Table 3. Change in shrub area from 1982 to 1992 for fire units 
  
  
  
1982 1992 
Fire unit Total area Shrub % area Shrub % area in 
(ha) area (ha) inshrub area (ha) shrub 
T-10-J 229 0 0 6 3 
T-10-K 216 13 6 13 6 
T-10-L 286 8 3 6 2 
T-16 358 25 7 108 30 
T-17 141 32 23 66 46 
C-15-C 609 65 11 173 28 
C-15-D 180 1 1 37 21 
  
areas were often at least double of 1982 
levels. Of particular note are units T-16, T- 
17, C-15-C, and C-15-D, where each had over 
20% area in shrub in 1992. The four units are 
located continuous to one another and in a 
location that is approximately 7.5 km south of 
the other three units, which are also 
continuous to one another. Table 4 shows 
that the four units with the most shrub area 
also had the largest change in number of shrub 
patches. The increases might have been 
expected in units C-15-C and C-15-D since 
they received only one burn during the ten 
year period. The other five units all had four 
or five burns during the period. Note, 
however, that T-16 and T-17 started with the 
large relative amounts of shrub in 1982. 
These two units also had the largest percent of 
shrub patches in the low PAR quartile, 
indicating that they had many large patches 
(see Figure 1 for example fire unit T-17). 
Large patches of shrub may be less 
susceptible to fire. If a fire were to burn 50 
meters into each patch, it would effectively 
eliminate small patches with only a minimal 
effect on large patches. In addition, 
vegetation would remain adjacent to the 
burned shrub areas in large patches, potentially 
acting as a vector for regeneration or spread 
of vegetation in the area. 
Table 4. Change in number of shrub patches 
from 1982 to 1992 for study fire units. 
  
  
  
Number of shrub 
polygons 
Fire unit 1982 1992 change 
T-10-J 0 7 7 
T-10-K 23 30 7 
T-10-L 16 19 -3 
T-16 10 36 26 
T-17 22 34 12 
C-15-C 4 35 31 
C-15-D 32 72 40 
  
112 
Several severe freezes during the study 
period (Provancha et al. 1986) are blamed for 
reducing the areal extent of mangrove in the 
area. | C-15-C and C-15-D contained the 
largest area in mangrove vegetation in 1982. 
We estimated that mangrove area declined 
from 96 ha to 41 ha in C-15-C and from 45 ha 
to 20 ha in C-15-D. This may account for a 
portion of the shrub increase in those units. 
For the most part, shrub patches 
expanded in areas currently with some shrub 
patches. One notable exception to this 
appeared to be isolated areas once classified as 
mangrove. 
  
  
3.2 Error 
CI 
81% ac 
occurring 
types of | 
the shrub 
40 times ( 
of shrub t 
group). 
correctly ‘ 
Be 
present 3 
variance | 
was low, 
total shr 
confidenc 
estimated 
T-10-L. 
polygons :