1 Holm Oak and Holm Oak Forests: An Introduction
Jaume Terradas
Why should we study the Mediterranean evergreen forests of holm oak.
(Quercus ilex L.)? Besides the pursuit of knowledge, two major reasons can
be put forward. First, holm oak. forests are a dominant type of vegetation in a
transition zone between temperate forests, mostly dominated by deciduous
trees and the scrublands (maquis, chaparral, phrygana, etc.) that herald the
tropical regions. In this transition zone, plants have had to cope with a selective pressure resulting (rom a double stress - winter cold and summer
drought - that has determined their morphological and ecophysiological
evolutive responses. One of our aims is to provide an insight into the features
of holm oak. as related to environmental factors and in comparison with
other tree types (broadleaved deciduous hardwoods, needle-leafed conifers).
Second, holm oak. is distributed throughout areas harbouring large human
populations, massive tourism and, in places, intense industrial activity. Furthermore, these are zones where we can reasonably expect a very sensitive
response to global change processes. Climate change could decrease water resources beyond the threshold of the forests' needs (Pinol et al. 1995) and the
resulting changes in landscape would be dramatic. The great number of
ecotones (favoured by a great heterogeneity in bedrocks and soils, and by a
steep terrain) along aridity gradients in the boundaries between shrub and
forest formations should be highly sensitive to change. Land use patterns are
also rapidly changing, mainly in two opposite directions for the north and
south rims of the Mediterranean Basin: land abandonment, with young,
poorly managed and fuel-accumulating forests in the north; and a fast increase in firewood extraction and unsustainable forest abuse in the south.
Wildfire frequency could increase due to higher temperature, higher evapotranspiration and increased human activities, accelerating these changes. An
understanding of forest function concerning aspects such as individual recruitment and mortality, canopy regeneration, hydrology, nutrient use, biodiversity and others would be essential to coping with all these future events
(Romane and Terradas 1992).
The aim of this chapter is to summarize the major ecological characteristics of holm oak. and holm oak forests. Many of these characteristics will be
Ecological Studies, Vol. 137
Ferran Roda et al. (eds) Ecology of Mediterranean
Evergreen Oak Forests
© Springer-Verlag, Berlin Heidelberg 1999
Jaume Terradas
Why should we study the Mediterranean evergreen forests of holm oak.
(Quercus ilex L.)? Besides the pursuit of knowledge, two major reasons can
be put forward. First, holm oak. forests are a dominant type of vegetation in a
transition zone between temperate forests, mostly dominated by deciduous
trees and the scrublands (maquis, chaparral, phrygana, etc.) that herald the
tropical regions. In this transition zone, plants have had to cope with a selective pressure resulting (rom a double stress - winter cold and summer
drought - that has determined their morphological and ecophysiological
evolutive responses. One of our aims is to provide an insight into the features
of holm oak. as related to environmental factors and in comparison with
other tree types (broadleaved deciduous hardwoods, needle-leafed conifers).
Second, holm oak. is distributed throughout areas harbouring large human
populations, massive tourism and, in places, intense industrial activity. Furthermore, these are zones where we can reasonably expect a very sensitive
response to global change processes. Climate change could decrease water resources beyond the threshold of the forests' needs (Pinol et al. 1995) and the
resulting changes in landscape would be dramatic. The great number of
ecotones (favoured by a great heterogeneity in bedrocks and soils, and by a
steep terrain) along aridity gradients in the boundaries between shrub and
forest formations should be highly sensitive to change. Land use patterns are
also rapidly changing, mainly in two opposite directions for the north and
south rims of the Mediterranean Basin: land abandonment, with young,
poorly managed and fuel-accumulating forests in the north; and a fast increase in firewood extraction and unsustainable forest abuse in the south.
Wildfire frequency could increase due to higher temperature, higher evapotranspiration and increased human activities, accelerating these changes. An
understanding of forest function concerning aspects such as individual recruitment and mortality, canopy regeneration, hydrology, nutrient use, biodiversity and others would be essential to coping with all these future events
(Romane and Terradas 1992).
The aim of this chapter is to summarize the major ecological characteristics of holm oak. and holm oak forests. Many of these characteristics will be
Ecological Studies, Vol. 137
Ferran Roda et al. (eds) Ecology of Mediterranean
Evergreen Oak Forests
© Springer-Verlag, Berlin Heidelberg 1999