Types of rotations?
- Biological (Use MSY or culmination MAI) based on volume*
- Economic (Maximum return over shortest time. Slightly shorter than biological in general) based on value* (The lower the discount rate, the longer the rotation)
- Ecological: typically the longest rotation since the goal is to maintain structural values that are intrinsic to a specific seral stage.
- Technical: stands managed to meet specific product objectives.
- Pathological: set by the earliest expected onset of decay.
What is MSY
Max sustainable yield is the max yield that does not deplete the timber at the forest estate level beyond its ability to effectively regenerate.
What is NPV?
The current value of the stand based on today’s market value. A projection.
Net present value is the basis for economic rotations. It is calculated by Present value of revenue - Present value of cost.
Usually slightly ahead of MAI
What Factors affect Rotations?
- Growth of dominant species (if more than one spp, focus on dominant tree in stand).
- Site index (By spp.)
- Intended product. (poles vs logs)
- Value of products
- Expected rate of return / Discount rate
- Non timber values (variety of seral stages)
- Harvest levels (AAC)
What is the difference between the typical NPV graph and the MAI graph?
- The NPV graph looks very similar to that of a maximum MAI graph but is much tighter
- Rotation at any age before or after R will cause the expected profit to drop.
- Maximum NPV is normally slightly ahead of the MAI.
- Expected Rate of Return must also be considered.
What is the goal of an ecological rotation?
A portion of the forest estate must be maintained in a specific successional stage with specific structural values usually for wildlife habitat such as is required for mountain Caribou.
When would a technical rotation be desirable?
- if the foresters goal was to meet specific product objectives such as pulp, silage, poles, Christmas trees etc.
- another reason would be to meet specific sawmill requirements.
What are some spp that would be subject to pathological rotations?
Mostly early seral spp. Except Hw.
- red alder, cottonwood, aspen, western hemlock.
- rotation set at earliest expected onset of decay.
What is the typical metric for setting the rotation on crown land and private land?
Crown: use site index to determine MAI
Private: use economic rotation regardless of site where the net present value and the expected rate of return are used.
What determines an economic rotation?
The economic rotation is set for the year in which the cost of carrying the stand exceeds the value of the crop.
- Because of constantly changing log values, ER’s for each stand have to be recalculated annually.
- on a graph the economic rotation would be where the carrying cost and NPV intersect. After that the NPV drops as the carrying cost increases resulting in a loss in profit.
Why do carrying costs increase?
Because the value of the stand increases. At some point the carrying costs end up being more than the expected return. This is what determines the economic rotation.
How can you extend an economic rotation?
Reduce the rate of return. The higher the desired rate of return, the shorter the rotation since carrying costs will exceed NPV sooner.
