Agriculture Reference
In-Depth Information
(Keane
et al
.
2003
; Pausas
2006
; Pausas & Lloret
2007
). These models simulate
ecological succession scenarios based on different fire regime characteristics and
allow scientists to examine the relative role of different factors. For example, Cary
et al.
(
2006
) found that for five very different forest types, and with different
landscape models, predictions of fire activity were generally more sensitive to
variations in climate and weather than to complexity of the terrain or fuels.
Such landscape models are sometimes used to estimate fire sensitivity to predicted
climate change scenarios (Cary & Banks
1999
).
LANDIS is a forest succession model that predicts the impact of fire and other
disturbances on successional changes (Mladenoff
2004
). It has been modified for
crown fire shrublands and used to predict the impact of different fire frequencies
on plant life histories (Syphard
et al
.
2006
). FATELAND (Pausas
2006
)isa
landscape model that also includes a fire regime and a vegetation dynamics
simulator, and supports many types of vegetation. The vegetation dynamics of
this model are based on key plant functional attributes related to disturbance
(Noble & Slatyer
1980
; Moore & Noble
1990
), and thus it is very appropriate
for predicting vegetation changes in MTV under different disturbance regimes
(Pausas
et al.
2006c
; Pausas & Lloret
2007
).
Mediterranean-type Climate Ecosystem Fire Regimes
Mediterranean-type climate shrublands and woodlands are largely dominated by
crown fire regimes that have historically burned in high-intensity fires and these
ecosystems are remarkably resilient to such conditions. MTC savannas and some
forests are more commonly burned by low-intensity surface fires.
MTC vegetation is one of the most fire-prone ecosystems, perhaps only outdone
by tropical C
4
grasslands with their capacity for high annual production that
rapidly dries to become available fuels. In terms of woody-dominated vegetation,
MTC regions differ from other ecosystems in that the climate imposes an annual
fire risk, unlike other regions that may be dependent on infrequent decadal-scale
climate anomalies to create high fire danger.
MTC ecosystems illustrate the critical importance of seasonality in creating
highly fire-prone ecosystems. Sufficient primary productivity to fuel fires results
from the relatively moderate winter and spring growing conditions. At these
latitudes and with varying levels of marine influence, portions of these landscapes
typically initiate the growing season with the onset of rains and growth is sus-
tained in most years for 4-6 months. Thus, for part of the year these ecosystems
sustain productivity long enough to produce rather dense stands of contiguous
biomass of potential fuels. The predictable summer drought couples greatly
diminished rainfall with high temperatures, which together convert a substantial
fraction of these potential fuels into available fuels. The widespread importance
of high winds in many MTC regions further exacerbates the fire potential
(see
Box 1.3
).
