The Experts below are selected from a list of 40509 Experts worldwide ranked by ideXlab platform
Ben Somers - One of the best experts on this subject based on the ideXlab platform.
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Urban Tree Health Classification Across Tree Species by Combining Airborne Laser Scanning and Imaging Spectroscopy
Remote Sensing, 2020Co-Authors: Dengkai Chi, Jeroen Degerickx, Ben SomersAbstract:Declining urban Tree Health can affect critical ecosystem services, such as air quality improvement, temperature moderation, carbon storage, and biodiversity conservation. The application of state-of-the-art remote sensing data to characterize Tree Health has been widely examined in forest ecosystems. However, such application to urban Trees has not yet been fully explored—due to the presence of heterogeneous Tree species and backgrounds, severely complicating the classification of Tree Health using remote sensing information. In this study, Tree Health was represented by a set of field-assessed Tree Health indicators (defoliation, discoloration, and a combination thereof), which were classified using airborne laser scanning (ALS) and hyperspectral imagery (HSI) with a Random Forest classifier. Different classification scenarios were established aiming at: (i) Comparing the performance of ALS data, HSI and their combination, and (ii) examining to what extent Tree species mixtures affect classification accuracy. Our results show that although the predictive power of ALS and HSI indices varied between Tree species and Tree Health indicators, overall ALS indices performed better. The combined use of both ALS and HSI indices results in the highest accuracy, with weighted kappa coefficients (Kc) ranging from 0.53 to 0.79 and overall accuracy ranging from 0.81 to 0.89. Overall, the most informative remote sensing indices indicating urban Tree Health are ALS indices related to point density, Tree size, and shape, and HSI indices associated with chlorophyll absorption. Our results further indicate that a species-specific modelling approach is advisable (Kc points improved by 0.07 on average compared with a mixed species modelling approach). Our study constitutes a basis for future urban Tree Health monitoring, which will enable managers to guide early remediation management.
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airborne imaging spectroscopy for assessing soil sealing effect on urban Tree Health
Workshop on Hyperspectral Image and Signal Processing: Evolution in Remote Sensing, 2018Co-Authors: Jeroen Degerickx, Maarten Van Geel, Olivier Honnay, Ben SomersAbstract:Soil sealing in urban areas imposes a large impact on vegetation Health and its functioning in providing ecosystem services. Yet, quantitative assessment of soil sealing effect on urban Tree Health status remains challenging. Here, we investigate the feasibility of using airborne imaging spectroscopy and leaf reflectance for assessing the effect of soil sealing on leaf chlorophyll content of Trees and their spectral responses. Results showed that soil sealing decreased the leaf total chlorophyll content and the ratio of carotenoids to chlorophyll. Chlorophyll spectral indices extracted from airborne and leaf reflectance data were both highly correlated with chlorophyll. Spectrally predicted chlorophyll variations allowed for the discrimination of different soil sealing conditions. This study demonstrates the great potential of using airborne remote sensing data to assess the Health status of urban vegetation as well as for biomonitoring soil sealing impacts.
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Urban Tree Health assessment using airborne hyperspectral and LiDAR imagery
International Journal of Applied Earth Observation and Geoinformation, 2018Co-Authors: Jeroen Degerickx, Dar A. Roberts, Joe P. Mcfadden, Martin Hermy, Ben SomersAbstract:Abstract Urban Trees provide valuable ecosystem services but are at the same time under continuous pressure due to unfavorable site conditions. In order to better protect and manage our natural capital, urban green managers require frequent and detailed information on Tree Health at the city wide scale. In this paper we developed a workflow to monitor Tree defoliation and discoloration of broadleaved Trees in Brussels, Belgium, through the combined use of airborne hyperspectral and LiDAR data. Individual Trees were delineated using an object-based Tree detection and segmentation algorithm primarily based on LiDAR data with an average accuracy of 91%. We constructed Partial Least Squares Regression (PLSR) models to derive Tree chlorophyll content (RMSE = 2.8 μg/cm²; R² = 0.77) and Leaf Area Index (LAI; RMSE = 0.5; R² = 0.66) from the average canopy spectrum. Existing spectral indices were found to perform significantly worse (RMSE > 7 μg/cm² and >1.5 respectively), mainly due to contamination of Tree spectra by neighboring background materials. In the absence of local calibration data, the applicability of PLSR to other areas, sensors and Tree species might be limited. Therefore, we identified the best performing/least sensitive spectral indices and proposed a simple pixel selection procedure to reduce disturbing background effects. For LAI, laser penetration metrics derived from LiDAR data attained comparable accuracies as PLSR and were suggested instead. Detection of Healthy and unHealthy Trees based on remotely sensed Tree properties matched reasonably well with a more traditional visual Tree assessment (93% and 71% respectively). If combined with early Tree stress detection methods, the proposed methodology would constitute a solid basis for future urban Tree Health monitoring programs.
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WHISPERS - Airborne Imaging Spectroscopy for Assessing Soil Sealing Effect on Urban Tree Health
2018 9th Workshop on Hyperspectral Image and Signal Processing: Evolution in Remote Sensing (WHISPERS), 2018Co-Authors: Jeroen Degerickx, Maarten Van Geel, Olivier Honnay, Ben SomersAbstract:Soil sealing in urban areas imposes a large impact on vegetation Health and its functioning in providing ecosystem services. Yet, quantitative assessment of soil sealing effect on urban Tree Health status remains challenging. Here, we investigate the feasibility of using airborne imaging spectroscopy and leaf reflectance for assessing the effect of soil sealing on leaf chlorophyll content of Trees and their spectral responses. Results showed that soil sealing decreased the leaf total chlorophyll content and the ratio of carotenoids to chlorophyll. Chlorophyll spectral indices extracted from airborne and leaf reflectance data were both highly correlated with chlorophyll. Spectrally predicted chlorophyll variations allowed for the discrimination of different soil sealing conditions. This study demonstrates the great potential of using airborne remote sensing data to assess the Health status of urban vegetation as well as for biomonitoring soil sealing impacts.
Maarten Van Geel - One of the best experts on this subject based on the ideXlab platform.
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Soil organic matter rather than ectomycorrhizal diversity is related to urban Tree Health
PLoS ONE, 2019Co-Authors: Maarten Van Geel, Gerrit Peeters, Kasper Van Acker, Miguel Ramos, Cindy Serafim, Pierre Kastendeuch, Georges Najjar, Thierry Ameglio, Jérôme Ngao, Marc SaudreauAbstract:Urban Trees provide many ecosystem services, including carbon sequestration, air quality improvement, storm water attenuation and energy conservation, to people living in cities. Provisioning of ecosystem services by urban Trees, however, may be jeopardized by the typically poor quality of the soils in urban areas. Given their well-known multifunctional role in forest ecosystems, ectomycorrhizal fungi (EcM) may also contribute to urban Tree Health and thus ecosystem service provisioning. Yet, no studies so far have directly related in situ EcM community composition to urban Tree Health indicators. Here, two previously collected datasets were combined: i) Tree Health data of 175 Tilia tomentosa Trees from three European cities (Leuven, Strasbourg and Porto) estimated using a range of reflectance, chlorophyll fluorescence and physical leaf indicators, and ii) ectomycorrhizal diversity of these Trees as characterized by next-generation sequencing. Tree Health indicators were related to soil characteristics and EcM diversity using canonical redundancy analysis. Soil organic matter significantly explained variation in Tree Health indicators whereas no significant relation between mycorrhizal diversity variables and the Tree Health indicators was found. We conclude that mainly soil organic matter, through promoting soil aggregate formation and porosity, and thus indirectly Tree water availability, positively affects the Health of Trees in urban areas. Our results suggest that urban planners should not overlook the importance of soil quality and its water holding capacity for the Health of urban Trees and potentially also for the ecosystem services they deliver. Further research should also study other soil microbiota which may independently, or in interaction with ectomycorrhiza, mediate Tree performance in urban settings.
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airborne imaging spectroscopy for assessing soil sealing effect on urban Tree Health
Workshop on Hyperspectral Image and Signal Processing: Evolution in Remote Sensing, 2018Co-Authors: Jeroen Degerickx, Maarten Van Geel, Olivier Honnay, Ben SomersAbstract:Soil sealing in urban areas imposes a large impact on vegetation Health and its functioning in providing ecosystem services. Yet, quantitative assessment of soil sealing effect on urban Tree Health status remains challenging. Here, we investigate the feasibility of using airborne imaging spectroscopy and leaf reflectance for assessing the effect of soil sealing on leaf chlorophyll content of Trees and their spectral responses. Results showed that soil sealing decreased the leaf total chlorophyll content and the ratio of carotenoids to chlorophyll. Chlorophyll spectral indices extracted from airborne and leaf reflectance data were both highly correlated with chlorophyll. Spectrally predicted chlorophyll variations allowed for the discrimination of different soil sealing conditions. This study demonstrates the great potential of using airborne remote sensing data to assess the Health status of urban vegetation as well as for biomonitoring soil sealing impacts.
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Foliar optical traits indicate that sealed planting conditions negatively affect urban Tree Health
Ecological Indicators, 2018Co-Authors: Maarten Van Geel, Pierre Kastendeuch, Georges Najjar, Thierry Ameglio, Tobias Ceulemans, Willem Geerts, Miguel Marcos Ramos, Nadine Sousa, Paula M. L. Castro, Jérôme NgaoAbstract:Urban Trees play a key role in mitigating environmental problems in cities, but they often face harsh environmental conditions as they generally grow in sealed soils that have small rooting space and low water availability. In this context, rapid monitoring and assessment of Tree Health status is critical to maintain urban Trees and secure the provisioning of urban ecosystem services. Across three European cities we selected 187 Tilia tomentosa Trees growing under following planting conditions: (i) sealed, Trees planted in small soil pits or strips surrounded by highly sealed surfaces (concrete, pavement or asphalt); and (ii) unsealed, Trees planted in roomy soil surfaces (e.g. parks). We measured leaf reflectance and fluorescence and derived a set of optical traits from the measurements. We examined whether these non-destructively measured optical traits differ between planting conditions and whether they correlate with leaf functional traits, e.g. specific leaf area (SLA), leaf water content (LWC) and leaf water per area (LWA). Compared to the unsealed Trees, sealed Trees showed decreased SLA and LWC while increased LWA. Leaf optical traits differed between the unsealed and sealed Trees. Highly sealed soils accelerated leaf senescence of the sealed Trees compared to the unsealed Trees, embodied in the temporal trend of optical traits. Sealed planting conditions negatively affect urban Tree Health status and phenology. These negative effects can be estimated by leaf optical traits, demonstrating the great potential of optical traits in assessing Tree Health status. Our findings provide insights into facilitating urban green management using optical traits and remote sensing data.
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WHISPERS - Airborne Imaging Spectroscopy for Assessing Soil Sealing Effect on Urban Tree Health
2018 9th Workshop on Hyperspectral Image and Signal Processing: Evolution in Remote Sensing (WHISPERS), 2018Co-Authors: Jeroen Degerickx, Maarten Van Geel, Olivier Honnay, Ben SomersAbstract:Soil sealing in urban areas imposes a large impact on vegetation Health and its functioning in providing ecosystem services. Yet, quantitative assessment of soil sealing effect on urban Tree Health status remains challenging. Here, we investigate the feasibility of using airborne imaging spectroscopy and leaf reflectance for assessing the effect of soil sealing on leaf chlorophyll content of Trees and their spectral responses. Results showed that soil sealing decreased the leaf total chlorophyll content and the ratio of carotenoids to chlorophyll. Chlorophyll spectral indices extracted from airborne and leaf reflectance data were both highly correlated with chlorophyll. Spectrally predicted chlorophyll variations allowed for the discrimination of different soil sealing conditions. This study demonstrates the great potential of using airborne remote sensing data to assess the Health status of urban vegetation as well as for biomonitoring soil sealing impacts.
Jeroen Degerickx - One of the best experts on this subject based on the ideXlab platform.
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Urban Tree Health Classification Across Tree Species by Combining Airborne Laser Scanning and Imaging Spectroscopy
Remote Sensing, 2020Co-Authors: Dengkai Chi, Jeroen Degerickx, Ben SomersAbstract:Declining urban Tree Health can affect critical ecosystem services, such as air quality improvement, temperature moderation, carbon storage, and biodiversity conservation. The application of state-of-the-art remote sensing data to characterize Tree Health has been widely examined in forest ecosystems. However, such application to urban Trees has not yet been fully explored—due to the presence of heterogeneous Tree species and backgrounds, severely complicating the classification of Tree Health using remote sensing information. In this study, Tree Health was represented by a set of field-assessed Tree Health indicators (defoliation, discoloration, and a combination thereof), which were classified using airborne laser scanning (ALS) and hyperspectral imagery (HSI) with a Random Forest classifier. Different classification scenarios were established aiming at: (i) Comparing the performance of ALS data, HSI and their combination, and (ii) examining to what extent Tree species mixtures affect classification accuracy. Our results show that although the predictive power of ALS and HSI indices varied between Tree species and Tree Health indicators, overall ALS indices performed better. The combined use of both ALS and HSI indices results in the highest accuracy, with weighted kappa coefficients (Kc) ranging from 0.53 to 0.79 and overall accuracy ranging from 0.81 to 0.89. Overall, the most informative remote sensing indices indicating urban Tree Health are ALS indices related to point density, Tree size, and shape, and HSI indices associated with chlorophyll absorption. Our results further indicate that a species-specific modelling approach is advisable (Kc points improved by 0.07 on average compared with a mixed species modelling approach). Our study constitutes a basis for future urban Tree Health monitoring, which will enable managers to guide early remediation management.
-
airborne imaging spectroscopy for assessing soil sealing effect on urban Tree Health
Workshop on Hyperspectral Image and Signal Processing: Evolution in Remote Sensing, 2018Co-Authors: Jeroen Degerickx, Maarten Van Geel, Olivier Honnay, Ben SomersAbstract:Soil sealing in urban areas imposes a large impact on vegetation Health and its functioning in providing ecosystem services. Yet, quantitative assessment of soil sealing effect on urban Tree Health status remains challenging. Here, we investigate the feasibility of using airborne imaging spectroscopy and leaf reflectance for assessing the effect of soil sealing on leaf chlorophyll content of Trees and their spectral responses. Results showed that soil sealing decreased the leaf total chlorophyll content and the ratio of carotenoids to chlorophyll. Chlorophyll spectral indices extracted from airborne and leaf reflectance data were both highly correlated with chlorophyll. Spectrally predicted chlorophyll variations allowed for the discrimination of different soil sealing conditions. This study demonstrates the great potential of using airborne remote sensing data to assess the Health status of urban vegetation as well as for biomonitoring soil sealing impacts.
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Urban Tree Health assessment using airborne hyperspectral and LiDAR imagery
International Journal of Applied Earth Observation and Geoinformation, 2018Co-Authors: Jeroen Degerickx, Dar A. Roberts, Joe P. Mcfadden, Martin Hermy, Ben SomersAbstract:Abstract Urban Trees provide valuable ecosystem services but are at the same time under continuous pressure due to unfavorable site conditions. In order to better protect and manage our natural capital, urban green managers require frequent and detailed information on Tree Health at the city wide scale. In this paper we developed a workflow to monitor Tree defoliation and discoloration of broadleaved Trees in Brussels, Belgium, through the combined use of airborne hyperspectral and LiDAR data. Individual Trees were delineated using an object-based Tree detection and segmentation algorithm primarily based on LiDAR data with an average accuracy of 91%. We constructed Partial Least Squares Regression (PLSR) models to derive Tree chlorophyll content (RMSE = 2.8 μg/cm²; R² = 0.77) and Leaf Area Index (LAI; RMSE = 0.5; R² = 0.66) from the average canopy spectrum. Existing spectral indices were found to perform significantly worse (RMSE > 7 μg/cm² and >1.5 respectively), mainly due to contamination of Tree spectra by neighboring background materials. In the absence of local calibration data, the applicability of PLSR to other areas, sensors and Tree species might be limited. Therefore, we identified the best performing/least sensitive spectral indices and proposed a simple pixel selection procedure to reduce disturbing background effects. For LAI, laser penetration metrics derived from LiDAR data attained comparable accuracies as PLSR and were suggested instead. Detection of Healthy and unHealthy Trees based on remotely sensed Tree properties matched reasonably well with a more traditional visual Tree assessment (93% and 71% respectively). If combined with early Tree stress detection methods, the proposed methodology would constitute a solid basis for future urban Tree Health monitoring programs.
-
WHISPERS - Airborne Imaging Spectroscopy for Assessing Soil Sealing Effect on Urban Tree Health
2018 9th Workshop on Hyperspectral Image and Signal Processing: Evolution in Remote Sensing (WHISPERS), 2018Co-Authors: Jeroen Degerickx, Maarten Van Geel, Olivier Honnay, Ben SomersAbstract:Soil sealing in urban areas imposes a large impact on vegetation Health and its functioning in providing ecosystem services. Yet, quantitative assessment of soil sealing effect on urban Tree Health status remains challenging. Here, we investigate the feasibility of using airborne imaging spectroscopy and leaf reflectance for assessing the effect of soil sealing on leaf chlorophyll content of Trees and their spectral responses. Results showed that soil sealing decreased the leaf total chlorophyll content and the ratio of carotenoids to chlorophyll. Chlorophyll spectral indices extracted from airborne and leaf reflectance data were both highly correlated with chlorophyll. Spectrally predicted chlorophyll variations allowed for the discrimination of different soil sealing conditions. This study demonstrates the great potential of using airborne remote sensing data to assess the Health status of urban vegetation as well as for biomonitoring soil sealing impacts.
Christopher P. Quine - One of the best experts on this subject based on the ideXlab platform.
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the social amplification of Tree Health risks the case of ash dieback disease in the uk
2018Co-Authors: Julie Urquhart, John Fellenor, Julie Barnett, John D. Mumford, Clive Potter, Christopher P. QuineAbstract:The risks posed by Tree pests and diseases have been widely recognised in expert circles, but the degree to which this awareness is shared by publics and stakeholders is still unclear. There is a potential conflict between government attempts to manage the risks, media coverage and the ways in which publics and stakeholders make sense of the threats. The Social Amplification of Risk Framework (SARF) was adopted in this study as a means of exploring the interrelationships of media representation, expert assessments and public perceptions of the ash dieback outbreak in the UK. By exploring the dynamic interactions between these different actors and the social, psychological and cultural processes through which they determine risk, the study provides a more nuanced understanding of Tree Health risks that can inform risk communication strategies and outbreak management.
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Public acceptance of Tree Health management: Results of a national survey in the UK
Environmental Science & Policy, 2016Co-Authors: Lauren Fuller, Christopher P. Quine, Mariella Marzano, Andrew Peace, Norman DandyAbstract:Abstract Assumptions about public stakeholder attitudes to pest and disease management can influence the decisions of forest managers and NGOs involved in responding to pests and diseases; however, they are rarely assessed directly. Evidence on the social acceptability of Tree Health management methods is required to inform government led policy and management. A nationally representative survey of 2000 members of the UK public was used to address two research questions: (1) How acceptable are Tree Health management methods to the public? (2) How do opinions about woodland functions, concern and awareness of Tree pests and diseases, and demographics influence acceptance of management methods? We found that public stakeholders are highly supportive of Tree Health management; however, knowledge about Tree pests, diseases, and management options is low. Methods seen as more targeted and ‘natural’ were preferred, e.g. felling and burning only affected Trees and using biological control rather than chemical control. There were demographic differences in attitudes: men and older people are more likely to support management interventions and stronger management methods than females and younger people. Acceptance of management can also differ according to location and local context (e.g. management is less supported when it may impact on wildlife) and values (e.g. those with economic values are more supportive of management). These findings provide evidence to support current government initiatives on Tree Health and should improve confidence amongst managers tasked with carrying out Tree pest and disease management. However, there is a need for in-depth qualitative studies to explain the beliefs which influence demographic variations in acceptance and the influence of concepts such as ‘nativeness’ and ‘naturalness’.
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Resilience and Tree Health: a basis for implementation in sustainable forest management
Forestry, 2015Co-Authors: Lauren Fuller, Christopher P. QuineAbstract:Resilience is rapidly becoming a prominent concept in research, policy and practice. However, it is apparent that there is no consistent meaning of resilience being used by those involved in governing and managing forests and Tree Health. We aimed to (1) identify how the concept of resilience is defined in a range of decision-making contexts, (2) develop an understanding of resilience, which will be useful in the context of Tree Health and forestry and (3) suggest how managers could use this understanding more broadly as a framework for decision-making on resilience within the forestry sector. Implementation of resilience for Tree Health needs to encompass a range of functions and services, management objectives and threats, all present at a variety of scales. We conclude that, due to the complexityof the resilience concept and forest systems, no single definition of resilience can be sufficient and it is more appropriate to explicitly consider four resilience components: resistance, recovery, transformation and adaptation. We propose a set of decision steps which stakeholders can use to develop a Resilience Implementation Framework to guide management for their system of interest.
Jérôme Ngao - One of the best experts on this subject based on the ideXlab platform.
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Soil organic matter rather than ectomycorrhizal diversity is related to urban Tree Health
PLoS ONE, 2019Co-Authors: Maarten Van Geel, Gerrit Peeters, Kasper Van Acker, Miguel Ramos, Cindy Serafim, Pierre Kastendeuch, Georges Najjar, Thierry Ameglio, Jérôme Ngao, Marc SaudreauAbstract:Urban Trees provide many ecosystem services, including carbon sequestration, air quality improvement, storm water attenuation and energy conservation, to people living in cities. Provisioning of ecosystem services by urban Trees, however, may be jeopardized by the typically poor quality of the soils in urban areas. Given their well-known multifunctional role in forest ecosystems, ectomycorrhizal fungi (EcM) may also contribute to urban Tree Health and thus ecosystem service provisioning. Yet, no studies so far have directly related in situ EcM community composition to urban Tree Health indicators. Here, two previously collected datasets were combined: i) Tree Health data of 175 Tilia tomentosa Trees from three European cities (Leuven, Strasbourg and Porto) estimated using a range of reflectance, chlorophyll fluorescence and physical leaf indicators, and ii) ectomycorrhizal diversity of these Trees as characterized by next-generation sequencing. Tree Health indicators were related to soil characteristics and EcM diversity using canonical redundancy analysis. Soil organic matter significantly explained variation in Tree Health indicators whereas no significant relation between mycorrhizal diversity variables and the Tree Health indicators was found. We conclude that mainly soil organic matter, through promoting soil aggregate formation and porosity, and thus indirectly Tree water availability, positively affects the Health of Trees in urban areas. Our results suggest that urban planners should not overlook the importance of soil quality and its water holding capacity for the Health of urban Trees and potentially also for the ecosystem services they deliver. Further research should also study other soil microbiota which may independently, or in interaction with ectomycorrhiza, mediate Tree performance in urban settings.
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Foliar optical traits indicate that sealed planting conditions negatively affect urban Tree Health
Ecological Indicators, 2018Co-Authors: Maarten Van Geel, Pierre Kastendeuch, Georges Najjar, Thierry Ameglio, Tobias Ceulemans, Willem Geerts, Miguel Marcos Ramos, Nadine Sousa, Paula M. L. Castro, Jérôme NgaoAbstract:Urban Trees play a key role in mitigating environmental problems in cities, but they often face harsh environmental conditions as they generally grow in sealed soils that have small rooting space and low water availability. In this context, rapid monitoring and assessment of Tree Health status is critical to maintain urban Trees and secure the provisioning of urban ecosystem services. Across three European cities we selected 187 Tilia tomentosa Trees growing under following planting conditions: (i) sealed, Trees planted in small soil pits or strips surrounded by highly sealed surfaces (concrete, pavement or asphalt); and (ii) unsealed, Trees planted in roomy soil surfaces (e.g. parks). We measured leaf reflectance and fluorescence and derived a set of optical traits from the measurements. We examined whether these non-destructively measured optical traits differ between planting conditions and whether they correlate with leaf functional traits, e.g. specific leaf area (SLA), leaf water content (LWC) and leaf water per area (LWA). Compared to the unsealed Trees, sealed Trees showed decreased SLA and LWC while increased LWA. Leaf optical traits differed between the unsealed and sealed Trees. Highly sealed soils accelerated leaf senescence of the sealed Trees compared to the unsealed Trees, embodied in the temporal trend of optical traits. Sealed planting conditions negatively affect urban Tree Health status and phenology. These negative effects can be estimated by leaf optical traits, demonstrating the great potential of optical traits in assessing Tree Health status. Our findings provide insights into facilitating urban green management using optical traits and remote sensing data.
