A single tree model to consistently simulate cooling, shading, and pollution uptake of urban trees

Abstract

Extremely high temperatures, which negatively affect the human health and plant performances, are becoming more frequent in cities. Urban green infrastructure, particularly trees, can mitigate this issue through cooling due to transpiration, and shading. Temperature regulation by trees depends on feedbacks among the climate, water supply, and plant physiology. However, in contrast to forest or general ecosystem models, most current urban tree models still lack basic processes, such as the consideration of soil water limitation, or have not been evaluated sufficiently. In this study, we present a new model that couples the soil water balance with energy calculations to assess the physiological responses and microclimate effects of a common urban street-tree species (Tilia cordata Mill.) on temperature regulation. We contrast two urban sites in Munich, Germany, with different degree of surface sealing at which microclimate and transpiration had been measured. Simulations indicate that differences in wind speed and soil water supply can be made responsible for the differences in transpiration. Nevertheless, the calculation of the overall energy balance showed that the shading effect, which depends on the leaf area index and canopy cover, contributes the most to the temperature reduction at midday. Finally, we demonstrate that the consideration of soil water availability for stomatal conductance has realistic impacts on the calculation of gaseous pollutant uptake (e.g., ozone). In conclusion, the presented model has demonstrated its ability to quantify two major ecosystem services (temperature mitigation and air pollution removal) consistently in dependence on meteorological and site conditions.

Hydraulic Efficiency of Green-Blue Flood Control Scenarios for Vegetated Rivers: 1D and 2D Unsteady Simulations

“…Thus, grey scenarios do not deliver multiple environmental benefits, also known as "Ecosystem Services", apart from flood control or peak discharge and water level reduction effects. On the other hand, based on the proposal of low-impact developments (LID) and best management practices (BMP), which aim at balancing the need for improved hydraulic efficiency and the need to mitigate the environmental impact of the hydraulic infrastructures, green-blue scenarios constitute a very promising scientific and practical advance in terms of flood control engineering solutions at low ecological impacts [24][25][26][27][28][29].…”

Ecosystem Services Provided By Urban Forests In The Southern Caucasus Region: A Modeling Study In Tbilisi, Georgia

“…3-5). Furthermore, rainfall allows to increase the soil water content and ensures a higher stomatal conductance and therefore, a cooling effect and uptake of gaseous pollutants (Pace et al 2021b). Another important selection criterion is the choice of non-VOC emitting species (Churkina et al 2015), such as the species within the genus Acer, Fraxinus and Tilia, to ensure high ozone removal (Sicard et al 2018) by preventing its formation (Calfapietra et al 2013).…”

Ecosystem Services Provided By Urban Forests In The Southern Caucasus Region: A Modeling Study In Tbilisi, Georgia

“…5-7). Furthermore, rainfall allows to increase the soil water content and ensures a higher stomatal conductance and therefore a cooling effect and uptake of gaseous pollutants (Morani et al 2014;Pace et al 2021b). Another important selection criterion is the choice of non-VOC emitting species (Churkina et al 2015), such as species within the genus Acer, Fraxinus and Tilia, to ensure high ozone removal (Sicard et al 2018) by preventing its formation (Calfapietra et al 2013).…”