Agriculture Reference
In-Depth Information
Fig. 9.2
Araucaria
is a southern hemisphere taxon that dates to the Jurassic and was an
important component of the Jurassic gymnosperm forests that Francis (1984) reported had
tree-ring patterns indicative of a mediterranean-type climate (MTC) and charred fossil evidence
of light surface fires. (Photo of contemporary
Araucaria
forest in Chile by Thomas Veblen.)
Thus, the Paleozoic record shows that fire has been a potential factor in
plant evolution since the origin of land plants, and later Mesozoic fossils
reveal a plethora of evidence for a widespread presence of global fire (e.g. Scott
2000
,
2010
; Jones
et al.
2002
; Marynowski & Simoneit
2009
). These demonstra-
tions are particularly remarkable because they represent a fossil record that
is highly biased against deposition of materials from fire-prone environments
(Kemp
1981
). These fires were apparently ignited by lightning and there is
substantial evidence that those ecosystems occupied climatically seasonal envir-
onments (Finkelstein
et al.
2005
), one of the key elements to creating fire-prone
ecosystems (see
Fig. 2.1
). In addition, fires in these late Paleozoic forests led
to postfire successional sequences of different plant functional types, indicating
successional sequences of plant replacement and recolonization (Glasspool
2000
;Calder
et al.
2006
).Asisthecasetoday,thesefiresweresometimesmassive
landscape-scale events covering thousands of square kilometers of forests
and causing massive postfire sediment loss (Nichols & Jones
1992
). The earliest
Paleozoic ferns were associated with fire and have characteristics of a disturb-
ance-dependent nature (DiMichele & Phillips
2002
).BytheLateCretaceous
there is evidence that some taxa were already specialized for fire-prone environ-
ments (Watson & Alvin
1996
; Collinson
et al.
1999
). These observations
suggest that early in land plant evolution, fire was an ecosystem process
with the potential for selecting fire-adaptive traits and affecting community
assembly.