IT IS NECESSARY TO UNDERSTANT PRO & CONs OF FOREST FIRE ,ITS EFFECT ON SUCCESSION OF FOREST ECOLOGY

1. Fire Ecology
S. P. Singh
FRI , Dehradun, India
E. Mail: surps@yahoo.com

2. All lands affected by natural
fires
• Globally 5,130 Tg biomass consumed
annually by fire, emitting 8,200 Tg/yr CO 2, 413
Tg/yr CO and 19.4 Tg/yr methane.
• Lightning
• Sparks from falling rocks
• Volcanic activity
• Natural combustion

3. Human evolution and domination linked
to fire , and so are some ecosystems
• Mediterranean xeric shrub communities- chapparal,
fynbos, mattorals
• African savannas, Brazil’s cerrado, prairies,
Himalayan Chir pine , they together account for 40%
of vegetation.

4. In India most fires are man-made ;
affect 3.7 million ha annually
• To grow grasses
• Shifting cultivation
• Collection of NTFPs
• Due to stay in fringe areas
• To keep wild animals away

5. fire points in 000
Years

6. CO2 emission due to forest fires in India
Tg CO2 emission
Years

7. Black carbon (BC) concentration at a mountain site (Nainital), India
Note: The black carbon concentration is lowest during the months of the
summer monsoon
Source: Dumka et al. (2010)

9. Types of fire
Surface -
• Spreads over ground, generally burns only litter, seedlings,
herbs, and lower parts of trees partially.
• Ground temp. 90-1200 C
Crown-
• Ignited by a surface fire flame; flame travels from one tree
crown to another; common in coniferous forests;
• A windy condition more damaging
Ground-
•Flameless, consumes organic matter below litter layer
accumulated over hundreds of years, can consume rhizomes,
roots and seeds,causing lasting damages

10. • El Nino- Southern Oscillation (ENSO) caused by
cyclic climate variability can lead to widespread fires in
South Asia; In seasonal tropical forests (monsoon) of
quite common
• Agricultural burning causing catastrophic fires in
Central America, Indonesia, Mexico.
• Shifting cultivation in tropical forest areas
• Savannas

11. Fire behaviour
• Fuel- amount and quality (dry or wet)fuel size, C:N
ratio, higher surface to volume ratio of litter; less
compaction (means more O2 and more inflammability)
e.g. some Australian eucalypts highly flammable due
to oil
• Fire intensity (I) = Heat (H, Kcal g/ dry matter)X
Fuel availability (g dry matter m-2) X Rate of spread
(R, m sec-1) (Wakimoto 1977)
• A wind can bring a fresh supply of oxygen

13. Effect of fire on air
• Combustion is generally incomplete
• Releases CO2, H2O, CO, CH4, N2O, NH3, trace
hydrocarbon, volatile organic compounds,
ozone (Crutzen & Goldmmer 1993)
• Black carbon, other aerosols

14. Effect of fire on Soil

15. Effect of fire on soil…..

16. Effect of fire on soil
• Soil temperature raised- e.g.,
6900 C in intense burn
4100 C in moderate burn
2400 C in light burn at surface,
but the rise at 5 cm soil depth being 11.6%, 17.1%
and 25% of surface respectively also persistent rise
due to the reduced albido

17. Some nutrients and organic matter lost
• N& K compounds volatilized, released and lost by distillation;
N loss little up to 2000C, but up to 60% at 7000C ; also lost
are Fe, Zn, Na at high temperatures
• Moderate rise in temperate region raises the release of Ca,
Na, Mg, hence cycling enhanced (De Bano et al. 1977).
• Organic matter - Cation Exchange Capacity -
Capacity to hold nutrients -
• N2 fixers increase: Alnus, Robinia, Lespedeza, Desmodium
• Erosion loss- Annual sediment yield after a wild fire 14- 28
fold of pre-burn stage (Helvey et al. 1985), cascade range,
Washington P-14 times, Ca, Mg- 26 times, K-38 times.

18. Soil and nutrient losses after a wildfire in NW
Pacific, USA
Altitudes 610 m to 2,135 m, with average slope ~ 50%
a mature forest of Ponderosa Pine (P. Ponderosa) and
Douglas fire( Pseudotsuga menziesii)
 Precipitation average 58 cm, only 10% from June to
September, 70% snow.
 No fire for last 40 years.
Changes after fire in 5 km 2 watershed
Pre fire (1967- 1970) Post fire (1971- 1977) 1972
Sediment 21- 100 269-4003 3800
yield (kg)

19. Sediment transport increased due to wild
fire and result in the loss of nutrients
 Total N increased 40 times
 Available P increased form 0.001 to 0.014
kg/ha/yr.
 Ca, Mg, K, Na combined loss in sediment
increased from 1.98 kg/ha/yr to 54.3 kg/ha/yr.
Ca, Mg, K, Na solution loss for 19.3 to 42.3
kg/ha/yr.
But the solution loss occurs from a larger area,
while sediment transport is limited to riparian
areas; then solution losses of nutrients are in
available from.

20. Losses of nutrients through Debris flow
(torrents) losses
• 13.9 kg/ha/yr N
• 3.4 kg/ha/yr P
• 3,851 kg/ha/yr Ca, K, Na, Mg
Compared to suspended sediment debris
flow losses were 83 times greater for total N,
243 times for available P, 71 times for cat
ions.
Debris torrents occur occasionally, channels
are scoured to bedrock in most places,
limiting vegetation establishment.

21. Soil moisture loss
• Organic matter destroyed bulk
density raised increased runoff/
reduced infiltration drier soil
• Ash and charred crust resulting from fire
reduce micropores.

22. In some conifer forests a non-wettable
/ water repellent layer resulting from
decomposition is established below
soil surface restricting water
infiltration e.g., Sequoiadendron
giganteum, Pinus ponderosa, Abies
concolor

23. pH increases
• Because of loss of litter which is acidic
• Greater loss of N P and Cl which form anions than
of Ca, K and Mg which form cations

24. Soil biota reduced
• Because of: direct killing: reducing their food
bases
• But can increase after a few years
• Higher pH favour bacteria than fungi
(Ahlgren 1974)
• Grasses turn more nutritious (more protein)
• But frequent burning can bring down biota
permanently

25. Fire Impacts on Plants and Vegetation (based on
Heinselman 1993; Pyne et al.1996)
• Recurrent fires herbs +, woody plants –
• Creates bare soil, a seed bed required by many
species.
• Temporary reduction in competition for light,
moisture, nutrients, and some species have
competitive advantage.
• Influences community composition and succession
• Release of seeds in lodge pole pine, jack pine,
some birch, eucalypts

26. Fire Impacts on Plants and Vegetation…….
• Stimulates flowering and fruiting in some species
• Promotes sprouting from root collar in Oaks , maples,
alders; roots sucking in aspen
• Creates patchy condition
• In prairies, prevents invasion of woody species
• The Californian Chaparral depends on fire for the
nutrient generation and reduction in litter and
allelochemicals

27. Plant Adaptation and Response to Fire
• Enhanced seed setting and reproduction e.g
Cyndon dactylon (Bermuda grass), gives competitive
advantage
• Serotiny (late to open) closed cone produced over
several years, opens only with burn: lodgepole pine
requiring 45-500C, knobane pine 2000C; other
examples are P. Attenuata, P. Banksiana, P.
contorta, P. muricata, Cupressus macrocarpa,
Sequoiadendron giganteum (Biswell 1989)
• Fire burn resin and thus open cones.

28. • Fire induced upsurge in height growth due to
the mobilization of stored carbohydrates in
roots.

30. Seed Germination Promoted
• Seed requiring Scarification for germination e.g.
legumes such as Astragalus and Trifolium – fire
ruptures and splits seed coat, thus water and
oxygen permeates germinates
• Seeds of grasslands like Bromus mollis can survive
>2000C for 2 minutes (Daubenmire 1968); Avena
seeds can germinate even after getting charred.

31. • Heat shocks stimulates germination in many
species of Fabiaceae, Rhamnaceae,
Convolvulaceae, Sterculiaceae. (Khurana &
Singh 2001)
• Long seed viability in fire adapted community
like chaparral ;remains dormant between two
fire events e.g. Ceanothus velutinus remain
viable in litter for up to 575 years (Zavitkovski
and Newton 1968)

32. Bud Protection and Re-sprouting
• Dormant buds enclosed in litter in grasses and shrub of
chaparral communities survive fire and resprout due to
burn.
• Sprouts from burls or ligno-tubers (turnip shaped or
tubular swellings, up to 4 m across in some eucalypts)
which have buds below ground surface is another
adaptation to fire.

33. • Thick bark particularly a sapling/ young tree
stage helps trees to survive e.g. pines.
• High crowns, open stands, large buds, long
needles in pines, deep roots give fire
resistance e.g. Larix occidentalis, an
extremely fire resistant conifer Pinus
roxburghii

34. Fire resilience (capacity of species to
come back after fire) (based on Brown et al.
2000)
Short fire cycle- favours species which have juvenile
sprouting, can store seeds in soil, can invade a brunt
side from outside, short lifecycle, bear seeds at an
early stage (precocious seed bearers)
Intermediate fire- favours species- the mature
individual of which resist fire.
• Stores seeds in crown
• Sprout well
• Colonize a site

35. Long interval fire- favours species less resistant to
fire and regenerates through seeds.
Some ecosystem characters promote fire and
species that have them
- e.g. high flammability due to a high proportion of
dead woods, high volatile compounds, loose and
flaky barks.
- Get burned and burns and other, and then
comeback.

36. Fire in Indian forest ecosystems
• States vary from having 30% to 80% fire prone
areas
• Largely man-made
• Pine and Sal forests particularly fire tolerant
• Between two major pines, P. roxbughii is fire tolerant
and P. wallichiana is fire resilient.
• Jhum, which involves man-made fires is quite common
in North-east Himalaya

37. Fire as Management Tool
• To promote desired species e.g., grasses many of
which have buds protected by soil and litter; pines, or to
remove unpalatable grasses which dominate heavily
grazed grasslands.
• To maintain species diversity periodic burning is done
e.g. Kwongan, a shrub community.
In this area near crop-field is burned frequently to keep
shrubs away; far off areas burned after a longer interval
(~20 years) so that shrubs grow and flower and maintain
pollinators populations- crop yield increased.

38. -To produce succulent grass tissues
- To keep fuel load low, to pre-empt big fires.
- To provide bed for seedling establishment and
growth.
- To control insects and pests.
- To create breeding grounds for some birds which
require specific shrubs.

40. Thanks