ESTIMATING TOP-KILL VOLUMES WITH LARGE-SCALE PHOTOS ON TREES DEFOLIATED BY THE JACK PINE BUDWORM

The estimation of tree top-kill volumes is an important component of q uantifying defoliation impact of severe budworm (Choristoneura pinus F reeman) defoliation on jack pine (Pinus banksiana Lamb.) trees. Field survey is the only method by which this assessment is currently undert aken. This study evaluated an alternative methodology based on large-s cale aerial photo (1:900) measurements and a taper model fitted for ja ck pine. This included generating linear models for the prediction of actual top-kill length from photo-measured top-kill length, the predic tion of DBH from photo-measured tree height and crown area, and the es timation 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 t rees not visible on photographs was less than 1% of the volume of all damaged trees, and therefore adjustment for missed trees was not consi dered necessary. The methodology is convenient to implement, and if co mbined with forest sampling procedures, the projection of tree top-kil l volumes to the stand level can provide an estimate of defoliation im pact. The methodology is also potentially suitable for assessing other insect defoliation impacts that cause top kill.