Holm Oak Trees Research Articles

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 in crown density of Quercus ilex L. (holm oak) in a permanent sample plot. The behaviour of crown density has been compared with litterfall pattern and aging processes in leaves. The results of this study confirm the important impact of climate on crown condition in Mediterranean broadleaves, so that even the role of nonacute pollution can be disguised. Xeromorph adaptations in holm oak leaves are also a mechanism providing a greater protection against pollutants.

Deposition on holm oak leaf surfaces of accidentally released radionuclides

The retention of aerosols by canopies of holm oak trees in a typical Mediterranean forest is studied. Firstly, dry deposition is measured both under and outside the canopy during several months. No clear differences are observed either in the amount or in the chemical composition of the particles collected under and outside the canopy. Secondly, the leaf morphology and anatomy as well as the aerosol deposited onto the leaf surfaces are studied by scanning electron microscopy. Cuticle thickness is measured and differences are observed between young and old leaves. The distribution of aerosol particles over leaf surface is also established. Finally, the possible incorporation into leaves of a radioactive aerosol released in an accidental situation is studied, by means of a sequential extraction procedure using water and an organic solvent. From the results it can be deduced that neither the abiotic layer nor the cuticle play any important role in the retention of caesium. The studied radionuclides are mainly found in particulate form, soluble in water, or incorporated into leaves.

Deposition on holm oak leaf surfaces of accidentally released radionuclides

The retention of aerosols by canopies of holm oak trees in a typical Mediterranean forest is studied. Firstly, dry deposition is measured both under and outside the canopy during several months. No clear differences are observed either in the amount or in the chemical composition of the particles collected under and outside the canopy. Secondly, the leaf morphology and anatomy as well as the aerosol deposited onto the leaf surfaces are studied by scanning electron microscopy. Cuticle thickness is measured and differences are observed between young and old leaves. The distribution of aerosol particles over leaf surface is also established. Finally, the possible incorporation into leaves of a radioactive aerosol released in an accidental situation is studied, by means of a sequential extraction procedure using water and an organic solvent. From the results it can be deduced that neither the abiotic layer nor the cuticle play any important role in the retention of caesium. The studied radionuclides are mainly found in particulate form, soluble in water, or incorporated into leaves.

Biogeografía y series de vegetación de la provincia de Málaga (España)

Se ha realizado una sectorización biogeográfica de la provincia de Málaga, reconociéndose 7 sectores y 12 subsectores. Se han identificado 18 series de vegetación; 11 de carácter climatófilo (encinares, alcornocales, quejigares, pinsapares, melojares y sabinares) y 7 de carácter edafófilo (sabinares, pinares, pinsapares y acebuchales). Se describen dos subasociaciones nuevas: Chamaeropo humilis-Juniperetum phoeniceae genistetosum haenselerii y Daphno latifoliae-Aceretum granatensis quercetosum alpestris.