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2.1 Type, Duration and Occurrence
Forest fires in Thailand annually
occur during the dry season from December to May with
their peak in February-March. Fires, Mostly classified
as surface fires, mainly take place in; Mixed Deciduous
Forest, Dry Dipterocarp Forest, and Forest Plantations,
and to some extent in Dry Evergreen Forest, Hill
Evergreen Forest or event in some parts of the Tropical
Rain Forest. In certain extremely dry sites, double
burning in one season is common. These surface fires
consume surface litter, other loose debris on the forest
floor and small vegetation.
Table 1. Area burnt in each type
of forests in 2000
|
Forest type |
Area burnt |
|
Hectare |
% |
|
1. Mixed Deciduous |
63,420 |
68.0 |
|
2. Dry Dipterocarp |
20,279 |
21.7 |
|
3. Secondary Growth |
3,628 |
3.9 |
|
4. Forest Plantation |
2,193 |
2.4 |
|
5. Hill Evergreen |
1,858 |
2.0 |
|
6. Dry Evergreen |
1,021 |
1.0 |
|
7. Bamboo |
835 |
0.9 |
|
8. Natural Pine |
90 |
0.1 |
|
Total |
93,324 |
100 |
Although other types of
fire are not typical to the forest of these region, in
recent years a notable number of crown fires took place
in Pine Plantations. Also ground fires occurred in swamp
forest. Such incidents of swamp forest fires are clear
indication that climatic changes already have occurred
in Thailand.
2.2 Duration
Forest fires in Thailand annually occur during the dry
season from December to May with their peak in February-March.
(Figure1)
Figure 1. Fire duration (data average from 1998-2003)
During the day, most fire activities
concentrate from noon to 4 pm.
Figure 2. Fire frequency round the clock.
2.3 Fuel types and loads
Since fires mainly
taking place in seasonal forests, therefore it largely
depend on dead fuel accumulated on forest floor during
dry season especially dry litter and dead grass. However,
undergrowth and dry twig also contribute to loads of
fuel. Fuel load in Dry Dipterocarp is est. 4,000-5,000
kg/ha., while Mixed Deciduous contains 5,000 kg/ha. (Table
2)
Table 2. Fuel types and loads
|
Forest type |
Site
(province) |
Fuel loads (Kg/ha.) |
|
Litter |
Grass |
Undergrowth |
Twig |
Total |
|
Dry
Dipterocarp |
Chiangmai |
1,980 |
1,480
|
1,070 |
660 |
5,190 |
| |
Kanchanaburi |
1,920 |
1,470 |
1,050 |
570 |
5,010 |
| |
Petchaburi |
1,645 |
1,230 |
889 |
548 |
4,312 |
| |
Uthaitani |
|
|
|
|
|
| |
Sakonnakorn |
- |
- |
- |
- |
4,133 |
|
Mixed Deciduous |
Nakornrachasima |
2,470 |
2,180 |
660 |
180 |
5,470 |
|
Grassland |
Saraburi |
- |
- |
- |
- |
11,170 |
|
Peatland* |
Naratiwat |
- |
- |
- |
- |
9,800
cu.m/ha |
Table 3. Fire behaviors
|
Forest type |
Site
(province) |
Fire behaviors |
|
Rate of
spreads (m/m) |
Flame length
(m.) |
Fire intensity
(kw/m) |
|
Dry
Dipterocarp |
Chiangmai |
1.72 |
- |
249.26 |
| |
Kanchanaburi |
2.81 |
- |
- |
| |
Petchaburi |
3.09 |
- |
- |
| |
Uthaitani |
|
0.7 |
110.71 |
|
Mixed Deciduous |
Chiangmai |
3.41 |
- |
- |
|
Grassland |
Saraburi |
8.29 |
5.7 |
2,165.8 |
2.4 Fire behaviors
The common surface
fires in Dry Dipterocarp as well as Mixed Deciduous
Forests are quite moderate in intensities. Rate of fire
spread approximately 2-4 metre/minute in fair condition.
However rate of spread increases shapely upon the
increase of slope. While in grasslands and dry-out
bamboo forests, fires behave in a much more severe
manner, flame length can reach 15-20 metres in steep
slope or strong wind. Some data from experimental fires
were shown in Table 3.
Table 3. Fire behaviors
|
Forest type |
Site
(province) |
Fire behaviors |
|
Rate of spreads (m/m) |
Flame length
(m.) |
Fire intensity
(kw/m) |
| Dry Dipterocarp |
Chiangmai |
1.72 |
- |
249.26 |
| |
Kanchanaburi |
2.81 |
- |
- |
| |
Petchaburi |
3.09 |
- |
- |
| |
Uthaitani |
|
0.7 |
110.71 |
| Mixed Deciduous |
Chiangmai |
3.41 |
- |
- |
|
Grassland |
Saraburi |
8.29 |
5.7 |
2,165.8 |
[Type and Duration]
[Causes][Annual
burnt areas][Fire
Impacts]
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