Agriculture Reference
In-Depth Information
and a uniquely fire-adapted pine.
Pinus canariensis
(Canary Island pine) is a
long-lived tree with thick bark and serotinous cones, and a strong resprouting
capacity from epicormic buds (Climent
et al.
2004
), a trait that is rather rare in
pines and other gymnosperms (Keeley & Zedler
1998
). Fires are frequent due to
lightning and possibly volcanic activity and this pine has the capacity to regenerate
its crown rapidly following crown fires, not unlike many Australian eucalypts
(see
Chapter 3
).
Other Mediterranean Basin Vegetation Types that Rarely Burn
One type of oak woodland that rarely burns is the
dehesa
(Spain) or
montado
(Portugal) on the Iberian Peninsula. These are mainly open oak woodlands or
savannas of anthropogenic origin (Klein
1920
; Stevenson & Harrison
1992
). They
are dominated mainly by evergreen oaks (
Q. ilex
ssp.
ballota
,
Q. suber
) although
deciduous oaks may also be common (
Q. pyrenaica
,
Q. faginea
). These woodlands
were traditionally used for raising livestock such as cows, sheep and pigs, and for
cultivation of cereal crops. The original natural vegetation is, in most cases, oak
woodlands that were modified by thinning, leaving trees for acorn production and
shade for livestock, or for cork production in
Q. suber dehesas
. The consequence
of this agroforestry system is that the oaks in
dehesas
are aging with a lack of
regeneration (Pulido
et al.
2003
; Pausas
et al.
2009
). In these ecosystems intense
grazing reduces the herbaceous surface fuels required to carry fire. When grazing
is excluded, these open woodlands tend towards more close oak forests, and then
they can sustain crown fires. Some other species, such as
Olea europaea
var.
sylvestris
,
Arbutus unedo
,
Pistacia atlantica
,
Castanea sativa
or
Ceratonia siliqua
,
may also form
dehesas
in some places.
Argania spinosa
(the only member of the
Sapotaceae in the Mediterranean Basin) also forms
dehesa
-type woodlands in
western Morocco, in very warm areas with very low rainfall but high air moisture
from the Atlantic. The tree is grazed by goats, and the fruits are used as a source of
cooking oil and for cosmetics.
In the mountains and high plateaus, with cooler summers and colder winters,
occur weakly flammable woodlands dominated by conifers. These include
Juni-
perus phoenicea
(throughout the basin),
J. thurifera
(western basin),
J. excelsa
and
J. drupacea
(eastern basin),
Pinus sylvestris
and
P. uncinata
(Iberian mountains),
and other conifer species of restricted distributions like
Cedrus
(North Africa and
the Near East) and
Abies
(North Africa, Greece and southern Spain). These
conifers have no mechanism to persist after crown fires, and thus may have
historically suffered a very low frequency of crown fires with subsequent coloniza-
tion from the edges (Stahli
et al.
2006
). In the event fires are limited to understory
fuels, some of these species can survive such surface fires (
Fig. 4.8
; Vega
2000
).
Many of these conifers have been heavily logged for millenia, to be used in the ship
industry and house building, and their current distribution is dramatically
reduced.
