Brazil`s neglected biome: The South Brazilian Campos

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Perspectives
in Plant Ecology,
Evolution and
Systematics
Perspectives in Plant Ecology, Evolution and Systematics 9 (2007) 101–116
www.elsevier.de/ppees
Brazil’s neglected biome: The South Brazilian Campos
Gerhard E. Overbecka,, Sandra C. Müllerb, Alessandra Fidelisa,
Jörg Pfadenhauera, Valério D. Pillarb, Carolina C. Blancob, Ilsi I. Boldrinic,
Rogerio Bothd, Eduardo D. Forneckd
a
Chair of Vegetation Ecology, Department of Ecology, Technische Universität München, Am Hochanger 6,
85350 Freising, Germany
b
Laboratory of Quantitative Ecology, Department of Ecology, Universidade Federal do Rio Grande do Sul,
Avenida Bento Gonçalves 9500, Porto Alegre 91540-000, RS, Brazil
c
Department of Botany, Universidade Federal do Rio Grande do Sul, Avenida Bento Gonçalves 9500,
Porto Alegre 91540-000, RS, Brazil
d
Laboratory of Landscape Ecology, Department of Ecology, Universidade Federal do Rio Grande do Sul,
Avenida Bento Gonçalves 9500, Porto Alegre 91540-000, RS, Brazil
Received 16 October 2006; accepted 20 July 2007
Abstract
The South Brazilian grasslands occupy some 13.7 million ha and support very high levels of biodiversity. This paper
reviews the current state of ecological knowledge on South Brazilian Campos and of threats and challenges associated
with their conservation. The principal factors shaping grassland physiognomy and diversity are discussed, and
information is presented on diversity of plant species; best estimates suggest that 3000–4000 phanerophytes occur in
the South Brazilian grasslands.
It is argued that, despite their high species richness, Campos vegetation is not adequately protected under current
conservation policies. In the past three decades, approximately 25% of the grassland area has been lost due to land use
changes, and this trend continues. However, representation of Campos grasslands in conservation units is extremely
low (less than 0.5%), and the management in most of these is inadequate to preserve the grasslands, as grazing and fire
are important factors for their persistence. In conclusion, the following urgent needs are identified: (1) to create more
conservation units in different regions, including different grassland types throughout southern Brazil, (2) to develop
proper management strategies where grasslands are subject to shrub encroachment and forest expansion, (3) to
conduct research on biodiversity and ecological processes in the Campos region and (4) to raise public awareness of the
value and vulnerability of this vegetation type.
r 2007 Rübel Foundation, ETH Zürich. Published by Elsevier GmbH. All rights reserved.
Keywords: Biodiversity; Conservation; Grassland; Land use change; Plant species; Preservation
Corresponding author. Academy of Spatial Research and Planning, Scientific Section III: Natural Resources, Environment, Ecology,
Hohenzollernstraße 11, 30161 Hannover, Germany.
Tel.: +49 511 3484 222.
E-mail address: [email protected] (G.E. Overbeck).
Introduction
Brazil is one of the world’s megadiverse countries (e.g.
Barthlott et al., 1996; Lewinsohn and Prado, 2005), but
1433-8319/$ - see front matter r 2007 Rübel Foundation, ETH Zürich. Published by Elsevier GmbH. All rights reserved.
doi:10.1016/j.ppees.2007.07.005
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the threats to its wildlife and natural landscapes are
dramatic (e.g. Brandon et al., 2005; Mittermeier et al.,
2005). In a recent special section in Conservation
Biology (vol. 19(3); Lovejoy, 2005), a number of papers
discussed biodiversity and nature conservation in Brazil.
According to the current official classification of
vegetation in Brazil by IBGE (2004), Brazil possesses
six major continental biomes – Amazonia, the Atlantic
Forest (with inserted discontinuous grassland areas,
especially on plateau sites in its southern part), the
Caatinga, the Cerrado, the Pantanal, the Pampa – and
additionally the coastal areas (Fig. 1). The grassland
vegetation in southern Brazil – referred to here as the
Campos (grassland) region – is thus included in two
separate biomes in the IBGE (2004) classification: the
biome of the Pampa, in the southern half of Rio Grande
do Sul state, and the Atlantic forest biome. The latter
includes the grasslands of the South Brazilian Plateau
that form a mosaic with forests in the northern half of
Rio Grande do Sul and in the states of Santa Catarina
and Paraná (see Fig. 1). In the special section in
Conservation Biology, the grasslands in southern Brazil
were barely mentioned (see e.g. Brandon et al., 2005)
and the grassland areas in the Atlantic Forest biome and
the Pampa biome were not discussed in any detail.
In this paper, we provide a review of the ecological
characteristics of South Brazilian grasslands and of their
present state of conservation. We briefly characterize the
vegetation throughout the grassland region, identify the
principal ecological factors responsible for grassland
biodiversity, and initiate a discussion on sustainable
management and biodiversity conservation. Like other
non-forest vegetation types in Brazil (e.g. Cerrado; see
Cavalcanti and Joly 2002), the Campos region has not
been treated as a conservation priority in the past: The
current threats, successes and conservation challenges
are presented in this paper. As most research has been
conducted in Brazil’s southernmost state Rio Grande do
Sul, and as this state contains approximately 75% of the
grassland area, much of the available data is from this
state.
Present-day vegetation in southern Brazil – an
overview
Due to its geographic position around the 301S
parallel of latitude, at the limit for tropical vegetation
types (Cabrera and Willink, 1980), and its position on
the eastern side of South America, southern Brazil
occupies a transitional zone between tropical and
temperate climates, with hot summers and cool winters
and no dry season. Variation in geological substrate and
altitude further contribute to the diversity of vegetation
types in the region (Waechter, 2002). The natural
vegetation in South Brazil is a mosaic of grassland,
shrubland and different forest types (Teixeira et al.,
1986; Leite and Klein, 1990). Atlantic forest (Atlantic
forest sensu stricto, Oliveira-Filho and Fontes, 2000)
Fig. 1. Location of South Brazilian grasslands: (a) overview, (b) official Brazilian classification of biomes (IBGE, 2004) and (c)
distribution of grasslands in Brazil’s southern region (abbreviation of states: RS: Rio Grande do Sul; SC: Santa Catarina, PR:
Paraná).
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occupies the eastern slopes and valleys of the South
Brazilian Plateau from the northeast of Rio Grande do
Sul to the coastal plain and highland slopes of Santa
Catarina and Paraná. Araucaria forest, physiognomically dominated by Araucaria angustifolia (Bertol.)
Kuntze in the upper stratum, is found mostly on the
plateau in Paraná, Santa Catarina and Rio Grande do
Sul states, forming mosaics with natural Campos, the
area of the latter increasing towards the south. Seasonal
deciduous forest, which together with Araucaria forest is
included in Atlantic forest sensu lato (Oliveira-Filho and
Fontes, 2000), can be found in western Santa Catarina
and Paraná, along the upper Uruguai river and in the
Ibicuı́ and Jacuı́ river basins in the central lowlands of
Rio Grande do Sul. The northern section of Paraná
state likewise is characterized by seasonal semideciduous
forest, and some Cerrado (Brazilian savanna) fragments. The same forest type occurs in the southeastern
highlands (Serra do Sudeste) in Rio Grande do Sul. In
the westernmost tip of Rio Grande do Sul state, an
Acacia–Prosopis parkland vegetation provides a transition to the Chaco and Espinal formations further to the
west (Waechter, 2002). The grasslands of the southern
and western parts of Rio Grande do Sul often are
included in the literature in the Rı´o de la Plata
grasslands that extend into Argentina and Uruguay
(Burkart, 1975; Soriano et al., 1992; Bilenca and
Miñarro, 2004).
Phytogeographically, the South Brazilian Campos are
in the Neotropical Region and are part of two
biogeographical domains, Amazonian and Chacoan,
represented by the Paraná (Paraná state, Santa Catarina
state and the northern part of Rio Grande do Sul state)
and Pampean (southern part of Rio Grande do Sul)
provinces (Cabrera and Willink, 1980), respectively. The
boundary between these provinces more or less corresponds to the 301S latitude line that separates the Mata
Atlântica and Pampa biomes in the Brazilian biome
classification (IBGE 2004; more explanation further in
this paper). In the Paraná province, the relief is
undulating (South Brazilian Plateau), precipitation is
high (1500–2000 mm) without a dry season, and mean
annual temperature ranges from 16 to 22 1C except at
the highest elevations (reaching 1800 m in Santa
Catarina state) where it is 10 1C (Nimer, 1990). While
summers are warm, frosts can occur in winter, especially
at higher elevations. The grassland vegetation, which cooccurs with subtropical and Araucaria forests, is
considered as forming a separate zone within the Paraná
province, but geographically more or less interwoven
with the flat southern Pampean province (Cabrera
and Willink, 1980). In the Pampean province, i.e. the
southern half of Rio Grande do Sul and adjacent
areas of Uruguay and Argentina, annual precipitation
(ca. 1200–1600 mm) and mean annual temperatures
(13–17 1C) are both lower. Grass-dominated vegetation
103
types prevail, with many herb, shrub and treelet species
co-occurring within the grass matrix. Most of the
flora stems from Chacoan domain, but there also are
species from Andean–Patagonean and Amazon domains
(Cabrera and Willink, 1980).
Past climate changes and vegetation history
A century ago, Lindman (1906) noted the contradiction between the presence of grassland vegetation in
southern Brazil and climatic conditions that allow forest
to develop. Similarly, the presence of grasslands in the
Rı́o de la Plata region in areas where the climate is
apparently capable of supporting forest vegetation has
led to an intense debate of the so-called ‘‘Pampas
problem’’ (e.g. Walter, 1967; Eriksen, 1978; Box, 1986).
Palynological research clarified the climatic and vegetation history of southern and southeastern Brazil
(e.g. Behling, 1998, 2002; Ledru et al., 1998; Behling et
al., 2001, 2004, 2005; Behling and Pillar, 2007) and
supported earlier theories by Rambo (1956a, b). In
summary, four distinct climatic periods can be recognized from the late Pleistocene until today. Between
about 42,000–10,000 years before present (BP), i.e.
including the last glacial maximum, grasslands dominated in the region, indicating a cold and dry climate.
Most of the region was probably treeless, with forest
elements restricted to sites in deep river valleys and in
the coastal lowlands. After 10,000 years BP, temperatures rose but Araucaria forest did not expand because
the climate remained dry. However, Atlantic forest
migrated southwards along the coast where conditions
must have been wetter. From the beginning of the
Holocene onwards, fire became more frequent, as
indicated by the greater abundance of charcoal particles
in peat profiles (Behling et al., 2004, 2005); this was
probably related to the arrival of indigenous populations in the region coupled with a more seasonal climate.
At roughly the same time, large grazing animals went
extinct (Kern, 1994). Indigenous people most likely used
fire for hunting and for land management (Kern, 1994;
Schmitz, 1996), but no direct evidence exists. After the
mid-Holocene, around 4000 years BP, the climate
became moister, allowing for a slow expansion of forest,
principally along rivers. The speed of expansion greatly
increased after 1100 years BP, leading to a more
pronounced substitution of grassland by forest vegetation, forming larger areas of continuous forest cover on
the Plateau and riparian forests in the lowlands (Behling
et al., 2004, 2005, 2007; Behling and Pillar, 2007). In the
17th century, Jesuit missionaries introduced horses and
cattle into the region (Pillar and Quadros, 1997), and
beef cattle production became an important land use in
southern Brazil, and remains so today. As has been
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shown on other continents (e.g. Bond et al., 2003 for
South Africa; Sauer, 1950; Vogl, 1974; Anderson, 1982
for North America), fire and/or grazing are probably the
principal factors impeding forest expansion in grassland
areas where climatic conditions are favourable for forest
(see below).
A classification of South Brazilian grasslands
The national project of vegetation classification
(RADAMBRASIL; Instituto Brasileiro de Geografia e
Estatı́stica (IBGE), 1986) divided the South Brazilian
grasslands into two large phytoecological regions, the
savannas and the steppes (Teixeira et al., 1986). This
classification was based on vegetation physiognomy,
with the term ‘steppes’ being used to characterize low,
single-layer grasslands in the eastern part of Rio Grande
do Sul, and ‘savannas’ to describe grassland composed
of two layers. In the last edition of the official map of
vegetation and biomes of Brazil (IBGE, 2004), building
on work by Leite (2002) who used the term steppe for all
grassland types in southern Brazil, the southern part of
Rio Grande do Sul state was denoted Pampa Biome
(IBGE, 2004), corresponding to 63% of the area of the
state. The natural grassland vegetation that occurs on
the Plateau of Rio Grande do Sul and Santa Catarina
and to a smaller extent in Paraná, and that forms
mosaics with forest formations, was considered as
part of the Atlantic Forest Biome (IBGE, 2004), thus
reflecting the phytogeographic provinces of Cabrera and
Willink (1980).
According to most vegetation classifications, steppe
and savanna are inappropriate terms to describe the
grasslands of southern Brazil. Steppes are usually
considered to be semi-arid grasslands with a cool
temperate climate, such as tall and short grass prairie
in North America, or Eurasian grasslands from Ukraine
to Mongolia (e.g. Breckle, 2002; Bredenkamp et al.,
2002; Schultz, 2005). In all of these regions, low
precipitation, generally less than 250 mm during the
warm season, restricts the development of forest
vegetation, but this is clearly not the case in southern
Brazil. In South America, steppes can be found only in
eastern Patagonia (Schultz, 2005). The term ‘‘Pampa’’
also seems unfortunate, because it usually is associated
with the grasslands south of the Rı́o de la Plata (Soriano
et al., 1992). Savannas generally are defined as vegetation types possessing a mixture of woody and herbaceous life-forms in distinct strata that occur in tropical
regions with strongly seasonal precipitation (Walker,
2001). In Brazil, the term savanna is applicable to
Cerrado vegetation (Oliveira and Marquis, 2002);
however, used more loosely (Cerrado sensu lato) the
term Cerrado also includes the tropical grasslands
known as campo limpo or campo sujo (e.g. OliveiraFilho and Ratter, 2002). Describing the South Brazilian
grasslands as savannas and steppes is thus in disagreement with the accepted international use of these terms
(also see Marchiori, 2002).
Classical botanical and phytogeographical studies
(e.g. Lindman, 1906; Rambo, 1956a) and more recent
works on grassland vegetation in southern Brazil
(e.g. Boldrini, 1997; Pillar and Quadros, 1997; Overbeck
and Pfadenhauer, 2007), although without classificatory
objectives, prefer to refer to grassland formations in
southern Brazil simply as Campos. However, terms as
Campo limpo (clean grassland, i.e. without a woody
component) and Campo sujo (dirty, i.e. shrubby grassland) have become commonly used. In trying to
differentiate different types of grasslands within the
Campos region, most studies reflect the two different
biogeographical domains (see above; see Tables 1 and 2
for a compilation of characteristic species) and regional
differences in Campos flora, with notably higher
contribution of C3 grasses (e.g. from the genera Briza,
Piptochaetium, Poa, Stipa) in the southern half of Rio
Grande do Sul (Burkart, 1975; Valls, 1975). Boldrini
(1997) describes six physiognomic regions of Campos
vegetation in Rio Grande do Sul state, considering local
floristic variations associated with climate, topographic
variation and soil heterogeneity. However, a good
portion of the variation in grassland physiognomy
(e.g. distinction between campo limpo and campo sujo)
and in the composition of the dominant species,
irrespective of region, seems to be determined by grazing
and fire regimes (Pillar and Quadros, 1997). Altogether,
internal classification of the Campos grasslands is still in
need of further research concerning floristic and
structural differentiation and relative impacts of climate,
substrate and management. Henceforth, when we refer
to Campos or South Brazilian Grasslands, or Campos/
grassland region, without any further qualification, we
mean both grasslands associated with Araucaria forest
and the grasslands collectively considered as Pampa in
the current classification of biomes by IBGE (2004) (see
Fig. 4 for some impressions of Campos landscapes).
Main factors shaping grassland vegetation:
grazing and fire
Grazing – which is one of the main economic activities
throughout the South Brazilian Campos (Nabinger
et al., 2000) – is often considered the principal factor
maintaining the ecological properties and physiognomic
characteristics of the grasslands (Senft et al., 1987;
Coughenour, 1991; Pillar and Quadros, 1997). After its
introduction east of the Uruguay River in the 17th
century, feral cattle rapidly spread over a large area of
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Table 1. Characteristic families and species of grasslands in the Atlantic Forest biome (grasslands in northern Rio Grande do Sul,
Santa Catarina and Paraná)
Amaryllidaceae
Hippeastrum breviflorum Herb.
Apiaceae
Eryngium horridum Malme
Eryngium pandanifolium Cham. & Schltdl.
Eryngium urbanianum H. Wolffa
Eryngium zozterifolium H. Wolffa
Asteraceae
Baccharis milleflora (Less.) DC.
Baccharis sagittalis (Less.) DC.
Baccharis uncinella DC.a
Calea phyllolepis Baker
Hypochaeris catharinensis Cabrera a
Noticastrum decumbens (Baker) Cuatrec.
Senecio juergensii Mattf .
Senecio oleosus Vell.a
Trichocline catharinensis Cabreraa
Campanulaceae
Lobelia camporum Pohl
Cyperaceae
Ascolepis brasiliensis (Kunth) Benth. ex C.B.Clarke
Bulbostylis sphaerocephala (Boeck.) C.B. Clarke
Carex brasiliensis A.St.-Hil.
Carex longii Mack. var. meridionalis (Kük.) G.A. Wheeler
Eleocharis bonariensis Nees
Lipocarpha humboldtiana Nees
Pycreus niger (Ruiz & Pav.) Cufod.
Rhynchospora barrosiana Guagl.
Rhynchospora globosa (Kunth) Roem. & Schult.
a
Fabaceae
Adesmia ciliata Vogel
Adesmia tristis Vogel
Eriosema longifolium Benth.
Galactia neesii DC.
Lathyrus paranensis Burkart
Lupinus reitzii M. Pinheiro & Miottoa
Lupinus rubriflorus Planchueloa
Lupinus uleanus C. P. Sm.a
Macroptilium prostratum (Benth.) Urb.
Rhynchosia corylifolia Mart. ex Benth.
Trifolium riograndense Burkart a
Poaceae
Andropogon lateralis Nees
Andropogon macrothrix Trin.
Axonopus siccus (Nees) Kuhlm.
Axonopus suffultus (Mikan ex Trin.) Parodi
Bromus auleticus Trin. ex Nees
Paspalum maculosum Trin.
Paspalum pumilum Nees
Schizachyrium tenerum Nees
Stipa melanosperma J. Presl
Stipa planaltina A. Zanin & Longhi-Wagnera
Solanaceae
Petunia altiplana Ando & Hashimoto
Verbenaceae
Glandularia megapotamica (Spreng.) Cabrera & Dawson
Verbena strigosa Cham.
Endemic species.
the lowlands south and west of the Plateau. In the
grassland islands of the Plateau, cattle were not
introduced until the beginning of the 18th century
(Porto, 1954). In 1996, Rio Grande do Sul state had 13.2
million animals, corresponding to 50% of the total
number of cattle in South Brazil (IBGE, 2005). Cattle
raising in southern Brazil generally occurs by continuous and extensive grazing, and natural grasslands
remain the base for cattle farming (Nabinger et al.,
2000). However, excessive grazing results in decreased
soil cover and risk of erosion, and in the replacement
of productive forage species by species that are less
productive and of lower quality, or even in the complete
loss of good forage species. On the other hand,
extremely low grazing pressure can result in dominance
of tall grasses of low nutritional value or of shrubs and
other species of low forage quality, mainly from the
genera Baccharis (Asteraceae) and Eryngium (Apiaceae)
(Nabinger et al., 2000). For a sustainable grazing
regime, the balance between forage production, grassland diversity and soil preservation needs to be
identified. Creation of gaps and reduction of competition through grazing in general leads to an increase in
plant diversity, in terms of species (Boldrini and Eggers,
1996) and plant functional types (‘functional diversity’).
Under grazing, allocation of aerial biomass is concentrated closer to the ground, and prostrate plant types,
e.g. Axonopus affinis Chase and Paspalum notatum
Flugge (both Poaceae) with stolons or rhizomes are
favoured over taller species (Dı́az et al., 1992, 1999;
Boldrini and Eggers, 1996; Landsberg et al., 1999;
Lavorel et al., 1999). Usually, grazed grassland communities show two distinct layers – a short layer of
prostrate species that are intensively grazed and a taller
layer of plants with a more or less patchy distribution;
the latter is often composed of caespitose grasses with
low forage value species and other species that are
unattractive for grazing animals (shrubs, thorny species
such as Eryngium spp.). Grazing exclusion leads to a
change in structure, with dominance of tall tussock
grasses (Boldrini and Eggers, 1996; Quadros and Pillar,
2001; Rodrı́guez et al., 2003) that are better competitors
for light under exclusion of grazing and fire (Bullock,
1996).
As grassland productivity varies greatly between the
cool winter season and the hot, but usually sufficiently
moist summers, ranchers adjust the stocking rate of their
pastures according to the carrying capacity in winter.
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Table 2.
G.E. Overbeck et al. / Perspectives in Plant Ecology, Evolution and Systematics 9 (2007) 101–116
Characteristic families and species of grasslands in the Pampa biome (grasslands in southern Rio Grande do Sul)
Apiaceae
Eryngium elegans Cham. & Schltdl.
Eryngium horridum Malme
Eryngium sanguisorba Cham. & Schltdl.
Asteraceae
Acmella bellidioides (Sm.) R. K. Jansen
Aspilia montevidensis (Spreng.) Kuntze
Aster squamatus (Spreng.) Hieron.
Baccharis coridifolia Spreng.
Baccharis dracunculifolia DC.
Baccharis trimera (Less.) DC.
Chaptalia runcinata Kunth
Eupatorium buniifolium Hook. et Arn.
Gamochaeta spicata (Lam.) Cabrera
Senecio brasiliensis (Spreng) Less. var. brasiliensis
Senecio cisplatinus Cabrera
Senecio oxyphyllus DC.
Stenachenium campestre Baker
Vernonia flexuosa Sims.
Vernonia nudiflora Less.
Cyperaceae
Carex bonariensis Desf. ex Poir.
Carex phalaroides Kunth
Carex sororia Kunth
Cyperus luzulae (L.) Retz
Eleocharis bonariensis Nees
Eleocharis dunensis Kük.a
Eleocharis sellowiana Kunth
Kyllinga brevifolia Rottb.
Pycreus polystachyos (Rottb.) P. Beauv.
Rhynchospora holoschoenoides (Rich.) Herter
Rhynchospora megapotamica (A. Spreng.) H. Pfeiff.
Fabaceae
Adesmia araujoi Burkarta
Adesmia bicolor (Poir.) DC.a
Adesmia latifolia (Spreng.) Vogel
Arachis burkartii Handroa
Clitoria nana Benth.
Desmodium incanum DC.
Lathyrus pubescens Hook.& Arn.
Macroptilium prostratum (Benth.) Urb.
Rhynchosia diversifolia M. Micheli
Stylosanthes leiocarpa Vog.
Trifolium polymorphum Poir.a
Hypoxidaceae
Hypoxis decumbens L.
Iridaceae
Herbertia pulchella Sweet
Sisyrinchium micranthum Cav.
a
Juncaceae
Juncus capillaceus Lam.
Juncus microcephalus Kunth
Oxalidaceae
Oxalis articulata Savigny
Oxalis eriocarpa DC.
Oxalis perdicaria (Molina) Bertero
Poaceae
Andropogon lateralis Nees
Andropogon selloanus (Hack.) Hack.
Andropogon ternatus (Spreng.) Nees
Aristida filifolia (Arechav.) Herter
Aristida jubata Arech.
Aristida laevis (Nees) Kunth
Aristida spegazzinii Arech.
Axonopus affinis Chase
Bothriochloa laguroides (DC.) Herter
Bouteloua megapotamica (Spreng.) O. Kuntzea
Briza subaristata Lam.
Coelorachis selloana (Hack.) Camus
Danthonia secundiflora Presl
Dichanthelium sabulorum (Lam.) Gould & C.A. Clark
Elyonurus candidus (Trin.) Hack.
Ischaemum minus J. Presl
Melica eremophila M.A. Torres
Melica rigida Cav.a
Panicum aquaticum Poir.
Paspalum dilatatum Poir.
Paspalum nicorae Parodi
Paspalum notatum Fl.
Paspalum pauciciliatum (Parodi) Herter
Paspalum pumilum Nees
Piptochaetium lasianthum Griseb.
Piptochaetium ruprechtianum Desv.
Piptochaetium stipoides (Trin. & Rupr.) Hack.
Saccharum trinii (Hack.) Renvoize
Stipa filifolia Neesa
Stipa megapotamia Spreng. ex Trin.
Stipa nutans Hack.
Stipa philippii Steud.a
Stipa setigera C. Presl
Rubiaceae
Borreria verticillata (L.) G.F.W. Meyer
Richardia humistrata (Cham. et Schlecht.) Steud.
Verbenaceae
Glandularia subincana Tronc.
Lippia asperrima Cham.
Phylla canescens (H.B.K.) Greene
Endemic species.
As a result, a large part of the biomass produced by
highly productive C4 grasses in summer is not consumed, and the grasslands are therefore burned
approximately every 2 years (Vincent, 1935), usually at
the end of winter (August), to facilitate sprouting of
fresh biomass. Further, grassland fires are used to
reduce the shrub cover (Gonçalves et al., 1997). This
could be achieved by mechanical removal as well,
though at higher costs and work effort. The use of fire
for land management is controversial, and reliable
scientific studies on its impact on species or functional
type composition and soil properties are scarce. Fires in
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107
Table 3. Diversity and vegetation structure in relation to time since last burn in 0.25 m2 grassland plots in Porto Alegre, RS, Brazil
(data from Overbeck et al., 2005)
Time since last fire
Diversity (Shannon)
Number of species
Open soil (% cover)
Litter (% cover)
Standing dead biomass (% cover)
3 months
1 year
2 years
3 years
2.72 a
28 a
46.6 a
3.2 a
6.7 a
2.4 b
22.50 b
31.2 b
7.8 b
8.2 a
2.43 b
21.75 b
5.1 c
13.1 c
18 b
1.84 c
15.07 c
1d
37.2 d
28 c
Columns indicate different time since the last burn (3 months, 1 year, 2 years, 3 years or more). For each variable (row), different letters behind data
indicate significant differences between plots with different time since the last fire (po0.05), tested by randomization testing with analysis of variance.
winter or early spring are known to diminish the
contribution of cool season C3 grasses at the expense
of warm season C4 grasses (Llorens and Frank, 2004).
The common burning practice can thus be considered
counterproductive from an agronomic point of view
because it favours C4 grasses and therefore decreases
forage availability in the critical winter period (Nabinger
et al., 2000). Furthermore, fires tend to favour
caespitose over rhizomatous or stoloniferous grasses,
which usually is not a desired effect due to the lower
forage quality of the tussock grasses (Jacques, 2003). In
general, however, the majority of grassland species seem
to be adapted to frequent (i.e. annually or every few
years) burning (Quadros and Pillar, 2001; Overbeck and
Pfadenhauer, 2007), even though no studies exist on the
effect of different burning seasons and differences
between grassland types. For ungrazed grassland subject
to regular anthropogenic fires near Porto Alegre, Overbeck et al. (2005) showed that burning led to an increase
in species number and diversity at the plot scale as
competitive dominance by caespitose C4 grasses was
reduced and a large number of inter-tussock species,
principally forbs, were able to establish. With increasing
time since fire, many species – especially small forbs –
were gradually outcompeted by dominant grasses or
were unable to regenerate under the thick litter layer
that developed: although some of these species were lost
from aboveground vegetation, they persisted with their
belowground organs (Overbeck and Pfadenhauer, 2007;
see Table 3). Abandoned grassland, i.e. grasslands where
neither grazing nor burning takes place, shows high
dominance of usually few tussock grass species and low
diversity of herbaceous species. In grasslands situated in
mosaics with Araucaria forests in the highlands of
northern Rio Grande do Sul, species richness in 0.25 m2
plots ranged from 3 to 13, compared to maxima of 28
species on recently burned grasslands in the Porto
Alegre region (Overbeck et al., 2005). Species richness of
abandoned grassland can only be maintained by fire,
and in the long run the grassland vegetation itself may
be lost due to shrub encroachment (Overbeck et al.,
2005, 2006; see below). If livestock grazing is to remain
an economically sound activity, understanding the
impact of fire on soil properties becomes important. It
has been suggested that grassland burns, although
leading to short-term increases of total N, K, Ca, Mg
and pH values in the uppermost soil layer (Rheinheimer
et al., 2003), have negative effects on soil fertility and
thus forage production in the long run (Heringer et al.,
2002; Jacques, 2003); however, there have been too
few studies to allow for general conclusions, especially
concerning different frequencies and seasons of fire.
Forest–grassland dynamics
In the absence of fire and grazing, grasslands are
subject to shrub encroachment and, when in the vicinity
of forest vegetation, to forest expansion (Machado,
2004; Oliveira and Pillar, 2004; Müller et al., 2006); this
has been found for the South Brazilian plateau and for
the Central Depression, but there have been no studies
from the southern part of Rio Grande do Sul. Similar
results were found by Safford (2001) for highland
grasslands of southeastern Brazil. Increased density of
shrubs and trees in grassland and savanna vegetation
has been observed throughout the world in the last three
decades (e.g. Archer, 1990; van Auken, 2000; Roques
et al., 2001; Cabral et al., 2003), with different
hypotheses being proposed to explain these patterns
(such as climatic shifts or elevated global CO2 levels; e.g.
Longman and Jenı́k, 1992; Bond and Midgley, 2000;
Sternberg, 2001). As the climate in southern Brazil is
conductive to the development of forests, changes in the
disturbance regime, especially grazing and fire regimes,
should be decisive factors for vegetation changes at
forest–grassland boundaries (Pillar and Quadros, 1997;
Scholes and Archer, 1997; Pillar, 2003; Langevelde et al.,
2003; Bond, 2005). Modelling of vegetation development in South Africa has shown that areas above a
certain precipitation limit (650 mm for South Africa)
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under appropriate conditions such as the absence of
severe fires or the presence of safe sites, e.g. rock
outcrops (Müller, 2005). Seed dispersal by animals also
plays an important role in this process (Forneck et al.,
2003; Duarte et al., 2006a, b). As long as there is a
(possibly discontinuous) disturbance regime that prevents the grasslands from turning into forests, high
floristic and structural diversity is promoted, since
woody species from grassland and forest can be found
in close proximity. In grasslands that are ungrazed but
regularly burned, shrub and tree species richness and
density tends to be higher close to the forest border,
should be covered by woody vegetation types in the
absence of fire (Higgins et al., 2000; Bond et al., 2003).
In Brazilian Cerrado, protection from fire leads to shifts
in vegetation physiognomies to more closed forms
(Hoffmann and Moreira, 2002; Miranda et al., 2002).
In southern Brazil, colonization by forest species leads
to a gradual but clear shift of forest–grassland
boundaries or to the development of woody thickets
within the grassland (Forneck et al., 2003; Machado,
2004; Oliveira and Pillar, 2004). In forest–grassland
mosaics, many species common in local forests play the
role of pioneer woody trees, expanding forest vegetation
number of tree individuals
26
24
22
20
18
16
14
12
10
8
6
4
2
0
24
22
20
18
16
14
12
10
8
6
4
2
0
44
40
36
(a)
last fire in grassland: >3 years
> 80cm
> 30cm to < 80cm
< 30cm
(b)
last fire in grassland: 2 years ago
(c)
last fire in grassland: 1 year ago
32
28
24
20
16
12
presence
of rock
outcrops
8
4
0
31 28 25 22 19 16 13 10
grassland
7
-
4
border
1
2
-
5
8
11 14 17 20 23 26
forest (m)
Fig. 2. Number of tree individuals along the forest–grassland gradient according to size class intervals (height) in a natural
forest–grassland mosaic under the influence of fire in South Brazil (data from Müller, 2005). Grassland areas in (a) have not burned
for more than 3 years, in (b) were burned 2 years ago and in (c) 1 year ago. Please note different scales on the y-axes.
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where fires are less severe. Farther away from the
border, with typically higher frequency and severity of
fires, grassland shrubs manage to increase their density
significantly after a period of 2 years without fire
(Fig. 2). Absence of fire leads to shrubby grassland with
increasing densities of trees and shrubs, either as solitary
individuals or clumped together, usually associated with
rock outcrops (safe sites) (Müller, 2005). Further studies
on the ecology of shrubs and forest pioneer trees are
currently under way; as of now, exact determinants and
likely vectors of successional processes at the forest–
grassland interface are still not clear.
Campos biodiversity
Information on plant biodiversity of the Campos is far
from complete. Boldrini (1997) estimated a total number
of 3000 grassland plant species in Rio Grande do Sul
state alone, and Klein (1975, 1984) estimated approximately 4000 species. While this is lower than the number
proposed for Brazil’s Cerrado region (6000 vascular
species; Furley, 1999), it should be noted that Cerrado
(total area 2 million km2) covers a much larger area than
South Brazilian Campos, and therefore also includes a
wider range of climatic and edaphic conditions (Furley,
1999) than the comparatively uniform Campos region
(Ministério do Meio Ambiente (MMA), 2000); thus it
also includes a greater diversity of vegetation types from
grassland to forest physiognomies (e.g. Oliveira-Filho
and Ratter, 2002 for an overview).
The federal government’s ‘‘Project of Conservation
and Sustainable Use of Brazilian Diversity’’ (PROBIO;
MMA, 1996) sponsored workshops that identified
approximately 900 priority areas to be conserved
throughout the country (MMA, 2002; Silva, 2005) and
led to floristic and faunistic inventories in areas
previously unstudied in southern Brazil as well. Grasslands on the South Brazilian plateau, i.e. grasslands
within the Atlantic forest biome (totalling 1,374,000 ha,
i.e. 1/10 of total Campos area), in Rio Grande do Sul
and Santa Catarina where included in this project: 1082
species, 95 of them endemics and 35 endangered by
extinction, could be listed in the course of these studies,
taking into account the available literature, herbarium
records and field investigations (Boldrini, 2007). No
exhaustive compilations exists for grasslands in the
southern or more western parts of Rio Grande do Sul.
Despite these recent advances, the South Brazilian
grasslands remain one of the regions for which large
portions are still ‘‘insufficiently known’’ (Giulietti et al.,
2005). A thorough analysis of the flora of the entire
grassland region is still not possible (as is probably the
case in other Brazilian biomes as well), but some broad
patterns are clear. The most species-rich plant families
109
throughout the Campos region are Asteraceae (ca. 600
species), Poaceae (ca. 400–500), Leguminosae (ca. 250)
and Cyperaceae (ca. 200; numbers based on Boldrini,
1997, 2002; Araújo, 2003; Longhi-Wagner, 2003;
Matzenbacher, 2003; Miotto and Waechter, 2003).
Many species, especially of the C4 grasses, also occur
in the Cerrado biome (where few C3 species are present),
whereas many of the C3 species occur in the temperate
grasslands further south, in the Rı́o de la Plata region.
This co-existence of C3 and C4 species is one of the
distinct characteristics of the South Brazilian grasslands.
Floristic and phytosociological surveys throughout
the entire grassland region are needed in order to obtain
more realistic estimates of the species richness. Only this
will allow for meaningful floristic classification of the
grasslands and for comparison with other grassland and
savanna regions in South America, including studies on
floristic connections. And only this will provide information on the diversity and endangerment status of
different community types, thus serving as a basis for
conservation efforts in the grassland biome. These
studies should include investigations about the spatial
aspects of diversity such species–area relationships or
information on diversity at the plot level. Overbeck et al.
(2005) found that a grassland area near Porto Alegre
(burned grassland in a forest–grassland mosaic) had a
very high fine-scale diversity with an average of 34
species on a plot of 0.75 m2. In total, approximately 450
vascular plant species can be found in the 220 ha of
grassland at the study site (Overbeck et al. 2006), placing
these grasslands among the most species-rich grassland
communities in the world.
Land use and transformation of South Brazilian
grasslands
Expansion of agri- and silvicultural production
Up to now, land use changes in southern Brazil have
been poorly documented compared to other regions of
Brazil (e.g. Cerrado; Klink and Moreira, 2002; or
Amazonia; Fearnside, 2005), and the socio-economic
causes and consequences of these changes have scarcely
been investigated (see Naumov, 2005, for an overview
for Brazil). As no analyses are available, here we mostly
refer to data from the Brazilian agricultural census from
1996 (IBGE, 2005). In 1970, the total grassland area in
Brazil’s southern region was 18.0 million ha (Nabinger
et al., 2000) while in 1996 it was 13.7 million ha
(i.e. 23.7% of the total land area in this region), with
10.5 million ha in Rio Grande do Sul (total area: 28.2
million ha), 1.8 million ha in Santa Catarina (9.6 million
ha) and 1.4 million ha in Paraná (20.0 million ha): thus,
a decrease of 25% in the total area of natural grasslands
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has occurred in the past 30 years due to a strong
expansion of agricultural activities. Production of corn
(Zea mays), for example, has increased from 1.4 to 11.8
million tons from 1940 to 1996, production of soybeans
from 1530 ton in 1940 to 10.7 million tons in 1996, and
production of wheat from 95 thousand tons to 1.4
million tons during the same period (agricultural census
from 1996; data from IBGE), with increases in area
primarily at the expense of natural grasslands. In Rio
Grande do Sul alone, in 2000/2001 7.0 million ha
were used for production of soybeans (Bisotto and
Farias, 2001). The three southern states of Brazil
currently produce 60% of the rice in Brazil (50% in
Rio Grande do Sul alone), totalling 6.5 million ha in
area (EMBRAPA, 2005).
The cultivation of exotic trees has received many
incentives from both private industries and the government, e.g. for pulp production. The present area of tree
cultivation in southern Brazil is about 1.9 million ha
(IBGE, 2005; data for 1996) and new projects will
increase this area in the near future. Particularly in the
grasslands on the South Brazilian Plateau, former cattle
production areas have been transformed into plantations of Pinus sp. over large areas. Since economic
returns are higher for plantations than for cattle
production, areas planted with Pinus sp. are increasing
rapidly every year. Plantations are usually not sylvipastoral systems where at least part of the original species
composition remains but dense monocultures that due
to lack of light do not allow for any understory plants to
grow. Nearby grassland areas are often being invaded
by Pinus sp. because of its effective seed dispersal
and germination capacity in open vegetation types
(Bustamante and Simonetti, 2005), easily observable
throughout the region. In the southern part of Rio
Grande do Sul, plantations of Eucalyptus sp. (and to a
lesser extent Acacia sp.) are rapidly increasing in area,
also leading to loss of grassland species (Pillar et al.,
2002). More specific data on the impact of these
plantations on flora and fauna are missing thus far for
southern Brazil, as are reliable and recent data on the
spatial expansion of tree plantations.
Cultivated pastures
The intensification of farming systems has led to
increases in the area of cultivated pastures. Despite the
high productivity and forage potential of many native
species, they are not commercially exploited, and
cultivated pastures are mainly formed using exotic
species (Nabinger et al., 2000). In 1996, 7.0 million ha
in the southern region of Brazil were covered by sown
pastures, mainly with non-native species. Important
cultivated grass species are e.g. Axonopus jesuiticus
(Araujo) Valls, P. notatum var. saurae Parodi, both
native species, and the exotics Pennisetum americanum
K. Schum. or Urochloa P. Beauv. spp. (syn. Brachiaria
(Trin.) Griseb. spp.) (summer species), Lolium multiflorum Lam. and Avena strigosa Schreb. (winter species),
along with some exotic Leguminosae (e.g. Nabinger
et al., 2000). While these species have high forage value,
their large-scale introduction leads to losses of natural
grasslands. Not all introduced exotic forage species
have positive economic effects. Eragostis plana Nees
(Poaceae), an African species introduced in the 1950s,
proved to be of low palatability and did not satisfy the
nutritional demands of cattle; however, it spread rapidly
throughout the region because of high seed production
along with allelopathic effects. At present, it is estimated
that about 400,000 ha in Rio Grande do Sul state
have already been invaded by this species, with negative
impacts on grassland diversity and forage quality
(Medeiros et al., 2004).
Overgrazing and erosion
Currently, the low productivity of pastures in southern Brazil reflects unsuitable management (Maraschin,
2001). Limited herbage production over the winter
results in overgrazing during this period, with heavy
weight losses of cattle under inappropriate management.
Overgrazing has negative consequences for soil cover,
facilitating degradation in regions with vulnerable soil
conditions. The most drastic example of this comes from
the southwestern part of Rio Grande do Sul where
severe erosion and desertification has occurred, forming
extensive sand patches on unconsolidated arenitic
substrates (Trindade, 2003). In 2002, this region was
included as a ‘‘Special Attention Area’’ in Brazil’s
desertification diagnosis map, with the affected total
area reaching 37 km2 (Suertegaray et al., 2001). Where
edaphic conditions were susceptible to erosion, overgrazing accelerated these processes greatly. Trindade
(2003) showed that temporary cattle exclusion may be
effective in permitting the colonization of eroded areas
by plant species from the surrounding communities; of
these species, the grasses Elionurus sp. and Axonopus
pressus (Nees) Parodi proved to be the most tolerant of
sand burial. Adequate grassland management, directed
towards maintenance of the vegetation cover and thus
protection of soil from hydric and aeolic erosion would
prevent these problems of degradation in the future.
Conservation in the Campos region
Only 453 km2, i.e. less than 0.5% of the South
Brazilian grasslands, are currently under legal protection in conservation units without direct land use
(Ministério do Meio Ambiente (MMA), 2000), the
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111
26°S
30°
Gap Status Level
1
2
3
4
5
water
34°
58°
54°
50°W
Fig. 3. Levels of representativeness (gap status levels) in conservation units larger than 1,000 ha of the different phytoecological
regions in Rio Grande do Sul state. The levels range from 0% (1) to 7.1% (5). The ranges of each level of representativeness are not
equal neither are levels continuous. See text for exact values for the different vegetation types.
largest part being in mosaics of Campos and Araucaria
forest in the National Parks of Aparados da Serra, Serra
Geral and São Joaquim (northern Rio Grande do Sul
and Santa Catarina). In order to identify which
vegetation types in Rio Grande do Sul were underrepresented or not represented at all in the existing
network of protected areas, we conducted a regional gap
analysis (Jennings, 2000) for the whole of Rio Grande
do Sul (both forest and grassland), including areas over
1000 ha protected under the categories I, II, III and IV
of the World Conservation Union (IUCN; Olson and
Dinerstein, 1998). The status categories used in the
analysis were adopted from Stoms (2000). The result of
the analysis were five different gap status levels (Fig. 3),
all below the 10% minimum cover for effective
biodiversity conservation as suggested by the IV World
Congress on National Parks and Protected Areas
(McNeeley, 1993) which has been adopted by the
Brazilian government. The levels range from 0% to
7.1% of representativeness (Seasonal semideciduous
forest (0%, i.e. no protected areas 41000 ha at all):
first level; Campos (0.14%): second level; Araucaria
forest (0.36%) and seasonal deciduous forest (0.41%):
third level; pioneer formations (2.62%) and Atlantic
Forest (3.61%): fourth level; Acacia–Prosopis parkland
(7.09%): fifth level). Thus, despite their high species
richness and the threat from changing land use, the
Campos is almost unrepresented in the conservation
units. Further, no protected areas under categories I to
IV at all exist in what the IBGE (2004) recognises as
the Pampa biome i.e. the southern half of Rio Grande
do Sul.
Only legal protection can effectively prohibit transformation of natural grassland in the region into
agricultural or silvicultural area and thus prevent
complete loss of Campos vegetation. However, at least
in the regions where most of the studies have been
conducted, grasslands cannot be maintained in areas of
integral protection, i.e. with a conservation status
that does not allow for human interference, in the long
run. Under the Brazilian system of conservation
units, conservation in National Parks excludes all
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anthropogenic interference and ‘‘disturbances’’ such as
grazing and fire. As discussed above, grasslands without
management with grazing and/or fire in many areas are
subject to shrub encroachment and subsequently will
change into forests, even though this may take decades
depending on the local situation and the proximity to
forest borders. In mosaics of forest and grassland, as in
the existing conservation units on the South Brazilian
Plateau, this process seems to be quite fast (Oliveira
and Pillar, 2004). Grasslands currently protected in
conservation areas with integral protection (IUCN
categories I–III; see Rylands and Brandon, 2005), such
as the National Parks, thus seem to be doomed to
extinction if no management can be applied. No data
exists on whether sufficiently frequent natural burns
would occur in these areas to preserve the grasslands
under today’s climatic conditions, as it is the case, for
example, for protected Cerrado areas (e.g. Ramos-Neto
and Pivello, 2000; Medeiros and Fiedler, 2004). Fire
thus should be considered as a legal tool for conservation in South Brazilian grasslands, at least in areas
where grazing is not feasible. Nonetheless, the fire
regime applied (e.g. period and frequency of burns)
should be carefully evaluated, as current knowledge is
insufficient to be able to assure desired management
results. Perhaps more importantly, continuation of
extensive cattle grazing over wide areas should be
supported and promoted by governmental institutions
(Pillar et al., 2006). The aim should be to reconcile
economic purposes and sustainable grazing practices,
encouraging the reintroduction of native forage grasses
and stimulating regular resting of pastures via rotational
grazing (e.g. Gonçalves et al., 1999). Protection areas
under IUCN categories IV, V or VI, i.e. less strict
conservation that allows for certain kinds of land use,
thus should be more adequate and successful than
higher-level conservation areas: management is essential
for grassland conservation. Nonetheless, Campos areas
inside conservation units under integral protection
provide a invaluable opportunity for research into
vegetation dynamics and successional processes that
are not currently well understood. For example, in the
absence of fire and grazing will grassland turn into forest
vegetation in all parts of the grassland region? How long
will this process take, and what are the intermediate
stages? These apparently simple questions are far from
being answered in many parts of the Campos region.
Particularly in what is referred to as the Pampa biome in
the IBGE (2004) classification, i.e. the southern half of
Fig. 4. South Brazilian Campos landscapes, Top: Grazed
grassland in mosaic with Araucaria Forest. Bom Jesus,
highlands in northern Rio Grande do Sul (RS). The dominant
grass species is Andropogon lateralis Nees. Forests are often
found in small valleys or along escarpments. Photo: I.
Boldrini. Middle: Baccharis uncinella DC. (Asteraceae) shrubs
invading grassland areas abandoned for almost 15 years. São
Francisco de Paula, highlands in northern RS. Dominant
grasses are Sorghastrum setosum (Arechav.) Herter and
Andropogon lateralis Nees. Photo: V. Pillar. Bottom: Remnants of grazed Aristida jubata (Arechav.) Herter (Poaceae)
grassland near Passo Fundo, northwestern RS. Most of the
region has been transformed into intense agricultural lands
(soy bean and wheat production). Baccharis trimera (Less.)
DC. (Asteraceae) and Eryngium horridum Malme (Apiaceae),
in the foreground, are usually rejected by cattle. Photo: V.
Pillar.
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Rio Grande do Sul, grasslands may be quite stable even
in the absence of management, in contrast to the
grasslands in close contact with forest vegetation on
the Plateau discussed above, but long-term studies are
not available for these regions. The results from
successional studies would provide an essential basis
for developing strategies for the sustainable management of South Brazilian grasslands. Conservation action
is urgent if losses of grassland area are to be stopped and
extinction processes to be avoided – but conservation of
grassland biodiversity must reflect ecological properties
and successional processes and therefore allow for
adequate management practices.
Acknowledgements
The research leading to this paper was part of cooperation projects supported by CAPES (Brazil), the
German Academic Exchange Service (DAAD), the
German Research Foundation (DFG) and the State of
Bavaria (Germany). V.P. received support from CNPq
(Brazil). Our thanks go to Peter J. Edwards and to
Catherine Burns for checking the manuscript.
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