Table 7. — AREA OF MATURE AND OVERMATURE CONIFER 

 TIMBER BY FOREST TYPES AND RISK CLASS 



Type 



High risk 



Low risk 



Total 



Subalpine fir 



1,448 



Acres 



375 



1,823 



Douglas-fir 



2,900 



9,729 



12,629 



Lodgepole pine 



75,511 



57,059 



132,570 



Ponderosa pine 



1,392 



9,601 



10,993 



Spruce 



7,530 



35,076 



42,606 



Total 



88,781 



111,840 



200,621 



Table 8. — NUMBER OF LODGEPOLE PINE TREES 

 KILLED BY MOUNTAIN PINE BEETLES, 

 1956—1961 



Year 





Thousands 



1956 





100.0 



1957 





108.6 



1958 





192.0 



1959 





199.2 



1960 





304.6 



1961 





300.0 





Total 



1,204.4 



Losses during this epidemic varied from stand to stand. However, the damage was 

 most severe in older stands, particularly the ones heavily infected with dwarfmistletoe. 

 Between 1956 and 1961 more than a million lodgepole pine trees were killed by pine beetles 

 (table 8). Since these insects usually concentrate on the larger trees, the volume loss has 

 been high. Data are not available to show the exact volume of the utilizable-size trees that 

 have been killed; however, many sawtimber stands have been reduced to ghost forests of 

 dead trees. A few timber inventory plots examined in 1962 had lost about 40 percent of 

 their sawtimber volume in the preceding few years. 



Dwarfmistletoe is putting the finishing touch on the deterioration of many North Slope 

 forests. This plant parasite has constantly plagued the lodgepole pine on the North Slope. 

 However, it has become an increasingly serious problem in the past century. There are 

 several reasons for this. In the first place, dwarfmistletoe thrives best where stands are 

 open. Logging for railroad ties was largely a selective process that opened up stands. The 

 substantial losses in older stands due to insects and other agents have created more open- 

 ings; thus, conditions have been ideal for spread and intensification of dwarfmistletoe in- 

 fection. Effective fire control in the past half century has aggravated the problem because 

 fires had periodically destroyed the timber on infected areas and thus cleared the way for 

 dwarfmistletoe-free young stands. 



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