The role of localized stem profile models in cross border comparisons of timber harvest structures

1
The role of localized stem profile models in
cross border comparisonsof timber harvest
structures

• W.T. ZakrzewskiMNR, Ontario Forest Research
  Institute D.W. MacFarlane
• Michigan State University, Forestry Department

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How to measure timber?

• Are currently used methods and procedures
  defendable statistically, legally?
• How these methods contribute to assuring fairness
  in the cross border comparisons of harvest
  structures, and fairness in the international
  timber trade in general?
• Are the timber product volume estimates locally
  valid, accurate, comparable, consistent across
  the markets?

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Challenges associated with merchantable volume
estimation

• In the past, when merchantability standards were
  relatively stable, separate individual tree
  volume equations were developed for each set of
  merchantability limits. With rapidly changing
  standards, this approach becomes infeasible...
  (Reed and Green, 1984)
• in the ongoing softwood lumber dispute between
  the United States and Canada, outdated U.S. log
  rules in Washington, USA were designated as a
  benchmark for converting board foot prices (U.S.)
  to cubic meter scales in British Columbia,
  Canada, leading to considerable imprecision in
  cross border comparisons. (Spelter 2002).

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Better is the enemy of the goodVoltaire
5
H

• Stem Profile Models (SPM) offer
• a robust solution to the timber product
  mensurational problems.
• SPMs allow for the
• cross-sectional area (ca) of a tree stem or log
  to be assessed at any points along the stem
  length.
• SPMs allow for precise estimation of stem (or
  stems section) volume.
• Once stem sectional volume is estimated (dashed
  solid)
• quantity of wood products of any dimension
  (shaded board) can be precisely obtained using
  analytical geometry.

ca
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Example of using Ontario stem profile model by
OMNR during current softwood lumber dispute

• Objective
• To recover timber product volume structure using
  butt scaling records (millions of measurements
  completed over a long period of time)
• Steps
• Use tree species specific inside bark measurement
  at the stump level and average for Ontario
  height-diameter relationship predict
  size-specific stem profile
• Use stem profile model to merchandize stems
  according to pre-defined log lengths and
  diameters consider losses for kerf/brommage

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Great Lakes Stem Profile Modelling Project
(GLSPMP)

• The specific objective of the project is to
  develop/validate the taper model for major
  commercial tree species for the whole Great Lakes
  eco-region. The intention is to evaluate the
  model predictions against American and Canadian
  standards. This will enable meaningful
  cross-border comparisons of timber product based
  harvest structures.

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GLSPMP partners

• Ontario Ministry of Natural Resources, Sault
  Ste. Marie
• David W. MacFarlane, Michigan State University,
  Lansing
• Doug Heym, DNR Michigan, Lansing
• George Deegan, DNR Minnesota, Grand Rapids
• Mark Heyde, DNR Wisconsin, Madison
• Ronald McRoberts, Mark Hansen, Michael VanDyck,
  USDA
• Margaret Penner, Forest Analysis, Huntsville,
  Ontario
• Frank Schnekenburger, Spatialworks Inc., Sault
  Ste. Marie

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Components of the GLSPMP

• Stem Profile Model specification
• Development of the Stem Analysis Data Base
  Management System
• Model calibration
• Technology transfer

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Stem Profile Model

• W.T. Zakrzewski, 1999. North. J. Appl. For.
  16(3)138-143.

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Features of Zakrzewskis taper model

• Based on geometric assumptions (Elastic
  Similarity Principle ESP )
• Mathematically tractable
• Intrinsically linear
• Allows for variable height location of input
  diameter ( location of DBH )
• Conforms to the paradigm of stem profile curve
  (two points of inflection)

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http//www.forestyield.com

• BUCK

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Stem Analysis Data Base Management System
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Model calibration challenges

• 1. Is it possible to apply a single parametric
  data-driven model (or model family) to solve the
  stem form modelling problem?
• 2. Autocorrelation of errors (longitudinal data),
  correlations in hierarchically organized
  populations (stands, trees)
• 3. Calibration of system of equations
  (simultaneous estimations)

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Taper model for Red Pine in Michigan and Ontario
(stem diameter predictions)
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Stem diameter predictionsOntarioMichig
an
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Cross-sectional area residuals () vs. tree
relative height

• Ontario
• Michigan

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Model implementation and maintenance

• we start with modelling stem profile of
  individual tree, however, rarely a single tree is
  of interest to foresters
• standards for timber cruising/inventory systems
  which employ taper models are needed
• efficient solutions to assure local validity of
  the timber product mix estimates are highly
  desired (e.g., mixed model theory)

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Consideration of market differences and
applicability of SPM approach

• Michigan buyer and seller speculate on the
  amount of a specific timber product in a volume
  of raw wood
• Wood suppliers would benefit from flexibility in
  estimating potential market value of raw wood.
• Ontario prices set by sole (government) vendor
  of round-wood they are not a sole decisive
  factor in wood utilization economics of the
  latter is determined by infrastructure, and also
  by the owners value function
• Flexibility in estimating timber products offered
  by stem profile models will be of smaller use.

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Conclusions

• We are aware that in cross border comparison of
  parameters, which are significant to examination
  of fairness of the rules governing the
  international timber trade, one has to consider
  many factors determined by differences in systems
  of wood pricing and timber sale.
• We believe that through recommending timber
  measurement minimum standards, acceptable across
  the borders, we could contribute to removing grey
  zones created by a lack of comparable estimates
  defining harvest structures for the regions of
  interest. Through this, we may contribute to
  improvements in efficiency of communication
  between the trade partners.