MWMA Summary

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

Natural Disturbance and Succession

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

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

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

Understanding Mixedwoods

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

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

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)

Practices to Produce and Grow Mixedwoods

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)

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

Projection and Policy

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.

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