Harvesting and silviculture applications in SORTIE

Presented by Christian Messier.

Forestry paradigm

There are new preoccupations in forestry:

• Forest ecosystems are complex - previously foresters were trained to create order out of a "mess"
• One should try to maintain the ecological integrity of our forests
• Biodiversity now matters
• Can we have our cake and eat it too? Sustainable development is in! (But is it possible?)
• Market driven certification is also in! Big companies want to be certified as "green" - so they want ecologists to help them do a better job

This has caused a paradigm shift to emulation of natural disturbance

A proposal for Canadian forestry

Use the zoning principle.

• Very intensive forestry for larch and poplar - 3% of land
• Traditional forestry - native species - 12% of land
• Ecosystem management - 70% of land
• Protected areas - 15%

Under this proposal, total wood production can even increase. It is important to vary the type of cutting, since disturbances vary in intensity.

Discussion of this talk

Question: What are the rules for leaving forest patches? There's a lot of research to be done - there are guidelines like "leave 10%" but the placement is left open. Currently there are always strips left along waterways. There are minimum patch sizes in order to preserve a more complete structure

Question: Where is the extra productivity coming from in the zone position? Because there's almost no traditional intensive forestry.

Why would a timber company invest money in forestry in boreal forests when they are so much less productive? They want certification. The government will probably need to step in to preserve jobs as well.

SORTIE harvest demonstration

Presented by Dave Coates.

Discussion for this talk

Question: How would you use this? To do a replicated experiment, or to figure out how to cut a target amount.

Question: Could you replicate scarification? Yes, by properly setting up substrate.

Question: Can you validate the model? There's some plans with new work that's being done.

Use of SORTIE in management of deciduous forests of Quebec

Presented by Marilou Beaudet.

Research questions

• How will various types of harvesting affect the species composition of Sugar Maple dominated forests?
  • Effect of varying the harvesting intensity
  • Effect of varying the spatial configuration of tree removal
• What combinations of silvicultural systems could favor the maintenance of tree species diversity?
• How do initial stand conditions affect the forest response to a given type of harvesting?

Project

Study species:

• Sugar maple
• Beech
• Yello birch
• White ash
• Black cherry
• Red maple
• Striped maple

Parameterization

Based on field studies:

• Tree allometry and light transmission - power functions better described tree allometry - and model was sensitive to these variations
• Juvenile radial growth = f(light)
• P (juvenile mortality) = f(previous radial growth). Juvenile mortality parameterization was difficult - on the desired study sites, mid-shade-tolerant dead saplings were hard to find
• Regeneration establishment - when parameterizing seedbed cover - differentiating between skidpath and nonskidpath is very important.
• Seedbed cover and dynamics

Based on permanent plot data and literature: Adult tree growth and mortality

Site selection criteria

• Sites selected within a single ecological sub-region to minimize heterogeneity in conditions
• Forest type: Sugar Maple dominated
• Sampled stands were on mesic sites
• Dystric brunisols and podzols
• Derived from glacial till rich in mica-schist and sandstone

Issues to consider

• Is the representation of the following objects / behaviors necessary to capture the forest dynamics response to harvesting?
  • understory vegetation (grid layer, need knowledge of dynamics)
  • effect of harvesting operations on soil properties (other than relative to seedbeds cover) (e.g. compaction)
  • effect of harvesting on adult tree mortality (other than through a decrease of neighborhood competition)
  • response of crown allometry to canopy openings (gap closure through lateral crown growth of trees bordering gaps)
• Validation and timeframe: Simulations performed to address silvicultural questions are often over a much shorter timeframe than the one for which the model has been validated (i.e. ~ 100 yrs vs ~ 1000 yrs, in Pacala et al. 1996)
• Should this be a concern ? How could we try to validate harvesting simulation results?

Discussion of this talk

Can we study old cuts to validate? After 30 years it is hard to find stumps.

Re: soil compaction effects - in NZ - there are striking effects for some species' growth - may need to modify growth.

Re: Crown allometry shape change in gap - and ability to simulate stand self-thinning - is there a possibility to include density-dependent crown allometry? We're not capturing spatial interactions up in the canopy - as results of foraging, etc. Let's have this discussion later.

Mixedwood forests of Quebec

Presented by Julie Poulin.

Hypothesis - can silvicultural practices accelerate succession?

Comparing SORTIE results to old fire history maps - the current situation was well simulated in the control plot (no logging).

Simulated logged plots - they have a similar situation after 50 years as the control plot had after 100 years - answer to the hypothesis is yes.

Discussion of this talk

Question: Are there types of treatments that cannot be simulated in the current version? Yes:

• Ability to be more clumped in the cutting pattern - harvesting trees in groups of 2,3,4,5
• Trees near an existing cut tree have higher probability of being cut
• Existing cuts are too uniformly distributed

If you want to argue for leaving adults behind, you have to show that there are benefits - to show that trees grow faster instead of dying. If trees grow faster, does wood quality decline? This is an issue. Long-suppressed trees that are released have wood with two different densities, and wood from these trees warp more. The goal might be to keep constant moderate growth. For some species (ring-porous), faster growth is preferred.

DOMTAR (forest company) was very interested in model results - but we need to make clear that we cannot predict what would happen to a specific stand.