The effect of Armillaria root disease on lodgepole pine tree growth

Growth of lodgepole pine (Pinus contorta Dougl. ex Loud. var. latifolia Eng elm.) trees infected with Armillaria ostoyae (Romagn.) Herink growing in di sease centres were compared with the growth of uninfected trees from two st ands in west-central Alberta. Sample trees were measured (height, diameter at breast height, and height to live crown) and disks removed for stem anal ysis. The standing wood volumes inside disease centres of the two sites wer e 54 and 15% of the volume in surrounding stands. There were no significant differences in height or diameter at breast height between infected and un infected trees. Expected growth rates determined by stem analysis revealed, however, that there were conservative losses of 43% in annual volume incre ment, 32% in specific volume increment, and 23% in height increment. The pa ttern of stem growth of infected individuals was that typically found in op en-grown trees, in marked contrast to the pattern found in uninfected trees growing outside the disease centre. Tree growth chronologies suggested tha t disease centres were present early in the stands' development as trees gr ew rapidly before they became infected; however, the characteristic open-gr own pattern of trees found in disease centres did not change after they bec ame infected.