Mediterranean-type Climate Ecosystems and Fire - Fire in Mediterranean Ecosystems - page 24

Table 1.2 Floristic comparisons of the shrubland plant families dominant in the five MTC regions of the world

Mediterranean California Chile South Africa Australia

Anacardiaceae Anacardiaceae Anacardiaceae Asteraceae Casurinaceae

Cistaceae Ericaceae Asteraceae Ericaceae Ericaceae

Ericaceae Fabaceae Fabaceae Fabaceae Fabaceae

Fabaceae Fagaceae Fagaceae Proteaceae Myrtaceae

Fagaceae Rhamnaceae Lauraceae Rhamnaceae Proteaceae

Rhamnaceae Rosaceae Rhamnaceae Rutaceae Xanthorrhoeaceae

genera and most of the same families ( Table 1.2 ). At the most arid end of the
gradient are low stature semi-deciduous sage scrub shrublands and these are
displaced by larger stature evergreen sclerophyllous-leaved chaparral shrublands
( Fig. 1.6c ) on north-facing slopes near the coast, and on most slope faces between
roughly 600 m and 1500 m (Keeley 2000 ). Many shrub species resprout after fire
and some have lignotubers, but a substantial number of species do not resprout
and regenerate after fire strictly by seeds. Shrublands form complex mosaics with
evergreen oak woodlands and alien-dominated annual grasslands . Above about
1500 m shrublands give way to forests with a mixture of deciduous hardwoods
( Quercus kelloggi ) and pines ( Pinus ponderosa ), and higher still mixed conifer forests
( Fig. 1.7a ) that include other pines, firs ( Abies ) and several other conifer genera
(Holland & Keil 1995 ).
East of the California Floristic Province on the rain shadow side of the interior
mountain ranges are desert scrub types that are generally not considered part of
the MTC due to very low rainfall, which is exceeded by the rainy season potential
evapotranspiration (Rundel 2010 ). On these landscapes the MTC summer
drought dominates the climate and this drought pattern continues further north
into eastern Washington and Idaho. In the southwestern USA chaparral
shrublands occur in disjunct pockets in central and southern Arizona, which has
bimodal annual rainfall (Fotheringham 2009 ), and in the eastern Sierra Oriental
of mainland Mexico with winter drought and summer rain (Keeley 2000 ). Similar
fire-prone MTV shrublands continue eastward controlled largely by edaphic
conditions (Menges & Kohfeldt 1995 ; Carrington & Keeley 1999 ). Evergreen
sclerophyllous forests dominated by the genus Pinus are widely distributed
in non-MTC regions of western North America and further east along the south-
ern part of the USA, forming similar fire-prone forests to those in the MTC
(e.g. Platt 1999 ). This extension of MTV far outside strictly MTC regions illustrated
by Pinus resembles a similar pattern with evergreen sclerophyllous Eucalyptus in
Australia.
In California along the elevational gradient as shrublands merge into wood-
lands and then into forests, fuel structure changes markedly, as do fire regimes
(see Chapter 2 ). The lower elevation chaparral burns in high-intensity crown fires
whereas the forests are more prone to low-intensity surface fires. The proportion
of human-ignited fires vs. lightning-ignited fires varies from mostly human