Rossiter N.A., Setterfield S.A.,
Douglas M.M. and Hutley L.B. (2003), "Testing the grass-fire cycle:
alien grass invasion in the tropical savannas of northern
Australia" Diversity and Distributions, 9 (3), pp. 169 - 176.
The current and rapid spread of the African
grass Andropogon gayanus (Gamba grass) in the tropical
savannas of northern Australia has lead to significant concerns
about its potential impact on fire regimes and more specifically
its ability to contribute to the grass-fire cycle by promoting
intense, late dry season fires due to increased fuel loads.
In an attempt to determine how much Gamba grass
has contributed to the grass-fire cycle, fuel load and fire
intensities at sites invaded by the species were compared to sites
that only contain native grasses.
This study was carried out at Wildman Reserve in
the Top End of the Northern Territory.
The results of this study indicate that areas
invaded by Gamba grass have fuel loads up to seven times higher
than those dominated by native grasses and can support a fire that
on average is eight times more intense than those recorded in
native grass savannas at the same time of the year.
The results also support the assumptions of
D’Antonio and Vitousek’s grass-fire cycle:
that alien grass invasion alters the fuel
characteristics of the savannas which in turn leads to an increase
in fire intensity
Rossiter et al. indicate that invasion by Gamba
Grass will result in substantial changes to the savanna fire
regime. These changes may to burn areas invaded by Gamba grass on
an annual basis to reduce both fuel loads and the likelihood of
wildfire.
Rossiter et al. conclude that the results of
this study clearly indicate that Gamba grass invasion of savanna
areas has created conditions to initiate a grass-fire cycle.
Invasion also alters ecosystem structure, nutrient, water and
carbon cycles. The authors conclude that the current concern about
the continued spread and invasion of this grass are highly
justified and requires greater attention from savanna land
managers.
Reference:
D'Antonio C.M. and Vitousek P.M. (1992), "Biological invasions
by exotic grasses, the grass/fire cyclye, and global change",
Annual Review of Ecology and Systematics, 23, pp. 63 -
87.
