The short history of forest management in the Cassiar Timber Supply Area has made it difficult to collect the type of detailed information about the forests that is required to complete an accurate timber supply analysis. Two factors are of particular concern to Cassiar Forest District staff.
• Forest inventory
The current forest inventory, which describes the species, ages and size of the existing forests, was completed in the mid 1970s. This inventory has been updated periodically to record wildfires and forestry activities, and to incorporate new information, such as sensitive site mapping. Given the size and diversity of the Cassiar Timber Supply Area, it is likely that this inventory data is not entirely accurate. However it was used in the timber supply analysis as it was the best information available at the time.
• Timber growth estimates
The short history of timber harvesting and forestry activities in the Cassiar Timber Supply Area makes it impossible to confirm the estimates of timber growth and merchantable volume used in the timber supply analysis. Tests were completed in the timber supply analysis to evaluate the impact of changes to these growth estimates.
When the estimated merchantable timber volumes in the existing mature forests were increased, the impact on the timber supply forecast was as follows:
• a 10 per cent increase in volume created a 4.5 per cent higher timber supply forecast over the first 70 years, to 880,400 cubic metres
• a 25 per cent increase in volume created a seven per cent higher timber supply forecast over the first 70 years, to 924,400 cubic metres.
Figure 5 illustrates the impacts of reducing the estimated merchantable timber volumes in the existing mature forests.
Figure 5 Impacts of reducing the estimates of merchantable timber volume in the existing mature forests
Changing the estimated timber volumes for regenerated forests also affected the timber supply forecast. Table 1 summarizes these impacts.
|
Change in estimated merchantable volume |
Timber supply impact |
|
Increase volume estimates by 10 or 25 per cent |
No impact on short term timber supply; timber supply increased by same per cent after 140 years |
|
Reduce volume estimates by 10 per cent |
Timber supply reduced to 782,400 cubic metres (seven per cent below the initial base case level) |
|
Reduce volume estimates by 25 per cent |
Timber supply reduced to 682,400 cubic metres (19 per cent below the initial base case level) |
Table 1 Impacts of changing the estimated merchantable timber volume in regenerated forests.
