Download Deliverable 3.5-2-40 Relationship between fire and

Project no. FP6-018505
Project Acronym FIRE PARADOX
Project Title FIRE PARADOX: An Innovative Approach of Integrated Wildland Fire
Management Regulating the Wildfire Problem by the Wise Use of Fire: Solving the Fire
Paradox
Instrument Integrated Project (IP)
Thematic Priority Sustainable development, global change and ecosystems
Deliverable 3.5-2-40
Relationship between fire and grazing
“Assessing relationships among fire-herbivory and man-modified
vegetation types in the Chaco region of Argentina”.
Due date of deliverable: Month 40
Actual submission date: Month 38
Start date of project: 1st March 2006
Duration: 48months
Organisation name of lead contractor for this deliverable: INTA (P33)
Revision (1000)
Project co-funded by the European Commission within the Sixth Framework Programme
(2002-2006)
Dissemination Level
PU
Public
PP
Restricted to other programme participants (including the Commission Services)
RE
Restricted to a group specified by the consortium (including the Commission Services)
CO
Confidential, only for members of the consortium (including the Commission Services)
X
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Authors:
Carlos Kunst (P33: INTA)
Roxana Ledesma (P33: INTA)
Pablo Tomsic (P33: INTA)
Sandra Bravo (P33: INTA)
Ada Albanesi (P33: INTA)
Analia Anriquez (P33: INTA)
Luciano Lorea (P33: INTA)
Marta Leiva (P33: INTA)
Executive summary
Originally, WP 3.5 was proposed because it addresses a well known fact: the
interaction between livestock grazing and fire: the aboveground plant biomass eaten
by livestock is not longer available for wildfires. Either lack of grazing or presence of
grazing produces a change in the fire regime. So grazing is a disturbance that may be
negatively related to fire. Specifically, grazing and grazing management are related to
2 of the four pillars of the fire paradox: wildfire initiation and wildfire propagation.
Grazing could be seen as alternative to prescribed burning in sensitive areas. However,
since several vegetation types need fire and fire keeps the equilibrium toward grass,
grazing should be managed so there is enough fuel to keep the balance among plant
types, specially brush-trees and grasses. When INTA became a member of the Fire
Paradox Project, research in fire-grass-shrub relationships were addressed by research
activities within the INTA Specific Project PNCAR 1503, ‘Range Improvement’ (20062009) that are continued with the Specific Project 263051 ‘Range Improvement
Techniques (2009-2011). These activities are related to the use of fire to keep
the balance among plant types, i. e. prescribed burning.
Specific points related to research in the prescribed fire-livestock grazing interaction
are:
 burn rotation time, related to the fuel load and grazing management, since fuel
and forage are the same thing;
 season of burning, related to fire effects in soils and vegetation; and
 fire effects on shrubs and trees.
These points were addressed using the following approaches in the deliverable 3.5.2:
1. Developing and supporting field experiments,
2. Prescribed burns in private ranches
3. Literature review.
In the following table objectives, aspects and activities of the Deliverable are presented
so the relationships among them are clear:
Number
1
2
Objectives
To determine the relationship between
fire and different vegetation types
(savanna in Central and Southern
Africa, degraded and man-treated
in Chaco) with regard to biomass,
age, wildlife and domestic herbivory,
climate and season of burn.
To quantify the fire –tree, shrub and
grass species relationships in these
vegetation types
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Aspects
Grazing and fire
effects
on
shrubs
and
trees.
Activities
Literature
review
Developing and
supporting field
experiments
Burn
rotation
time, related to
the fuel load
and
grazing
management,
since fuel and
Literature
review
Prescribed burns
in
private
ranches
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forage are the
same
thing;
season
of
burning, related
to fire effects in
soils
and
vegetation
3
1.
To check about similarities between
the
southern
and
northern
hemispheres in the above matters.
Literature
review
Developing and supporting field experiments:
The paucity of field research in the interactive effects of fire and grazing could be
attributed to the practical limitations and design complexity of implementing factorial
field experiments. This obstacle was removed since the Santiago del Estero
Experimental Station specifically set aside Paddock No 7 (size 500 ha) of the ‘La Maria’
Experimental Station for research purposes related to fire and Fire Paradox (28º 03’ S
y 64º 15’ 0). This paddock (Fig. 1) was fenced with funds of the project to avoid
unplanned grazing. Al research activities took place in that paddock.
Fire Paradox through WP 3.4 gave specific support to these two ungoing research
activities:
a) Effect of fire on the dynamics of shrubs and grass species. The objective
of this experiment, started in 2005, is to assess the recruitment of grass and
shrub individuals in an ecotonal grassland after a late season fire. Two
treatments: control and fire were applied at random in plots size 10 m x 15 m,
in 3 replications. New plots were burned in 2006 and 2007, and plant
germination and recruitment were monitored during 3 growth seasons after the
fire, until 2009. Data of the 2005 trial was the base of a masters thesis, and
data from the 2006-2009 and 2007-2010 trials are being processed.
b) Grazing and fire gradients in La Rioja. As a request of INTA La Rioja
Experimental Station, two gradients of fire and grazing along a 70 km transects
were assessed in the La Rioja Plains, using dendochronology, grass standing
crop, botanical composition and assessment of soil features such as Total
Organic Nitrogen, Total Organic Carbon and some soil microorganisms groups.
Cross sections of Prosopis pugionata and Aspidosperma quebracho blanco of
different heights from the grounds were used to estimate fire frequency and
fire damage. Cross sections are being processed. Preliminary results of soil
features suggest that both fire and grazing may affect soil properties (Fig. 2).
The information gathered in the activities a and b is being processed.
2.
Prescribed burns in private ranches.
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The years 2008 and 2009 were of late rains. Only two prescribed burns in private
ranches were performed: the ‘Picat’ Ranch (Catamarca Province) and the ‘Toro Negro’
Ranch (Santiago del Estero).
2.1 Picat Ranch. The objective of the burn was to assess the fire interval needed to
reduce the canopy of woody species, benefit grazing and to compare fire with
mechanical treatments. Density of woody species was assessed by the T-square
method. Grass standing crop was assessed by clipping 10 quadrats size = ¼ m2
randomly located. In Annex 1 of this report it is presented a detailed description of the
burn. This burn was also used for training purposes (see WP 9).
2.2 Toro Negro Ranch. Objectives of this burn were: (a) to assess the use of fire in
the disposal of woody residues in roller chopper native pastures, and (b) to assess
burn rotation time in order to maintain improvements such as accesibility. Density of
woody species was assessed by the T-square method. Grass standing crop was
assessed by clipping 5 quadrats size = ¼ m2 located in 5 transects. In Annex 2 of this
report it is presented a detailed description of the burn. This burn was also used for
training purposes (see WP 9).
Other two prescribed burns targeted to paddocks 7 and 12 of the Experimental Ranch
had to be postponed to 2010 due to lack of appropriate weather conditions. Only
blacklines were burned in the Paddock 12 (Fig. 3).
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2.
Literature review 1
Part 1.
Relationship between fire and grazing:
Historical aspects determining the relationship between fire, herbivory and vegetation
types in the argentine Chaco, South America.
1 INTRODUCTION
2 CHARACTERISTICS OF THE CHACO
2.1 Location
2.2 Climate and Relief
2.3 Vegetation
2.4 Singularities of the Chaco
2.4.1 Scarcity of Large Herbivores
2.4.2 Ants
2.4.3 Events of severe defoliation by insects
2.4.4 Primitive vegetation
3 THE MAN, THE FIRE AND THE CHACO VEGETATION
3.1 Fire-man relationships
3.2 The aboriginal presence in the Chaco Region
3.3 Fire use by the aborigines of the Chaco
3.4 Fire as an ecological factor in the Chaco Region
1
Some parts of this literature review were presented in the 1st South American Symposium on Fire
Ecology and Management, June 2009, Centro Nacional Patagónico-CENPAT, Puerto Madryn, Chubut,
Argentina.
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4 THE STATE OF THE ART OF THE VEGETATION, THE HERBIVORY AND THE FIRE IN
THE CHACO
4.1 Changes process
4.2 Fire
5 CONCLUSIONS
6 BIBLIOGRAPHY
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1 INTRODUCTION
Human activities in the Argentinean Chaco Region developed similarly to what
happened in other regions of the planet and despite being a quite special environment
human activity effects on it show characteristics that are common to similar
environment located in other continents.
The Argentinean Great Chaco shares the same characteristics with Australia, Africa and
the rest of America regarding the development of the natural resources exploitation by
man.
Exception made of the Inca and Azteca Civilizations, the inhabitants of these lands
before the European colonization possessed a life style that identifies itself with the
landscape; the use of the resources was compatible with their technologies and, in
turn, these consistent with the awareness of their needs. They were peoples adhered
and enchained to nature, dependent on their resources and varying their habits in
accordance with them (Romero, J. L., 2004). By the time Europeans discovered
America, such a life style adhered to nature had been abandoned and certainly
forgotten several centuries ago.
Europeans (the Spaniards) arrived to America in early 16th Century. As much as the
humanistic thought and the painting of that time of History, the Conquest is signaled
by the Renaissance (Romero, J. L., 2004) as well. In this case, the Renaissance sign is
made apparent when the European natural resources utilization practices started being
applied in America. Agriculture and livestock are samples of such practices.
Along with the Discovery, colonization came and together with it the importation of
European technologies meeting Old World needs accelerating and intensifying thus the
use of American natural resources. A process that otherwise might either have taken
decades of centuries to evolve or never occurred because of the original dwellers of
these lands was implanted and spread in less than five centuries. FIRE was one of such
tools involved in the process.
In the Chaco, native peoples recognized fire as a natural event and as a tool for
controlling the environment before the conquest. Their knowledge on and use of fire as
well as its utilization by the conquerors and by the settlers afterwards kept recorded in
narratives and chronicles by militaries, travelers and naturalists that walked along
these Chaco lands.
What did they use fire for? What did they get from it? What were the effects on the
environment? What was the relation between fire and livestock developed by settlers
later on? What are the consequences of such activities nowadays?
This report is a bibliographic compilation of papers by known authors from various
sciences, ordered in such a way that its narration allows for the sketching of responses
to these questionings and the understanding of fire, grazing and their mutual
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interaction through the process of Chaco natural resources utilization, essentially the
effect of these factors upon vegetation.
This report consists of three sections that in order to receive and attest the concepts
mentioned before, are enriched by citing historic documents related to the exploration
of the Chaco territory:
Characteristics of the Chaco
A description is made of the Chaco and of the landscape the colonizers found
The Man, the Fire, and the Chaco Vegetation
The man-fire-vegetation relationship is analyzed under general ideas and hypotheses
about these relationships referred to the Chaco; the fire ecological character in this
region is described.
The state of the art of the vegetation, the herbivory and the fire
The modifications of this interaction in time and the state of the art of the Chaco
resources after five centuries of changes in their use are described.
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2 CHARACTERISTICS OF THE CHACO
2.1 Location
Since late 16th Century, the indigenous voice “chaco” has been used to indicate a vague
region that with time embraced a vast area with well-determined limits (Maeder, 1967).
The Chaco Region (Great Chaco) comprises 1,140,000 km2 (Naumann & Madariaga, 2004)
within the South American continent being the biggest forest area following the
Amazonia. It occupies 22% of the continental area of the Argentinean Republic and large
territories of Bolivia, Paraguay and a small portion of Brazil. It is the largest forest area in
Argentina.
Figure 1. Location of the Chaco in South America including Argentina.
The Argentinean Republic possesses 58% of the total area of the Great Chaco, about
675,000 km2 (Naumann & Madariaga, 2004) covering eleven provinces: the entire Chaco,
Formosa, and Santiago del Estero and important portions of Santa Fe, Cordoba,
Catamarca, San Luis, Salta, Jujuy, Tucuman and La Rioja.
2.2 Climate and Relief
In general the Argentinean Chaco appears in most of its extent (about 500,000 km2) as
an extremely flat plain with very smooth slopes that go down 20 to 40 cm/km eastwards.
Its vast extent creates two important climatic gradients: rainfalls decrease westwards
while temperature diminishes southwards.
From a geo-morphological standpoint it is a sunken block filled in with sediments and
propagules transported by the Pilcomayo, Bermejo and Juramento rivers from their
headwaters placed in the Andes.
The slight steepness of the entire Chaco region and the seasonal ferocity of the rivers
favor the river-morphological processes that generate an irregular local topography with
elevated terrains as to the surroundings creating mounds on the riversides or as it happen
frequently occurring river-bed siltation that brings about river-bed shift (Morello &
Adámoli, 1974).
Due to the internal heterogeneity of the Chaco Region within Argentina a distinction of at
least two sub-regions needs to be done in terms of its climatic and geomorphological
criteria: the Dry Chaco and the Humid Chaco Regions.
The Dry Chaco Region comprises sectors of east Formosa and Chaco, north Santa Fe and
a small sector of southwest Santiago del Estero; its climate is humid temperate with an
annual average temperature of 22ºC, and maximum absolute temperatures higher than
40ºC and minima below zero and 290 frost-free days per year. The annual average
relative humidity is about 70%. Rainfalls follow a strong longitudinal gradient with
maximums higher than 1,300 mm in the east area close to the Paraguay River (up to
2,200 mm) diminishing up to 750 mm westwards (Ginzburg & Adamoli, 2005).
The Dry Chaco Region (most of the Argentinean Chaco Region) covers almost the entire
province of Santiago del Estero; sectors of Cordoba, Tucuman, Salta, Jujuy, Catamarca
and La Rioja; west Formosa and Chaco; and a sector of north San Luis. Both rainfall and
temperature present far notorious local deviations in this region due to variations in relief
components (i.e. height and exposure) along its broad extent.
Judiciously, as a general model for Dry Chaco, it can be considered 21ºC as the annual
average temperature with maximum absolute temperatures higher than 40ºC (being
48.9ºC the one for South America) and minimum ones falling below zero with about 300
frozen-free days per year. Rainfalls range from 300 to 800 mm decreasing northwest to
southwest though frequent local variations occur within the Region as that brought about
by the Sub-Andean Hills (in Salta, Tucuman and Jujuy) where the orographic rains make
rainfalls reach up to 1,500 mm (east hillside).
2.3 Vegetation
The plant cover varies notoriously along this expanded region. In all Chaco, though more
remarkably in the humid Chaco, vegetation is closely related to the diverse types of
landscape in which it develops (Morello & Adamoli, 1974). However, a sketch of its more
frequent architecture can be suggested.
Morello and Adamoli (1968) point out that whatever the level of analysis is the Chaco
Region can be considered as a dynamic system where the recurring components making
up the landscape mosaics are forests, pasturelands, along with their interfaces and that
the stability of the whole depends on the relationship set up between both.
The Chaco plant cover is mostly made up of pasturelands, scrublands, savannahs, and
forests. It is much alike a mosaic on whose surface alternate pasturelands and scrublands
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with forests of different kinds. The domineering expression or physiognomy, i.e. the most
representative plant formation becomes the matrix while the other physiognomic
components that insert in it become the patches. Thus there are mosaics made up of
patches of pasturelands in a wooded matrix, patches (“islets”) of woods in a matrix of
either pasturelands or scrublands and broad savannahs.
The general tree vegetation are the xerofilous woodlands, adapted to the seasonally dry
conditions.
While trees of several species occupy different spaces throughout the Chaco environment,
grass pasturelands develop, in general, in terrains somewhat elevate and over sandy soils
left by the rivers in their tidal range though they are also found in somewhat lower
grounds where the savannahs. In the humid Chaco scrublands occur in those lowlands
where water accumulates for periods no longer than six months (Ginzburg & Adamoli,
2005).
The following historical narratives outline this mosaic model for the Chaco vegetation.
In 1774 Geronimo Matorras refers to the ambient he found in the Chaco: “On the 13rd our
march walked spirited about 7 leagues, 4 through sparse woods with some spots in the
surroundings formed with good grass, the other 3 across the open with mature and
abundant grass a nothing special happened to us.”
Later, Matorras writes: “On the 17th we walked some 12 leagues, 4 of which were across
a beautiful palm grove but not as high as the others formerly referred to in this diary; and
after several stretches of wood, one or the other dense, we went out into a delicious
countryside of good and abundant grass with a big lagoon surrounded by algarrobo
groves …”
In 1790 Fernandez Cornejo sailing across the Bermejo River wrote: “This day we sailed
eastwards and along a space of twelve and a half leagues of sailing, the river keeps on
winding a lot towards south, south-east, and east to north-east forming big forest-free
meadows with only beautiful grass, in the outside vast campaigns are seen at each band
with a few forests of round algarrobos.”
In 1804 Felix De Azara describes the Chaco vegetation and scenery: “Everything other
than forest in here is scrubland, high and so dense that nowhere the soil is seen and even
the waters are held up by the undergrowth…”
Felix De Azara keeps on saying: “…and dominates with his sight many leagues of the
Chaco where much unevenness are unnoticed but many islands of wood with fields
between.”
2.4 Singularities of the Chaco
In comparing the Chaco with environmentally similar regions in Africa and Australia, it is
found that some of its characteristic features as for the plant-herbivorous complex were
present at the time the pioneers arrived. These are described below.
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2.4.1 Scarcity of Large Herbivores
While in Africa herbivores group into from dozens to hundreds of individuals, the groups
of South American herbivores are small and solitary species are not rare (De Vivo &
Carmignotto, 2004).
Gligo and Morello (1980) point out that by the time Europeans arrived, Latin America
characterized by the dominance of browser ruminants over grazer ones, the low densities
of herds and flocks, a quite loose distribution of herds with few individuals, by the small
biomass of adult individuals weighing less than 150kg, and by very low diversity (10
cervid species in Latin America against 89 in Africa).
In the Chaco Region the group of large herbivores was composed of the guanaco (Lama
guanicoe), the deer of the swamps (Blastocerus dichotomus), the Pampa deer
(Ozotoceros bezoarticus), the tapir (Tapirus terrestris) and the corzuela (Mazama
Americana) (Bucher, 1980).
During the Pleistoscene, on the contrary, this groups was far much rich if compared with
the contemporary fauna. According to Patterson and Pascual (1972) in addition to the
species mentioned above co-existed other grazer, browser, and leaf-eater herbivores
belonging to the Euquidae, Glyptodontidae, Gomphoteridae, Machrauchenidae,
Megatheriidae, Mylodontidae, Toxodontiade (Fig.2).
Figure 2. Large Herbivores of the Chaco Region. Present and extinct Individuals of
the Pleistocene that might occur in the region (Taken from Bucher, 1987). A-Camelide; BCervidae; C-Tapiridae; D-Gomphotheridae; E-Equidae; F- Megatheriidae; G-Toxodontiade;
H-Mylodontidae; I-Glyptodontidae; J-Machrauchenidae
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It seems that the interaction between the Pleistocene mega-fauna and vegetation made
the latter develop anti-herbivory strategies as a consequence of big selective pressure in
its evolution (Bucher, 1987) as it will be seen below.
Acarete du Biscay, in 1658, describes fauna nearby Santiago del Estero as follows:
“Abundant are tigers which are ferocious and voracious; lions that are tame and guanacos
as big as horses with a very long neck and small head and very short tail ...”
Father Garbiel Patiño, in 1721, makes reference to some specimen of the native fauna in
his narration about the way Chaco people treated him: “They hurried in taking us
guanacos, palo santo resine, deer hide, red deer, otter, corzuela, ostrich feathers, honey,
wax, woolen and chaguar clothes, all together signs of the kindness of the country…”
2.4.2 Ants
Leaf cutting ants are extremely abundant and diverse in the Chaco Region (Kusnezov,
1963; Bucher, 1980). Two genuses are the dominant: Atta and Acromyrmex. The species
Atta vollenweideri and Atta saltensis are found in the open, they live in big nests
(colonies-anthill) that are quite notable while those from the genus Acromyrmex are
found below the canopy and live in small and less striking nests (Bucher, 1987).
Both genuses use (herb or tree) leaves to supply the substratum of the fungus they live
on. The species of the genus Acromyrmex eat the leaves of the trees under which they
live while those of the genus Atta are grass cutters. It is known that the species Atta
vollenweideri may consume 230 kg of grass (dry weight) per year and per colony.
On the basis of colony densities and their intense activity, it is estimated that the leaf
cutting ants evolved by diversifying their niches to take up those left empty after the
extinction of species of the diverse herbivorous fauna of the Pleistocene (Bucher, 1987)
Pedro Lozano, in 1732, in his journey across the Chaco describes what likely Atta sp.
colonies were as follows: “… and only were found some palm groves and small fields that
however not having trees were full of continue and multiplied anthills … These anthills
delay the march a lot since it was necessary to take a long way around to avoid them …
because of their size they seem bread ovens.”
2.4.3 Events of severe defoliation by insects
The sporadic occurrence of massive defoliation brought about by lepidopterae like the
case of the caterpillar of the Megalopyge chacoma species over the quebracho blanco tree
(Aspidosperma quebracho-blanco) is an American phenomenon that takes place not only
in the Chaco Region. On the contrary though being a specific case, similar events by
ortopterae insects do not occur in North America. Not very long ago along the whole
Chaco Region were there periodic and irregular invasions of the Schistocerca americana
locust (Bucher, 1987) that devoured most of the vegetables found in its way.
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2.4.4 Primitive vegetation
The Chaco tree vegetation, namely that of the Dry Chaco, shows some species endowed
with defensive mechanisms such as thorns of every kind in their foliage and stings on the
trunk which are all characteristic defensive elements against herbivores.
When comparing Chaco vegetation with that of similar environmental conditions in
Australia and Africa (the genus Acacia is shared by all three continents) it is seen that in
Africa trees show all kind of defenses as well while in Australia plants have none of these
adaptations. Even though in Africa there exist and have existed large herbivores since
thousands of years ago, it is not the same in Australia where vegetation has not been
subjected to pressures of large predators (Bucher, 1987).
In Africa, acacias lost their thorns on those sections of their crowns about 5 m above the
ground where giraffes have not Access (Cummings, 1982). Chaco woody species like vinal
(Prosopis vinal) or itin (Prosopis kuntsei) possess crowns almost fully covered by thorns.
The itin (Prosopis kuntsei), in particular, has photosynthetic thorns but no leaves. This
defensive stock may be considered as excessive in terms of the moderate size of the
present herbivores.
On considering additionally, seed endozoic dispersion as a survival guarantee, it can be
thought that the features of some species of the genuses Prosopis, Acacia, and Chorisia
are “anachronisms” in the Chaco Region (Bucher, 1987); a sort of indicator of evolving
inertia as an strategy against predation by extinct large herbivores that come into our
days.
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3 THE MAN, THE FIRE AND THE CHACO VEGETATION
3.1 Fire-man relationships
The earth is a planet of fire. P.D. Moore (1982) points out that “fire has a history in
this planet and it is as much extended as that of the terrestrial vegetation.” Geological
clues of forest fires show that they are as old as the forest vegetation itself: 350
millions of years (Goudsblom, 1992).
The first “men” that dwelled in the Earth discovered that fire which they considered
just another element of the environment as much as rain, wind, and seasons was out
of their control. They, therefore, should provisionally keep apart from it. At any time,
however, they observed that after such dramatic and devastating events of fire some
situations favoring their quality of life and that they could harness occurred
(Goudsblom, 1992).
Observation was followed by experimentation. Thus they started to follow the wildfires,
then they learnt how to keep them burning, later to transport it and eventually to
generate fire by themselves. How long this process took is uncertain, only consensus
exists there in the estimation that fire was utilized by the Homo-erectus 400,000 years
ago, far before the Homo-sapiens species to which we all belong (Goudsblom,1992).
Those primitive human groups lived on hunting and prey collection, were nomads, and
were already leaving marks of their presence in the scenery they lived by using fire as
its major agent.
Goudsblom (1992) describes the customs of these human groups as follows:
“They moved from one place to another and lighted fire where they made the decision
of staying … collectors and hunters light fire purposely. One basic reason was that of
provoking animals to run away from their hideaways in the underbrush. Fire may also
expel predators and snakes and in combination with smoke may kill off insects and
parasites. Once the fire was extinguished it was possible to collect tubercles and fruits
hidden in the ground more easily. There were more advantages. One of the immediate
effects of clearing weeds and shrubs must have been that hunters were able to see
farther and move faster. Other benefits must have been gained in the long term. A fire
could create favorable conditions for certain plants, especially grasses and legumes
that need direct sunlight. Fire, as humans noticed, could also be used to promote this
kind of vegetation, which in its turn may appeal to edible animals.”
As it can be seen, there existed a whole series of facts enchained after a plot had been
exposed to the action of fire. Human beings learnt to recognized such a phenomenon
and could also take a step further and provoke fire at will to create in this way
ecological conditions from which they gained benefit (Goudsblom, 1992).
Regarding the Chaco Region, facts were not different at all. Its inhabitants before the
Spaniards came possessed this knowledge. The aboriginal voice “chaco” stands for
“getting together for hunting animals” in quechua constitutes the most compact
document explaining their life style. Fire was their tool.
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Ecologist Jorge Morelllo (1970) points out that chaco is a word that in all its senses
conveys implicitly the idea of disturbing the green cover by the use of fire. Fire cannot
be ignored when describing the Chaco Region.
3.2 The aboriginal presence in the Chaco Region
The Chaco Region was inhabited by human beings before the conquerors came into
these lands. Several researchers agree on the estimation that South America counted
on a population ranging between 7 and 11 millions of inhabitants without including
peoples in the Andes and the Caribe (Denevan, 1992).
At the beginning of the 16th Century, in Argentina lived aboriginal groups that showed
various levels of cultural progress and had generated several ways of adaptation to the
new natural conditions of the environment. As to the number of individuals, Bark and
Gelman (2001) suggest being cautious and considering such figures as an order of
magnitude since they are influenced by the feeling that numerical effect caused on the
observers in those times; in any case it can be said that the figures usually cited are
between 100,000 and 200,000 aborigines in the Chaco Region at early 16th Century
(Barsky & Gelman, 2001).
Within the aboriginal population of the Chaco Region, some groups were hunters,
fishermen, and collectors as the Guaycuru, the Mataco-Mataguayos, and the LulesVilelas who made some seasonal agriculture (corn, gourd). On the other hand, within
the same Chaco Region, there was the Chiriguano-Chane family that practiced the
Amazonian-like agricultural system (roza) together with a little of collection and
hunting (Barsky & Gelman, 2001).
In one of the earliest incursions into the Chaco territory, Alonzo de Vera (1585)
describes the Matara Indians, an agricultural people of the Chaco Region, as follows:
“… thoughtful people, they are the best farm laborers I have ever seen, because I
promise to Your Excellency the Most Reverend that I found them more than 20,000
sacks of corn; beauty is the farms they have. I force myself to people in order to not
suffering from necessity.”
It seems reasonale to admit that the environment of that time was modelled by the
aboriginal occupation; the scenery the conquerors found was the result of the
accumulate effect of their activities from already thousands of years then.
3.3 Fire use by the aborigines of the Chaco
At the arrival of Europeans as it can be noticed, there already existed since
uncountable centuries before a big amount of peoples and human beings in America.
Nature as pictured by the first Europeans as virgin, wild, similar to earthly Paradise was
a fiction since nature had always been intervened an interfered by human actions
starting from centuries of aboriginal occupation previous to the conquerors arrival
(Denevan, 1992). However, the images of an immaculate nature have had a long life
up today; at the same time, one of the contemporary appearances has backed up
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native communities whose behaviors may be sued as model of ecological practices as
to preservation and harmony (Gascon, 2007).
Fire was the major tool of the aborigines in the Chaco Region and they counted on it
for various aims. Guisburg and Adamoli (2005) point out that even in pre-hispanic
times the Chaco aborigines used fire for moving and concentrating hunting,
communicating by the smoke and as a war instrument. Fire was the tool for managing
aerial biomass and the herbaceous necromass used for building up habitats,
diversifying successional stages, mobilizing and concentrating prey populations, getting
rid of hematophagious fauna temporarily, communicating each other, and fighting in
war (Barquez, 1997).
Morello et al. (2006) indicate that during this period aborigines preferred pasturelands
to forests for whether a temporary or permanent settlement. This preference was
based upon the fact that fire was the tool they used with varied purposes and
masterfully and because it runs rapidly and homogeneously along the pasture as the
fuel is homogeneous in composition whereas in the Chaco forest it is harder that a
wave of combustion that runs rapidly throughout broad surfaces be built up.
Such a mosaic of pastureland is enriched by patches of successional stages that are of
different age and flower composition. The fire by patching technique is later embodied
by the white man as managing tool and is referred to as “spotted burning” (Morello et
al., 2006).
Historical cites confirm these statements. In his narration, Father Pedro Lozano (1732)
looks at the behavior of a people living in the Humid Chaco and writes: “No tilling or
sowing is made on the fields of the mataguayos as these are wetlands but only the
burning of grass broken down twenty days before for it to dry and burn …” These
aborigines cleared the wetlands in this way in order to have a better sight of their
lands and appeal the preys towards the tender grasses growing after the fire.
Another religious man, Father Guevara (1770) outlines a primitive agricultural system
of the Guaranies Indians established in the eastern area of the Humid Chaco: “The
benefit and sowing of the ground were in accordance with their innate laziness and the
instruments they had to cultivate the land. To labor the ground, with immeasurable
urge, they cleared a parcel of wood and once the logs became dried and suitable to be
burnt, they put them into fire and used the ashes to manure the soil.” Father Guevara
assumes they knew the beneficial effects of ash-fertilization.
One hundred years later while assessing the Bermejo River navigability across the
Chaco Region, Castro Boedo (1873) notices: “… one of the most dreadful arms of the
aborigines is fire. They take special care in keeping specific points unburnt along the
entire year for either protecting themselves in the fire from an external attack or
having success when undertaking an aggression … they are also used to announcing
themselves with clouds of smoke.”
Evidence on the use of fire on the part of aborigines of the Chaco is unbeatable. Father
Gabriel Patiño, in 1721, writes down is his navigation diary: “Day 21st (Aug). 8 leagues.
In the end of the day, the whitish water; the slow running; continued forests. The
Indians burn the fields (alarm warning among them, when foes appear) and the
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whinny of their horses is heard. Depth: more than 10 varas; water somewhat salttasting.”
Later on, Geronimo Matorras, in 1774, refers to extended field burnings carried out by
natives: “On the 15th we walked around 10 leagues crossing plain fields that were all
burnt; about two in the afternoon we arrived soon to a big town that we found
depopulated, of the Tobas nation …”
As it can be seen, the Chaco itself must be considered as resulting from the
environmental manipulation on part of the aborigines; paraphrasing Hallam (1975) it
can be asserted that when the Spaniards came to the Chaco Region they did not find it
as God had been created it but as the Indians had made it.
3.4 Fire as an ecological factor in the Chaco Region
In the Chaco Region most of the fires affect the herbaceous layer primarily. Fire is an
important factor that models landscape at a regional level and a very important
ecological constituent in the design of vegetation that becomes apparent periodically
(Ginsburg & Adamoli, 2005; Torrella & Adamoli, 2005). Fire plays an essential function
in the dynamic balance existing between woody and herbaceous species within the
mosaics of vegetation.
In the Humid Chaco Region, because of the higher water availability, the productivity
of the herbaceous layer is quite high prevailing pasturelands, tall scrublands of fiber
species and scrublands of bañados. In the Dry Chaco Region, productivity is lower
(Herrera et al., 2003) and its most prominent components are the graminae such as
Trichloris sp., Gouinia sp, and Setaria argentina (Torrella & Adamoli, 2005).
As a consequence of the characteristics of the existing herbivorous fauna by the time
the Europeans came to these lands, herbivory was not enough for consuming all plant
production, mainly grasses, which brought about the buildup of edible material. This
favored vegetation fires to be set and changed fire into a key factor for the
herbaceous/woody species relationship since in restricting woody species survival to
that of those being fire-tolerant, favored herbaceous development (Herrera et al.,
2003).
Some woody species are adjusted to resist frequent exposition to fire being some of
them favored for this process. Pasturelands respond positively to burnings by
accelerate growth, reproduction, and germination.
The origin and conservation of a given plant formation are both related to the coexistence of multiple environmental factors although in those sites where some factors
favor to pasture development prevail, it is fire that tilts the scale.
Fire has been responsible for a number of patches of pasturelands sprinkling the forest
matrix; patches that persist only whether fire is recurrent since, otherwise, forest
would invade pastureland.
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In his journeys across Chaco lands, military Felix de Azara (1790) observes fires on
vegetation and describes their behavior and indicates the obstacles they find in their
advance and propagation: “Only are these burnings stopped by stream and roads
spreading themselves as much as the wind..”
Afterwards, the same author pays attention to the natural limit where the fire stops
and shows it up in its role of herbaceous/woody balance regulator by writing down:
“As forest borders are always quite dense and green, they stop the fire as well …”
As to forest being an obstacle for fire advance, Father Pedro Lozano (1732) records:
“Fronting were the guides that opened a path with axes since all that way was a
continuum of forest impossible to be fell by fire because there is no grass beneath the
trees to feed it.” It was a custom those times that paths with dense vegetation were
set into fire before the march started. So doing visibility, safety and comfort were
enhanced.
Felix de Azara (1790) concludes after observing the fire event: “In these fires
innumerable insects, reptiles, and small quadrupeds perish all the same and both
eagles and hawks fly down to these burnings to scavenge for food in this remainders.”
The same as De Azara, Father Gabriel Patiño (1721) writes down in his diary: “The
fields burnt; many deers on them; excellent grasses with clover and yerbas
somewhere, belts of palm groves, many ducks and a variety of birds.”
Out of both the comment of this religousman and last words of the military it comes
out that the Chaco fauna knew quite well about fire effects, it was used to it and
harnessed the situation.
It can be asserted that the Chaco pastureland ecology is deeply connected to fire since
pre-Colombian times. Fires, whether natural or provoked, are fundamental part of the
design and functioning of the Chaco landscape (Ginsburg & Adamoli, 2005).
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4 THE STATE OF THE ART OF THE VEGETATION, THE HERBIVORY AND THE
FIRE
4.1 Process of change
Together with the arrival of white man to the Chaco Region, a process started in which
vegetation patterns appearing as mosaics would be seen altered. Morello and Saravia
Toledo (1959a, b) faced this alteration, fifty years ago, as a result of the modifications
of the spatial and functional relationships between forests and pasturelands.
The original scenery was transforming, with changes following a trend by which while
forests remain as such, pasturelands become brushwoods or shrublands (Morello et al.,
2006). Pasturelands diminished their share within the mosaic and this space was taken
up by woody species that do not shape a forest but a new kind of dense and thorny
vegetation made up of scrublands which is locally referred to as fachinal; a particular
successional stage of the forest.
Despite the unbalance between the share of forests and pasturelands seems to
originate out of several factors (Morello et al., 2006), it can be asserted that the one
affecting the most, i.e. the agent behind the process, has been the increase of the
livestock herbivorous pressure.
By the time the first cattle signal was registered in Cordoba in 1574 (Barsky & Gelman,
2001), domestic animals already propagated over the Chaco Region.
Neither deer nor the guanaco or any other native ruminant did make up a trophic link
with large biomass in the Chaco savannahs and pasturelands. Livestock coming from
Spain filled in those big empty niches of ruminants with large biomass. The existence
of such empty niches though with great deal of food explains the explosive
multiplication of cows, horses, sheep, etc. (Gligo & Morello, 1980)
It is verified that pasturelands and savannahs stability and dynamics may strongly be
affected by herbivores since they influence over plant community composition and
structure. Bucher (1987) indicates that putting in domestic livestock during the
European colonization of the Chaco Region led to the most severe disturbance of the
ecosystem.
Cows and, in lesser extent, horses and mules multiplied with no obstacle at all since
they were favored by the Chaco environment. Field vastness and lack of stockyards
brought about the spread of big amounts of every type of livestock that unmanaged
soon became wild. Grazing changed into overgrazing over extensive areas with
negative consequences.
Different authors assert that this process of degradation of the Chaco vegetation is a
process common to many other parts of the world. Torrella and Adamoli (2005) point
out that such overgrazing in the natural pasturelands already described disturbed the
relationship between woody and herbaceous species. Adamoli et al. (1990) argue that
overgrazing affected pasture by diminishing its height and interrupting its cover
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continuity that favored germination of woody species seeds that found no competence
for light and water from the herbaceae.
Torrella & Adamoli (2005) indicate that livestock activity diminishes competitive ability
of herbaceae and favors that of woody species that advance into pasturelands up to
change them into shrublands.
Barbaran & Arias (2001) point out that ancient pasturelands were colonized by woody
species such as vinal (Prosopis ruscifolia) and tusca (Acacia aroma) determining the
loss in field receptivity as oberserved in the district Rivadavia (Salta) by Peleschi
(1886), Campos (1918) and Gauffin (1932, 1933).
Military Felix de Azara (1790), a well-known nature watcher, writes the following about
the overgrazing effects in the Chaco Region: “…vegetation in the fields with no forests
suffers from the disturbance of man and quadrupeds; because in the ranches or farms
having livestock and herdsmen, those high grasses and scrublands are removed, and
the common lawn and stunted burr with very small leaf come out.”
As a consequence of pasture scarcity, livestock had to graze within the forests
composing the mosaic of vegetation, something that has strongly modified its structure
and specific composition as well. Half-shadow pastures conforming the herbaceous
layer within the forest were almost eliminated as well giving room thus to the invasion
of shrubs and small trees that make the forest more dense and thorny.
Not only because of the small amount of pastures but also their composition was the
grazing land abandoned by livestock. The disappearance of palatable species occurred
in both pasturelands and forests afterwards. Livestock then started pressing over the
forest going from grazing to browsing and fruit foraging (Morello & Saravia Toledo,
1959a, b).
Many woody species are favored in their germination process when passing through
the digestive tract of livestock which acts as dispersing agent, being the seeds of these
species laid on the pastureland mixed up with their excrements. They all are
consequences of the compelled change in the diet.
4.2 Fire
Saravia Toledo and Barbaran (2001) point out that these negative effects are straight
consequence of an archaic ranching: “the strategy was just to use forage up to its end,
moving later the cattle to new grazing lands.” Such abandoned places changed into
fachinal cannot change back into pastureland but interposing fires that get rid of the
woody vegetation dominance.
On his part, Bucher (1987) outlines two fundamental processes in the disturbance of
the balance among both types of vegetation:

Pastureland invasion by woody species due to overgrazing that made fire
regimens over natural pasture disappear by depleting (consuming) the combustible
material
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
Alteration in forest composition and structure due to the selective predation of
some palatable woody species renewals and the spread of woody species with
palatable fruits whose seeds were transported in the digestive tract of domestic
herbivores.
It remains crystal clear as well the way fire share was affected in its role of balance
regulator. After the European colonization fire occurrence decreased as aborigines
retreated and livestock depleted pasturelands, the fuel needed for fires (Saravia Toledo
& Del Castillo, 1988a; Trinchero, 1997).
Overgrazing and the concomitant removal of fire are the responsible for the change of
pasturelands, forests, and savannahs into the fachinales that cover extended areas of
the Chaco Region today. These areas are so vast that someone travelling across the
Chaco Region today will believe that all what their eyesight can reach is a natural
landscape when, indeed, they are looking at a quite modified environment. In this
respect, the Dry Chaco Region was more affected than the Humid Chaco Region.
Nowadays in those places where enough pasture is stored, fire is utilized as a tool for
managing ranch production. What is sought is that once the new shoot of the
herbaceous layer occurs, shortly after the burning, the nutritional value and nitrogen
and gross protein concentration reach all their maximum levels. The field burning
culture was borrowed from the aborigines and utilized by white man almost from his
arrival to the Chaco Region. Felix de Azara (1790) records this activity as follow:
“When plants are already hard and dry, they set them on fire for them to sprout and
feed livestock…”
It is estimated that only in the Humid Chaco Region between 2,000,000 and 4,000,000
ha of pasturelands and savannahs are burnt today (Herrera et al., 2003). This activity
usually performed quite expeditiously and without much ability not always gives the
expected results. In 1790, Felix de Azara observed certain complications originiated by
fire misuse in the Chaco Region: “For the cattle to feed on tender grass they set fields
on fire from time to time and from this plants reduce to few species since those that
are sensitive to burning die with fire or the same happens if it is done after a drought o
in bad weather.”
Even though very different situations of vegetation degradation there exist, there also
exist proposals reasonably practical for its restoration. Some authors suggest that
managing under low grazing and fire pressure may promote changes in vegetation
from the scrups brought about by overgrazing to savannahs and patches of forest and
pasturelands keeping competence favorable to both latter (Adamoli et al., 1990).
Knowledge allowing to keep the balance in the relationship between vegetation and
herbivory by domestic animals having fire as its moderator is still missing. The types of
vegetation sought (the original mosaic) would be guaranteed in great extent when this
balance is conquered.
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5 CONCLUSIONS
Even before the most recent forest exploitations for wood and of the transformation of
large areas for intensive agricultural crop have occurred, the Chaco vegetation was
already affected by the pressure from the domestic herbivores put in by the
Europeans.
When reviewing the history of the fast alteration brought about in the Chaco Region by
the white man since their arrival in the 16th century, it is valid that at least two
questions are raised to the observer:
1. On the one hand, as Krech (1999), we can wonder: are aboriginal societies an a
good example of appropriate natural resources management? Did they have a
philosophy on nature that allows for a “rational” harvesting of forests and
pasturelands? Or were they predators as we are today though being less in
number they caused a lesser negative impact on natural environments?
2. On the other hand, not counting on information about the earliest times of the
Chaco Region we, the same as Mailin (1956), wonder: did pasturelands appear
as a consequence of the use of fire by native peoples or grow far before under
suitable climatic conditions and keep by fire action?
As to the former it is understood that the environmental pressure on the Chaco Region
did increase since Europeans arrived up to our days; however, most of the negative
effect stemmed from its increasing population might have been mitigated if they would
have counted on and applied some knowledge.
Aborigines had some knowledge on the environment that had likely been modeled
throughout the centuries. Nicholson (1981) highlights certain features of such
aboriginal knowledge gained by trial and error that let them conserve the environment
in such a way that they obtained everything they needed from it:

Aborigines operated out of a quite different cultural basis than that brought in
by Europeans and which is starting being understood not long ago.

Aborigines used fire with full control and understanding for both domestic life
and obtaining food from the environment in which they lived.

Not only do aborigines collect their food for the day but protect the resource for
its permanent availability.

Fire regimens propitiated by the aborigines had evolved along centuries of
experience
Even though part of this knowledge was adopted by the white man, it was applied
partially and disorderly or overdemanding the ecosystem as it is the case with the use
of fire and hervibory.
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The second question leads us to recognize that our current challenge is to create and
conserve an environment that in addition to supply its corresponding services it is
productive and provide us with items meeting our needs. As the environment kept by
the aborigines did.
The natural environment can be seen as a reason and something that has been given,
before which, culture must answer creatively. About this reality, J. Steward (1963)
wrote that every society might find a solution for the various challenges which is
different from that of similar natural environment. The knowledge about the elements
that are part of these challenges is indispensable.
The element fire, in particular, has been far little understood within the Chaco
ecosystems and has been subjected to both excessive use and discrimination. Its direct
and indirect effects upon vegetation remain still controversial.
In this sense Malin (1956) argued that generalizing is always dangerous even worse
when vegetation is the topic because the variables relating vegetation to fire are too
many.
To fill in the gap existing between the ecological theory and environment management
in the Chaco Region it becomes a need to master the knowledge on such variables and
the effects of their manipulation. Only in this way could the relationship between fire,
vegetation and hervibory be foretold and controlled.
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44. Naumann, M. & M. Madariaga. 2004. Atlas del Gran Chaco Sudamericano.
Sociedad Alemana de Coperación Técnica (GTZ), Buenos Aires.
45. Nicholson, P. H. 1981. Fire and the australian aborigine: An enigma. In:Gill, A.
M.; Groves, R. H. and I. R. Noble. 1981. Fire and the australian biota. The
Australian Academy of Science. Canberra.
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46. Patiño, G. 1721. Diario de Navegación. En: Alvarez de Arenales, J. I. & T.
Haenke. 1833. Noticias Históricas y descriptivas sobre el gran país del Chaco y
Río Bermejo, con observaciones relativas a un plan de navegación y
colonización que se propone. Editada en Buenos.
47. Patterson, B. & R. Pascual. 1972. The fossil mammal fauna of southamerica. In:
Bucher, E. H. 1987. Herbivory in arid and semi-arid regions of Argentina.
Revista Chilena de Historia Natural 60: 265-273.
48. Pelleschi, Giovanni (1886). Eight months on the Gran Chaco of the Argentine
Republic.Simpson Low, Marston, Searle and Rivington. London, England. Citado
por: Barbarán, F. & H. Arias. 2001.
49. Romero, Jose Luis. 2004. Breve Historia de la Argentina. Colección Tierra Firme.
Fondo de la Cultura Económica.
50. Saravia Toledo, C. J. & E.M. del Castillo. 1988. Micro y macro tecnologías, su
impacto en el bosque chaqueño en los últimos cuatro siglos. En: Actas del VI
Congreso Forestal Argentino, Vol. II. Ediciones Gráficas El Liberal. Santiago del
Estero, Argentina. Pp:853-855.
51. Steward, Julian H.. 1963. Theory of culture change: the methodology of
multilinear evolution. Urbana : University of Illinois Press.
52. Torrella S. A. & J. Adámoli. 2005. Situacion ambiental de ecorregión Chaco
Seco. En: Brown, A. U. Martinez Ortiz, M. Acerbi y J. Corcuera (Eds.). La
Situación Ambiental Argentina 2005, Fundación Vida Silvestre Argentina,
Buenos Aires, 2006. Pp: 75-82.
53. Trinchero, H. H. (1997) Relaciones interétnicas y usufructo del ambiente: una
historia social y ambiental del Chaco Central. En: Reboratti, C. (comp.) de
hombre y tierras. Una historia ambiental del Noroeste Argentino. Proyecto
Desarrollo Agroforestal en Comunidades Rurales del Noroeste Argentino.
Sociedad Alemana de Cooperación Técnica (GTZ). Salta, Argentina. Pp: 125136.
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Part 2.
Relationship between fire and grazing:
Fire as a tool for rangeland improvement in Northwestern Argentina
The Chaco region is a vast plain located in northwestern Argentina and surrounding
countries. The vegetation of the Chaco region is a mosaic of forests, woodlands,
savannas and shrublands. Forests occupy the upland sites, while the woodlands and
savannas are located on the intermediate and lowland sites, respectively. Sites have
different soil and drainage related to the geomorphological processes associated with
river levees and flats. Climate of the region ranges from humid to arid, but it is
strongly seasonal. Winters are dry and cold (mean July air temperature, 14 ºC), while
summers are hot and rainy (mean January air temperature, 28 ºC). Soils belong to the
orders Mollisol to Aridisol. The objective of this part of the literature review is to
analyze and discuss fire research related to pasture and livestock management.
Fine fuels accumulate in savannas and grasslands during summer and fall; and are at
appropriate burning conditions during late winter and early spring. Atmospheric
conditions include steady winds from the north/north-east (mean velocity 20-40 km/h),
air temperatures up to 30 - 35ºC, and relative air humidity down to 20% at noon and
early afternoon. These conditions are used to setting the fires, generally to achieve
objectives of shrub clearing and control, and the promotion of new grass growth. Fires
lit in the savanna borders spread quickly into this vegetation type, killing all
aboveground shrub biomass within the savanna. However, fire propagates into the
forests rarely: few crown fires have been reported in the literature. It seems that
savannas and forests have different fire regimes. The native species of the Chaco are
rich in terpenes and other volatile compounds, thus suggesting an interaction with fire
since geological times.
Fire has been always present in the Chaco. The original peoples used it extensively for
war, hunting and agricultural purposes, as it has been recorded in travellers and
soldiers accounts (Morello y Saravia Toledo 1959). The first mention of the specific use
of fire for livestock raising and pasture management in the Chaco area comes from
Hieronymus (1874), a naturalist under contract of the Argentine government that
helped in the implementation of the National Academy of Exact Sciences in Cordoba.
Not only he describes the use of fire but informs about large savannas and grasslands
along the road from Santiago del Estero to Tucuman, where today only exist either
agricultural fields, secondary forests and small shrub vegetation types. The purpose of
fire was to create green forage early in the spring season. As a naturalist, he
condemned the use fire for several reasons, the main being the loss of valuable grass
species due to a negative interaction with grazing and a loss of soil nutrients. This
negative view was shared by Tortorelli (1947) that also condemned the use of fire in
livestock and agricultural operations because of the potential damage to native forests.
However, Papadakis (1951), an ecologist working for the Ministry of Agriculture
recommended the use of fire in Chaco savannas for shrub control. Later, Morello and
Saravia Toledo (1959) and Morello and Adamoli (1968, 1974) recognized fire as a
ecological factor helping in maintaining the balance between tree/shrub and grass
dominated vegetation types and also recommended research in the use of fire as a tool
for the management of the native range. How this contradiction happened? As all over
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the world, opposite theories, concepts and ideas about the plant succession, ecological
and economical value and use of vegetation types, etc. clashed and did not help to
solve the issue bad – good fire until today.
Fire is a disturbance that eliminates biomass. As a disturbance, it should be
characterized describing its intensity, severity, frequency, return times and other
attributes. Fire is not different from other disturbances such as grazing (herbivory) and
even pruning and thinning in industrial forests. Disturbances are a part of ecosystems
and should be taken into account when sustainability is considered. Besides its
spectacularity, differences among disturbances are born from its frequency, return
times and human points of view. Naveh (2004) stated that research in disturbance
features is essential for the management of complex systems such as pasture
management.
Research conducted in the Santiago del Estero Experiment Station, the Faculty of
Agronomy and the Faculty of Forestry of the National University of Santiago del Estero
with the recent support of the Fire Paradox Project has gathered information in fire as
an ecological factor and as a tool for pasture management in the Chaco region. Bravo
et al. (2001) using dencrochronological techniques found that the fire return interval
(fire frequency) of a Elionorus muticus savanna is 3-3,5 years, very similar to other
world savannas and grasslands (Fig. 4). Fire intensity as estimated by the height of
scars in trees and by direct observation of flame length could be considered ‘high’ (Fig.
5). Gonzalez et al (2002) have reported that savannas burned at this ‘average’ fire
return interval presented the same nitrogen and carbon status as savannas burned at
10-11 year intervals. However, savannas burned every year had their carbon and
nitrogen pool depleted. On the other hand Kunst et al. (2003) informed that burned
savannas increased their diversity up to 3-4 years after a fire, because of the
apparition of broadleaf species (especially herbaceous legumes) and short grasses that
were dominated by the dominating species (Fig. 6). Kunst et al. (2001) informed that
fire controlled –not killed- Acacia aroma, an undesirable shrub species in the savannas
for up to 3-4 years. Cornacchione et al. (2001) reported the nutritive quality of burned
pastures were higher than unburned pastures and that improvement was present early
in the spring season, a fact that clearly benefits the livestock. However, Morello (1971)
informed that overgrazing eliminated the pulse of fire, a factor clearly associated to
pasture management. There must be enough fine fuel to burn.
These fire effects were probably known empirically by the cattlemen of old, and used
to their advantage. So, who was wrong? Hieronymus or Papadakis? The ecologists or
the cattlemen? The case for the fire is strong as the case against it. Burning every year
was probably ‘wrong’, but the evidence indicates that burning was not totally wrong
and should not be quickly condemned. Probably, what was missing in the puzzle for
Hieronymus was grazing management, the concept of disturbance and its
characterization. Research continues in order to incorporate grazing as a disturbance in
fire research.
From a cattlemen’s point of view, the main objectives for burning pastures in the
Chaco region are two: eliminate old growth and biomass of poor quality, so ‘creating
forage’, and to control ‘undesirable’ vegetation that hinders and compete with
‘desirable’ vegetation. A third objective is to get rid of residues left by mechanical
treatments. We will analyze the research findings related to each objective in order to
develop management recommendations.
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The first objective has been proven: in tallgrass grasslands such as those found in
most of the Argentine territory (rainfall above 400 mm) fire stimulates plant new
growth by increasing light availability and also by generating a flush of fertility that has
no match in the agricultural tools (Sacido 1993, 2003). The killing of the aboveground
biomass of the dominating species also creates space for short grasses and broadleaf
species with high nutritive value. The main concern of using fire, the increase of soil
temperature to lethal thresholds was considered harmless when grass –fine fuel- was
burned (Casillo et al. 2006b, Casillo 2008).
The control of ‘undesirable’ vegetation is based in the liberation of energy generated
by combustion. Kunst et al. (2000), Casillo et al. (2006a) have studied the effect of fire
on the shrub population, specially in Acacia aroma and Celtis pallida paying attention to
phenological status of the plant (‘timing of fire’). Fires at the early and mid winter
season kill the above ground structure of shrubs, but plant regenerate easily because
they are at a dormant stage (Fig. 7). So, fires only control the shrub population, does
not erradicate it. Fires at early spring season are more effective, since target plants
receive the treatment when all reserves are up in their structure. So, fires should be
planned late in the season in order to achieve maximum results.
Casillo (2008) studied the effects of fire in two ‘bottlenecks’ of pasture management:
the germination and recruitment of grasses and shrubs, and its interaction with water
availability (rainfall above historical average). Its conclusion was that fire and water
availability stimulate grasses rather than shrub and broadleaf plants, so perpetuating in
time the grass state.
In the late 80 and 90’, the poor and sub-poor range condition of most the Chaco
ranges brought the advent of mechanical treatments to control the ‘undesirable’ woody
vegetation. Subtropical grass species, especially Panicum maximum cv gatton panic
enter the picture, since they are quite valuable to increase the forage standing crop of
depleted ecosystems. Recent research suggest that mechanical treatment followed by
fire keep the pastures ‘clean’ of undesirable vegetation (Kunst et al. 2008). However,
these aspects interact with what is considered ‘undesirable’ species and the change of
the fire regime of the Chaco since the subtropical grasses are not native and more
productive than the natural vegetation, increasing the amount of standing fire fuel and
potentially changing the fire regime. Also they bring the discussion to our third
objective: how to get rid of woody residues. There exist highly valuable native tree
species in the Chaco, such as Schinopsis lorentzii, Aspidosperma quebracho blanco,
etc. that are source of wood, fire wood and other goods. The burning of large piles of
wood also created concern about fire effects on soils and the untreated surrounding
vegetation. Results of the use of fire in mechanically treated areas and the study of
fuel loads and the dynamics of their moisture (Kunst et al. 2006a and 2006b), brought
the recommendation that mechanical disturbances should be of medium to low
intensity, in order not to use fire initially by creating small fuel loads that are quickly
degraded naturally.
Research conducted by Navall et al. (2005) and Bravo et al. (2009, this symposium)
suggest that as in the case of shrubs, fire do not erradicate the population of tree
species, only ‘controls’ them by killing their aboveground structure. Plants regenerate
easily from buds located in the crown and the branches not affected by fire. A field trial
that introduces forest management, mechanical treatments, brush and forage
management including the use of prescribed fire and grazing is already undergoing in
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the Experimental Ranch. This trial tries to integrate the attributes of all disturbances,
especially their return interval, severity and intensity. The characterization of these
attributes is essential to develop management recommendations.
All these above results should be interpreted in the context of a ranch and livestock
management. To use fire properly to control brush, an average of 3000 kg MS.ha-1 of
fine fuel must be present, which means that pastures should be deferred, a matter of
concern of cattlemen. A ranch is a complex system where factors such as commercial
concerns, herd management, sanitary plans, etc., interact with climatic and other
ecosystem features. So the use of fire may be or not may be appropriated in all
circumstances. As usual, the diagnostic of a professional is essential for success. Our
mission is to provide information and evidence to make the diagnostic and application
right and will keep doing so in the future.
Acknowledgments
The research and extension personnel of the Santiago del Estero Experimental Station,
the Microbiology Chair of the Faculty of Agronomy, the Denchronology and Bionenergy
Chairs of the Faculty of Forestry Sciences and the Fire Paradox project are the source
of most of this findings and observations, and should be accordingly thanked: Rodolfo
Renolfi, Arnaldo Fumagalli, Mónica Cornacchione, Marcelo Navall, Joaquin Casillo, Niní
Carrizo, Pablo Tomsic, Eliseo Monti, Miguel Perotti, José L. Gelid, Alejandro Radrizzani,
María C. Sánchez, Fabio Moscovich, Julio D. Herrera, Marta Leiva, Luciano Lorea, Marta
Rueda, Celia Gonzalez, Silvia Velez, Ana Giménez, Graciela Moglia, Francisco Lopez,
Victor Navarrete and Jose Lopez. The owners and administrators of following ranches
should be also properly thanked: El Mangrullo, Los Itines, Santa Teresita, Toro Negro,
Buena Agua and Maulhardt SA.
Literature consulted and cited
Bravo S., C. Kunst, A. Giménez y G. Moglia. 2001. Fire regime of Elionorus muticus
savanna, western Chaco region, Argentina. International Journal of Wildland Fire 10:
65-72.
Casillo J. 2008. Efectos de la disponibilidad hídrica y el fuego en la germinación y
establecimiento de herbáceas y leñosas en una sabana del Chaco Semiárido. Tesis para
optar al titulo de Magister Scientiae, Escuela de Graduados, Facultad de Agronomía,
Univ. Nacional de Buenos Aires.
Casillo J., Kunst C., Ledesma R., Godoy J. 2006a. Control de Celtis spp (tala) mediante
fuego prescripto. Actas Ecofuego 185-188.
Casillo, J., Kunst, C., Ledesma, R., Godoy, J. 2006b. Dinámica temporal de la
temperatura en la superficie y a 1 cm de profundidad del suelo en quemas en sabanas
del Chaco semiárido. Memorias Ecofuego. p. 126.
Cornacchione M., Kunst C. y Argañaraz M. 2001. Prácticas de control del fachinal: II.
Efectos sobre la calidad del forraje disponible. Memorias 1er Congreso de Pastizales
Naturales. Asoc. Arg. Manejo Pastizales Naturales 84-85.
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Falce M. 1977. El fuego como modelador de sistemas pastoriles en la Provincia de
Salta. Universidad Nacional de Salta, Consejo de Investigación. Salta 20 p.
Gonzalez C., G. Studdert, C. Kunst y A. Albanesi. 2002. Comportamiento de algunas
propiedades del suelo en una sabana del Chaco semiárido occidental bajo distintas
frecuencias de fuego. Ciencia del Suelo 19: 92-100.
Hieronymus J. 1874. Observaciones sobre la vegetación de la Provincia de Tucumán.
Boletin de la Academia Nacional de Ciencias Exactas de Córdoba, Tomo I: 185-234.
Kunst C., Bravo S., Moscovich, J. Herrera, J. Godoy y S. Vélez. 2003. Fecha de
aplicación de fuego y diversidad de herbáceas en una sabana de Elionorus muticus
(spreng) O. Kuntze (aibe). Rev. Chilena de Historia Natural 76: 105-115
Kunst C., Ledesma R., Casillo J., Godoy J. 2006a. Rolados y residuos leñosos: I.
Estimación de la carga de combustibles. Actas Ecofuego 197-198.
Kunst C., Ledesma R., Casillo J., Godoy J. 2006b. Rolados y residuos leñosos: II
Dinámica del contenido de humedad de combustibles de origen leñoso. Actas Ecofuego
217: 219.
Kunst C., Ledesma R., Navall M. 2008. RBI. Rolado selectivo de baja intensidad. INTA
EEA Santiago del Estero Informe Técnico No 57. Santiago del Estero. 139 p.
Kunst C., S. Bravo, F. Moscovich, J. Herrera, J. Godoy y S. Vélez. 2000. Control de
tusca (Acacia aroma Gill ap. H. et A.) mediante fuego prescripto . Rev. Arg. Prod.
Animal. 20: 199-213.
Laterra P. 2003. Desde el Paspaletum: bases ecológicas para el manejo de pajonales
húmedos con quemas prescriptas. Cap. 9. En Kunst C., S. Bravo y J. L. Panigatti (eds):
Fuego en los ecosistemas argentinos. INTA EEA Santiago del Estero.
Morello J. 1970. Modelo de relaciones entre pastizales y leñosas colonizadoras en el
Chaco argentino. IDIA 276: 31-52.
Morello J., Adámoli, J. 1974. Las grandes unidades de vegetación y ambiente del
Chaco argentino. 2da Parte. INTA Serie fitogeográfica, Nº13.
Morello J., Saravia Toledo, C. 1959. El bosque chaqueño I y II. Rev. Agronómica del
Noroeste Argentino, 3: 5-81/209-258.
Navall M., Kunst C., Ledesma R., Casillo J., Godoy J. 2005. Efecto de la quema
prescrita sobre la regeneración natural de especies forestales en un bosque rolados del
Chaco semiárido. Resumen presentado en el 3º Congreso Nacional sobre manejo de
Pastizales Naturales. Facultad de Ciencias Agropecuarias de Oro Verde - UNER y
Asociación Argentina para el manejo de Pastizales Naturales. p 80.
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Naveh Z. 2004. Multifunctional, self organizing biosphere landscapes and the future of
our total human ecosystem. World Futures, 60: 469–503.
Papadakis, J. 1951. Posibilidades agrícolas de La Rioja, Catamarca, Tucumán, Salta,
Jujuy, Corrientes, Santiago del Estero, sudoeste de Buenos Aires, sudeste de La Pampa
y noreste de Río Negro. Ministerio de Agricultura y Ganadería, Buenos Aires. 230 p.
Sacido M. 2003. Fuego prescripto en Pastizales Naturales de la Pampa Deprimida
Bonaerense. Cap. 22, en: Kunst C., S. Bravo y J. L. Panigatti (eds): Fuego en los
ecosistemas argentinos. INTA EEA Santiago del Estero.
Sacido M., Cauhépé M. 1993. Uso del fuego en pastizales: efecto sobre la calidad de
los rebrotes. En C. Kunst. (Eds.) Memoria de Seminario-Taller: Ecología y Manejo del
Fuego en Eccosistemas Naturales y Modificados. EEA, Sgo del Estero (INTA).
Tortorelli L. 1947. Los incendios de bosques en la Argentina. Ministerio de Agricultura,
Dirección Forestal, Buenos Aires, 238 p.
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Figure 1. ‘La Maria’ Experimental Ranch, INTA Santiago del Estero Experimental Station: the
paddock set aside for fire research is Number 7.
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Figure 2. Preliminary results of a fire-grazing gradient: analysis of soil features.
La Rioja Plains – San Bernardo
COT (g
COT
(gC kg-1)
C kg-1)
COP (g C kg-1)
COP (g C kg-1)
8
7
6
5
4
3
2
1
0
6
5
4
3
2
1
0
pH
pH
NOT (g N kg-1)
0,16
0,14
0,12
0,10
0,08
0,06
0,04
0,02
0,00
NOT (g N kg-1)
10
8
6
4
2
0
Range Condition Decreases
Fire frequency Decreases
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Figure 3. Burning blacklines in Paddock 7, ‘La Maria’ Experimental Ranch, Santiago del
Estero Experimental Station.
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Figure 4. Fire frequency in a Elionorus muticus savnna, western Chaco region: Weibull
probability distribution of the fire interval (FI), in years, of the entire savanna patch of
‘La Maria’ Experimental Ranch, INTA Sgo del Estero Exp. Sta., Northwestern Argentina.
50
Shape=1.5 Scale=3.7
40
P
e 30
r
c
e
n 20
t
10
0
0
2
6
4
8
10
FI
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Figure 5. Number of scars per fire episode classified by height (m) and category class,
Elionorus muticus savanna, western Chaco region, Argentina.
Height of the scars (m)
Category class
4.5
III
3.6
2.7
II
1.8
I
0.9
0
1925
33
44
58
67
72
77
82
86
90
1994
Fire episode
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Indice de Shannon (H')
Figure 6 Temporal dynamics of: (a) Shannon-Wiener diversity index (H’); and (b)
difference of H’ observed before and after the fire (H’t), in four fire application dates
in a Elionorus muticus savanna (Spreng.) O. Kuntze. Experiment initiated in 1993 (EXP
1). ‘La María’ Experimental Ranch, INTA EEA Sgo del Estero. EF: Fire application dates.
3
2
1
0
1993
1994
1995
1996
Año de observación
EF 1
EF 2
EF 3
EF 4
1
0.8
't
0.6
0.4
0.2
0
-0.2
-0.4
1
2
3
4
Fecha de aplicación de fuego
1994-1993
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1995-1993
1996-1993
Page 41 of 50
14
0.4
7
0.2
0
0
1
2
3
4
Volumen promedio de
copa postfuego (m3)
Número promedio de
rebrotes postfuego
Figure 7. Effect of fire application dates on structural features of tusca individuals. La
Maria Experimental Ranch.
5
Fechas de aplicación de fuego
NR
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Annex 1
Prescribed Burn in the Picat Ranch
SITE
Country code, region, town, place year
Argentina, Chaco region, Catamarca, Estancia ‘Picat’, November 11, 2008
TIME
PARTICIPANTS
11:50 hs
INTA Personnel: Carlos Kunst, Jose Godoy, Roxana Ledesma, Dario Coria,
Pablo Tomsic
Ranch Personnel (3)
Prescribed burning: Controlled application of fire to wildland fuels in either their natural or
modified state, under specified environmental conditions (prescribed), which allows the fire to
be confined to a predetermined area, and produce the fire behavior and fire characteristics
required to attain planned fire treatment and resource management objectives. A prescribed
burning is a tool that needs a clear objective, some experience in the use and a big ability in the
execution. For that reason it has to be used by experts, but it gives very good ecological results,
and it is an economically income-producing tool if it is used in places where there are not
enough money to delete the fuel in another way in the prevention of forest fires and other
management objectives.
PLOT
DESCRIPTION
Area: 1 ha. General Slope: < 1%.
Vegetation Structure:
MOTIVATION AND OBJECTIVES
General: Brush control.
Specific: Prune low branches of shrub plants and small trees in
order to facilitate transit and forage availability for livestock
PRESCRIPTION WINDOW (summary)
Variable
Low
Wished
Alto
Air Temperature (ºC)
20
25
40
Air Relative Humidity (%)
20
30
60
Mid flame Wind speed (km/h)
1
8
20
7
10
20
1
3
4
Ignition pattern (1 = strip head fire, 2 = back 1
fire, 3 = flank fire, 4 = ring fire, 5= spot head
fire, 6 = (strict) head fire))
5
6
Soil moisture content (%)
1-h fuel moisture content (%)
10-h fuel moisture content (%)
10-h, 100-h fuel, live herbaceous, live woody
moisture content (%)
Use:
Livestock grazing
Rate of spread (m/min)
Flame length (m)
PLANNING AND EXECUTION
Fine fuel load:
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Plot (1/4 m2)
1
2
3
4
5
Mean (DM)
Kg DM.ha-1
Mean
Transect 1
61.3
56.2
44.5
31.9
62.7
51.32
2052.8
Transect 2
43.1
11.7
80.1
98.9
111.8
69.12
2764.8
Transect 3
46.6
13.3
64.3
60
71.4
51.12
2044.8
Transect 4
45.5
72
63.3
41.7
33.8
51.26
2050.4
2228.2
Plot preparation: Ploughed lines width = 3 m were used as support. A slip-on unit was used as main support,
plus rakes and backup pump.
Execution: Proceeded as planned
Hour
11:50
12:05
12:45
13:00
Air temp
(oC)
32
32.8
34
35
Air relative humidity
(%)
30
25
24
24
Midflame wind speed
(km.h-1)
4.9-10
4.1 (gusts = 24)
6.6 (gusts = 25)
8 (gusts = 25)
Direction
NE
NE
NE
NE
Some photos and their footnotes (burning’s days)>
Building black lines
A Prosopis sericantha plant burning
Setting the headfire
FIRE EFFECTS
In July 2009 the plots were assessed for fire effects. Low branches of trees and shrub species were effectively
pruned by fire (see photo), facilitating livestock grazing. Forage standing crop increased to 3500-4000 DM kg.ha
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Parallel pictures: prior and after burning.
Prior to burning
After burning
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Annex 2
Prescribed Burn in the Toro Negro Ranch
Country code, region, town, place year
Argentina, Chaco region, Santiago del Estero, Estancia ‘Toro Negro’,
SITE
November 12, 2009
9:25-18 hs hs
TIME
INTA Personnel: Carlos Kunst, Jose Godoy, Roxana Ledesma, Victor
Navarrete
Owner of the Ranch: Mr Aldo Calliera. Consulting Firm: Ing. Zoot.
PARTICIPANTS
Sofia Padilla
Ranch Personnel (7)
Prescribed burning: Controlled application of fire to wildland fuels in either their natural or modified
state, under specified environmental conditions (prescribed), which allows the fire to be confined to a
predetermined area, and produce the fire behavior and fire characteristics required to attain planned fire
treatment and resource management objectives. A prescribed burning is a tool that needs a clear
objective, some experience in the use and a big ability in the execution. For that reason it has to be used
by experts, but it gives very good ecological results, and it is an economically income-producing tool if
it is used in places where there are not enough money to delete the fuel in another way in the prevention
of forest fires and other management objectives.
PLOT
DESCRIPTION
Area: 60 ha. General Slope: < 1%.
Vegetation Structure:
MOTIVATION AND OBJECTIVES
General: Disposal of woody residues resulting from roller –
chopper treatment – Check burn rotation
Specific: Reduce quantity of fuels diameter > 3 cm. Enhance
forage accessibility – brush control. Training of Ranch
Personnel
PRESCRIPTION WINDOW (summary)
Variable
Low
Wished
Alto
Air Temperature (ºC)
20
25
40
Air Relative Humidity (%)
20
30
60
Mid flame Wind speed (km/h)
1
8
20
7
10
20
1
3
4
Ignition pattern (1 = strip head fire, 2 = back 1
fire, 3 = flank fire, 4 = ring fire, 5= spot head
fire, 6 = (strict) head fire))
5
6
Soil moisture content (%)
1-h fuel moisture content (%)
Grassland with scattered woody residues.
Use:
Livestock grazing
10-h fuel moisture content (%)
10-h, 100-h fuel, live herbaceous, live woody
moisture content (%)
Rate of spread (m/min)
Flame length (m)
PLANNING AND EXECUTION
Fine fuel load:
D3.5-2-40-1000-1
Page 46 of 50
Transect
Plot
Fine fuel
gr
DM*0.25m-2
1
1
2
3
4
5
1
2
3
4
5
1
2
3
4
5
1
2
3
4
5
1
2
3
4
142
190
0
131
79
215
131
118
155
143
157
0
0
124
107
114
165
0
0
96
132
126
0
71
5
0
2
3
4
5
Fine fuel
Average
Kg DM*ha-1
Kg DM*ha-1
4336
3833.6
6096
3104
3000
2632
Woody fine, medium and heavy fuels corresponding to burn date 12/11/2009. Native range,
roller chopped, 60 ha. Brown’s method.
Transect
Line length
Counts
k
G
d2
ton.ha-1
nw
1 m (0-0.5)
2 m (0.5-2.5)
5 m (>2.5 )
0
6
4
1.234
1.234
1.234
0.57767958
0.57767958
0.57767958
0.09741955
1.86451991
17.8064878
ne
1m
2m
5m
4
3
1
1.234
1.234
1.234
0.57767958
0.57767958
0.57767958
0.09741955
1.86451991
17.8064878
centro
1m
2m
5m
8
3
1
1.234
1.234
1.234
0.57767958
0.57767958
0.57767958
0.09741955
1.86451991
17.8064878
se
1m
2m
5m
9
1
2
1.234
1.234
1.234
0.57767958
0.57767958
0.57767958
0.09741955
1.86451991
17.8064878
sw
1m
2m
5m
6
2
3
1.234
1.234
1.234
0.57767958
0.57767958
0.57767958
0.09741955
1.86451991
17.8064878
0
3.98
10.15
14.14
0.27
1.99
2.53
4.81
0.55
1.99
2.53
5.08
0.62
0.66
5.077
6.36
0.41
1.32
7.61
9.36
Average
7.95
Plot preparation: Ploughed lines width = 3 m were used as support in the south side. A slip-on unit was used as main
D3.5-2-40-1000-1
Page 47 of 50
support, plus rakes and backup pump. A black line was build in the west side of the pasture
Ploughed lines in the south side
Burning blacklines
A slip-on unit was used as main support, plus rakes and backup pump.
Execution: Proceeded as planned
Hour
9:25
11:07
12:40
15:05
Air Temp
(oC)
26
27
31.5
35
Air RH
(%)
60
55
54
34
Wind Speed
(km.h-1)
1
3.3
3
4.7
15:45
16:20
32.5
32.4
46
47
3.5
2.9
Wind
direction
E-Cloudy
E
E
NE – Cloudy
N-NE –
Cloudy
N-NE
Flame
length
(m)
2
3
3
2
Type of
fire/firing
technique
Pointfire
Stripfire
3
3
Some photos and their footnotes (burning’s days)>
D3.5-2-40-1000-1
Page 48 of 50
Stripfire technique
Point fire technique
Finishing the job
FIRE EFFECTS
Fire effects will be assessed in April 2010, one growth season after the fire.
Parallel pictures: prior and after burning.
Prior to burning
D3.5-2-40-1000-1
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Prior to the roller chopping treatment
After the roller chopping treatment
After burning
D3.5-2-40-1000-1
Page 50 of 50