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Silviculture and Its Relationship to Timber SupplyTSR 101Patrick Bryant ([email protected])
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TOPICS
•Assumptions•Results• Influencing Timber Supply
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ASSUMPTIONS
Initial ConditionsRules of ChangeObjectives, Criteria and Indicators
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?
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Assumptions – Initial Condition
• Land Base Netdown (ordered removals from THLB)• Total Area
• Less areas that cannot produce timber• Forest Management Land Base (FMLB)
• Less areas that meet non-timber objectives (e.g., parks)• Less forested areas that not merchantable or operable
• Timber Harvesting Land Base(THLB)
• Harvest and grow timber
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Netdown table
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Assumptions – Initial Condition
• Age Class Distribution (also species, volumes, products, land base type, etc.)
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5Reported in other periods (e.g., 50yrs, 100yrs, 200yrs)
Assumptions – Rules of Change
• Stand development (growth and yield)• Aggregate stand types with similar development patterns to
reduce complexity • Stands under various regimes or eras, typically: Existing natural;
Existing regenerated; and Future regenerated. • Link to silviculture options/investments• Operational adjustment Factors (OAFs)
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Assumptions – Rules of Change
• Natural disturbance (non-harvest removals)• THLB = Non-recoverable losses
• Simply added to Harvest Rate (‘harvested’ but not reported)• NHLB = Periodic disturbance events (forest health)
• Several approaches (e.g., Age Reset by Natural Disturbance Type – Biodiversity Guidebook – every 200 years for CWH in NDT2)
• If ignored, this could significantly misrepresent desired conditions for non-timber resources
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Assumptions – Criteria & Indicators
• Management objectives and options• Harvest treatments
• Utilization levels (net volume)• Merchantable criteria (min harvest age - max too)• Harvest flow pattern
• Silviculture treatments• Basic silviculture typically “assumed” (informed by, but not actual data)• Tree improvement• Incremental silviculture (e.g., Type 4 strategies)
• Treatment Types• Eligible Stands• Response• Windows available to optimize investments
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Assumptions – Criteria & Indicators
• Management objectives and options (continued)• Forest cover requirements (non-timber)
• Habitat suitability; ECA recovery; VQO, Green-up
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9Levels for targets & accounts / Ages for constraints & recovery
Assumptions – Criteria & Indicators
• Cont’d... Forest cover requirements (non-timber)• Patch size and distribution
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Assumptions – Criteria & Indicators
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Monitor over “time”
Product profile
Build and Run Model
• “…and then some magic happens…”
REALITY CHECK• Only interpreting a construct; not the real forest • If an assumption was not explicit – it’s not in the model
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Forest Estate Models
• A discussion for another time… by someone more knowledgeable…
• Several models commonly used in BC (no single model is the “prescribed”)
More important to work towards understanding the forest-level dynamics
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RESULTS
Harvest FlowsSensitivitiesMetrics
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Harvest Flow - Elements
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rise
Harvest Flow - Sensitivities
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Compare the impacts on harvest flow of changing one or more assumptions
Metrics - Indicators
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Harvest Profile by age class
Harvest Profile by average age, area, & volume
Metrics - Indicators
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Sustainable = stable growing stock & harvest rate
Pinch-point & cushion limits harvest flow
Merchantable growing stock directly influences harvest rate; and vice-versa
Growing stock is the PRIMARY INDICATOR
Metrics – Value
• Operability Assessments• Costs for harvesting, road building and silviculture• Develop and link blocks to roads• Values for existing and regenerated stands
(based on species/age/products/market prices)• Adapt harvest flows to report NPV
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Forest-level NPV over time
INFLUENCING TIMBER SUPPLY
Methods of InfluenceExamples
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Growing stock
Harvest rate
Stand Yields
Methods of Influence
• Fit the solution to the problem – consider growing stock• Aim to treat stands eligible for harvest in the right period by:
• ∆ development pattern of individual stands• ∆ age structure of a group of stands• ∆ treatment assumption
• Explore in the field then develop assumptions… or vice versa• Plug: typically knowledge gaps – need to support with real data
• ACE – risky, so “use caution”
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Methods of Influence – by Era
• Existing Natural Stands• Scheduled for harvest over the next ~20 years• ∆ age structure of a group of stands (harvest pattern)• Few ‘silviculture’ opportunities
• Existing Regenerated Stands• Scheduled for harvest after ~20+ years• ∆ age structure of a group of stands• Typically incremental silviculture treatments
• Future Regenerated Stands• Scheduled for harvest in ~60+ years• ∆ the development pattern of individual stands • Typically basic silviculture
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Examples - Site Index and Species
• Regenerated SI – SIBEC/SIASI is the biggest lever (∆ development pattern)
• “Use species wisely” (ecologically suited; species adaptation strategies; product values)
• Simply prorate yields for mixed or multi-layered stands
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Examples - Site Index
• But beware the “Evils of Averaging”… …for Tactical Planning
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(Interior example)
Examples - Minimum Harvest Age
• Minimum age at which harvesting is commercially viable• Determines merchantable growing stock• Criteria: Volume, % CMAI and/or diameter
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38%
25yrs
Examples - Minimum Harvest Age
• A big lever (∆ treatment assumption)• Reducing MHAs also lowers long-term harvest level• Easy to model; resolves some issues quickly – but risky…
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Examples – Initial Density
• Beyond a certain level, initial density has little effect on yield (so it’s not just about TPH)
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Examples – Method (Spatial Patterns)• TIPSY uses hybrid of initial density and one
of 3 spatial distribution patterns (species dependent)
• So be careful with regen method
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Natural
Clumped
Planted
Examples – Stocking
• Initial density in TIPSY ≠ total or well-spaced stems• Ultimately, analysts tweak initial density and regen
method/patterns to mimic stocking (considering reports generated at different ages)
• Are we aiming for maximum site occupancy? (wood quality/value)
• silviculture surveys results do not provide easy inputs for stand-/forest-level modeling
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TSR vs. Scenario AnalysisTimber Supply Review
What was/is…
• Past and current practices
• Balance uncertainties• Periodic• AAC implemented
immediately• Some scenario analysis
to support AAC determination
Timber Supply Scenario Analysis What if…
• Forward-looking assumptions
• Explore possible scenarios
• Anytime• Used to support
programs; implemented ONLY after responses are verified (years)
• Aimed to modify AAC
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What do we know?
• Access to very good inventories (compared to other locales)• Robust stand development models; knowledgeable people;
methods for sharing information• Array of suitable forest estate models
• But… How well do our assumptions reflect our existing regenerated stands? • Depends where you’re at; forest health impacts • Incorporating RESULTS information into forest-level analyses is
NOT EASY (including depletion)
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What do we need?
• Adapt to address climate change, forest health and products – ongoing progress
• Better GY – mixed species stands• Better inventories – young stands • But… How good are our predictions of stand development to
rotation? • Okay on average but treatments are typically required with
stands “on the fringes”
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What do we need to know?
• Information needed to support silviculture assumptions:• Treatment criteria, windows, response and cost
• So… How do we build defensible assumptions for
developing timber supply scenarios?• Trials? Track the right information? Accounts?
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Many thanks to those whose ideas I’ve borrowed…• FAIB (too many to name)• Bryce Bancroft• Gordon Baskerville• Cam Brown• Reg Davis• Jeremy Hachey• Peter Kofoed• Bill Kuzmuk• Antti Makitalo• Colin Mahony
• Eleanor McWilliams• Jeff McWilliams• Simon Moreira-Munoz• Ed Mulock• Stephen Smyrl• Jordan Tanz• Guillaume Therien• Jim Thrower• Gordon Weetman• Doug Williams
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