Agriculture Reference
In-Depth Information
Environmental
template
Climate
Fire
Geology
Functional
types
Feedback
processes
Flammability
traits
Biotic
interactions
Realized
niches
Community
assembly
Fig. 14.1
Schematic model of the environmental template and functional type evolution in
fire-prone landscapes.
climate are major influences on fire regimes (Pausas & Bradstock
2007
). However,
this is not just a story about how climate shapes fire, but how fire shapes vegeta-
tion, which in turn shapes fire regimes. Plant traits that affect flammability are one
of the clearest examples of feedback processes that can result in niche construction
(Bond & Midgely
1995
; Schwilk
2003
) and illustrate the inadequacy of a resource-
based theory to account for fire regimes and vegetation patterns. While inclusive
fitness theory can accommodate flammability, fires can only occur when sufficient
numbers of neighbors contribute to fire spread and here is where fire, climate and
geology meet in dictating fire regimes. Indeed, the size of fire-prone patches will
affect the probability of ignitions, as Wardle
et al.
(
1997
) has shown on islands,
and in this regard, soils and climate are important determinants of vegetation
patterns conducive to fire spread.
Thus, a comprehensive approach to understanding fire lies in an integration of
the interplay between climate, geological resources, fire-adaptive traits and phylo-
genetic legacies that place limits on potential plant functional types (
Fig. 14.1
).
A brief examination of the strengths and weaknesses of “resource” and “fire”
theories pinpoints the elements needed to develop a more integrated approach.
A strength of resource theory is the demonstrable correlation between patterns
of climate and soil variation and vegetation distributions and boundaries. Statis-
tical modeling based on these influences can be used to successfully predict
species and community distributions (Franklin
2010b
). Although such correlative
power is reassuring, mechanistic insights are limited. Models of this kind essen-
tially define realized niches of species and species combinations but give little
insight into potential niches. Factors such as fire may play a role in confining
species to particular realized niches in concert with other factors such as compe-
tition. A long-running debate about the determinants of rainforest distribution in
