1
Update Strategies for Stand-Based Forest
InventoriesSteve Fairweather Forest Inventory
Systems ManagerMason, Bruce Girard,
Inc.Portland, Oregon
PNW GMUG Portland, OR 9/11/03
2

• Total Inventory ?(Stand Inventories)

Cruised 2003
Cruised 1995, Grown to 2003
Never cruised, stratum average in 2003
PNW GMUG Portland, OR 9/11/03
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Update Strategy Combination of cruising,
growing, and expanding
Cruise 10 of stands each year expand in first
year grow each stand until it is cruised.
PNW GMUG Portland, OR 9/11/03
4

Update Strategy Combination of cruising,
growing, and expanding
Cruise 10 of stands each year expand each year
grow each stand until it is cruised.
PNW GMUG Portland, OR 9/11/03
5

Update Strategy Combination of cruising,
growing, and expanding
Cruise 10 of stands each year expand each year
no growth modeling.
PNW GMUG Portland, OR 9/11/03
6

Update Strategy Combination of cruising,
growing, and expanding
Cruise all stands every 10 years no expansion
grow each stand until it is cruised.
PNW GMUG Portland, OR 9/11/03
7

Update Strategy Combination of cruising,
growing, and expanding
Cruise all stands every year no expansion no
growth modeling.
PNW GMUG Portland, OR 9/11/03
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• Criteria for evaluating inventory update
  strategies
• Provide an accurate estimate of the total forest
  inventory at any point in time - for valuations.
• Provide accurate volume estimates at the stand
  level - for operations planning.
• Minimize fluctuations in the inventory estimate
  from year to year due to the update process being
  used.
• Within time/cost constraints.

PNW GMUG Portland, OR 9/11/03
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• Sources of Inaccuracy
• Cruising - sampling error
• violation of required sample size according to
  rules
• Growth modeling - prediction error (on top of
  original sampling error)
• Stratification error - original misclassification
  of stands by forest type

PNW GMUG Portland, OR 9/11/03
10

Alternative Update Strategies
Cruise everything
Cruise 10 and re-expand
Cruise 10, expand, grow
Cruise grow for 10 yrs
PNW GMUG Portland, OR 9/11/03
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Alternative Update Strategies
Most accurate, most expensive
Possible large fluctuations
Smaller fluctuations, low cost
Cost spike growth model dep.
PNW GMUG Portland, OR 9/11/03
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• How to explain/explore/evaluate alternative
  update strategies?
• Simulation model in Excel workbook
• Define a forest stratum of 20 stands, with
  perfect knowledge of inventory in each stand
  for an 11-year period define stand-to-stand
  variation
• Define the proposed update strategy
• Describe cruise estimation and growth model
  errors
• Assign costs for cruising and modeling
• Run repeated trials collect statistics on
  performance

PNW GMUG Portland, OR 9/11/03
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• Update Strategy Simulator - Defining the true
  inventory over time -

Acres
Beginning volume/acre
PNW GMUG Portland, OR 9/11/03
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Update Strategy Simulator - Defining true growth
for inventory over time - Use sigmoid yield
function to define mai, pai, and annual growth as
percent of volume use equation to determine
true annual growth
PNW GMUG Portland, OR 9/11/03
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Update Strategy Simulator - Defining growth model
errors -
PNW GMUG Portland, OR 9/11/03
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• Update Strategy Simulator - Defining the proposed
  update strategy -

Precision Forestry Seattle, WA 6/17/03
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Simulation Results -
64,765
PNW GMUG Portland, OR 9/11/03
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Simulation Results - 100 replications
64,765
PNW GMUG Portland, OR 9/11/03
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Simulation Results - 100 replications
64,765
PNW GMUG Portland, OR 9/11/03
20

Simulation Results - 100 replications
64,765
PNW GMUG Portland, OR 9/11/03
21

Simulation Results -
6,614
PNW GMUG Portland, OR 9/11/03
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Simulation Results - 100 reps (No growth error)
6,614
PNW GMUG Portland, OR 9/11/03
23

Simulation Results - 100 reps (No growth error)
6,614
PNW GMUG Portland, OR 9/11/03
24

Simulation Results - 100 reps (No growth error)
6,614
PNW GMUG Portland, OR 9/11/03
25

Simulation Results - 100 reps (No growth error)
64,765
6,614
PNW GMUG Portland, OR 9/11/03
26

Simulation Results - 100 reps (No growth error)
64,765
6,614
PNW GMUG Portland, OR 9/11/03
27

Simulation Results - 100 reps (No growth error)
64,765
6,614
PNW GMUG Portland, OR 9/11/03
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A New Wrinkle - Growth Modeling Errors -
PNW GMUG Portland, OR 9/11/03
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Simulation Results - 100 reps
No Growth Model Error
Growth Model Error
PNW GMUG Portland, OR 9/11/03
30

Simulation Results - 100 reps
No Growth Model Error
Growth Model Error
PNW GMUG Portland, OR 9/11/03
31

Simulation Results - 100 reps
No Growth Model Error
Growth Model Error
PNW GMUG Portland, OR 9/11/03
32
Update Strategies for Stand-Based Forest
InventoriesSteve Fairweather Forest Inventory
Systems ManagerMason, Bruce Girard,
Inc.Portland, Oregonsfairweather_at_masonbruce.com
503-224-3445
PNW GMUG Portland, OR 9/11/03