Silviculture in Red Alder Stands

In the past, there has been an emphasis on conifer tree species in forestry operations in British Columbia. As a result, there is a serious lack of information regarding disease and decay problems in most hardwood tree species. This presentation reports the results of recent studies on levels of decay in natural red alder stands, and on the formation of stain in harvested alder logs. Disease problems of paper birch are also discussed. In a study to determine levels of decay in red alder (Alnus rubra Bong.), 383 trees were examined at 38 sites representing broadly diverse geographical and climatic habitats on Vancouver Island. Decay was observed in trees of all ages; the incidence of decayed trees increased with tree age. A variety of pathological indicators, including scars, forks, crooks, branch stubs, and dead and broken tops were observed in association with decay. Scars were the most common indicator associated with decay (36%). Scars were also the best predictor of decay; 51% of the scars visible on standing trees were associated with decay. Most of the decay observed in living alder was incipient and often compartmentalized. Decay volumes were generally low (median decay volume was 0.0024 m3). A number of decay fungi were isolated from living alder, including Armillaria sinapina Bérubé & Dessureault, Sistrotrema brinkmannii (Bres.) J. Eriksson, Heterobasidion annosum (Fr.:Fr.) Bref., Pholotia adiposa (Fr.:Fr.) P. Kumm., Trametes pubescens (Schumach.:Fr.) Pilát, Meruliopsis corium (Fr.:Fr.) Ginns., and Stereum ostrea (Blume & Nees:Fr.) Fr. A reddish stain is formed on the surface of freshly cut alder wood, as well as in response to the invasion of wood tissues by fungi. Superficial staining can generally be removed through proper kiln-drying procedures, but fungal-induced stain results in reduced wood quality and reduced economic value. Storing logs under conditions that inhibit fungal growth will result in less staining of wood. In general, storage in cool, moist conditions will retard staining. Logs may be stored in the winter for up to six months with little staining. Logs cut in the spring and summer should be milled as soon as possible after harvest. There is some evidence that fungicidal wood preservatives can be used to slow the development of fungal-induced stain. Very little research has been directed at pathogen problems affecting paper birch (Betula papyrifera Marsh.) in B.C. Studies conducted in eastern Canada, where birch has a more important commercial profile, have shown serious losses due to stain and decay in mature trees (15–45% of merchantable volume). Fungi responsible for significant levels of stain and decay in eastern birch