Agriculture Reference
In-Depth Information
fires has occurred in recent years in Los Lagos Regio´ n of south-central Chile,
often in areas of secondary vegetation or in tree plantations. About 35% of the
fires occur in native forests and 15% in plantations of Monterey pine (
Pinus
radiata
)and
Eucalyptus
.
Humans are the cause of virtually all fires in central Chile. The high Andean
Cordillera to the east prevents summer convective thunderstorms from moving
westward from Argentina (see
Fig. 10.4
) and, as a result, lightning is rare to
virtually non-existent over much of the MTC region (Armesto & Gutie´ rrez
1978
; Montenegro
et al.
2003
). On a geological timescale this is a relatively recent
effect and lightning-ignited fires may have been relatively common in central Chile
through much of the Miocene, until the Late Miocene completion of the Andean
uplift formed an effective barrier to westward storms (see
Chapter 10
).
Historically the primary cause of fires in Chile has been accidental ignitions
associated with human traffic and transport through wildland areas, but
arson fires have become the primary cause in recent years. This increase in
intentional fires has been particularly evident in the forest lands and plantations
of south-central Chile.
As in other MTC regions of the world, fires in Chile include both stand-
replacement crown fires and lower-intensity ground fires. Fires in matorral shrub-
land, sclerophyll woodland, and young Monterey pine and
Eucalyptus
plantations
are characteristically intense stand-replacement fires that consume the majority of
aboveground biomass. Fire in the humid temperate forests of
Nothofagus
, mixed
evergreen trees and conifers are generally of low to moderate intensity and
consume understory vegetation without killing the forest canopy trees.
Fire in Matorral Shrublands
Natural disturbance regimes in the matorral have been altered greatly over the last
four and a half centuries since European settlement, due to land clearance, fire,
grazing, charcoal production and invasive herbivores such as the European rabbit
(Armesto
et al.
2010
).
As a consequence of the absence of natural fire as a major disturbance factor in
matorral, the flora shows fewer life history specializations to fire than found in the
other four MTC regions (Montenegro
et al.
2003
). For example, none of the
Chilean matorral shrubs have strict postfire seedling recruitment and there is no
postfire ephemeral flora as in other systems. However, fire-adaptive traits are not
entirely lacking either. There are a few annuals that do germinate in profusion
after fire (see
Loasa
sp. under the shrub skeleton in
Fig. 11.2
d), although not
strictly tied to fire. All shrubs resprout after fire (see
Table 3.1
; Araya & A
´
vila
1981
, Armesto & Pickett
1985
; Ginnochio
et al.
1994
; Montenegro
et al.
2003
).
Although resprouting
per se
is not unique to fire-prone environments, lignotubers
(see
Fig. 3.1
and
Table 3.2
), which are closely associated with fire-prone environ-
ments (see
Chapter 9
), are present as ontogenetic traits that develop early in seedling
growth in several woody Chilean matorral species (Hoffmann & Kummerow
