Quality assessment of urban trees: A comparative study of physiological characterisation, airborne imaging and on site fluorescence monitoring by the OJIP-test

The purpose of this paper is to demonstrate the complementary utility of chlorophyll fast fluorescence OJIP transient (from 50 mus to 1 s) measurements in the aerial study of rows of trees. We identify limitations in photochemical events induced by urban injuries on Platanus acerfolia L., using the JIP-test procedure. The Performance Index (PIABS) showed the largest dynamic range to characterise the vitality of trees. Individual trees were graded into three quality groups based on the individual PIABS value compared to the overall average for trees in the alley. These groups are: high performers, with PIABS 50 % higher than the alley average; normal trees, with a deviation from the alley average between -50 % and +50 %; and poor performers, whose deviation from the alley average was -50 % or less. Trees also were grouped into five vitality categories on the basis of a stereoscopic and morphologic observation of the symmetry of tree crowns, percentage of defoliation and reflectance property in the visible and infra-red range. Here, we report a remarkable correlation between the airborne remote sensing data and the on-site fluorescence measurements.