Quantifying the spatial influence of Platanus trees on local airborne pollen concentrations

Plane trees ( Platanus spp.) provide important ecosystem services but are also among the most allergenic urban tree species. Although local pollen sources are expected to strongly influence pedestrian-level exposure, the spatial relationship between pollen sources and measured pollen concentrations remains poorly understood. In particular, quantitative information on the effective dispersal distance of pollen grains remains limited, constraining the development of high-resolution pollen forecasts. We measured Platanus pollen concentrations at ground level (four sites) and at a rooftop reference site during the 2025 pollen season in Poznań, Poland. Platanus crown volume was estimated from airborne LiDAR data and integrated with wind conditions to calculate a daily pollen source strength index. Incremental buffer analysis (100–1600 m) was performed to identify the distance at which surrounding trees best explained local pollen concentrations. Pollen concentrations showed substantial spatial variability; however, no statistically significant differences were observed between co-located ground- and rooftop-level samplers. The strongest correlation between local pollen concentrations and surrounding pollen sources was observed within an 800 m radius ( r = 0.406, p < 0.001), whereas both smaller and larger buffer distances showed weaker relationships. These findings indicate that the effective influence distance of local Platanus pollen sources is approximately 800 m, suggesting that trees beyond this distance have only a limited influence on local pollen concentrations. Our findings provide an evidence-based parameter for source-area delineation in local pollen forecasting models and may support allergy management and urban tree planting strategies.