Effects of management on the provisioning of ecosystem services by mature urban trees

The aim of this research was to evaluate the effects of organic mulching and irrigation on CO2-uptake, cooling, and PM removal by urban trees in Rimini and Krakow. In each city, 72 established trees from 6 species were selected within two experimental areas (size was 250 and 470 ha in Rimini and Krakow, respectively) in summer 2018. Dendrometric traits, leaf area index (LAI), and leaf gas exchange of the trees were monitored for 1 year (baseline period). Since December 2019, the irrigation and mulching treatments were imposed on half of the trees (pilot) while the remaining half was left untreated (control). Organic mulching was done using compost. Irrigation was supplied manually. Irrigation scheduling and amount were estimated using a ETP-based approach. After the imposition of treatments, stem DBH, crown radius, LAI, daily leaf gas exchange, and PM adsorption were monitored for 18 months (impact period). CO2 emissions associated with mulching and irrigation were also estimated using a LCA approach. Measured values of net CO2 assimilation, stomatal conductance, and transpiration per unit leaf area were upscaled to the whole tree using a multi-layer approach. PM adsorption and leaf gas exchange per unit leaf area were little affected by mulching and irrigation. Nonetheless, pilot management increased plant leaf area, thus generally increasing ES provisioning per tree. However, higher CO2 emissions for mulching and, more importantly, for irrigation may offset, at least in part, the higher benefits of mulched and irrigate trees.