Chlorophyll fluorescence for phenotyping drought-stressed trees in a mixed deciduous forest

Among the environmental constraints affecting growth, productivity and health of crops and forests ecosystems, drought is known to be a key factor particularly in the Mediterranean area, where the typical dry and hot summer conditions may be exacerbated as a consequence of the foreseen Global Climatic Changes. Despite the drought stress response of forest trees has been intensively investigated, phenotyping for functional traits associated to drought adaptation in the field still remains particularly challenging, due to the intrinsic difficulties in screening tall trees in forest environment. In this work, we have applied a high-throughput phenotyping approach to investigate the drought response of two coexisting deciduous tree species (Quercus cerris L. and Fraxinus ornus L.) in a natural mixed forest (Circeo National Park, Central Italy). Our results have shown that the measurement of Chlorophyll fluorescence with the JIP-test application is particularly suitable for phenotyping the drought stress response of adult trees in the field. In particular, among the phenotypic traits investigated, the Total Photosynthetic Performance Index (PITOT) has proven to be the most suitable non-invasive marker of plant response to drought, which is able to provide reliable, fast and synthetic information on plant ecophysiological status.