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Modified Stand Hazard Ma Here ene t
Figure 7. Modified hazard map (left panel) incorporates in:formation on lightning-struck hosts and existing infestation
centers. This map also contains information on the dispersal behavior of D. ¢?o_talis. The dispersal distance was
represented as an area (a circle with a 1 km radius) around the lightning-struck hosts and infestation centers. Dis-
persal and host selection behavior of the insect link the network of high hazard stands, infestation centers, and
lightning-struck host. The heterogeneity map (right panel) was developed using the AMI index applied to the
modified hazard map, using the moving-window calculation. This map illustrates how the network of high hazard
:stands, liglhtning-struck hosts, and existing population centers is connected through dispersal behavior of the insect.
The Heterogeneity Map. Third in the sequence is the functional heterogeneity map (Fig. 7 - right panel). In this
particular example, tile AMI index was applied to the modified hazard map, using the moving-window calculation described
above. Recall that the AMI index is sensitive to dispersion of landscape elements. The functional heterogeneity index allows
for integration of the information on landscape structure and insect behavior known to influence epidemiology of D. frontatis.
The heterogeneity map (Fig. 7-right panel) is a visualization of the results. This map illustrates how the network of high
hazard stands_ lightni_g.-struck hosts, and existing population centers is connected through dispersal behavior of the insect.
Knowledge of this interaction will certainly increase with new research on epidemiotogy, and this added complexity can be
accommodated by the approach, Figure 7 (right panel) is a characterization of only one point in time. During the course of
the year, functional heterogeneity of the landscape will change for the reasons outlined above. Functional heterogeneity will
also change during successive years of an insect outbreak, as herbivory creates additional fragmentation of the forest matrix.
Furthermore, there will be a flux in habitat available to the insect in successive years, as high hazard stands are depleted
through herbivory and new stands grow into the vulnerable age classes. The index values are a quantitative measure of
ftmctional heterogeneity and therefore can be used for tile analysis and description of sequential map data. Recall, also, that
the tt_ree indices are sensitive to dilYerent aspects of landscaPe pattern. Therefk)re, each index will provide alternative insights
into how O_ ._f?ontatis perceives and reacts to its environment.
Host Defenses and Epidemiology of Dendroctonus frontalis
"Ik_summarize, at the onset of this study, we indicated that epidemiology of D. frontalis was related to the distribution
of host defenses in forest landscapes. Previous research had clearly established that infestations typically occur in high
hazard stands consisting of hosts with reduced capacity for defense against colonization by bark beetles. Hazard rating
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