. Hazard-rating systems in forest insect pest management : symposium proceedings, Athens, Georgia, July 31-August 1, 1980. Forest insects Biological control United States Congresses; Forest insects United States Analysis; Forest insects United States Management. of the variation in the dependent varia- ble than is possible with any other set of subgroups. Results are readily visual- ized as branching diagrams. The AID analysis of tree mortality delineated nine mutually exclusive groups of plots and the proportion of loss in each group. Six variables defined the tree-loss classification system.
. Hazard-rating systems in forest insect pest management : symposium proceedings, Athens, Georgia, July 31-August 1, 1980. Forest insects Biological control United States Congresses; Forest insects United States Analysis; Forest insects United States Management. of the variation in the dependent varia- ble than is possible with any other set of subgroups. Results are readily visual- ized as branching diagrams. The AID analysis of tree mortality delineated nine mutually exclusive groups of plots and the proportion of loss in each group. Six variables defined the tree-loss classification system. Figure 5 shows the tree-loss profiles. Stands at elevations of 1,000 ft or higher and in which 20 percent or more of the trees had poor crowns before infestation (Group 9) had the highest mortality-42 percent, compared with 13 percent for the total sample. This group accounted for 6 per- cent of the Figure mortality variables. The average stand mortality is shown for each group. The decimal fraction on each leg shows the proportion of sam- ple in that group. Stands with the least tree loss (Group 6) were effectively identified by one characteristic: crown condition class. Thus, stands having no trees with poor crowns (24 percent of the sample) had only 5 percent mortality—one-eighth as much as in the highest mortality group. Similarly, intermediate groups, with tree mortality rates ranging from 7 to 26 per- cent, can be identified. In some cases, value loss rather than tree loss may be the desirable basis for decisionmaking. Figure 6 presents the AID results expressed in percentage of stand value loss. Percentage of trees with poor crowns was the criterion that most sharply separated value loss. The crown condition and elevation combination that defined the highest tree mortality group also selects the group (Group 9) with the greatest timber value loss--51 percent, compared with the sample average of 12 percent. Species, basal area, aspect, and site index
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