CROWN STATUS OF HOLM OAK (QUERCUS-ILEX L) TREES AS RELATED TO PHENOLOGY AND ENVIRONMENTAL-STRESS

In order to study the possible interactions between air pollution and climate conditions in Mediterranean evergreen broadleaf species, since 1987 we have been monitoring the annual and infra-annual variations i n crown density of Quercus ilex L, (holm oak) in a permanent sample pl ot. The behaviour of crown density has bear compared with litterfall p attern and aging processes in leaves. The results of this study confir m the important impact of climate on crown condition in Mediterranean broadleaves, so that even the role of non-acute pollution can be disgu ised. Xeromorph adaptations in helm oak leaves are also a mechanism pr oviding a greater protection against pollutants.