Agriculture Reference
In-Depth Information
Other vegetation types that rarely burn because of low fuel levels and low fuel
continuity are the scrublands that appear in semi-arid continental MTCs, forming
a transition toward the steppe (e.g. central Iberian and Anatolian peninsulas).
These low shrublands have been traditionally overgrazed and are thorny forma-
tions (
Genista
,
Sarcopoterium
), often with abundant aromatic plants (e.g.
Thymus
,
Rosmarinus
,
Salvia
). Toward the southern and eastern regions, with low rainfall,
vegetation is dominated by perennial grasslands such as
Stipa tennacissima
(tussock grass), together with some small shrubs (e.g.
Artemisia
). Cover is typically
low, and the bare soil between tussocks inhibits the spread of fires. Where aridity
is combined with high water table, salt bushes (e.g.
Atriplex
,
Salsola
,
Suaeda
)
appear extensively. Another semi-arid community found in northern Africa is
the woodland dominated by
Acacia gummifera
, which yields abundant gum
marketed locally and is the only species of this genus that can be considered to
reach the Mediterranean Basin, in a transition toward desert vegetation.
In Mediterranean Basin mountains a number of winter semi-deciduous (mar-
cescent) oaks are common that are within the MTC and form a transition to
temperate forests. These may coexist with evergreen oaks in moist gullies and
pole-facing slopes or with deciduous oak woodlands. Examples are
Quercus
faginea
,
Q. cerrioides
,
Q. pyrenaica
and
Q. canariensis
in the west, and
Q. ithabur-
ensis
and
Q. infectoria
in the east. Typical/fully winter-deciduous species also occur
in the basin, but are restricted to especially mesic sites and include oak woodlands
of
Q. pubescens
(
Q. humilis
),
Q. frainetto
,
Q. trojana
,
Q. petrea
and communities
of
Ostrya carpinifolia
,
Carpinus orientalis
,
Fraxinus ornus
,
Sorbus
,
Acer
,
Aesculus
.
Sweet chestnut or
Castanea sativa
woodlands also occur in sub-mediterranean
environments; this deciduous species is considered indigenous to the Balkan
peninsula and northern Turkey but it is widespread and naturalized throughout
southern Europe. Most of these deciduous species are resprouters and have been
coppiced for a long time and fires are very rare. The Italian chestnut and pasture
landscapes are the product of a historical management based on burning the dead
leaves on the floor to promote pasture under trees (Grove & Rackham
2001
).
At the tops of mountains and ridges, where wind is a limiting factor, together
with grazing, spiny cushion-shaped dwarf shrubs with
Erinacea
species and
Juni-
perus sabina
form oro-mediterranean communities. Fuels are low and discontinu-
ous and fires are small and infrequent.
Riparian vegetation in the north and at high altitudes, with constant water
flows, may seldom be subjected to fires and these sites sometimes act as refugia
for temperate deciduous trees at their southernmost boundaries or Tertiary
(see
Fig. 9.1
) relict species like the
Liquidambar orientalis
(Altingiaceae, Turkish
sweetgum). These riparian ecosystems also harbor high biodiversity because they
provide refugia for species near the edge of their distribution (Hampe & Petit
2005
). Under drier conditions in the lowlands and further south, water flow is
seasonal and may dry sufficiently to carry fire. As with woody riparian species
throughout the world these trees are obligate resprouters and include
Nerium
oleander
, species of
Salix
,
Populus
and
Ulmus
. Resprouting in these lineages may
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