Agriculture Reference
In-Depth Information
Box 1.1 (
cont.
)
about midway between summer and winter. In addition, between MTC regions
there is much variation inmean winter and summer temperatures (
Table B1.1.1
).
Rainfall reliability appears to vary across MTC regions and it has been
hypothesized to account for differences in fire responses (Cowling
et al
.
2005
), although most fire-related traits likely predate current precipitation
regimes (see
Chapter 10
). The impact of regional differences in rainfall patterns
needs to be considered in the context of differences in substrate (see
Fig. 1.5
)
and topography, all of which affect soil water-holding capacity and may select
for differences in drought tolerance between plant taxa in different MTC. The
nexus between climate and fire is complicated and needs to be considered in a
multivariate context.
The boundaries around MTC regions are not uniformly agreed upon by all
sources. Some limit MTC to areas that not only exhibit the characteristic
winter rain/summer drought pattern but include total precipitation limits
and temperature limits. A more liberal interpretation than used in this topic
would include much greater portions of southwest Asia in the Mediterranean
Basin, a substantially greater part of the Pacific Northwest and Great Basin
in western North America, much of the eastern foothills of Argentina in
South America, and portions of New South Wales and Victoria in Australia
(Le Houerou
2004
).
Fig. 1.3
Global distribution of fire-prone and fire-free landscapes
.
(From Krawchuk
et al.
2009
.
)
common in MTC regions and are interpreted as responses to low rainfall and low
nutrient availability (Yates
et al
.
2010
). However, small leaves also increase
flammability and thus, as selection for small sclerophyll leaves increases, land-
scape flammability increases, affecting ignitions and fire spread, and the predict-
ability of fire in the environment, which in turn affects trait selection (e.g. Ojeda
et al
.
2010
).
The thesis of this topic is that explaining the origin of plant traits and assembly
of communities based on climate and/or geology alone is inadequate, particularly
