-— 7 
"a dying tree showing visible discoloration of foliage on aerial color 
photography." It is a pleasure to read reports where the terms are 
precisely defined but the problem is: a dead tree is still a dead tree, 
regardless of what killed it. From an overview of the literature it 
seems that the words "vegetation damage" are a collective term to indi- 
cate both dead and dying vegetation which has been noted because of a 
deviation from the normal pattern (both morphologic and physiologic) 
displayed by the vegetation. In some literature reports, damage indi- 
cates only vegetation in declining health or in the process of losing 
normal vitality. In either case it is recommended that authors precisely 
define their use of terms. For the remainder of this paper I have defined 
vegetation damage as "any type and intensity of an effect on one or more 
plants, or parts thereof, produced by an external agent, that temporarily 
or permanently reduces the financial or aesthetic value, or impairs or 
removes the biological capacity for growth and reproduction, or both". 
The above definition of vegetation damage is designed to be 
all encompassing, but in specific applications damage types can be 
clearly indicated. On the basis of the above definition, four damage 
types are recognized on their air-photo appearance: I, vegetation that 
is completely defoliated; II, vegetation that displays some defoliation; 
III, vegetation that shows foliage as a color inconsistent with the normal 
foliage color of the species, and IV, vegetation that shows no visible 
sign of damage, but has a deviation from its normal spectral reflectance 
pattern in the non-visible light range (Murtha 1972). Type IV damage 
was included in the dichotomous key (Appendix I) because of literature 
reports suggesting damage "detection" in the non-visible, near-infrared 
region of the spectrum (Murtha and Hamilton 1969; Remeyn 1972; Weber 
and Polcyn 1972). A total of 29 individual damage types were described 
in the four basic damage type categories (Appendix I). It has been 
suggested that the key to damage types presents an ordered method of 
classifying vegetation damage and subsequently aiding in interpretation 
of damaging agents from their appearance on air photos (B.J. Myers: 
1975, Pers. Comm)*. Even with the damage types available to describe 
their photo appearance it is still necessary to verify on the ground the 
exact cause of remote sensing detected damage (De Mars, et al. 1974). 
This will be necessary until remote sensing interpretations have pro- 
duced the necessary catalogue of a priori information to increase the 
confidence level of interpretation to the point where randomly selected 
verification checks are adequate. It is recommended that a universal 
method of classifying damage to vegetation be adopted to avoid the 
confusion of many descriptive terms and to provide a means for comparison 
of results. It is also recommended that a library of information on 
damage types that any given agent may cause, be assembled, and it be cross- 
referenced with other agents that may cause similar damage syndromes.  Par- 
ticular attention should be paid to spectral reflectance signatures for 
application in multispectral analysis, and every effort should be made to 
obtain the signature in situ from an airborne remote sensing platform. 
  
*Forestry and Timber Bureau, Canberra, Australia