winter burning of grass fuels in the act - … burning of grass fuels in the act adam leavesley,...
TRANSCRIPT
Winter Burning of Grass
Fuels in the ACT
Adam Leavesley, Jennie Mallela, Neil
Cooper and Dylan Kendall
Introduction
La Nina from 2010-2012
Lots of rain brought lots of grass
Phalaris – 9t/ha
Canberra’s surrounded by grass
Parliament House 800km of grassy interface
Fuel management zones
Inner Asset Protection Zone (IAPZ)
Outer Asset Protection Zone (OAPZ)
Strategic Fire Advantage Zone (SFAZ)
Urban-rural interface
IAPZ (Mowed)
OAPZ (Under grazing)
SFAZ Under grazing
Fuel management standards
IAPZ = height <200mm when curing >70%
OAPZ = GFH <35 when curing >70%
SFAZ = GFH <50 when curing >70%
GFH = Grass fuel hazard
GFH = % cover x height (m)
High Fuel Loads...
... and fuel continuity across the landscape
An average of 60 burning days/year
Similar budget to previous years
What if we burn in winter?
Fraser
Mulanggari
Fraser – urban-rural interface
Fraser Primary School
Slashed grass Fire ground
Fraser – burn map
Fraser
Mulanggari
Franklin Early Childhood School
Mulanggari Grasslands
Gungahlin Town Centre
Fraser – urban-rural interface
Phalaris canariensis (exotic pasture species)
Grows in spring (cool season)
4 paddocks
Fuel load measured 23 July 2012
Burnt 22 August 2012
Measured February
Mulanggari Grasslands
Themeda triandra (native)
Grows in summer (warm season)
3 paddocks
Fuel load measured 24 July 2012
Burnt 3 September 2012
Measured February
Study design
Before-After-Control-Impact
Paddocks divided into burnt and unburnt
areas
All areas measured before
Paddocks burnt (impact), and unburnt areas
left (control)
All paddocks measured after
Method
5 x 1m2 plots per replicate (10 plots /paddock)
MEASUREMENTS
Fuel load (t/ha)
Fuel moisture content (% dry weight)
Grass height
Grass cover (%)
Grass Fuel Hazard = Height (m) x Cover (%)
Method
Cut the grass one paddock at a time (10 plots)
Collect grass curing, cover and height
Weigh grass at CSIRO
Dry at 105°C for 24 hours (Matthews, 2010)
Weigh again
Analysis
Distribution
Kolgomorov-Smirnov test
Differences
ANOVA (normal)
Wilcoxon signed ranks (non-normal)
Correlation
Pearsons (normal)
Spearmans (non-normal)
Distribution
Fuel load (Z = 0.9, p = 0.4)
Fuel moisture content (Z = 0.9, p = 0.3)
Curing (Z = 1.4, p = 0.04)
Grass height (Z = 1.2, p = 0.1)
Grass fuel hazard (Z = 1.2, p = 0.1)
All normally distributed except for Curing
Before – Fuel load
0
2
4
6
8
10
12
14
16
18
B U B U B U B U
Bravo Charlie Delta Echo
Oven
-dri
ed
Weig
ht
(t.h
a-1
)
0
2
4
6
8
10
12
14
16
18
B U B U B U
Alpha Bravo CharlieO
ve
n D
rie
d W
eig
ht
(t.h
a-1
)
Pasture grass (Phalaris) Native grass (Themeda)
Before – Fuel moisture content
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%
B U B U B U B U
Bravo Charlie Delta Echo
Fu
el M
ois
ture
Co
nte
nt
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%
B U B U B U
Alpha Bravo CharlieF
ue
l M
ois
ture
Co
nte
nt
Pasture grass (Phalaris) Native grass (Themeda)
Before – Curing
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%
B U B U B U B U
Bravo Charlie Delta Echo
Cu
rin
g
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%
B U B U B U
Alpha Bravo CharlieC
uri
ng
Pasture grass (Phalaris) Native grass (Themeda)
Before – Height
0
100
200
300
400
500
600
700
B U B U B U B U
Bravo Charlie Delta Echo
He
igh
t (m
m)
0
100
200
300
400
500
600
700
B U B U B U
Alpha Bravo CharlieH
eig
ht
(mm
)
Pasture grass (Phalaris) Native grass (Themeda)
Before – Grass fuel hazard
0
10
20
30
40
50
60
70
80
90
100
B U B U B U B U
Bravo Charlie Delta Echo
Gra
ss F
uel H
azard
Pasture grass (Phalaris) Native grass (Themeda)
0
10
20
30
40
50
60
70
80
90
100
B U B U B U
Alpha Bravo CharlieG
rass
Fu
el H
azar
d
Before - summary
The experimental units of the same species
were not different
There were differences between species
Phalaris at Fraser Themeda at Mulanggari
Impact - Fraser
Burnt 22 August 2012
Impact - Mulangarri
Burnt 3 September 2012
After - Fraser
Residue and regrowth 37 days after the burn
After - Mulanggari
Regrowth 30 days after the burn
Alpha sector control
After – fuel load
0
2
4
6
8
10
12
14
16
18
B U B U B U B U
Bravo Charlie Delta Echo
Ove
n-d
rie
d W
eig
ht
(t.h
a-1
)
0
2
4
6
8
10
12
14
16
18
B U B U B U
Alpha Bravo CharlieO
ve
n D
rie
d W
eig
ht
(t.h
a-1
) (P < 0.001)
Pasture grass (Phalaris) Native grass (Themeda)
After – fuel moisture content
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%
B U B U B U B U
Bravo Charlie Delta Echo
Fu
el M
ois
ture
Co
nte
nt
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%
B U B U B U
Alpha Bravo CharlieF
ue
l M
os
itu
re C
on
ten
t
Pasture grass (Phalaris) Native grass (Themeda)
After – grass curing
(P < 0.001)
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%
B U B U B U
Alpha Bravo CharlieC
uri
ng
Treatment required when curing >70%
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%
B U B U B U B U
Bravo Charlie Delta Echo
Cu
rin
g
Treatment required when curing >70%
Pasture grass (Phalaris) Native grass (Themeda)
After – grass height
(P < 0.001) 0
100
200
300
400
500
600
700
B U B U B U B U
Bravo Charlie Delta Echo
He
igh
t (m
m)
IAPZ fuel standard = 200mm
0
100
200
300
400
500
600
700
B U B U B U
Alpha Bravo Charlie
He
igh
t (m
m)
Pasture grass (Phalaris) Native grass (Themeda)
After – grass fuel hazard
(P < 0.001) 0
10
20
30
40
50
60
70
80
90
100
B U B U B U B U
Bravo Charlie Delta Echo
Gra
ss
Fu
el H
aza
rd
0
10
20
30
40
50
60
70
80
90
100
B U B U B U
Alpha Bravo Charlie
Gra
ss F
uel H
azard
Grass Fuel Hazard
Standards
OAPZ ≤ 35
Pasture grass (Phalaris) Native grass (Themeda)
Summary
It works...
Late-winter/early spring burning:
1) Met the fuel management standards for OAPZ and
SFAZ
2) Met the IAPZ standards in native grass
3) Marginally failed the IAPZ standards in Phalaris
Correlations
Question:
How do the observations compare to the
measurements?
Correlations
Fraser - Phalaris
(r = 0.7, N = 80, p <0.001)
Mulanggari - Themeda
(r = 0.9, N = 60, p <0.001)
Fuel load and GFH
Correlations
Fraser - Phalaris
(r = 0.7, N = 80, p <0.001)
Mulanggari - Themeda
(r = 0.9, N = 60, p <0.001)
Fuel load and GFH
Correlations
Fraser - Phalaris
(Rs = -0.6, N = 80, p <0.001)
Mulanggari - Themeda
(Rs = 0.3, N = 80, p = 0.007)
Correlations
Fraser - Phalaris
(r = 0.7, N = 80, p <0.001)
Fuel load and GFH
Correlations
Mulanggari - Themeda
(r = 0.9, N = 60, p <0.001)
Fuel load and GFH
Summary
1) Themeda fuel loads can be as high as Phalaris even
though they don’t look it.
2) The FMC of Themeda is not necessarily well
represented by curing.
Acknowledgements
Thanks to:
CSIRO Bushfire Dynamics for use of the kiln and helpful
discussions.
My colleagues in the fire crews for all the cutting and
burning.