. 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. HAZARD-RATING SYSTEMS Systems for rating the risk of MPB outbreaks in lodgepole pine forests usual- ly have been based on (1) historical eval- uation of the frequency and intensity of infestations within a region; (2) correla- tion of damage intensity and habitat type; (3) evaluation of damage by climatic zones; (4) host tree character
. 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. HAZARD-RATING SYSTEMS Systems for rating the risk of MPB outbreaks in lodgepole pine forests usual- ly have been based on (1) historical eval- uation of the frequency and intensity of infestations within a region; (2) correla- tion of damage intensity and habitat type; (3) evaluation of damage by climatic zones; (4) host tree characteristics, including diameter and phloem thickness; (5) stand characteristics, including crown competi- tion, periodic growth rate, and basal area; and (6) various combinations of these fac- tors . A map of relative stand hazard from MPB has been developed for the central and northern Rockies, based on the fre- quency and intensity of past infestations (Crookston et al. 1977). The map is useful in drawing attention to stands in areas that have suffered repeated severe out- breaks, so that these stands can be rated using specific hazard-rating systems. Beetle-caused tree mortality has been related to habitat types (Roe and Amman 1970). The risk of growing trees to a specific diameter was considered the prod- uct of the proportion of trees killed in a diameter class times the proportion of stands on a given habitat type that showed evidence of prior infestation. For ex- ample, growing trees to 16 inches ( cm) would be a high hazard (75 per- cent probability of loss) on Abies lasio- carpa/Pachistima myrsinites type, where 82 percent of the trees were killed and 92 percent of the stands were infested. In contrast, the hazard of growing 16-inch trees on the Abies lasiocarpa/Vac- cinium scoparium type would be much less, with about two-thirds of the trees expec- ted to survive (36 percent probability of loss). However, because of the elevation range in some habitat typ
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