influencing spatial variation. The findings support the use of acoustic methods to assess the characteristics of soundscapes in human-built urban forests. Soundscape mapping visualizes hotspots and moments of ecoacoustic activity, and has great potential for development in the conservation and management of suburban forest soundscapes.     

城市生物多样性保护的行动计划与规划

由于高速城市化引发的一系列生态环境问题,导致城市生物多样性急剧降低,城市生物多样性的保护已成为全世界关注的焦点问题和人类实现可持续发展过程中面临的首要任务。鉴于生物多样性面临的严峻局面,我国各级政府都纷纷采取措施,致力于生物多样性的保护与可持续利用工作,制定了一系列生物多样性保护行动计划与规划,为城市的生物多样性保护和生态建设提供依据和保证。     

How can forest fragments support protected areas connectivity in an urban landscape in Brazil?

Cities continue to grow worldwide, and the highly modified urban landscape becomes an inhospitable environment for many species because the natural vegetation cover is commonly fragmented, and the remnants are often isolated. Protected Areas (PAs) located surrounding or within urban areas may not achieve their goal of protecting local or regional biodiversity. Thus, an urban ecological network is essential to support their PAs. Thus, this study aimed at assessing the PAs connectivity in an urban landscape in Brazil and understanding whether urban forest fragments can support an urban ecological network. Besides spatial models based on functional connectivity and graph theory, we used participatory techniques to design the resistance surface and the least-cost paths (LCPs) for Atlantic Forest birds. The results showed critical paths (LCPs), important areas for restoration programs for improving PAs connectivity, and essential forest fragments for conservation and restoration. Although the landscape has a forest structure with 1873 forest fragments and 516 links through which the LCPs were structured, most forest fragments and LCPs cannot provide the necessary support for the PAs connectivity. The current ecological network is dependent on forest fragments neighboring (outside PAs) and the flux dispersions occurred mainly in the peri-urban areas. Riparian zones and anthropic grasslands also showed importance for the PAs connectivity. We identified only 28 forest fragments spatially connected, presenting several sizes, and located near large forest areas, relevant PAs, and riparian zones. Six of these forest fragments, smaller than ten hectares and strategically located in the urban matrix, were indicated for restoration actions. The current low connectivity among PAs brings the importance of native vegetation restoration in the riparian zone and anthropic grassland and the importance of the periurban areas to promote biodiversity connectivity in the urban landscape.     

Willing partners? Residential support for municipal urban forestry policies

Cities across North America are adopting ambitious goals to grow their urban forests. As existing trees and new planting opportunities are often located on private property, residents’ support and participation is needed in order to meet these goals. However, little research has examined support for municipal urban forestry efforts, including policies specifically targeting residential areas. The objectives of this research are to (1) assess resident’ level of support for common urban forestry policies and (2) determine if there are specific household characteristics associated with different levels of policy support. The objectives are addressed through a statistical analysis of survey responses and a qualitative examination of follow-up interviews with residents in four neighborhoods located in Mississauga (Ontario, Canada). The survey participants and their properties vary in their socioeconomic characteristics, age of development, and urban forest conditions. Our results found that the majority of residents had neutral to very positive attitudes toward common municipal policies encouraging planting and restricting removal of trees, but support levels were lower for the policies than for general statements about desired presence and size of urban trees. Several characteristics are significantly related to level of policy support, including age of household members, education-level, property-level tree density, recent tree planting activity and age of house. Interviews also highlighted residents’ apprehensions about living among tall trees and older resident's concerns with tree maintenance. The results suggest that most residents would be willing partners in urban forestry efforts, with many of these residents already actively planting and maintain trees. However, to increase support and participation rates, different types of trees – including those smaller in stature and ones that require relatively little maintenance – should be part of any planting program to meet the varying needs of households.