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3.2 Classification 
Multitemporal shade images 1997 were divided in two sets of false color composition (FCC) (figure 2). The first one 
consisted of the images 1987, 1988 and 1993, attributing each of these to bands blue, green and red, respectively. The 
colors resulting from this combination allow us to identify the time frame of the deforestation and to infer the time 
frame of the land cover change. Combined with second set of FCC, consisting of the shade images 1993, 1996 and 
1997, all age classes of pasture related to land cover changes occurred in the period in study are represented. These 
FCC sets were used to extract training area for each age class and then the supervised classification (MAXVER 
classifier) was run so that all pasture ages information could be gathered in a single image. 
Land cover changes were divided in five classes: 1-2 years old, 3-5 years old, 6-10 years old, 10 years old and >10 
years old. The class “forest” was included as a control to indicate the natural soil fertility. These classes were chosen to 
represent most of the pasture chronossequence phases and associated soil fertility dynamics shown in Figure 1. 
However, one must recognize that this procedure also detects the time frame of land cover change that also include 
other uses than pasture that also shows up with low shade fraction. In this case other criteria are needed to identify 
pasture, such as size and form of the area. With that in mind, fieldwork was designed and the pre-selected sites were 
verified for future sampling. The area extent of 10 year old class turned out to be too small, so it was eliminated from 
the soil fertility decay study. To evaluate the results of the classification, a reference map of the deforested areas of the 
region was elaborated by analyzing visually each image of time series images used in this study. (for details, see 
Numata , 1999). 
     
(1987. __yo38 1993 1996 
  
  
  
Class 87—B | 88—G | 93—R |Resultant 
color 
Forest 
6-10 yrs X 
10 yrs X X 
>10yrs X X 
  
  
  
  
  
  
  
  
Figure 3. The color composition associated with the periods of the land use 
  
  
  
  
  
International Archives of Photogrammetry and Remote Sensing. Vol. XXXIII, Part B7. Amsterdam 2000. 1035