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© BUSHFIRE CRC LTD 2006
PROGRAM B
Changes to the grass layer after fire in a tropical savanna
Ken Scott, Samantha Setterfield, Michael DouglasCharles Darwin University, NT
Alan AndersenCSIRO Sustainable Ecosystems, NT
© BUSHFIRE CRC LTD 2006PROGRAM B : Presentation Title
Location of research
PROGRAM B: Changes to the grass layer after fire in a tropical savanna
Darwin
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© BUSHFIRE CRC LTD 2006PROGRAM B : Presentation Title
Tropical savannas
PROGRAM B: Changes to the grass layer after fire in a tropical savanna
© BUSHFIRE CRC LTD 2006PROGRAM B : Presentation Title
Annual cycle
PROGRAM B: Changes to the grass layer after fire in a tropical savanna
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© BUSHFIRE CRC LTD 2006PROGRAM B : Presentation Title
Research question
• How do fire regimes affect grass-layer biodiversity?
PROGRAM B: Changes to the grass layer after fire in a tropical savanna
© BUSHFIRE CRC LTD 2006PROGRAM B : Presentation Title
Methods (site)
every 3 yearslate dry season (October)
-no fires
every 5 yearsearly dry season (June)
every 3 yearsearly dry season (June)
every 2 yearsearly dry season (June)
annualearly dry season (June)
frequencyseason of fire
PROGRAM B: Changes to the grass layer after fire in a tropical savanna
“Randomised complete block design”
18 x 1 ha plots
3 replicate plots of burning in:
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© BUSHFIRE CRC LTD 2006PROGRAM B : Presentation Title
Methods (quadrats)
PROGRAM B: Changes to the grass layer after fire in a tropical savanna
Every year:• Number of plants of each species• Visual % cover of each species
36 x 1m2 quadrats per plot (648 at site)
© BUSHFIRE CRC LTD 2006PROGRAM B : Presentation Title
Grass species composition2004
PROGRAM B: Changes to the grass layer after fire in a tropical savanna
Before fire
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© BUSHFIRE CRC LTD 2006PROGRAM B : Presentation Title
Grass species composition2004 2005
PROGRAM B: Changes to the grass layer after fire in a tropical savanna
First growing season after fire
© BUSHFIRE CRC LTD 2006PROGRAM B : Presentation Title
Grass species composition2004 2005 2006
PROGRAM B: Changes to the grass layer after fire in a tropical savanna
Second growing season after fire
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© BUSHFIRE CRC LTD 2006PROGRAM B : Presentation Title
Fire increases density of annual grasses
1 2 30
10
20
30
40
50
60
70
80
90
PROGRAM B: Changes to the grass layer after fire in a tropical savanna
2 fires (consecutive years)
1 fire
No fire
Den
sity
(pl
ants
per
qua
drat
)
2004 2005 2006
© BUSHFIRE CRC LTD 2006PROGRAM B : Presentation Title
Fire increases number of forb species
2 33.0
3.5
4.0
4.5
5.0
5.5
6.0
6.5
7.0
7.5
PROGRAM B: Changes to the grass layer after fire in a tropical savanna
2 fires (consecutive years)
1 fire
No fire
Num
ber
of s
peci
es
2004 2005 2006
7
© BUSHFIRE CRC LTD 2006PROGRAM B : Presentation Title
Implications - biodiversityBurning results in a:• different grass composition, but takes time• high kill rate for perennial grasses (see poster)• higher density of annual grasses • higher number of forb species
PROGRAM B: Changes to the grass layer after fire in a tropical savanna
Fire exclusion Frequent fire
© BUSHFIRE CRC LTD 2006PROGRAM B : Presentation Title
Implications – end users (Bushfires Council NT)
• Fire removes bulky perennial grasses, ‘airy’ annuals colonisepatchy fuel layer is more continuous
• No increase in grass layer height no major change in flame height and fire intensity
• Increase in forb species richness and plant abundancebiodiversity goals achieved
PROGRAM B: Changes to the grass layer after fire in a tropical savanna
