Agriculture Reference
In-Depth Information
14
Climate, Fire and Geology in the
Convergence of Mediterranean-type
Climate Ecosystems
Integrating Climate, Fire and Geology in a Fire-prone World
Fire challenges the long-standing hegemony of ecology, biogeography and paleo-
ecology that climate and soils are sufficient to explain the origin and distribution
of plant species. In a world where half of the land surface is fire-prone (Krawchuk
et al.
2009
), understanding the past and predicting the future requires a close
integration of climate, fire and geology. The dogma that fire is an anthropogenic
phenomenon of little use in understanding paleoecology (Axelrod
1980
,
1989
), or
merely incidental to vegetation development (Hopper
2009
), is rapidly being
replaced with a better understanding of paleofire's impact on land plant evolution
(Scott
2000
; Pausas & Keeley
2009
). Attempts to model future global vegetation
patterns have been demonstrated to be inadequate without including both natural
and anthropogenic fire regimes (Bond
et al.
2005
).
Bond and Keeley (
2005
) outlined the conundrum posed by alternative explan-
ations for the present distribution of vegetation and assembly of communities.
Classical explanations have invoked resource-based mechanisms that are driven
by climate and soils. There are ecosystems where resource-based mechanisms may
be sufficient, but on many seasonally dry landscapes ecosystem processes such as
fire play a major role in the organization and evolution of vegetation.
The evidence in favor of resource-based explanations is formidable, but the
nexus between theory and evidence is largely correlative and not generally
informative about the importance of unrecognized sources of influence. For
example, many vegetation boundaries commonly correspond to measured or
perceived edaphic and climatic disjunctions such as the close relationship between
sclerophyllous vegetation and mediterranean-type climates (MTCs). Although
anomalies occur, these are often disregarded as unimportant exceptions, whereas
here we maintain that in MTC ecosystems in particular, and many other ecosys-
tems as well, fire is a critical factor that interacts with climate and geology to affect
plant traits, community assembly and ecosystem functioning.
There is widespread empirical and theoretical evidence that fire is an essential
factor determining species and community dynamics through time. For example,
fire regimes at continental and global scales covary strongly in concert with
climatic and vegetation patterns (Archibald
et al.
2009
; Bradstock
2010
), suggest-
ing that syndromes of productivity and fire weather determined, in part, by
