Canadian Forest Service Publications

Estimating top-kill volumes with large-scale photos on trees defoliated by the jack pine budworm. 1993. Hall, R.J.; Titus, S.J.; Volney, W.J.A. Canadian Journal of Forest Research 23(7): 1337-1346.

Year: 1993

Issued by: Northern Forestry Centre

Catalog ID: 11190

Language: English

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The estimation of tree top-kill volumes is an important component of quantifying defoliation impact of severe budworm (Choristoneurapinus Freeman) defoliation on jack pine (Pinusbanksiana Lamb.) trees. Field survey is the only method by which this assessment is currently undertaken. This study evaluated an alternative methodology based on large-scale aerial photo (1:900) measurements and a taper model fitted for jack pine. This included generating linear models for the prediction of actual top-kill length from photo-measured top-kill length, the prediction of DBH from photo-measured tree height and crown area, and the estimation of top-kill volumes from a jack pine taper model. The set of three linear equations fitted with ordinary least squares resulted in top-kill volume estimates that showed no bias. The volume of damaged trees not visible on photographs was less than 1% of the volume of all damaged trees, and therefore adjustment for missed trees was not considered necessary. The methodology is convenient to implement, and if combined with forest sampling procedures, the projection of tree top-kill volumes to the stand level can provide an estimate of defoliation impact. The methodology is also potentially suitable for assessing other insect defoliation impacts that cause top kill.