Development and application of an integrated photonic approach for urban vegetation monitoring under heterogeneous environmental conditions

Contemporary cities constitute increasingly complex environmental systems characterized by heterogeneous environmental conditions. Within this context, urban vegetation plays a central role in climate adaptation, environmental regulation, and urban sustainability, highlighting the need for tools capable of monitoring its variability under environmental conditions. However, available approaches, ranging from structural indicators to physiological and biochemical measurements, often provide information focused on specific aspects of plant responses and may be difficult to integrate within multidimensional monitoring strategies applied to heterogeneous environmental contexts. This highlights the need for complementary observational approaches capable of integrating information derived from different observational scales. This thesis develops, applies, and evaluates an integrated approach based on portable photonic technologies, including Raman spectroscopy (MiniRaman Lightnovo), the GreenSeeker NDVI sensor (Trimble), and the Dualex Force-A leaf analyser. By integrating information acquired at molecular, leaf, and canopy scales, the approach enables a multidimensional observation of vegetation variability through complementary optical and biochemical proxies. The approach was applied to Quercus ilex L. and Nerium oleander L., used as model species, through seasonal monitoring campaigns conducted in 2023 and 2024 under environmental configurations. Photonic measurements (DxChl, DxFlav, DxAnth, NBI, NDVI, R.I.1526, and R.I.1626) were integrated with biometric parameters, soil characteristics, atmospheric pollutant concentrations, and meteorological variables derived from a five-year environmental dataset (2019–2023). Overall, 2,232 measurements were acquired and analysed. The research assessed the applicability of portable photonic technologies under real environmental conditions, developing an integrated approach for analysing optical and biochemical variability in vegetation and exploring its potential applications for urban vegetation monitoring. The study was conceived as an exploratory proof-of-concept investigation aimed at evaluating the applicability of the proposed approach. The results show that the three photonic technologies provide complementary, non-redundant multiscale information associated with vegetation variability. Multivariate analyses revealed coherent patterns of optical and biochemical variability across species, seasons, and environmental conditions, while highlighting species-specific responses. Quercus ilex L. and Nerium oleander L. exhibited partially distinct configurations, suggesting their complementary use in comparative monitoring activities. Furthermore, the convergence among indicators derived from different technologies supported the internal consistency and methodological robustness of the approach across multiple observational scales. Overall, the research demonstrates the applicability of an integrated photonic approach for observing vegetation variability through non-destructive optical and biochemical proxies. Although not intended to replace established physiological instruments used for the direct measurement of physiological processes, the proposed approach represents a complementary tool capable of providing additional information on vegetation variability through rapid, non-invasive, and field-applicable procedures. Its value lies not in replacing traditional physiological measurements, but in integrating information that is normally acquired separately by combining signals associated with leaf biochemical composition, plant pigments, and vegetation reflectance within a single observational strategy. In this perspective, the approach provides a multidimensional representation of vegetation variability under real environmental conditions and constitutes a methodological basis potentially transferable to future monitoring, assessment, and management programmes for urban vegetation.