Development of multi-functional streetscape green infrastructure using a performance index approach

The file attached to this record is the author's final peer reviewed version. The Publisher's final version can be found by following the DOI link.This paper presents a performance evaluation framework for streetscape vegetation. A performance index (PI) is conceived using the following seven traits, specific to the street environments – Pollution Flux Potential (PFP), Carbon Sequestration Potential (CSP), Thermal Comfort Potential (TCP), Noise Attenuation Potential (NAP), Biomass Energy Potential (BEP), Environmental Stress Tolerance (EST) and Crown Projection Factor (CPF). Its application is demonstrated through a case study using fifteen street vegetation species from the UK, utilising a combination of direct field measurements and inventoried literature data. Our results indicate greater preference to small-to-medium size trees and evergreen shrubs over larger trees for streetscaping. The proposed PI approach can be potentially applied two-fold: one, for evaluation of the performance of the existing street vegetation, facilitating the prospects for further improving them through management strategies and better species selection; two, for planning new streetscapes and multi-functional biomass as part of extending the green urban infrastructure

The Impact of Root Temperature on Photosynthesis and Isoprene Emission in Three Different Plant Species

Most of the perennial plant species, particularly trees, emit volatile organic compounds (BVOCs) such as isoprene and monoterpenes, which in several cases have been demonstrated to protect against thermal shock and more generally against oxidative stress. In this paper, we show the response of three strong isoprene emitter species, namely, Phragmites australis, Populus x euramericana, and Salix phylicifolia exposed to artificial or natural warming of the root system in different conditions. This aspect has not been investigated so far while it is well known that warming the air around a plant stimulates considerably isoprene emission, as also shown in this paper. In the green house experiments where the warming corresponded with high stress conditions, as confirmed by higher activities of the main antioxidant enzymes, we found that isoprene uncoupled from photosynthesis at a certain stage of the warming treatment and that even when photosynthesis approached to zero isoprene emission was still ongoing. In the field experiment, in a typical cold-limited environment, warming did not affect isoprene emission whereas it increased significantly CO2 assimilation. Our findings suggest that the increase of isoprene could be a good marker of heat stress, whereas the decrease of isoprene a good marker of accelerated foliar senescence, two hypotheses that should be better investigated in the future

An ultra-spatially resolved method to quali-quantitative monitor particulate matter in urban environment

Monitoring the amount and composition of airborne particulate matter (PM) in the urban environment is a crucial aspect to guarantee citizen health. To focus the action of stakeholders in limiting air pollution, fast and highly spatially resolved methods for monitoring PM are required. Recently, the trees’ capability in capturing PM inspired the development of several methods intended to use trees as biomonitors; this results in the potential of having an ultra-spatially resolved network of low-cost PM monitoring stations throughout cities, without the needing of on-site stations. Within this context, we propose a fast and reliable method to qualitatively and quantitatively characterize the PM present in urban air based on the analysis of tree leaves by scanning electron microscopy combined with X-ray spectroscopy (SEM/EDX). We have tested our method in the Real Bosco di Capodimonte urban park (Naples, Italy), by collecting leaves from Quercus ilex trees along transects parallel to the main wind directions. The coarse (PM10–2.5) and fine (PM2.5) amounts obtained per unit leaf area have been validated by weighting the PM washed from leaves belonging to the same sample sets. PM size distribution and elemental composition match appropriately with the known pollution sources in the sample sites (i.e., traffic and marine aerosol). The proposed methodology will then allow the use of the urban forest as an ultra-spatially resolved PM monitoring network, also supporting the work of urban green planners and stakeholders.5s

Development of multi-functional streetscape green infrastructure using a performance index approach

This paper presents a performance evaluation framework for streetscape vegetation. A performance index (PI) is conceived using the following seven traits, specific to the street environments – Pollution Flux Potential (PFP), Carbon Sequestration Potential (CSP), Thermal Comfort Potential (TCP), Noise Attenuation Potential (NAP), Biomass Energy Potential (BEP), Environmental Stress Tolerance (EST) and Crown Projection Factor (CPF). Its application is demonstrated through a case study using fifteen street vegetation species from the UK, utilising a combination of direct field measurements and inventoried literature data. Our results indicate greater preference to small-to-medium size trees and evergreen shrubs over larger trees for streetscaping. The proposed PI approach can be potentially applied two-fold: one, for evaluation of the performance of the existing street vegetation, facilitating the prospects for further improving them through management strategies and better species selection; two, for planning new streetscapes and multi-functional biomass as part of extending the green urban infrastructure

Integrating Copernicus land cover data into the i-Tree Cool Air model to evaluate and map urban heat mitigation by tree cover

Cities host more than half of the world’s population and due to global warming and land use change their vulnerability to deadly heat waves has increased. A healthy vegetated landscape can abate heat wave severity and diminish the related urban heat island through the process of evapotranspiration. This research aimed to develop a methodology for cities to use publicly available Copernicus land cover maps within the i-Tree Cool Air water and energy balance model to map air temperature and humidity. The manuscript presents proof of concept using Naples, Italy with its Mediterranean climate characterized by limited soil water for cooling via evapotranspiration. The approach achieved strong correlations between predicted and observed air temperatures across the city (r ≥ 0.89). During the warm season of 2020, forested land cover was 5°C cooler than land cover dominated by impervious cover. Simulated land cover change, limited to a 10% increase or decrease in tree cover, generated an inverse change of 0.2°C in maximum hourly air temperature, with more trees obtaining cooler air. Soil water limited the cooling, with the generally wetter spring season enabling greater cooling of air temperatures, and summer droughts without irrigation had constrained cooling. Sustainable urban design will likely require an increase in plant cover along with a reduction of impervious surfaces that absorb and reradiate heat in order to improve community resilience to heat waves

Comparing the modeled deposition of PM2.5 with the Eddy Covariance flux and SEM analysis of an urban forest in Naples

Trees can remove particles from the air through the physical deposition on the leaf surface. This process depends on pollution concentration and weather conditions as wind speed and precipitation, in addition to leaf characteristics. Wind speed increases at the same time the deposition velocity and the resuspension of PM deposited, instead, the rain washes off into the soil the particles accumulated on the leaf. The PM flux removed by trees has been modeled in the i-Tree Eco model considering the effect of wind speed on deposition velocity and resuspension and fixing a threshold of leaf washing (0.2 mm x LAI). However, the results of the model have not been validated with measured data and especially the washing threshold and resuspension classes based on wind speed still remain uncertain. In this study, we compared the modeled deposition of PM2.5 with the Eddy Covariance flux measured in an urban forest in Naples. The results of the model have been further validated by comparing the expected PM2.5 accumulations on the leaf (net flux integral) with the average PM load experimentally determined in the same site where the model input data (i.e., PM concentration, wind speed and rain) have been collected. The model and Eddy Covariance presented a good agreement in assessing the deposition flux on leaves but we show that also precipitation events higher than the threshold are not able to wash all particles accumulated on leaves as confirmed by the higher accumulation of PM2.5 measured with the SEM analysis. Furthermore, a wind speed above 20 m s-1 strongly affects the deposition because of the high resuspension back to the atmosphere. Finally, we highlight the importance of including a species-specific parametrization in the model to take into account the influence of leaf characteristics on the deposition velocity, resuspension, and leaf washing