One of the first steps in the Timber Supply Review (TSR) process is the determination of the size of the timber harvesting land base (THLB). This is accomplished through a net-down procedure. At the outset, all lands within the TSA boundaries are considered. Non-forest land (lakes, alpine, etc) and land not managed for forestry (i.e. parks, special leases and licenses) are removed early in the process. Inoperable areas, where the company cannot be reasonably expected to harvest timber are then netted out. This inoperable area may be substantial. The following should be considered when making a determination regarding operability:
? Terrain stability
? Volume per hectare
? Species composition
? Timber quality
? Recoverable volume
? Selling price of the timber
? Expected access development costs
? Expected logging costs,
? Physical accessibility
? Local logging practices and economics.
Historically, operability was determined using inventory maps at scales between 1:20,000 and 1:50,000.
A forest engineer familiar with logging layout and with the terrain normally carried out the classification. Where time and budget permitted, questionable areas were reviewed from a helicopter. Early versions of operability maps were often a line around a drainage that excluded physically inaccessible timber, or areas where access and yarding costs would be too high (relative to the value of the timber) to make logging feasible. On these maps, all forested areas were designated as either ?Operable? or ?Inoperable?. Often, the operable area on these maps was further classified on the basis of expected yarding system.
Operability maps define areas that should be considered for strategic planning and timber supply analysis purposes. However, it is difficult to formulate sensitivity analyses around operability based on these static maps. For example, it is difficult to determine how much of the inoperable landbase might be potentially harvestable under changing market conditions. Past sensitivity analyses for operability have merely increased or decreased the size of the operable landbase by a fixed percentage. This, not unexpectedly, leads to a proportional increase or decrease in the long-term timber supply. The Base Case of a TSR is intended to model ?what is? rather than ?what if?. Consequently, the area contained within operability boundaries should be reasonably available for harvesting within the term of the plan given the logging standards and practices of the day. However markets, timber quality (MPB), logging technology and costs change. Therefore operability maps should be reviewed and revised on a
regular basis. Throughout the Interior, forestry companies increasingly operate outside of original operability boundaries. Technological changes, such as single-stem harvesting and changes to sawmilling 2 technology have made it possible for harvesting to occur in areas previously regarded as economically infeasible. Static operability maps, which have historically been used in timber supply analysis process,
are generally unable to capture and model these changes. In the latest AAC Rationale for the Boundary TSA1, the Chief Forester noted that current operability map contributed to uncertainty regarding sustainable harvest levels and recommended that improved information be gathered prior to the next timber supply review, which must be completed by 2011.