REFLECTANCE ASSESSMENT OF SUMMER OZONE FUMIGATED MEDITERRANEAN WHITE-PINE SEEDLINGS

Seedlings of Pinus halepensis L. grown for three summers in open top c hambers (OTC) in Northeastern Spain were exposed to three ozone (O-3) treatments: charcoal filtered air (CA), non-filtered (NF) and non-filt ered plus 40 nl l(-1) O-3 (FU). Ambient air plots (AA) in open air wer e established to assess the chamber effect A clear seasonal trend was found in the physiological response of these pine seedlings in summer periods, with lower needle chlorophyll concentrations, and higher abso rbance ratios for wavelengths at 435 nm and 665 nm (A435/A665) which i s indicative of carotenoid/chlorophyll a ratio. Old needles from the F U treatment had lower chlorophyll content and higher absorbance ratios (A435/A665) than those of other treatments. Spectral reflectance indi ces assessing green biomass (NDVI), chlorophyll concentration ('red ed ge'), the carotenoid/chlorophyll ratio (SIPI), and photosynthetic effi ciency (SIXI) clearly followed the same seasonal trend, but were not s tatistically distinguishable from those of different ozone levels. The se results are attributable to the dominance by the young needles in t he sensor's field of view, which showed no clear biological difference s with ozone treatment. Only ambient air seedlings presented different values for the reflectance indices in consonance with their lower chl orophyll content and higher carotenoid/chlorophyll ratio.