The effect of Armillaria root disease on lodgepole pine tree growth

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