752 
INTERPRETATION OF COLOUR-INFRARED PHOTOGRAPHS FOR THE ASSESSMENT OF FOREST DECLINE 
IN CENTRAL EUROPE 
Claus-Peter Gross Norbert Heidingsfeld 
Universität Freiburg i. Br. 
Abt. Luftbildmessung und Fernerkundung 
Werderring 6, D--7800 Frei bürg, FRG 
Forstliche Versuchsanstalt 
Rheinland-Pfalz, Abt. Waldschutz 
Schloss, D-6751 Trippstadt, FRG 
ABSTRACT 
In addition to the terrestrial assessment of new types of forest decline, the visual interpreta 
tion of large-scale Colour Infrared Photographs is a common and powerfull inventory method to 
detect and study new types of forest, damage in Central Europe. 
The paper summarizes on investigations of an international working team of experts in photo 
interpretation which allows to establish standard interpretation keys. 
KEY WORDS: Forest Damage, Photointerpretation, Colour-Infrared Photographs, Interpretation Keys 
1 TERRESTRIAL FOREST DAMAGE SURVEYS 
1.1 Main Symptoms and Assessment Methods 
The last decade saw a new type of forest de 
cline in many forest regions of Central Eu 
rope. The damage is widespread and indepen 
dent of 3ite conditions or proximity to in 
dustrial centres. The symptoms vary but gen 
erally point to air pollution. 
Main visible symptoms of the damages are: 
progressive loss of needle/leaf, discoloura 
tion affecting parts or the whole crown and 
also deformation of the crowns. Decreasing 
virour makes the afflicted trees prone to 
biotic as well as climatic effects. Further 
more remarkable decrease of timber increment 
can be observed. 
The situation is alarming and has led for 
estry and research institutes to develop ob 
servation and monitoring methods in order to 
inventory the extent, distribution and in 
crease of the forest, decline. In the Federal 
Republic of Germany (FRG), for example, this 
need has since 1983 been met by annual ter 
restrial inventories. The basis of data col 
lection ist a representative field survey 
using systematically distributed sample 
points tied to a geographic coordinate system 
(generally grids of 4 x 4 km). At each point, 
a number of sample trees are selected (gen 
erally 24 trees) and their crown condition is 
assessed every year /16/. 
For every single sample tree a visual assess 
ment. of defoliation is made in five classes 
separated according to needle/leaf loss per 
centage as follows /2/, /18/: 
Class 
Degree of 
Percentage of 
defoliation 
needle/leaf loss 
0 
not defoliated 
0 - 
10 % 
1 
slightly defoliated 
> 10 - 
25 % 
2 
moderately defoliated > 25 - 
60 % 
3 
severely defoliated 
> 60 - 
99 % 
4 
dead 
100 % 
Discolouration of the remaining foliage can 
additionally be assessed as in the following 
4 classes: 
Class Discolouration Percentage of 
foliage discoloured 
0 
None 
0 - 
10 
% 
1 
Slight 
> 10 - 
25 
% 
2 
Moderate 
> 25 - 
60 
% 
3 
Severe 
> 
60 
%