1. MWMA Summary

2. Four Mixedwood Themes Disturbance and Succession
Understanding Mixedwoods
Practices to Produce / Grow Mixedwoods
Projection and Policy

3. Natural Disturbance and Succession

4. Steve Cumming: Natural Disturbance in Boreal Forests
Fire behaviour (freq, size, severity) can be predicted as f (Forest Composition)
Aw vs SW = major driver
Can manipulate forest to minimize fire risk
Future forest composition will determine future fire risk
Differences between harvesting and fire
Cutblocks burn more

5. Dan MacIsaac: Succession and Stand Dynamics
Pre-harvest aspen gaps can be persistent after harvest
Post-harvest gaps account for up to 25% of area at 14 years
Gaps provide opportunity for spruce ingress
Small trees have highest mortality
Physical abrasion results in growth losses
Bad News: Mixedwood dynamics VERY complex
Good News: MGM projections are reasonable

6. Vic Lieffers: White spruce ingress
Factors affecting white spruce natural regeneration
Seedbed
Type and extent of receptive microsites
Seed Source
Distance to, and size of seed trees
Occurrence of mast years
Mortality
Can be used to model natural regeneration

7. Understanding Mixedwoods

8. Ken Stadt: Light and understory development
Lack of long-term data means we have to understand mixedwood function if we want to project stand development
Microclimates important in affecting tree growth
Influences of understory micro-climate on regenerating trees
Modeling microclimate conditions, and tree growth response, to project regeneration under a range of conditions

9. Cosmin Filipescu: Competition and facilitation
There are positive (facilitation) and negative (competition) interactions in mixedwoods
Both kinds of effects vary by stand age and geographically
Growth also known to vary by age, site, & location
Competition relationships are different in young vs mid-rotation stands
Why? Possible shift in roles of competition vs facilitation

10. Ellen MacDonald: Treatment impacts on biodiversity
Vascular plant richness (plots and stands) higher in Broadleaf vs (Conifer and Mixed Stands)
Canopy composition influences understory community (for reasons proposed by Stadt and Filipescu)

11. Practices to Produce and Grow Mixedwoods

12. Phil Comeau: Silvicultural systems
Aspen and spruce silvics are different
Can result in mixedwoods arranged through time and in space
Mixedwoods are mid-rotation stands in transition:
Policy Implications
Silviculture systems:
Clearcutting (with/without protection of advanced regen)
Understory Protection
Shelterwood (some limitations for Sw and (especially) Aw regen
Retention Systems (Biodiversity objectives)

13. Doug Pitt: Vegetation management for mixedwoods
Various combinations of chemical and manual tending can be used to grow mixes of aspen and spruce (by accident, and by using technology !)
Important to:
Consider silvics of aspen vs spruce
Define how much of each we need
Define how the mix should be arranged
Define when we need it – CROP PLAN

14. Projection and Policy

15. Mike Bokalo: Modeling silviculture practices with MGM
MGM’s architecture can simulate any treatments that can be represented as manipulations of tree lists
To circumvent lack of data, MGM uses a hybrid approach, modeling individual trees, and using some process-based algorithms
Focus on relative treatment effects vs absolute yields
Multi strata model can simulate treatments with known spatial effects – Strips, Gaps, etc.

16. Vic Lieffers: Mis-lead Regeneration policies
Demand for spruce timber:
Dictates shorter rotations
Demands higher levels of management intensity
Regenerate what you cut (even if the harvested stand represents a typically mid-rotation stand in transition)
Scientifically unjustifiable Free-to-Grow standards
Spruce Growth = f (Aspen BA) r2 = 2% ??
Solutions: Realistic rotations, incorporate mixedwood succession, replace FTG with measures of growth