they are exploited with cattle, these represent low productivity
pasture areas. This occurs due to the elevated soil cover with
natural regrowth (excessive shading) and the difficulties of
intensive management practices that imply the necessity of
mechanization (Numata et al., 2007). Thus, the most common
LUC trajectory was from forest to degraded forest, and to
deforestation with typical regrowth and regrowth with pasture.
Pasture/Rice
4%
Figure 3. Distribution of the LUC classes in 2011 in deforested
polygons without soy.
According to data from the TerraClass project, which classified
the land use cover in 2008 for the total deforested PRODES
presented in 2007, 46.7% of the deforestations were with clean
pasture. The natural regrowth class covered 21% of the
deforested areas and regrowth with pasture covered 8.7%.
Taking into account that annual crop occupied only 4.9% of the
deforested area, there was a significant discrepancy between
these results and those originating from TerraClass for the
classes of pasture and regrowth. It is likely that these differences
are due to the fact that in this work, only the first few years after
deforestation were evaluated, while TerraClass considered the
historical deforestation since 1988. Therefore, part of the
recently deforested areas currently in regrowth process or
covered with pasture with regrowth could still be converted to
clear pasture during the coming years.
Another observation for the polygons without soy is that, in 12
polygons (24.5%) did not occurred the total clearing of the area
after the shallow cut pointed by PRODES. In all these cases, it
was observed that subsequent pattern was clear pasture. This
result is coherent because the deforestation process is a costly
one and the investment made by the producer is only justified
when the goal is to use the area more intensively for either cattle
raise or agriculture.
It is also interesting to observe that only 2 polygons were
directly converted to agriculture in 2011. In the event that the
conversion actually occurred, the low EVI2 peak observed in
this crop year is likely to be associated with the cultivation of
rice, since legumes such as soy tend to have elevated EVI2
peaks at maximum crop development.
Areas with soy in crop year 2010/11
Out of the 50 selected polygons with soy in crop year 2010/11,
39 (78%) were from Mato Grosso, 11 (22%) from Para and
none from Rondonia. The soy selected polygons were also
classified according to the year of deforestation detected by
PRODES. Thirty-two polygons (64%) were from deforestation
International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, Volume XXXIX-B8, 2012
XXII ISPRS Congress, 25 August — 01 September 2012, Melbourne, Australia
detected in 2007; 13 polygons (26%) from 2008; 5 polygons
(10%) from 2009; and none from 2010 indicating that the
entrance of soy soon after deforestation is not a common
practice adopted by the farmers in the region. However, the 5
polygons from 2009 were directly converted to soy.
Rivero et al. (2009) and Brown et al. (2005) related that even
though the areas had been deforested with the objective of soy
cultivation, this transition generally did not occur immediately
after deforestation. There is a transition process in which the
cultivation of rice is a common practice during a period which
can vary from 1 to 3 crop years after deforestation. Our results
showed that for more than 70% of the analyzed polygons the
soy crop was likely to be preceded by rice crop. Two main
factors contribute to this commonly used transition. The first is
the lower demands for soil fertility and pH for rice cultivation,
which is corrected by the addition of chemical fertilizers and
limestone. The second is related to the difficulties of
mechanized harvesting of the crops, since it is a recently
deforested area, where generally many irregularities exist in the
terrain, caused by the pulling of stumps or the occurrence of
protruding roots. This hampers the operation of combine
harvester, especially for soy, since this is conducted with
platforms close to the ground. On the other hand, for rice
cultivation, the harvesting platform remains higher above
ground (20 to 30 cm), avoiding possible damage to the cutting
bar of the platform due to contact with roots or stumps that can
damage the combine harvester. During the rice cultivation new
stump and protruding root suppression operations are conducted
in a way to permit the entrance of soy in following years.
Nearly half of the soy polygons showed some indication of
forest degradation prior to the deforestation process which was
much lower than the 80% of degradation observed for the
polygons without soy. This might be motivated by the location
of the agricultural areas. In other words, the current centers of
agricultural production are concentrated in the oldest regions of
colonization of the Amazon region, where timber harvesting by
means of selective logging could have occurred before the year
2000. In addition, when the farmer makes a decision to increase
his cultivated area over forest land, this tends to occur in a more
direct way. The phase of induced fires, for example, during
several years before the deforestation could not occur if the
decision to increase the agricultural area is associated with an
instantly attractive agricultural commodity market price. It was
also possible to identify the year in which the total clearing of
the area was made in almost all cases, except for two polygons.
In approximately 20% of the cases, there were signs of the
beginning of the regrowth process after the clearing of the area,
which in none of the cases exceeded two years. Hence, there is a
transitional pattern which can occur in some cases when the
farmer does not finalize the preparation of the soil for
cultivation, immediately after the total clearing of the area,
concluding the preparation of the soil throughout the following
years.
Thus, in the polygons with soy in crop year 2010/11 it was
possible to identify and trace two main LUC trajectories: 1)
forest — forest degradation — total clearing of the area —
agricultural cultivation (predominantly rice) — soy; 2) forest —
total clearing of the area — agricultural cultivation
(predominantly rice) — soy. The average duration of the
transitional cultivation of an annual crop such as rice was two
crop years from total clearing to soy cultivation. It should be
noted that in contrast to the polygons without soy, the
occurrence of soy basically defines the end of the LUC
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