Measuring Multi-Scale Urban Forest Carbon Flux Dynamics Using an Integrated Eddy Covariance Technique

The multi-scale carbon-carbon dioxide (C-CO2) dynamics of subtropical urban forests and other green and grey infrastructure types were explored in an urbanized campus near Shanghai, China. We integrated eddy covariance (EC) C-CO2 flux measurements and the Agroscope Reckenholz-Tänikon footprint tool to analyze C-CO2 dynamics at the landscape-scale as well as in local-scale urban forest patches during one year. The approach measured the C-CO2 flux from different contributing areas depending on wind directions and atmospheric stability. Although the study landscape was a net carbon source (2.98 Mg C ha−1 yr−1), we found the mean CO2 flux in urban forest patches was −1.32 μmol m−2s−1, indicating that these patches function as a carbon sink with an annual carbon balance of −5.00 Mg C ha−1. These results indicate that urban forest patches and vegetation (i.e., green infrastructure) composition can be designed to maximize the sequestration of CO2. This novel integrated modeling approach can be used to facilitate the study of the multi-scale effects of urban forests and green infrastructure on CO2 and to establish low-carbon emitting planning and planting designs in the subtropics.

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Remote Sensing in Urban Forestry: Recent Applications and Future Directions

Remote Sensing ◽

10.3390/rs11101144 ◽

2019 ◽

Vol 11 (10) ◽

pp. 1144 ◽

Cited By ~ 7

Author(s):

Xun Li ◽

Wendy Y. Chen ◽

Giovanni Sanesi ◽

Raffaele Lafortezza

Keyword(s):

Remote Sensing ◽

Data Processing ◽

Urban Forest ◽

Scale Effects ◽

Urban Forestry ◽

Urban Forests ◽

Accurate Information ◽

Multi Scale ◽

Sensing Applications ◽

Multi Temporal

Increasing recognition of the importance of urban forest ecosystem services calls for the sustainable management of urban forests, which requires timely and accurate information on the status, trends and interactions between socioeconomic and ecological processes pertaining to urban forests. In this regard, remote sensing, especially with its recent advances in sensors and data processing methods, has emerged as a premier and useful observational and analytical tool. This study summarises recent remote sensing applications in urban forestry from the perspective of three distinctive themes: multi-source, multi-temporal and multi-scale inputs. It reviews how different sources of remotely sensed data offer a fast, replicable and scalable way to quantify urban forest dynamics at varying spatiotemporal scales on a case-by-case basis. Combined optical imagery and LiDAR data results as the most promising among multi-source inputs; in addition, future efforts should focus on enhancing data processing efficiency. For long-term multi-temporal inputs, in the event satellite imagery is the only available data source, future work should improve haze-/cloud-removal techniques for enhancing image quality. Current attention given to multi-scale inputs remains limited; hence, future studies should be more aware of scale effects and cautiously draw conclusions.

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Study of the Spatiotemporal Variation Characteristics of Forest Landscape Patterns in Shanghai from 2004 to 2014 Based on Multisource Remote Sensing Data

Sustainability ◽

10.3390/su10124397 ◽

2018 ◽

Vol 10 (12) ◽

pp. 4397 ◽

Cited By ~ 4

Author(s):

Yang Li ◽

Chunyan Xue ◽

Hua Shao ◽

Ge Shi ◽

Nan Jiang

Keyword(s):

Spatial Distribution ◽

Landscape Pattern ◽

Urban Forest ◽

Urban Forests ◽

Urban Ecosystem ◽

Landscape Patterns ◽

Forest Landscape ◽

Forest Patches ◽

Forest Coverage ◽

High Degree

The landscape patterns of urban forests not only reflect the influence of urbanization on urban forests, but also determines its function in urban ecosystem services. In the case of mastering the overall forest landscape pattern of a city, a study of the structure of urban forest landscapes at different scales and in urbanized regions is beneficial to a comprehensive understanding of the forest characteristics of a city. In the present study, an attempt was made to map and monitor the spatio-temporal dynamics of an urban forest in Shanghai from 2004 to 2014 using remote sensing techniques. Methods of landscape ecology analysis are followed to quantify the spatiotemporal patterns of an urban forest landscape by urban and rural gradient regionalization. The results show that the spatial structure of an urban forest landscape is essentially consistent with an urban landscape pattern. Due to strong interference from human activities, the ecological quality of forest landscapes is low. At the landscape level, the urban forest coverage rate increased from 11.43% in 2004 to 16.02% in 2014, however, the number of large patches decreased, there was a high degree of urban forest landscape fragmentation, landscape connectivity was poor, landscape patch boundaries were uniform, and weak links were present between ecological processes. Different urban and rural gradient division methods exhibit obvious gradient characteristics along the urban–rural gradient in Shanghai. The regional differences in the urban forest landscape ecological characteristics have further increased as a result of urban planning and zoning. The total amount of urban forest is located closer to the urban center, which has the smallest total amount of forest; however, in terms of urban forest coverage, the suburbs have more coverage than do the outer suburbs and the central urban areas. The urban forest landscape’s spatial distribution area is evidently different. Urbanization affects the areas closest to urban residential areas, which are markedly disturbed by humans, and the urban forest landscape has a high degree of fragmentation. The forest patches have become divided and unconnected, and the degree of natural connectivity has gradually decreased over the past 10 years. At the landscape class level, broadleaf forests are dominant in Shanghai, and their area exhibits an increasing trend; shrublands and needleleaf forests, however, show a decreasing trend. Compared with other forest types, the spatial distribution of broadleaf forest is concentrated in the suburbs, and the aggregation effect is relatively apparent. From the perspective of urban forest landscape pattern aggregation characteristics in Shanghai, the spatial distribution of urban forest landscape point patterns in the study area exhibit extremely uneven characteristics. The point density of urban forest patches larger than 1 ha in Shanghai increased from 2004 to 2014. However, the total number of patches with areas larger than 5 ha decreased, and this decrease plays an important role in the ecological environment. In the past 10 years, the concentration characteristics of urban forests with large patches has gradually decreased. In 2014, the urban forest landscapes decreased by 5 km compared to the intensity of aggregates in 2004, which also indicates that urban forests in Shanghai tend to be fragmented. The results of this study can be useful to help improve urban residents’ living environments and the sustainable development of the urban ecosystem, and they will also be vital to future management.

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Breeding density of the Tawny Owl Strix aluco in urban forests of Ljubljana City (Central Slovenia)

Acrocephalus ◽

10.1515/acro-2017-0003 ◽

2017 ◽

Vol 38 (172-173) ◽

pp. 31-35

Author(s):

Tjaša Pršin ◽

Darja Kušar ◽

Tanja Obermajer ◽

Al Vrezec

Keyword(s):

Urban Areas ◽

Urban Forest ◽

Urban Forests ◽

Forest Patches ◽

Tawny Owl ◽

Point Count ◽

Strix Aluco ◽

Nature Park ◽

Territory Density ◽

Point Count Method

SummaryResults of the survey carried out in the territories of Tawny Owl Strix aluco in Ljubljana urban forests (Tivoli, Rožnik and Šišenski hrib Nature Park and Golovec Hill) were compared with the species territory density in non-urban forest of Mt. Krim. Surveys were performed with the point count method using playback in the springs of 2002 and 2016. The density established at Golovec Hill was 9.3 territories / 10 km2, while in Tivoli, Rožnik and Šišenski hrib Nature Park it reached 10.4 territories / 10 km2, which was higher than at Mt. Krim (4.1-5.8 territories / 10 km2), although densities between sites were not statistically different. Based on our surveys, the estimated population size of the urban Tawny Owl in Ljubljana would consist of 57 to 65 pairs. Our results suggest that the Tawny Owl can adapt well to the living conditions in the city urban forests and indicate the importance of the forest patches in urban areas.

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Review on Urban Forests and Trees as Nature-Based Solutions over 5 Years

Forests ◽

10.3390/f12111453 ◽

2021 ◽

Vol 12 (11) ◽

pp. 1453

Author(s):

Xiangqi Kong ◽

Xinna Zhang ◽

Chengyang Xu ◽

Richard J. Hauer

Keyword(s):

Green Infrastructure ◽

High Frequency ◽

Urban Forest ◽

Urban Forests ◽

Urban Ecosystems ◽

Urban Environments ◽

Sustainable Living ◽

Keyword Analysis ◽

Research Pattern

As human living environments face increasing challenges with resilience, the concept of nature-based solutions (NBS) was proposed in recent years as a way to promote sustainable living in urban environments. Urban forests and trees play important roles in urban ecosystems, while their potential as an NBS is promising. A bibliometric analysis was first conducted to explore the research pattern of NBS in urban environments. Studies of urban forest and tree-based green infrastructure in NBS research were further investigated using a systematic literature review method. The initial studies on NBS have increased since 2015 with 493 documents published from 142 sources in over 70 countries and regions. Keyword analysis showed green infrastructure had a rather high frequency of utility and received considerable attention. As for urban forests as nature-based solutions (UF-NBS) research, the most prominent study approaches used at different scales and the main benefits and typologies of urban forest studied in the articles were identified. UF-NBS research is still relatively scarce at present. Despite the role of urban forest and trees in addressing environmental challenges being well recognized, UF-NBS studies still need to be conducted in a more comprehensive context, taking social and economic aspects into account.

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Evaluation of Forest Edge Structure and Stability in Peri-Urban Forests

Forests ◽

10.3390/f11030338 ◽

2020 ◽

Vol 11 (3) ◽

pp. 338

Author(s):

David Hladnik ◽

Andrej Kobler ◽

Janez Pirnat

Keyword(s):

Urban Forest ◽

Residential Buildings ◽

Canopy Structure ◽

Urban Forests ◽

Forest Edge ◽

Canopy Height ◽

Forest Edges ◽

Forest Patches ◽

Forest Patch ◽

Edge Structure

In the presented research, we studied the forest edge structure of urban and peri-urban forests on the outskirts of Ljubljana (Slovenia) consisting of a number of patches covering the collective surface of 1884 ha. They differ from each other according to the degree of fragmentation and by the share of the interior forest area. On the basis of LiDAR data, we conducted an analysis of the edges of the persistent forest patches and estimated them with regard to the land use they bordered on. The horizontal estimation of forest edges and the changes of forest edges, in the last decades, were estimated using digital orthophoto images of cyclic aerial surveys of Slovenia, from 1975 to 2018. The data, provided by LiDAR, were used to obtain an accurate estimate of forest edges and the metrics of their vertical canopy structure. On the basis of the canopy height model (CHM), we determined the height classes, the heights of the tallest trees, and indices of canopy height diversity (CHD) as variables subjected to a k-means cluster analysis. To determine the forest edge and trees stability, their heights and diameters at breast height (DBH) were measured and their canopy length and h/d (height/diameter) dimension ratios were estimated. In the study area of the Golovec forest patch, more than half of the forest edge segments (56%) border on residential buildings. After the construction of buildings, 54% of the newly formed forest edges developed a high and steep structure. Unfavorable h/d dimension ratio was estimated for 16% of trees, more among the coniferous than among the deciduous trees. Similar characteristics of newly formed forest edges bordering on built-up areas were determined in other sub-urban forest patches, despite the smaller share of such forest edges (19% and 10%, respectively). Tools and methods presented in the research enable the implementation of concrete silvicultural practices in a realistic time period and extend to ensure that adequate forestry measures are taken to minimize possible disturbances.

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Importance, Utilization and Health of Urban Forests: A Review

Notulae Botanicae Horti Agrobotanici Cluj-Napoca ◽

10.15835/nbha47111316 ◽

2018 ◽

Vol 47 (1) ◽

pp. 10-16

Author(s):

Alexandra D. SOLOMOU ◽

Eleni T. TOPALIDOU ◽

Rafaelia GERMANI ◽

Apostolia ARGIRI ◽

George KARETSOS

Keyword(s):

Ecosystem Services ◽

Literature Review ◽

Green Infrastructure ◽

Urban Areas ◽

Urban Forest ◽

Urban Forests ◽

Visual Image ◽

The Sustainable Development ◽

Academic Resources

Urbanization and development of cities are rapidly increasing across the world and urban forests constitute important tools that maintain the basic environmental and ecological functions of cities on which plant, animal and human existence depend. This paper presents a literature review on importance, utilization and health of urban forests that are important in providing ecosystem services for the sustainability of cities. Analysis of the literature from the main academic resources databases indicates that urban forest is a dynamic system which includes trees, shrubs, green space, soil and water that supports them. Urban forests provide many functions, services and benefits which are needed for the sustainable development of urban areas. In addition, health and appearance of trees’ composition are the most important factors in determining a city’s visual image and quality of life. Thus, urban forests are an important component of an ecosystem in any community development. Furthermore, management of urban forests can increase their potentials and therefore their functions, services and benefits. Green infrastructure and ecosystem services are the most efficient tools that cities can utilise to remain healthy, robust and liveable. Hence, the planners, architects, engineers, foresters, agriculturists and all those involved in decision making should be utilized the present literature review and incorporate the concept of urban forest in their plans and programs so as to achieve the sustainability of cities.

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Forest Structure and Anthropogenic Disturbances Regulate Plant Invasion in Urban Forests

10.21203/rs.3.rs-222579/v1 ◽

2021 ◽

Author(s):

Prakash Chandra Aryal ◽

Chandramani Aryal ◽

Kiran Bhusal ◽

Devendra Chapagain ◽

Man Kumar Dhamala ◽

...

Keyword(s):

Invasive Species ◽

Forest Structure ◽

Urban Forest ◽

Urban Forests ◽

Principal Component ◽

Anthropogenic Disturbances ◽

Invasion Success ◽

Anthropogenic Factors ◽

Forest Patches ◽

Factors Affecting

Abstract Urban forest ecosystems, the structure and functions therein, are subjected to anthropogenic disturbances. Native and sensitive species from those forests might be lost due to such disturbances. At the same time, supplemented anthropogenic resources might create opportunities for exotic and invasive species. Although, invasive species are considered as one of the major threats to the urban biodiversity and ecosystems, the researches on invasion dynamics in the Himalayas have mostly focused on the impacts of invasion on forest structure and productivity. This study aims to understand the influence of forest structure and anthropogenic factors in invasion success that are poorly covered in the existing literature. We selected 11 urban forest patches for the study considering the presence-absence of selected invasive species and structural attributes. We used Principal Component Analysis (PCA) to reduce co-linearity in the covariates and generalized linear mixed effects model (GLMM) to identify the factors affecting the invasion success. We found that the structural attributes of the forests and anthropogenic disturbances regulated invasion success in urban forests. This implies that maintaining urban forest structural attributes, especially maintaining the stands with large-sized trees, are essential to regulate and control invasion in the context of urbanization.

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Island biogeography theory and the urban landscape: stopover site selection by the silver-haired bat (Lasionycteris noctivagans)

Canadian Journal of Zoology ◽

10.1139/cjz-2021-0214 ◽

2022 ◽

Author(s):

Hannah Adams ◽

Liam McGuire

Keyword(s):

Island Biogeography ◽

Urban Forest ◽

Natural Habitat ◽

Negative Relationship ◽

Urban Forests ◽

Forest Patches ◽

Stopover Site ◽

Island Biogeography Theory ◽

The Impact ◽

Lasionycteris Noctivagans

Many migratory bats require forested sites for roosting and foraging along their migration path, but increased urbanization and intensive agricultural practices may reduce the availability of stopover sites. Urban forests may provide important stopover habitat, maintaining landscape connectivity in regions where the majority of natural habitat has been cleared for development. Island biogeography theory can be applied to urbanized temperate forest biomes where small urban forests represent islands separated from the larger “mainland” forest. We used acoustic monitoring during the fall migration period to investigate the use of urban forest habitat by the migratory species Lasionycteris noctivagans Le Conte, 1831. We predicted that recorded activity would have a positive relationship with forest patch area and shape and a negative relationship with isolation from other forest patches, as suggested by island biogeography theory. We observed greater activity at larger forest patches, and although relationships for shape and isolation were not statistically supported the observed patterns were consistent with predictions. Our results demonstrate the need for more in-depth research on the habitat requirements for both migratory and resident bat species and the impact that ongoing urbanization has on local bat populations.

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Emerging Urban Forests: Opportunities for Promoting the Wild Side of the Urban Green Infrastructure

Sustainability ◽

10.3390/su11226318 ◽

2019 ◽

Vol 11 (22) ◽

pp. 6318 ◽

Cited By ~ 7

Author(s):

Ingo Kowarik ◽

Anne Hiller ◽

Greg Planchuelo ◽

Birgit Seitz ◽

Moritz von der Lippe ◽

...

Keyword(s):

Species Richness ◽

Alien Species ◽

Green Infrastructure ◽

Urban Forest ◽

Urban Forests ◽

Tree Regeneration ◽

Carabid Beetles ◽

Alien Plant ◽

Urban Green ◽

Urban Green Infrastructure

Many cities aim to increase urban forest cover to benefit residents through the provision of ecosystem services and to promote biodiversity. As a complement to traditional forest plantings, we address opportunities associated with “emerging urban forests” (i.e., spontaneously developing forests in cities) for urban biodiversity conservation. We quantified the area of successional forests and analyzed the species richness of native and alien plants and of invertebrates (carabid beetles, spiders) in emerging forests dominated by alien or native trees, including Robinia pseudoacacia, Acer platanoides, and Betula pendula. Emerging urban forests were revealed as shared habitats of native and alien species. Native species richness was not profoundly affected by the alien (co-)dominance of the canopy. Instead, native and alien plant species richnesses were positively related. Numbers of endangered plants and invertebrates did not differ between native- and alien-dominated forest patches. Patterns of tree regeneration indicate different successional trajectories for novel forest types. We conclude that these forests (i) provide habitats for native and alien species, including some endangered species, (ii) allow city dwellers to experience wild urban nature, and (iii) support arguments for adapting forests to dynamic urban environments. Integrating emerging urban forests into the urban green infrastructure is a promising pathway to sustainable cities and can complement traditional restoration or greening approaches.

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Quantifying Tree Cover Loss in Urban Forests within Nairobi City Metropolitan Area from Earth Observation Data

Environmental Sciences Proceedings ◽

10.3390/iecf2020-07952 ◽

2020 ◽

Vol 3 (1) ◽

pp. 78

Author(s):

Francis Oloo ◽

Godwin Murithi ◽

Charlynne Jepkosgei

Keyword(s):

Land Cover ◽

Metropolitan Area ◽

Land Surface ◽

Urban Forest ◽

Urban Forests ◽

Earth Observation ◽

Tree Cover ◽

Observation Data ◽

Vegetation Health ◽

Earth Observation Data

Urban forests contribute significantly to the ecological integrity of urban areas and the quality of life of urban dwellers through air quality control, energy conservation, improving urban hydrology, and regulation of land surface temperatures (LST). However, urban forests are under threat due to human activities, natural calamities, and bioinvasion continually decimating forest cover. Few studies have used fine-scaled Earth observation data to understand the dynamics of tree cover loss in urban forests and the sustainability of such forests in the face of increasing urban population. The aim of this work was to quantify the spatial and temporal changes in urban forest characteristics and to assess the potential drivers of such changes. We used data on tree cover, normalized difference vegetation index (NDVI), and land cover change to quantify tree cover loss and changes in vegetation health in urban forests within the Nairobi metropolitan area in Kenya. We also used land cover data to visualize the potential link between tree cover loss and changes in land use characteristics. From approximately 6600 hectares (ha) of forest land, 720 ha have been lost between 2000 and 2019, representing about 11% loss in 20 years. In six of the urban forests, the trend of loss was positive, indicating a continuing disturbance of urban forests around Nairobi. Conversely, there was a negative trend in the annual mean NDVI values for each of the forests, indicating a potential deterioration of the vegetation health in the forests. A preliminary, visual inspection of high-resolution imagery in sample areas of tree cover loss showed that the main drivers of loss are the conversion of forest lands to residential areas and farmlands, implementation of big infrastructure projects that pass through the forests, and extraction of timber and other resources to support urban developments. The outcome of this study reveals the value of Earth observation data in monitoring urban forest resources.

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