TM 1 
Spect ral 
DN radiance 
Basal area cut, (7) 
TM 4 
Spectral 
Basal area cut, (7) 
TM 2 
Spec t ral 
DN radiance 
Basal area cut, C'/J 
TM 5 
Spec t ra1 
DN radiance 
Basal area cut, (7) 
TM 3 
Spect ral 
0 20 40 60 80 100 
Basal area cut, (7) 
TM 7 
Spect ral 
Figure 1. DN changes for the six TM channels used, as a function of thinning 
grade. Polynomials obtained by best subset least squares regressions. The 
vertical bars in the left part of the diagrams show the mean and +/- 1 
standard deviation of the residuals before the year of thinning. The spectral 
radiance values are in N m 2 sr~ x pm -1 . 
t— +/- 1 std 
■ before cut 
Thinnings 
Inter 
polai ion 
Seedling 
s t ands 
3.2 Influence of tree species compositions 
Figure 2 shows the DN response for thinnings 
grouped by tree species distribution after 
thinning. It is shown how pine dominated stands 
tend to have stronger DN response. This is 
especially clear in the visual channels TM 1- 
TM 3. Table 3 shows that the proportion of pine in 
this material does decrease with an increased 
grade of thinning. This might be one factor behind 
the reduction in DN respose in the first part of 
the curves in figure 1. 
1 2 3 4 5 7 
707 pine 
107 dec. 
707 pine 
107 dec. 
107 dec. 
TM channel 
In figure 3, the DN response is plotted by change 
in tree species distribution. Most obvious is the 
large decrease in TM 4 in the group with more than 
5 % decrease in the deciduous forest. 
DN 
> 57 pine 
> -57 dec. 
smal 1 
changes 
< -57 dec. 
Figure 3. DN response for the thinning cuttings 
only, grouped by change in tree species 
proportions. 
Figure 2. DN response for the thinning cuttings 
only, grouped by distribution of three species 
after thinning. 
853