1. Mitigating Projected Timber Supply Declines
Coastal Silviculture Committee Workshop
June 15, 2017
Doug Layden, MFLNRO

2. Coastal BC Base Case Click here to add text Click here to add text
I’ve been working on a study of the impacts on timber supply of the transition to second growth across Coastal BC.
Under current management we can expect about a 15% falldown over the next years as we move to a predominately second growth harvest.
This based on modeling the coast as one management unit and includes Haida Gwaii, the Great Bear Rainforest, Vancouver Island and the South Coast. It does not include the coastal portions of the Kalum TSA.
A large number of netdowns to a THLB and cover constraints were modeled.
The initial harvest level was set to the sum of the AACs of all the included management units.

3. Regeneration Assumptions
I used VDYP for existing, natural stands and TIPSY for existing harvested stands and future stands.
RESULTS planting records were used as input to generate a yield table for each planted opening. The yield tables were then aggregated into analysis units.
Regenerated each stand to the same leading species—that is, no species conversion.
Assumed all regenerated stands would be planted; did not model ingress.
One year regeneration delay.
The Forest Analysis section of FLNRO is working with Resource Practices Branch and will be generating yield tables using RESULTS records as inputs to TASS. The tables will have different regeneration assumptions than I have used. I’ll re-run the base case as soon as new yield tables are available.

4. Harvest by Age Class (years)
After years, the model shows over 50% of the harvest coming from stands less than 141 years old.
In the model, I selected stands for harvesting using a maximum volume rule. Targeting oldest stands first speeds up the transition to second growth.
Currently 35-45% of the cruising on coastal public lands is of second growth stands. It varies by year and we haven’t been collecting the data for long.
Note the stands being harvested that are less than 71 years are primarily good site Douglas-fir plus some alder stands that are included in the THLB.

5. Adjustments made to future managed yields
Impact of Various Management Options on Growing Stock at Base Case Harvest Level
Adjustments made to future managed yields
Because I had a model and base case already set up, it was easy for me to change some of the yield assumptions and explore the impact on the growing stock.
Given the theme of the workshop, I primarily looked at options that might increase the yield and mitigate the projected declining timber supply.
Three options resulted in increasing grow stock over the mid- to long-term:
Arbitrarily increasing the yield of future stands by 10%.
Increasing genetic worth by 5%.
Reducing the regeneration delay from 1 year to no delay.
The final option, harvesting stands at 90% of CMAI, as opposed to 95%, results in a declining growing stock.
I didn’t look at silvicultural treatments such as late rotation fertilization and commercial thinning where the gains will likely be experienced sooner than other treatments.
Increasing the yields and modeling no regeneration delay was straight forward. I increased the genetic worth of each species wherever genetically improved stock had been planted. I didn’t look at increased deployment.
The growing stock charts gave me an idea as to when to increase/decrease the harvest request and roughly by how much
Decades from 2016

6. Timber Supply Relative to the Base Case For Various Management Options
The next step was to adjust the harvest requests to see what level of harvest would be sustainable under the various changes to the silvicultural assumptions. Here I’ve shown the changes in the harvest flow relative to the base case.
By increasing the yield by 10%, a 10% increase in the mid- and long-term harvest level is sustainable years from now.
Increasing the genetic worth by 5% results in a sustainable harvest level that is over 2% higher than the base case.
By reducing the regeneration delay from 1 year to no delay, the sustainable harvest level increases by almost 2% over the base case.
Finally harvesting stands at a younger age (when they achieve only 90% of the CMAI volume) results in about a 2% decrease in the harvest level after about 100 years.
Decades from 2016

7. Conclusions
We have opportunities to change how we regenerate and grow our forests to mitigate the projected declining timber harvest.
An increase in yield may result in a proportional increase in the projected harvest.
Planting genetically improved stock and reducing regeneration delays also result in an increase in the projected timber supply and sustainable harvest level but the effect occurs later than an immediate across the board increase in yield.
My assumptions around increasing genetic worth are conservative.
I didn’t look at silvicultural treatments such as late rotation fertilization and commercial thinning where the gains will likely be experienced sooner than other treatments.