The licensee analysis uses a comparable net land base and similar area assignments for species groups and management zones to those used in the Timber Supply Analysis. However, uncertainty around land base and management assumptions and growth and yield modelling is interpreted as providing upward pressure on the allowable annual cut.
Model differences
When Ministry of Forests base case assumptions and data are entered into the licensee model, the resulting harvest flow projection indicates the current harvest level could be maintained for two decades rather than one. The difference is attributed to variation in the workings of the respective models.
Differing land base and volume assumptions
Another projection, incorporating small changes to the land base, the use of special site indexes, and the use of special batch volumes for unmerchantable stands, indicates the current harvest level could be maintained for three decades.
Base case recommendation
The base case projection recommended in the licensee analysis assumes a reaggregation of analysis units and the use of new yield estimates for existing and managed forest stands. The results indicate the current harvest level could be maintained for four decades before starting to decline.
Visual quality objectives
Visual quality objectives, which cover 55 percent of the timber harvesting land base, are a major concern because of their impact on timber supply. The licensee analysis questions the manner in which visual quality objectives are quantified. To model anticipated changes to visual management, the licensee analysis shifts 20 per cent of the area in the Retention zone into Partial Retention, and 20 per cent of the Partial Retention zone into Modification. The results indicate the current harvest level could be maintained for four decades.
If the existing visual quality objectives are maintained, but the maximum allowable disturbance within each visual quality objective zone is permitted, the current harvest level could be maintained for four decades.
Old-growth site indexes
Old-growth site index values likely underestimate future growth. The use of second-growth stands to determine site index is more reliable.
Composite harvest flow projection
The licensee analysis suggests that a harvest flow projection based on the use of special site indexes; revised volume estimates for unmerchantable stands and existing and managed stands; removal of the Tetrahedron from the productive forest; revised visual quality objectives; and reaggregation of analysis units could allow the current harvest level to be maintained for 10 decades.
Recommendations for the future
In conclusion, the licensee analysis recommends the following actions be taken before the next timber supply review for the Sunshine Coast:
• forest inventory data should be improved for riparian areas and identification of valid site attributes
• data should be obtained on the dispersion of inoperable productive forest in the timber harvesting land base
• old-growth site indexes should be reviewed
• data should be obtained on managed stand yields to support yield predictions; as well, inputs to managed stand yields, including the impacts of pre-commercial thinning and fertilization, should be reviewed
• further research should be undertaken on appropriate incremental silviculture regimes
