54 
Reflectance 
Figure 5 
Reflectance of beech branches of 
different damage classes, 5 branches 
piled up from trees of 1 = damage 
class 0/1; 2,3 = damage class 2/3, 
4 = damage class 3 
Reflectance of five piled up beech 
branches in the visible, description 
see figure 5. 
which will be superimposed by 
secondary effects. The order of 
magnitude may vary with the 
situation in nature. Branches of the 
same damage class showed yellowing of 
different degrees, which explains the 
spectral variation. The higher spec 
tral values for damage class 3 are 
the consequence of intensive 
yellowing. 
In its principle course reflectance 
of spruce branches, as displayed in 
figure 7, fits with the spectral 
reflectance curve of a damaged pine 
stand under water stress in the 
Stadtwald Frankfurt, see publications 
mentioned before. In the visible, as 
shown in figure 8, reflectance 
increases with increasing damage 
class as a consequence of 
discolouration (yellowing mainly) of 
needles. This tendency was also found 
in studies of Hoque et al., 1989, as 
part of the multilevel experiment 
DLR/GSF. The beginning of the slope 
to the NIR plateau shifts towards the 
blue and the gradient of the slope 
and the height of the NIR plateau, as 
well as the water absorption at NIR, 
decrease with increasing damage 
Reflectance of spruce branches of 
different damage classes, five 
branches piles up from trees of 
1 = damage class 0/1, 2 = damage 
Reflectance of five piled up spruce 
branches in the visible, description 
see figure 7. 
level. In the 1,4pm range curves are 
crossing. Then the reflectance raises 
with increasing damage level. 
5. Conclusion 
The measurements presented in figure 
1-8 show the spectral behaviour of 
tree components as a function of 
biomass or number of branches piled 
up of the same species, the influence 
of species and yellowing for healthy 
and damaged trees in the spectral 
region 0.49-2.50pm. Data from this 
spectral region is normally used for 
multispectral classification of vege 
tation. Further studies of Reinartz, 
1989, Kritikos et al., 1988, Kirchhof 
et al., 1986, on the separability of 
forest and forest damage classes 
confirm the result of our spectral 
measurements: Good sepration of tree 
species and yellowing could be ob 
tained by the use of spectral bands 
TM2 or TM3, TM4, TM5 and TM7 of the 
Thematic Mapper or the corresponding 
bands 3 or 5, 7, 9 and 10 of the 
Daedalus ATM scanner. For damage 
separation of the same species, the 
best results were reached with the 
ratios TM2/TM4 or TM3/TM4.