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WOODLOT for Windows 2.2 - Reference Manual | ||
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Appendix 14 - 2 Management Assumptions 2.1 How should we classify land that has now been rehabilitated, but was previously left as a residual stand? Treat rehab lands as if they are newly established stands. The stand age should be based on the average age of the newly established free growing stand. Ignore the contribution of the residuals unless you are sure they will release and become crop trees. 2.2 How do I model for a residual stand that has been severely selectively logged, but I wish to rehab to a new forest in 10 years time?
E.g. DrFd on the coast; AtSw in the Interior? Yield modelling in WOODLOT is based on VDYP and TIPSY. Neither of these models address stand dynamics for conversions particularly well, and this is a modelling limitation. Consider whether the total volume would change over time beyond the projected yield curve and comment on this aspect in the AAC rationale as an upward or downward pressure. 2.4 How do I split the cut by deciduous and coniferous species? There are two methods. Note that TIPSY does not model for deciduous species. VDYP now has the feature to include the volume of desired species. In the Polygon Data Screen, check on only the species in VDYP that you wish included in the analysis. Species with a check box left blank will not be accounted for in the harvest rate. This requires the user to also convert the stand from VDYP to TIPSY, and therefore, partial cuts cannot be used on this polygon. A second less accurate method is to apply a VAF in VDYP, as a rough estimate of the contribution by the % by species you wish to retain. This should be verified using VDYP. For example if you have 30% deciduous that will not be harvested, set the VAF to 0.7 to approximate the volume that will be harvested. If the deciduous contributes to the AAC, then there will be no netouts, and the VAF will be 1.0. 2.5 How do I treat a polygon in which I want to partial cut a portion and clearcut the remainder? Split the polygon into two sub polygons with the same forest information and relevant areas. Treat one as a partial cut, and the remainder as a clearcut polygon. 2.6 What are harvest parameters, and how do I change them? Harvest parameters establish the earliest age for which a polygon can be harvested, in terms of minimum diameter (dbh), volume/ha (volume) or possibly a minimum set age. The latest point in time will govern the earliest possible harvest age that a polygon could be harvested. The target harvest age you set in the Polygon Data screen will likely be older than the minimum harvest parameter. Minimum harvest parameters may be accessed in different areas in WOODLOT:
A regen delay will delay the growth of a new stand, and might result in future losses in AAC. Regen delay is entered in the Polygon Data Screen. If you enter empty square brackets [ ] in the regen delay data box, the default regen delay will be used. Refer to harvest parameters. 2.8 When would I want to change the harvest ages, and for what reasons? You might want to change harvest ages to allow for an economic rotation, to fill age class imbalances, or for other reasons. Check the yield table to see if the stand will have a sufficient volume/ha or piece size at the changed ages. By default, harvest ages are based on the culmination age and meeting all minimum harvest parameters. You should check that these ages are appropriate for the stand by viewing the yield curve information under the View Existing or Future Yields buttons in Polygon Data. 2.9 How do you determine your management assumptions, such as the regen delay to use and the type of management (planting, spacing) you expect? This is a judgement call, which should be based on the demonstrated performance of the licensee, or realistic expectations. Consider setting the assumptions conservatively for a weak performer (natural, long regen delay). Model the AAC after the expected harvest pattern, such as in the approved FDP. 2.10 What does the Partial Cut Adjustment Factor (PCAF) do? The PCAF was introduced as part of the partial cut modelling methodology. WOODLOT assumes that a partially cut stand regrows relative to the growth of the fully stocked natural stand with the now-lesser volume at an equivalent younger age. Since a partially cut stand will produce more or less incremental recoverable volume between multiple re-entry periods than an equivalent fully stocked, even-aged stand predicted by VDYP, the PCAF was introduced to scale that volume down (or up), to account for delays in stocking and site occupancy. Volume recovery in a partially cut stand should, to some extent, regrow over a fewer number of remaining trees, and eventually the new trees will replace the harvested trees. The PCAF is used as follows:
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