A Method to Determine Effects of Spruce Budworm on Stand Yield and Wood Supply Projections for New Brunswick

Abstract

An approach for dealing with yield reductions caused by spruce budworm (Choristoneura fumiferana (Clem.)) defoliation in forecasting forest development, using the model WOSFOP, is described. This method includes deriving a "nonbudworm" yield curve for a particular stand type, partitioning the nonbudworm yield curve into periodic growth and mortality, explicitly defining the level of budworm effects on stand growth and mortality, and then recalculating a budworm influenced yield curve based on the periodic growth/mortality data and budworm effects. An example using this approach to explore budworm effects indicated that if protection was withdrawn from two hypothetical spruce-fir forests in New Brunswick, maximum sustainable harvest would be reduced by 23-36% under moderate budworm outbreak conditions, and by 46-64% under severe outbreak conditions.