Introduction

Mediterranean-type ecosystems occur in areas characterized by winter rainfall and summer drought. Five ecoregions of the world possess a Mediterranean climate and form the Mediterranean biome: the Mediterranean Basin, California (see Chaparral), central Chile, the southern and southwestern Cape Province of South Africa (SW Cape), the southwestern and parts ofsouthern Australia (SW Australia) (Table 1). These Mediterranean ecoregions are all centered between 30° and 40° north or south of the equator, and are exposed to similar atmospheric and oceanic circulation patterns with cool ocean currents. Mediterranean ecoregions occur only along the

Table 1 Main environmental characteristics and major ecosystem-types of the Mediterranean ecoregions

North Hemisphere

South Hemisphere

Mediterranean Basin

California

Central Chile

SW Australia

Cape Region

Surface (km2)

2 300000

324000

140000

310000

90000

Topographic

High

High

Very high

Low

Moderate

heterogeneity

Climatic

Very high

Very high

High

Moderate

High

heterogeneity

Rainfall reliability

Moderate

Low

Very high

High

Main lithological

Calcareous rocks, occasional

Argillaceous and mafic igneous

Argillaceous and mafic igneous

Siliceous rocks (sandstones,

Siliceous, argillaceous and mafic

substrates

siliceous rocks

rocks, occasional ultramafic rocks

rocks

quartzites)

igneous rocks

Soil fertility

High-moderate

Moderate

High

Very low-low

Very low-moderate

Natural fire

25-50

40-60

Fire free

10-15

10-20

frequency

(year)

Forests and

Very diverse and heterogeneous;

Diverse forests with thermophilous

Very diverse, with semiarid Acacia

Patchy and open woodlands

Very patchy and scarce forests;

woodlands

with many sclerophyllous

conifers (Pinus attenuata, P.

caven and Prosopis chilensis

dominated by Eucalyptus (E.

composed of cool and humid

(Quercus ilex, Q. suber) and

sabiniana, Cupressus

forests in the north; subtropical

diversicolor, E. marginata); low

Afromontane plants, with warm

broad-leaved oaks (Quercus

macrocarpa) and oaks (Quercus

broad-leaved and sclerophyllous

woodlands with Banksia; thickets

subtropical elements;

pubescens, Q. faginea, Q.

douglasii, Q. agrifolia, Q. lobata),

forests with Peumus boldus and

with Acacia, Melaleuca, and

sclerophyllous trees and conifers

ithaburensis), and conifers (Pinus

and mesophilous conifers (Abies,

Cryptocarya alba in the central

Allocasuarina

(Afrocarpus, Podocarpus)

halepensis, P. brutia, Cedrus

Pinus...) at higher altitudes;

region; deciduous Nothofagus

atlantica, C. libani, Abies,

coast redwood (Sequoia

forests farther south, with

Juniperus)

sempervirens)

Araucaria araucana

Shrublands

Maquis with Erica, Arbutus on

Chaparrals with Adenostoma

Open shrubland with Acacia caven

Kwongan and scrub-heaths with

Fynbos with major plant types:

siliceous soils; garrigues with

(chamisal), Arctostaphylos

(espinal); matorrals with Lithraea

Proteaceae (Banksia, Grevillea,

restioids (Restionaceae),

Quercus coccifera, Cistus, Ulex,

(manzanita chaparral),

caustica, Quillaja saponaria;

Hakea) and ericoids plants

ericoids, proteoids (Proteaceae)

on calcareous soils; phryganas

Ceanothus, scrub oaks (Quercus

coastal matorrals with cacti

(Epacridaceae); mallee

and geophytes; renosterveld

with spiny shrubs

dumosa); coastal scrubs with

(Trichocereus) and bromeliads

dominated by shrubby

dominated by ericoids

(Sarcopoterium, Astragalus,

Artemisia, Baccharis, Salvia

(Puya)

Eucalyptus (E. incrassata, E.

(renosterbos: Elytropappus);

Genista)

oleosa, E. socialis)

succulent karoo with Aizoaceae

Grasslands

Very diverse grasslands with

Native perennial bunchgrasses with

Anthropogenic prairies with

Very scarce and patchy; grasslands

Very scarce, fire-prone grasslands

numerous annuals and

Stipa, Poa and Koeleria, replaced

numerous European herbs and

on granite outcrops with annual

and grassy shrublands

perennials herbs (Poaceae,

by annual grasslands with forbs

grasses; wet grasslands with

everlastings (Helichrysum;

dominated by geophytes

Fabaceae, Asteraceae); steppes

(Avena, Bromus, Lolium,

native Juncus procerus

Helipterum) or perennial

with Stipa tenacissima and

Erodium)

Lechenaultia

Lygeum spartum in North Africa

Data from Davis GWand Richardson DM (1995) Ecological Studies, Vol. 109: Biodiversity and Ecosystem Function in Mediterranean-Type Ecosystems. Berlin and Heidelberg: Springer; Cowling RM, Rundel PW, Lamont BB, Arroyo MK, and Arianoutsou M (1996) Plant diversity in Mediterranean-climate region. Trends in Ecology and Evolution 11: 362-366; Cowling RM, Ojeda F, Lamont BB, Rundel PW, and Lechmere-Oertel R (2005) Rainfall reliability: A neglected factor in explaining convergence and divergence of plant traits in fire-prone Mediterranean-climate ecosystems. Global Ecology and Biogeography 14: 509-519; Dalmann PR (1998) Plant Life in the World's Mediterranenan Climates. Oxford: Oxford University Press. Medail, ined.

western sides of continents, and occupy limited areas between deserts and temperate regions.

The most typical characteristics of Mediterranean ecosystems, compared to temperate or boreal biomes, are their spatial and temporal complexity inducing strong heterogeneities, in terms of physical factors (geography, geology, geomorphology, pedology, bioclimate) and of their biological components and species life-history traits. Paleogeographical and historical episodes, current geographical and climatic contrasts have molded both an unusually high biodiversity and ecological complexity, and favored the emergence of a functional uniqueness for several ecosystems. High species-richness and endemism due to contrasted biogeographical origins, and original functional dynamics at local and landscape levels linked to stress effects, represent indeed key components of these ecosystems.

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