6
Tau me Terradas
sources of information on the floristic composition of holm oak forests are
phytosociological studies, which are very detailed in the western part of the
Mediterranean Basin. Broadleaved evergreen associations are grouped in the
Quercetalia ilicis order, with the alliances Quercion ilicis and Oleo-Ceratonion
corresponding respectively to the areas where holm oak forests and Pistacia
lentiscus maquis are dominant in the western Mediterranean.
Holm oak forests are complex, rather diverse ecosystems, with a relatively
high degree of specificity, at least in their floristic composition. BraunBlanquet (1936) considers that a plot of 100 m 2 is usually needed to have a
good representation of the normal specific composition of holm oak forests:
in the Viburno-Quercetum ilicis (= Quercetum ilicis gallo-provinciale) association, there is an average of 34.7 vascular plant species per releve, whereas
at higher altitudes, above 400-500 m, holm oak forests of the AsplenioQuercetum ilicis (= Quercetum mediterraneo-montanum) association become
poorer in vascular plant species but richer in macrofungi.
Dense holm oak forests have usually a dominant tree layer 6-12 m high. In
many cases, mixed forests of holm oak with Pinus halepensis or P. pinea occur, pines being frequently taller. A lower tree layer can be formed by Arbutus
unedo and Phillyrea latifolia ssp. media (3-5 m). An upper shrub layer can
contain other species such as Viburnum tin us, Rhamnus alaternus and Pistacia lentiscus. Also, vines (evergreen or deciduous) like Hedera helix, Smilax
aspera, Clematis flammula, C. vitalba, Lonicera spp., Rosa spp., Rubia peregrina, Asparagus acutifolius or ramus communis can be an important part of
the system, mainly in coastal, relatively moist habitats, and give it a quasitropical appearance. The lower shrub layer is characterized mainly by Ruscus
aculeatus. The grass layer rarely reaches a 30% cover, including sometimes
Hedera helix as an important component.
In the reI eve table of holm oak forests provided by Braun-Blanquet (1936)
the dominant plant life forms are evergreen and deciduous phanerophytes
(37 and 17%, respectively, of the listed species), and hemicryptophytes
(24%), followed by chamaephytes (9%), geophytes (9%) and therophytes
(4%). This is a very different composition from that of a temperate deciduous
forest, a beech forest for instance, where hemicryptophytes and geophytes
can represent over 90% of the number of species present. Nevertheless, there
is a gradual transition between holm oak and deciduous oak forests. In the
montane communities, the vertical structure is simpler, the lower tree layer
disappears and the number of vine species decreases, whereas herbs greatly
increase. These changes show a transition to non-Mediterranean deciduous
forests patterns.
1.4 Biology of Holm Oak
According to Schwarz (1964) and d' Amaral Franco (1983), holm oak is a
monoecious, wind-pollinated oak tree included in the subgenus Sclerophyl-
Tau me Terradas
sources of information on the floristic composition of holm oak forests are
phytosociological studies, which are very detailed in the western part of the
Mediterranean Basin. Broadleaved evergreen associations are grouped in the
Quercetalia ilicis order, with the alliances Quercion ilicis and Oleo-Ceratonion
corresponding respectively to the areas where holm oak forests and Pistacia
lentiscus maquis are dominant in the western Mediterranean.
Holm oak forests are complex, rather diverse ecosystems, with a relatively
high degree of specificity, at least in their floristic composition. BraunBlanquet (1936) considers that a plot of 100 m 2 is usually needed to have a
good representation of the normal specific composition of holm oak forests:
in the Viburno-Quercetum ilicis (= Quercetum ilicis gallo-provinciale) association, there is an average of 34.7 vascular plant species per releve, whereas
at higher altitudes, above 400-500 m, holm oak forests of the AsplenioQuercetum ilicis (= Quercetum mediterraneo-montanum) association become
poorer in vascular plant species but richer in macrofungi.
Dense holm oak forests have usually a dominant tree layer 6-12 m high. In
many cases, mixed forests of holm oak with Pinus halepensis or P. pinea occur, pines being frequently taller. A lower tree layer can be formed by Arbutus
unedo and Phillyrea latifolia ssp. media (3-5 m). An upper shrub layer can
contain other species such as Viburnum tin us, Rhamnus alaternus and Pistacia lentiscus. Also, vines (evergreen or deciduous) like Hedera helix, Smilax
aspera, Clematis flammula, C. vitalba, Lonicera spp., Rosa spp., Rubia peregrina, Asparagus acutifolius or ramus communis can be an important part of
the system, mainly in coastal, relatively moist habitats, and give it a quasitropical appearance. The lower shrub layer is characterized mainly by Ruscus
aculeatus. The grass layer rarely reaches a 30% cover, including sometimes
Hedera helix as an important component.
In the reI eve table of holm oak forests provided by Braun-Blanquet (1936)
the dominant plant life forms are evergreen and deciduous phanerophytes
(37 and 17%, respectively, of the listed species), and hemicryptophytes
(24%), followed by chamaephytes (9%), geophytes (9%) and therophytes
(4%). This is a very different composition from that of a temperate deciduous
forest, a beech forest for instance, where hemicryptophytes and geophytes
can represent over 90% of the number of species present. Nevertheless, there
is a gradual transition between holm oak and deciduous oak forests. In the
montane communities, the vertical structure is simpler, the lower tree layer
disappears and the number of vine species decreases, whereas herbs greatly
increase. These changes show a transition to non-Mediterranean deciduous
forests patterns.
1.4 Biology of Holm Oak
According to Schwarz (1964) and d' Amaral Franco (1983), holm oak is a
monoecious, wind-pollinated oak tree included in the subgenus Sclerophyl-