Agriculture Reference
In-Depth Information
Fire in MTC Woodlands and Forests
The mesic MTC woodlands and forests of
Nothofagus
in south-central Chile
(Regiones VIII and IX) remain poorly known with respect to fire regimes and
fire history. Forests of
N. glauca
in the Coastal Cordillera experience a low incidence
of lightning and thus fire as likely as not has been a factor in natural disturbance
regimes. However, extensive clearing of these forests in recent decades for the esta-
blishment of Monterey pine plantations, often utilizing burning, has led to an
increased occurrence of fire with destructive impacts on vegetation structure and
soil characteristics (San Martin & Donoso
1995
; Litton & Santilices
2002
,
2003
).
Fire in Austral Forests
Fire has long been a natural disturbance regime in many austral forests
(Regiones IX and X), especially in areas dominated by coniferous species
(Aravena
et al.
2003
), although with a geographic gradient in the frequency of
fire from west to east. There is evidence of fires dating back to the beginning of the
Holocene (Moreno
2000
; Abarzu´ a & Moreno
2008
; Markgraf
et al.
2009
). Much
of what is known about fire history comes from studies not in Chile but across the
Andes in adjacent areas of Argentina where lightning-ignited fires from summer
convective storms are relatively common compared with fire frequency to the west
of the Andes (Kitzberger
et al.
1997
; Veblen
et al.
1999
,
2003
,
2008
; Mermoz
et al.
2005
). Nevertheless, there was widespread clearing and burning of forests over
much of the austral forest area by European settlers in the late nineteenth
century (Armesto
et al.
2010
). These fires have had very profound effects on
forest distribution and composition. Under reduced fire frequency over the
past century there has been a shift in dominance from short-lived resprouting
species (mostly shrubs) toward longer-lived species such as
Austrocedrus
chilensis
and
Nothofagus dombeyi
. Due to limited seed dispersal of these tree
species, the spatial configuration of remnant forest patches has played
a significant role in influencing current landscape patterns (Kitzberger &
Veblen
1999
,
2003
).
Fire is clearly an important component of the disturbance regime of
Austroce-
drus chilensis
on the eastern slopes of the Andes in Argentina. Regeneration of
Austrocedrus
in burned areas is very slow, and may depend on a series of environ-
mental and biotic factors, among which the availability of seeds could be
extremely important because of a variable soil seedbank that is greatly influenced
by the degree of fire disturbance (Urretavizcaya & Defosse
2004
; Urretavizcaya
et al.
2006
). Fire is certainly much less common in stands of
Austrocedrus
on the
west face of the Andes in Chile.
Historical records and tree ring reconstructions have been used to establish a
550-yr chronology of fire history of
Austrocedrus
stands on the east slope of the
Andes in Argentina (Kiztberger
et al.
1997
; Kitzberger & Veblen
1997
; Veblen
et al.
1999
,
2003
,
2008
) Long-term records suggest that El Nin˜ o-Southern Oscillation
