Impact of Armillaria root disease on succession in red pine plantations in southern Ontario

Abstract

Armillaria root disease created openings in southern Ontario red pine plantations that are gradually succeeding to hardwood-dominated mixedwoods through natural regeneration. A study of 13 root disease centres found several tree and shrub species colonizing the openings. Black cherry was the most important hardwood and white pine the most important conifer colonizer. Mortality of black cherry and white pine regeneration was greater than for other species. Long-term survival of conifers in the centres is doubtful, and high mortality of black cherry is expected. Other hardwood species may fare better but with growth and yield losses due to Armillaria infection.Key words: Armillaria root disease, red pine plantations, succession, disturbance ecology, Armillaria ostoyae Le poumdi6-agaric cr6e des ouvertures dans les plantations de pin rouge du sud de I'Ontario qui sont graduellement envahies par des peuplements m6langCs B dominance feuillue par voie de r6gCnCration naturelle. Une Ctude de 13 sites de pourridiBagaric a port6 sur les quelques arbres et espkes d'arbustes qui colonisent les ouvertures. Le cerisier tardif repr6sentait l'espke feuillue la plus importante accompagn6 du pin blanc cornme le plus important colonisateur r6sineux. La mortalit6 de la r6gCn6ration dans le cas du cerisier tardif et du pin blanc 6tait plus importante que pour les autres espkces. La survie B long terme des coniferes dans ces ouvertures est douteuse, et une importante mortalit6 du cerisier tardif est B pr6voir. Les autres espkces feuillues pourraient mieux se comporter, mais avec des pertes en croissance et en rendement par suite de l'infection par 1'Armillaria.

Restoring southern Ontario forests by managing succession in conifer plantations

“…Over time, the forest cover provided by these plantations has improved soil conditions (Wilde 1964, Stone 1975, McPherson and Timmer 2002 and moderated the microenvironment of these once-exposed, degraded lands, creating understory conditions conducive to the natural establishment of more shade-tolerant forest tree species (Russell 1955, Truax et al 2000, McLaughlin 2001, Hewitt and Kellman 2002. Disturbance by thinning and the natural mortality of single or groups of trees in older plantations has stimulated the development of this forest understory and accelerated the succession of these plantations to a more natural forest composition (Young 1933, Russell 1955, Goldblum 1998, McLaughlin 2001, Parker et al 2001.…”

“…Disturbance by thinning and the natural mortality of single or groups of trees in older plantations has stimulated the development of this forest understory and accelerated the succession of these plantations to a more natural forest composition (Young 1933, Russell 1955, Goldblum 1998, McLaughlin 2001, Parker et al 2001. In younger plantations with little disturbance history, very low understory light and thick litter layers impede the establishment of understory vegetation (Russell 1955, Gysel 1966, Anderson et al 1969, Truax et al 2000.…”

Identification of <i>Armillaria</i> Species in the Chequamegon-Nicolet National Forest

“…Changes in harvest practices, natural forest succession, and weather patterns contributed to these changes, but most likely so did insect outbreaks and diseases, including Armillaria root disease. Evidence of the significance of A. ostoyae in forest succession and composition has been reported by McLaughlin (2001b) in areas of southern Ontario. Hardwood species are colonizing openings where A. ostoyae has killed the red pine.…”

“…Beginning in the late 1980s, USDA Forest Service personnel observed tree mortality and decline in some areas of the Chequamegon. Armillaria root disease, important in several areas of North America (Bruhn et al 2000, Lundquist 2000, Mallett and Maynard 1998, McLaughlin 2001b, Morrison et al 2001, Rizzo and Slaughter 2001, was suspected of contributing to these observed declines, but no mycological investigations had been done in this area.The objectives of this study were to identify the species of Armillaria present in the Chequamegon, especially in declining stands, and to relate these findings to previously collected information about Armillaria, particularly in the western Great Lakes States, but also in other areas of North America. This is the first step in assessing the role of these fungi in the Chequamegon forest.…”

“…Beginning in the late 1980s, USDA Forest Service personnel observed tree mortality and decline in some areas of the Chequamegon. Armillaria root disease, important in several areas of North America (Bruhn et al 2000, Lundquist 2000, Mallett and Maynard 1998, McLaughlin 2001b, Morrison et al 2001, Rizzo and Slaughter 2001, was suspected of contributing to these observed declines, but no mycological investigations had been done in this area.…”