Identifying key environmental stressors shaping plant health in ultra-urban green infrastructure

Green infrastructure (GI) is increasingly deployed in ultra-urban environments to mitigate runoff and enhance ecological resilience, yet field evidence remains limited on how GI plants physiologically integrates short-term microclimatic stress exposure and subsequent recovery. In contrast to conventional urban greening plantings, GI plant operates within engineered soil–hydrologic systems (e.g., media properties, drainage/storage, and event-driven wetting–drying), which can decouple rainfall from plant-available water and reshape plant sensitivity to episodic heat–dryness stress. Here we investigate how temporally structured environmental exposures regulate plant performance in a functioning rain garden in Foshan, China, by pairing weekly physiological surveys with continuous high-frequency micrometeorological monitoring.

Eight plant indicators capturing chlorophyll fluorescence energy partitioning, pigment-related status, canopy structure, and leaf–air thermal coupling were measured over a multi-season observation period and analyzed against stress-relevant descriptors of the local atmospheric and radiative regime. Rather than relying on weekly averages alone, we characterize exposure in biologically meaningful time contexts that distinguish same-week forcing from preceding conditions, and we emphasize extreme- and duration-based signatures that better represent urban stress episodes. Across indicators, we observe a clear functional differentiation in time-scale sensitivity that fluorescence partitioning aligns most closely with short-term radiative forcing, whereas canopy and pigment traits exhibit stronger coupling to thermal conditions and atmospheric moisture demand and show a clear carry-over effect from earlier conditions. Extreme- and threshold-oriented descriptors consistently outperform central-tendency metrics in explanatory value, highlighting that short, intense stress periods contain information not captured by mean states.

Overall, the dominant constraints reflect a familiar radiation–heat–demand regime reported for urban vegetation, yet the engineered GI ecohydrological context elevates the importance of antecedent root-zone status and recovery potential relative to precipitation totals. These findings motivate climate-adaptive GI strategies that buffer radiative and heat–dryness extremes and enhance short-term recovery conditions through both general microclimate interventions (e.g., shading and exposure control) and GI-specific levers (e.g., media configuration, drainage/storage tuning, and recovery-aligned irrigation), while maintaining hydrological function.