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Exercise Background

Refer to the background material for the field exercise in Lesson 3, and for the elements of prescription design exercise.

There are five steps in prescription design:

  1. Review management objectives from higher level plans (HLP).
  2. Diagnose site and stand condition, capability and constraints.
  3. Integrate HLP objectives with site and stand condition by designing an appropriate ‘target stand’ condition.
  4. Consider the silviculture system and treatment regime necessary to move the stand from its current condition towards the target condition.
  5. Prepare the prescription documents and maps.

For this exercise, select target stand which would meet HLP objectives for the site. Consider this target in terms of windthrow risk and probability of prescription success, and suggest modifications to the target stand/treatment regime that make the desired outcome more likely.

For the RMA, review the ecological function of RMAs. Consider whether these functions are being met in areas with partial damage. Note the location of uprooted trees/mineral soil exposure relative to the stream channel, and consider under what stand, bank or channel situations impacts might be greater/lesser. Consider RMA design approaches that could reduce windthrow risk, and the pros and cons of salvage, and impact mitigation.

There is a shortage of well-designed trials on the impact of windthrow in riparian areas. For those that do exist, impacts are mixed. In most studies, windthrow along streams delivers little sediment unless trees are rooted into the bank or channel. However, some studies noted bank failures which delivered large quantities of sediment. Depending on the configuration of the side slopes, windthrow may be suspended well above the stream. Suspended stem material may deposit into the channel over the course of several decades as logs decay. Review the gully assessment course for further discussion of gully management issues.

 
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