The BC Ministry of Forest and Range?s TASS model (Tree and Stand Simulator) grows individual trees in specific stocking patterns/densities while considering interactions between individual trees (i.e. crown growth and competition). This model and its associated interpolation program TIPSY (Tree Interpolation Program for Stand Yields) are commonly used to predict yields for managed stands in Timber Supply Reviews. The model was built using research plots that measured growth under ideal conditions and full stocking. In order to reduce these ideal yields down to ?operational? yields it is necessary to apply Operational Adjustment Factors (OAF?s). There are currently two different types of OAF?s.
OAF 1 is a constant percent reduction of yields throughout the life of the stand and is meant to reflect factors constantly reducing productive area/capacity. The provincial default value is 15%. Albert Nussbaum of the Forest Analysis and Inventory Branch has previously indicated that OAF 1 should be thought of as consisting of 4 components:
OAF 1a (4%): non-productive areas (e.g. rock outcrops, swamps) not already addressed in the timber supply analysis process.
OAF 1b (4%): management effects of espacement and non-commercial cover (i.e. stocking gaps, non commercial species)
OAF 1c (4%): future losses due to endemic health factors (disease and pests)
OAF 1d (3%): future losses due to random risk factors (wind, snow, etc)
These percentages should be considered a general estimation of the components of OAF1 as there is little to no data to back them up. The first two components are measurable in the field but the estimation of future losses is more problematic.
The OAF1 values used in past and current Mid Coast Timber Supply Reviews (TSRs) were consistent with the provincial default of 15% and were not based on TSA-specific information. This OAF1 value is viewed as conservative by many foresters in the Mid Coast TSA and is the subject of this project.
OAF 2 is a factor that increases linearly as the stand ages (input value is reached at age of 100). It was primarily designed to reflect decay/waste/breakage and some forest health issues in earlier models, but there are now other ways to implement these factors in TIPSY (DWB factor, Armillaria specific OAF, other custom OAFs). In the absence of these other factors, the provincial default for OAF2 is 5%. This project is not attempting to refine OAF2 values.
In October 2009, International Forest Products Ltd., on behalf of the Mid Coast Timber Supply Area Group of Licensees requested proposals to complete Operational Adjustment Factor 1 (OAF1) Surveys for their Timber Supply Area (TSA). Forsite was subsequently awarded the contract and this project plan is the first phase of the project. Once this project plan has been reviewed and approved by licensees and key government staff, a detailed sampling plan (Phase 2) will be developed to direct the field sampling component (Phase 3). The survey results will be compiled (Phase 4) and an estimate of the measurable elements of OAF1 will ultimately be calculated.
The goals of this OAF1 project are to develop localized estimates of OAF1 a and b components (gaps and espacement patterns) for managed stands in the Mid Coast Timber Supply Area. The intent is to be able to use the results in future timber supply reviews. The future risks represented by OAF1 c/d components are not part of the project. One option would be to use the default values suggested by Albert Nussbaum to address the risk of future losses. It is likely that additional work will be required to further clarify the risks associated with future losses. Ideally, managed stand yields should be monitored with long term monitoring plots, but in the absence of these, refining OAF1 a/b values will reduce the uncertainty around managed stand volumes.