- Cooperation Agreement for Forestry Development
The latest spruce budworm [SBW] (Choristoneura fumiferana (Clem.)) infestation on Cape Breton Island, Nova Scotia began in 1974 (NSDLF, 1977; Ostaff and MacLean, 1989). The infestation reached a peak in 1976-1977 causing widespread mortality of balsam fir (Abies balsamea (L.) Mill.), white spruce (Picea glauca (Moench) Voss), and black spruce (Picea mariana (Mill.) B.S.P.) throughout Cape Breton (NSDLF, 1983). The budworm population declined to endemic levels by the fall of 1982 (Kettela, 1982). To minimize losses, an extensive harvest and silvicultural program was undertaken to salvage the dead and dying stands and restore their productivity. During the period 1974 to 1989, 11 million m3 (5 million cords) of softwood were either harvested or salvaged from Cape Breton Island (NSDNR, 1993).
What were the overall effects of the SBW infestation on the Island forests? A comparison of forest inventories for 1970 and 1985 (NSDLF 1970, 1985) shows that the standing volume of merchantable spruce/fir was reduced from 38.8 to 13.8 million m3 over this period (excluding Cape Breton Highlands National Park; HNP). This gives rise to a number of questions:
- How much of this reduction was due to the budworm infestation?
- How much can be attributed to normal mortality?
- How much growth was lost?
- Was fir more susceptible to budworm damage than spruce?
- Were mixedwood stands less vulnerable than softwood stands?
- Did softwood mortality result in an increase in hardwood growth
To help answer these questions, an analysis of data from the Nova Scotia Forest Inventory Permanent Sample Plots (PSPs) was carried out.