economical it might currently be to obtain satellite imagery in comparison to airphotos. This 
is not to imply that measurements of forest cover type should not or will not be made from 
satellite images. However, the forestry profession may have to continue to depend upon 
imagery from satellite sensors optimized and designed for other prime purposes. 
The greatest potential for the sustained application of space systems in the forest management 
process is the monitoring of areas where forest cover is subject to rapid alteration by either 
natural or manmade activities. These alterations are widely varied in their nature and causes, 
ranging from shifting cultivation, tropical forest exploitation, insect infestations, natural can- 
opy closure, and many others. However, the majority result in a significant alteration in the 
standing crop of leaf biomass present per unit area. Extensive research dealing with the grass- 
land ecosystem2 3 has already clearly shown that the alteration of the amount of leaf material 
per unit area is much more readily measured in the visible and photoinfrared spectral regions 
currently available on spacecraft, than are the subtle spatial variations in spectroreflectance 
due to variations in species composition in that ecosystem. Certainly the division of the for- 
ested areas of the world into the two *'big" ecosystem classes consisting of areas dominated 
by needle or broadleaf types can readily be made using Landsat satellite imagery. However, 
within these two subdivisions, the determination of the status of the forest canopy based 
upon variations in leaf biomass per unit area provides a much more viable alternative. It pro- 
vides a much clearer justification for a forestry remote sensing program from space platforms 
than to continue looking for the subtle variation in spectroreflectance needed to further sub- 
divide the forest ecosystem into more specific cover types or species classes. The improved 
management of the forest canopy which would result from using such information will 
certainly require yearly imagery, if not imagery at several key seasonal points during the year. 
Clearly, this requirement and associated techniques would provide a much more viable basis 
for justifying a space program dealing with forestry applications. 
Preliminary tests of the hypothesis that forest canopy alteration can be readily monitored 
with digital processing of Landsat-type imagery have been completed. No large quasi- 
operational program is yet underway, but this collection of small, individual research efforts 
will be presented to illustrate the results achieved to date in a variety of geographic settings 
around the world. All of the summaries which follow deal with digital analysis of the 
Landsat imagery, but these examples vary considerably in their complexity and the analysis 
procedures employed. Therefore, it is felt that as a group they serve as examples of the types 
of forest canopy monitoring which can be undertaken, the approaches available, and the 
potential results which can be achieved. Each of the summaries which follows has been delib- 
erately briefed to conserve space. However, references to detailed reports on each topic are 
provided and are readily available from the respective sources and/or researchers whose names 
and addresses are included for this purpose. 
  
2Pearson, R. L. and Miller, L. D., 1972. Remote mapping of standing crop biomass for estimation of the 
productivity of the shortgrass prairie, Pawnee National Grasslands, Colorado. Proc. of the 8th International 
Symposium on Remote Sensing of Environment, Univ. of Michigan, Ann Arbor. pp. 1357-1381. 
3Tucker, C. J., 1978. Hand-held radiometer studies of vegetation in situ: a new and promising approach. 
Proc. of the International Symposium on Remote Sensing for Observation and Inventory of Earth Re- 
sources and the Endangered Environment, International Society of Photogrammetry and the International 
Union of Forestry Research Organization, Freiburg, Germany. 6 p. 
  
   
  
    
  
   
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
   
    
  
   
  
   
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