Agriculture Reference
In-Depth Information
1
Mediterranean-type Climate
Ecosystems and Fire
This topic is about fire and the ecosystem role it plays in plant communities with
distributions centered in one of the five mediterranean-type climate (MTC)
regions of the world (
Fig. 1.1
). These landscapes are related by their marked
climatic seasonality, with precipitation in the winter under mild temperatures
and drought in the summer coupled with high temperatures (
Box 1.1
). MTCs
are regions where precipitation exceeds potential evapotranspiration during the
rainy season (Rundel
2010
), resulting in sufficient plant growth that becomes
highly flammable during the summer dry season, a unifying factor that has played
out in common ecological responses to fire. Collectively these regions comprise
only about 2% of the land area of the world but they house more than 15% of the
total vascular plant flora (Rundel
2004
). All are dominated by fire-prone
ecosystems often juxtaposed with major metropolitan centers (
Fig. 1.2
) and are
dominated by fire-adapted vegetation resulting from a long evolutionary associ-
ation with fire (Pausas & Keeley
2009
).
Although our focus is on the highly fire-prone landscapes with MTC, fire is
a global ecosystem process and one whose role in shaping the distribution of
fauna and flora is widely underappreciated. Over half of the land surface of
Earth is considered to be fire-prone (
Fig. 1.3
), with perhaps a third of the land
mass experiencing frequent intensive burning (Chuvieco
et al
.
2008
). The
emerging discipline of
pyrogeography
emphasizes the necessity for considering
fire in understanding local ecological interactions as well as global earth
system processes (Bowman
et al
.
2009
;Moritz
et al
.
2010a
). Fire is not a
new ecosystem process but rather one that has been part of land plant
evolution since the Paleozoic (Pausas & Keeley
2009
; Bond & Scott
2010
).
Historically the disciplines of ecology, biogeography and paleoecology have
considered climate and geology to be the key factors determining ecosystem
assembly and distribution.Butonmanyoftheselandscapesfireisafactorof
equal or greater importance and interactions between all three factors deter-
mine the potential pool of available functional types in both flora and fauna
(
Fig. 1.4
).
Through feedback processes fire, climate and geology are connected by different
functional types and attempts to understand community assembly without con-
sidering the interrelationships between these three factors may lead to misleading
conclusions about their origins and distribution. For example, small leaves are
