Use of Fire Regimes at the Ecoregion
Scale
13
Fire-excluded ecosystems are prone to changes
in composition and density and are susceptible to
catastrophic fire and invasion by nonnative species. The cause of the problem in many areas
includes more than a century of fire exclusion
and suppression along with increased human
development at the wildland-urban interface.
Grazing and logging have also contributed to
this problem.
To correct this problem, fire and land management must return ecosystems to a
healthier, sustainable condition. One way to
do this is to modify the current structure of
ecosystems to mimic natural structures (cf.,
Bailey 2002).
13.1 Ecosystem Structure and
Process
Ecosystem structure and process are related.
For example, riparian forests evolved with
flooding and fire-adapted forests evolved with
fire. However, the frequency of flood or fire
may vary place to place and year to year or
even decade to decade; and the intensity may
vary flood to flood or fire to fire. For
ecosystems to sustain natural structures, they
will need to experience the same kinds of processes in which they evolved (Allen et al. 2002;
Savage 2003).
13.2 Range of Variation
Restoration works best if ecosystems are
returned to within a “natural range of variation”
(Landres et al. 1999). Ecosystems, for example,
not only have variability through time because of
climate change, but also across the landscape and
the nation because of disturbance events, successional processes, and natural climatic variation
as distinct from climate change. From forests to
desert to steppe, the continent’s ecosystems vary
vastly. It is not possible to reconstruct how each
system looked in the past. Instead, we can
reset altered ecosystems back to within a range
of natural variability. As Savage (2003) puts it,
“If we can restore the natural processes, the natural structure should follow.”
It seems reasonable that regions differing substantially in background climate should therefore
have different fire regimes. In fact, fires burn
with more or less regular rhythms. The simplest
means to reveal a fire regime is to consider the
distribution of water within an ecosystem. If they
are too wet, they won’t burn. The ecosystem’s
moisture changes with the daily and seasonal
fluxes of the moisture of air masses as they
move through the region. Long-term fire records
around the Pacific Ocean trace nicely the pulses
of the Pacific Decadal Oscillation. In this oscillation, the Pacific alternates from warm to cool
phases and causes wet and dry periods on the
adjacent North American continent. These
R.G. Bailey, Ecoregions, DOI 10.1007/978-1-4939-0524-9_13, # Springer Science+Media, LLC 2014
127
Scale
13
Fire-excluded ecosystems are prone to changes
in composition and density and are susceptible to
catastrophic fire and invasion by nonnative species. The cause of the problem in many areas
includes more than a century of fire exclusion
and suppression along with increased human
development at the wildland-urban interface.
Grazing and logging have also contributed to
this problem.
To correct this problem, fire and land management must return ecosystems to a
healthier, sustainable condition. One way to
do this is to modify the current structure of
ecosystems to mimic natural structures (cf.,
Bailey 2002).
13.1 Ecosystem Structure and
Process
Ecosystem structure and process are related.
For example, riparian forests evolved with
flooding and fire-adapted forests evolved with
fire. However, the frequency of flood or fire
may vary place to place and year to year or
even decade to decade; and the intensity may
vary flood to flood or fire to fire. For
ecosystems to sustain natural structures, they
will need to experience the same kinds of processes in which they evolved (Allen et al. 2002;
Savage 2003).
13.2 Range of Variation
Restoration works best if ecosystems are
returned to within a “natural range of variation”
(Landres et al. 1999). Ecosystems, for example,
not only have variability through time because of
climate change, but also across the landscape and
the nation because of disturbance events, successional processes, and natural climatic variation
as distinct from climate change. From forests to
desert to steppe, the continent’s ecosystems vary
vastly. It is not possible to reconstruct how each
system looked in the past. Instead, we can
reset altered ecosystems back to within a range
of natural variability. As Savage (2003) puts it,
“If we can restore the natural processes, the natural structure should follow.”
It seems reasonable that regions differing substantially in background climate should therefore
have different fire regimes. In fact, fires burn
with more or less regular rhythms. The simplest
means to reveal a fire regime is to consider the
distribution of water within an ecosystem. If they
are too wet, they won’t burn. The ecosystem’s
moisture changes with the daily and seasonal
fluxes of the moisture of air masses as they
move through the region. Long-term fire records
around the Pacific Ocean trace nicely the pulses
of the Pacific Decadal Oscillation. In this oscillation, the Pacific alternates from warm to cool
phases and causes wet and dry periods on the
adjacent North American continent. These
R.G. Bailey, Ecoregions, DOI 10.1007/978-1-4939-0524-9_13, # Springer Science+Media, LLC 2014
127