High-frequency seasonal variation of leaf fluorescence and reflectance in Mediterranean forest species under natural environmental conditions

Abstract The strategies of two evergreen Mediterranean tree species (Arbutus unedo L. and Quercus ilex L.) to face annual temperature variability and extreme event responses has been monitored in continuum by leaf fluorescence and reflectance. The effect of chilling spells and the accumulation of cold days with chilling and freezing temperatures on winter photo-inhibition was discussed in terms of modulation capacity for fluorescence parameters to daily temperature and irradiance conditions. Throughout the winter Q. ilex resulted less photoinhibited than A. unedo, showing a more dynamic response in all fluorescence parameters and a higher non-photochemical quenching capacity. These characteristics effectively act to maintain a higher electron transport capacity in Q. ilex than in A. unedo. The implications for adaptation to climate change in the two species are also discussed.