Urban green proximal sensing with portable photonics-based devices: preliminary results in the metropolitan city of Cagliari

Abstract

Urban greenery is a vital component of city landscapes. With the increasing influence of extreme weather events and global warming, coupled with the pollution associated with urban activities, innovative solutions are needed to plan and manage green urban infrastructure for a healthy city ecosystem. This study focuses on utilizing portable photonic devices, to assess the physiological responses of Mediterranean selected plant species (Quercus Ilex L., Nerium Oleander L., and Prunus Cerasifera Ehrh) to variations in environmental conditions and pollution levels in representative areas of both the central and peripheral districts of Cagliari. During the post-summer period of 2023, a measurement campaign was executed, encompassing fundamental parameters like Leaf Area, Leaf Fresh and Dry Weight, and the plant canopy through the Normalized Difference Vegetation Index (NDVI). Portable sensors using fluorescence and Raman techniques were then employed to non-invasively monitor leaf component levels, correlating them with plant species and urban areas. Historical environmental and pollution data from 2019 to 2023 were gathered from monitoring stations in the Sardinia Region. Observations revealed a similar response of the plant species between the two zones, that is an imbalance in chlorophyll indexes, accompanied by opposite variations in polyphenol indexes. A characteristic feature was a greater index variability observed in Quercus Ilex L. and Nerium Oleander L. compared to Prunus Cerasifera Ehrh. This preliminary study initiated the design of a supporting protocol to select site-specific resilient plant species for urban greenery.