Some explanations:
What and where are the Tropical Savannas?
Savanna
A savanna is a tropical or subtropical
woodland ecosystem (Werner et al.
1991)1
Tropical savannas cover 12% of the
world’s land surface
(Williams et al. 2005)2
Map found at: http://www.blueplanetbiomes.org/savanna.htm
1 Werner, P. A., B. H. Walker, et al. (1991). "Introduction. Savanna Ecology and Management Australian Perspectives and
International Comparisons." P. A. Werner ed. Blackwell Scientific Publications.
2 Williams RJ, Carter J, Duff GA, Woinarski JCZ, Cook GD, Farrer SL (2005) Carbon accounting, land management, science
policy uncertainty in Australian savanna landscapes: introduction and overview. Australian Journal of Botany 53, 583-588.
Male lion on Savanna at Ngorongoro Conservation Area, Tanzania.
Savannas are characterised by the trees being sufficiently small or widely spaced
so that the canopy does not close.
Tropical woodland savanna, west Arnhem Land, Northern Territory, Australia
Tropical savannas are landscapes of grass and scattered trees,
as long as the canopy cover of the trees is not so dense that it shades out the grass.
Savannas are characterised by seasonal water availability,
with the majority of rainfall being confined to one season of the year.
400
Early
Dry
Season
350
Late
Dry
Season
300
250
200
150
100
50
0
may jun
jul
aug
sep
oct
DRY SEASON
YEKKE WURRKENG
DRY
LATE DRY
nov
dec
jan
feb
mar
apr
WET SEASON
KURRUNG KUNUMELENG KUDJEWK BANGKERRENG
BUILD UP
FIRST STORMS
WET
LATE WET
Mean Average Monthly Rainfall (mm) for Darwin, Northern Territory (~100 years) (Source: Bureau of Meteorology, Commonwealth of Australia)
In north Australia:
1.92 million km2
~25% of Australian
land mass
Savanna
Define some terms:
What and where are the Tropical Savannas?
Why do we need to know anything about fire?
Fire
the
ENIGMA
Source :
State of Environment 1996
Define some terms:
What and where are the Tropical Savannas ?
Why do we need to know anything about fire ?
What is fire severity ?
 Fire severity is a measure of the post-fire
affect of fire on the vegetation.
 Fire Intensity is a measure of the energy
released by a fire, usually measured in
kiloWatts per linear metre.
 Burn severity is a post-fire measure of the
time taken to reach a preferred state.
Simplified models of fire severity
(a)
Patchy
(b)
Low
(c)
Moderate
(d)
High
(e)
Extreme
Methods:
Collecting spectra†
† A remote sensing term that means EM energy or perhaps light
MODIS bands
ETM+ bands
atmosphere transmittance
1.0
Burnt Woodland (low-July)
Unburnt Woodland (July)
0.9
A Scorched Tree (July)
An Unscorched Tree (July)
0.8
Cured Grassland (July)
0.7
reflectance
0.6
0.5
0.4
0.3
0.2
0.1
0.0
400
600
800
1000
1200
1400
1600
1800
2000
wavelength [nm]
Visible
Near Infra-Red
Short Wave Infra-Red
2200
2400
Site 2: 12th May 2008
Illustrates the position of the 10 GPS points,
the average waypoint at the centre of the sampled area
within the pixeloid sampled by the spectrometer.
733460
733470
733480
733490
733500
733510
733520
733530
733540
8618140
8618140
733450
N
8618130
8618130
8618120
8618120
8618110
8618110
8
8
8 8
r8 8
88
8
8
8618100
8618100
733450
733460
733470
733480
733490
733500
733510
733520
733530
733540
8618080
8618080
8618090
8618090
Projection:
UTM Zone 52
Datum:
W GS84
Methods:
Collecting spectra
Collecting Ground Data †
† the real stuff
Methods
Transect
Proportions of cover
GROUND MEASUREMENTS
50m transect
Collected at the same GPS point
Describing proportions of cover
of the various fire affected or
unaffected phenomena in
various strata
5 x 5m quadrat
Methods
Transect
GROUND MEASUREMENTS
Floristics and Structure
50m transect
Collected at the same GPS point
Tree radii
Scorch
Height
Crown
Height
Tree
Height
Describing stand structure
The proportions of each variable
within each fire severity class
for each stratum
Low Fire Severity
Moderate Fire Severity
High Fire Severity
Ground Storey
Lower Storey
Mid Storey
Upper Storey
Unburnt
10
6
27
18
2
Groups of sites, H0: samples are drawn from normally distributed populations
with equal means and variances

0.8
0.8
0.7
0.7
0.6
u
l
u
0.6
h
0.5
0.5
0.4
0.4
0.3
0.3
0.2
0.2
0.1
0.1
0
-0.1
0
MODIS3 MODIS4 MODIS1 MODIS2 MODIS5 MODIS6 MODIS7 MODIS- MODISNDVI
NBR
-0.1
0.7
0.7
0.6
0.6
MODIS3 MODIS4 MODIS1 MODIS2 MODIS5 MODIS6 MODIS7 MODIS- MODISNDVI
NBR
l
m
m
0.5
h
0.5
0.4
0.4
0.3
0.3
0.2
0.2
0.1
0.1
0
-0.1
0
MODIS3 MODIS4 MODIS1 MODIS2 MODIS5 MODIS6 MODIS7 MODIS- MODISNDVI
NBR
-0.1
MODIS3 MODIS4 MODIS1 MODIS2 MODIS5 MODIS6 MODIS7 MODIS- MODISNDVI
NBR
Results
Field Spectra:
Severe v not-Severe
Low v Moderate v High
The Normalised Burn Ratio (NBR)
MODIS Channel 6
MODIS Channels 2, 5 and 7
Models derived a priori
and assessed using AICc from 50 sites
Results
on the ground:
DOES NOT indicate Fire Severity
DOES indicate Fire severity
The amount of Charred material
(blackened)
The amount of Ashened material
(whitened)
The amount of Green material
(photosynthetic vegetation)
The amount of non-Green & Green plant
material (non-photosynthetic and
photosynthetic vegetation)
Application
Binary Fire Severity Map of subset area
in Kakadu National Park/west Arnhem Land
Jabiru
Airport
Results
Model
Accuracy assessment
∆ NBR
Distinguish between Severe
and not-Severe fires
accuracy = 94%
∆ Band 6
Distinguish between Low and Moderate Severity Fires, however
the difference appears to vary through the fire season overall
accuracy = 50%
∆ (Bands 2, 5 and 7)
Distinguish between Low and Moderate Severity Fires, however
the difference appears to vary through the fire season overall
accuracy = 70%
Conclusion:
 Various models required;
 Normalisation is required;
 Calibration is required.