can be extracted from LANDSAT data. Knowledge of these relationships 
prior to beginning an analysis would enable the scientist to more ef- 
fectively plan a subsampling strategy to arrive at desired estimates 
of forest resource parameters. 
Pest Management 
Insects and disease continue to be serious pests of our forest re- 
sources. Large scale aerial photography has become an operational tool 
in the detection and evaluation of pest damage in forest stands.  Al- 
though Rohde and Moore (1974) and Rohde et al (1975) have reported the 
use of LANDSAT data for detecting and mapping hardwood defoliation, 
limited application of LANDSAT data for detecting disease or bark beetle 
damage is foreseen. 
It has been recognized that some insects can be controlled through 
proper silvicultural treatment of forest stands to reduce the suscept- 
ibility of stands to insect attack. For example, some forest stands be- 
come more susceptible to insect attack after a certain average stand age 
or stand density is achieved. Through sound thinning practices and 
shorter rotation ages, the incidence of insect attack is often reduced. 
Forest surveys will often provide the forest manager with inventory 
statistics indicating the area of forestland in different age classes or 
basal area classes. Planning and allocation of thinning operations or 
other silvicultural treatments require knowledge of the area as well as 
the areal extent of forest stands in various susceptibility classes. 
Research has shown that through highly controlled clustering tech- 
niques and digital analysis of LANDSAT data, a forest stand can be 
stratified into different density classes. Additional research is needed 
to define the extent to which forest stands can be stratified.  Simultan- 
eously, research efforts should focus on defining críteria of pest sus- 
ceptibility classes and the correlation of such classes with LANDSAT 
derived data. A project designed to test the capability of stratifying a 
ponderosa pine (Pinus ponderosae) type into three basal area classes 
( 60 sq. ft., 60-119 sq. ft, and 120+ sq. ft.) with LANDSAT digital data 
is being conducted by foresters at the EROS Data Center. Other studies in 
other forest types with various insect problems are needed to define the 
capabilities, document the procedures of analysis, and make these tech- 
niques available to forest scientists.