Agriculture Reference
In-Depth Information
Chile
Central Chile stands out among all MTC areas because natural fires are extremely
rare due to a general absence of lightning and other natural ignitions (see
Chapter 6
),
although this appears to be a relatively recent phenomenon beginning in the late
Tertiary (see
Chapter 10
). Thus, fire dynamics in central Chile provides an interest-
ing case study for evaluating the importance of fire on plant invasions (Pauchard
et al.
2004
,
2008
). Relatively few data are available on the interactions of alien
species and fire in central Chile, but it appears that frequent fire in matorral does
favor alien over native herbaceous species (A
´
vila
et al.
1981
;Sax
2002
). Matorral
and chaparral share a similar community architecture and are largely invaded
by the same species of annual grasses and forbs from the Mediterranean Basin
(Gulmon
1977
; Sax
2002
; Pauchard
et al.
2004
; Jimenez
et al.
2008
).
The Chilean matorral is invaded by alien plant species from other mediterra-
nean zones of the world where fires have been a recurrent component of disturb-
ance regimes throughout the Cenozoic. It has been hypothesized that
anthropogenic fires in central Chile may promote the invasion of alien plants with
adaptive traits not present in the native flora (Mun˜ oz & Fuentes
1989
; Segura
et al.
1998
; Holmgren
et al.
2000a
,
2000b
;G ´ mez-Gonza´ lez
et al.
2008
; Figueroa
et al.
2009
). Low-intensity fires have been shown to not significantly affect the
emergence of native herbs but do lead to increased alien species richness. High-
intensity fires beneath the canopy of closed and open matorral shrublands nega-
tively affect the seedling emergence of both native and alien species, but more
strongly in native species (Go
´
mez-Gonza
´
lez & Cavieres
2009
).
As in California, extensive areas of evergreen matorral in central Chile have
been type converted to alien-dominated annual grasslands (Holmgren
et al.
2000a
), with high frequency of anthropogenic fires (Kunst
et al.
2003
). Popula-
tions of invasive annual plants rebound quickly after fires whereas native peren-
nials recover slowly, much as in California chaparral, and thus the annual grass
fire cycle (see
Figure B12.1.1b
) fits well in the Chilean matorral. Floristically the
invasive floras are remarkably similar between California and Chile (Bustamante
et al.
2005
). One difference between these two systems is that the chaparral has
obligate seeder species whereas the Chilean matorral lacks this functional type,
and so the postfire regeneration of open spaces is more limited in the matorral,
thus making the system more susceptible to invasion. In addition, most shrubs
of the Chilean matorral need shade for recruitment (Fuentes
et al.
1984
) and thus
open spaces remain available to alien annuals for long periods of time. However,
there remain disagreements among authors on the importance of fires in the
invasibility of plant communities in central Chile (Figueroa
et al.
2004
).
Invasive woody legumes colonizing cut-over forest lands in south-central Chile
have almost certainly had a major impact on ecosystem processes and fire dynam-
ics but these remain poorly studied.
Ulex europaeus
(gorse), for example, has
become established over thousands of hectares and increases its relative domin-
ance with fire. Positive feedbacks of invasive woody species and fire frequency
