Agriculture Reference
In-Depth Information
Macedo
et al
., 2008; Machado
et al
., 2010;
Tabarelli
et al
., 2010).
500,000
450,000
400,000
350,000
300,000
250,000
200,000
150,000
100,000
50,000
Annual Crops and Pasture: Impacts
on Carbon Stocks and Dynamics
Carbon stocks in Cerrado soils are close to
those found under Brazilian rainforests, with
values varying from
133
to
236
Mg C ha
-
1
in
the 0-100 cm layer (Lopes-Assad, 1997;
Corazza
et al
., 1999; Bustamante
et al
., 2006).
Analysing data from the literature, we esti-
mate carbon stocks in the surface soil layer
(0-20 cm) of different Cerrado phytophys-
ionomies ('cerradão', 'cerrado
stricto sensu'
,
'campo limpo', 'campo sujo' and 'forest') to be
46
±
15
t C ha
-
1
,
being an important carbon
reservoir (Corazza
et al
., 1999; Freitas
et al
.,
2000; D'Andréa
et al
., 2004; Neves
et al
.,
2004; Silva
et al
., 2004; Bayer
et al
., 2006;
Corbeels
et al
., 2006; Siqueira Neto, 2006;
Frazão, 2007; Machado
et al
., 2007; Rangel
and Silva, 2007; Dieckow
et al
., 2009; Matias
et al
., 2009; Salton
et al
., 2011).
In general, the conversion of native vege-
tation to agricultural systems, especially under
conventional tillage, results in significant
reductions of these stocks (Corazza
et al
.,
1999; D'Andréa
et al
., 2004; Oliveira
et al
.,
2004; Silva
et al
., 2004; Bayer
et al
., 2006;
Bustamante
et al
., 2006; Jantalia
et al
., 2007).
Soil carbon stocks (SCSs) (0-30 cm) under
different land uses and soil classes in Brazil
were estimated by processing data from the
Embrapa Soil Information System's database
land-use maps available at the Brazilian
Ministry of Environment website (Fidalgo
et al
.,
2007). Latosols (Oxisols, USDA Soil Tax-
onomy) are the dominant soil order (49% of
total area) in the Cerrado biome, and the dis-
crimination between land uses is noticeable,
with 43.8, 40.6 and 34.2 Mg C ha
-
1
on average
for native vegetation, pasture and agricul-
ture, respectively, in a total of
113
soil profiles
(Elaine C.C. Fidalgo, personal communication).
In the rolling Pampas grassland (nor-
thern part of the biome), where soil organic
matter is the main C pool, converting pas-
tures and grasslands to annual croplands
decreased C stocks by 50% in one century
0
Sunflower
Wheat
Soybean
Fig. 21.3.
Evolution of areas cultivated with wheat,
sunflowers and soybeans in the La Pampa province,
Argentina, during the past decade. (From Gobierno
de La Pampa, 2009.)
(Neto
et al
., 2010). The Atlantic Forest is the
most threatened biome in Brazil (Schaffer
and Prochnow, 2002). Originally covering
about
1,315,000
km
2
(Plate 13), it was re-
duced to a discontinuous area of approxi-
mately
100,000
km
2
; that is, approximately
8% of its original extent (Morellato and
Haddad, 2000; Atlântica, 2012). This biome
contains a species diversity higher than
most of the Amazon forests, and is charac-
terized by high levels of endemism (Brown
and Brown, 1992).
Land-use dynamics of the Atlantic
Forest biome could be summarized by the
onset of the sugarcane (
Saccharum offici-
narum
) cycle, Brazil's first major export
crop, which started being planted by the
Portuguese settlers in the 16th century, fol-
lowed by coffee, introduced in the 18th
century. Timber extraction and charcoal
production has been a constant activity in
this biome (Dean, 1995; Morellato and
Haddad, 2000; Boddey
et al
., 2006; Salemi
et al
., 2012). The impact of forest clearing
for agriculture, followed by pastures, cre-
ated degraded landscapes, with significant
impacts on the provisioning of ecosystem
services (biodiversity conservation, soil
water retention, soil stabilization and car-
bon sequestration) (Boddey
et al
., 2006;
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