BIOHYPE - Biomonitoring of urban habitat quality with airborne hyperspectral observations

Project outcome

• Extensive dataset of leaf level fluorescence, chlorophyll and structure measurements;
• It was shown that stress induced by traffic pollution can be detected by steadystate Fluorescence Yield indices for leaves at the bottom branches of some urban tree species. Susceptibility to air pollution based on solar-induced Chl fluorescence measurements is however found species-dependent;
• Lessons from leaf level solar induced Chl fluorescence for the interpretation of remotely retrieved Chl fluorescence. Insights in the partitioning of bidirectional Chl fluorescence into an upward and downward component, determined by species' specific leaf structure and pigment content should be taken into account in the upscaling of Chl fluorescence from leaf to canopy level and when interpreting the top of canopy Chl fluorescence emittance. A correct estimation of canopy structural parameters (e.g. leaf area index, leaf angle distribution) through reflectance data is necessary for the interpretation of the Chl fluorescence signal obtained via remote sensing;
• It was demonstrated that atmospheric pollutants derived from fuel combustion by motorized traffic (i) can lead to modifications of the physiological functioning of higher plants. (ii) The examined species elicit various responses to traffic exposure;
• A detailed Chl map of the city of Valencia, except for use with species with palm-like leaves, based on a robust empirical relationship in urban environments between crown Chl measurements and NAOC index retrieved from high spatial reoslution hyperspectral CASI imagery;
• Identification on the map of trees with low crown Chl levels. These trees indicate areas with a low urban habitat quality and high urban traffic density.