- general comments
Complete inventory information for TFL 45 was collected between 1968 and 1971, and additional information was collected from ground sample plots in subsequent years. The inventory was updated to December 31, 1994 to account for depletions resulting from harvesting and fires that occurred since the last inventory was conducted, and any growth that had occurred in the forests to that date. The updated inventory information was used in the timber supply analysis.
- volume estimates for existing stands
Volume estimates for existing stands between the ages of 40 and 140 years were developed using the Variable Density Yield Prediction (VDYP) growth and yield model. Volume estimates for stands older than 140 years were taken from average volume lines, which are based on the original inventory information for the TFL.
Sensitivity analysis indicates that the timber supply is very sensitive to changes in existing volume estimates. If the volumes of stands older than 140 years have been overestimated by 10 percent, then the initial harvest level would have to decrease immediately to 165 000 cubic metres per year (a decline of approximately 25 percent from the base case) to avoid future timber supply disruptions. If average volume lines underestimated actual volumes by 10 percent, then the initial harvest level in the base case could be maintained an additional decade, and medium-term timber supply would be increased. Neither change would affect the long-term timber supply.
I am aware of the sensitivity of the timber supply to changes in these volume estimates, and consider it imperative that the inventory estimates be confirmed before the next AAC determination. Interfor has indicated that harvested volumes tend to be higher than volume estimates from the inventory. Although there is some uncertainty about the existing stand volume estimates, at this time there is no conclusive evidence to indicate that these estimates are inaccurate. To help assess the accuracy of the inventory, an inventory audit is being conducted and the results are expected in the winter of 1996. Pending the outcome of that audit, I accept the information presented to me as the best available, and as suitable for this determination.