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“Update Strategies for Stand-Based Forest Inventories” Steve Fairweather Forest Inventory Systems Manager Mason, Bruce & Girard, Inc. Portland, Oregon.

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Presentation on theme: "“Update Strategies for Stand-Based Forest Inventories” Steve Fairweather Forest Inventory Systems Manager Mason, Bruce & Girard, Inc. Portland, Oregon."— Presentation transcript:

1 “Update Strategies for Stand-Based Forest Inventories” Steve Fairweather Forest Inventory Systems Manager Mason, 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

3 “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

8 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

9 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%, expand, grow Cruise 10% and re-expand Cruise & grow for 10 yrs PNW GMUG Portland, OR 9/11/03

11 Alternative Update Strategies: PNW GMUG Portland, OR 9/11/03 Most accurate, most expensive Smaller fluctuations, low cost Possible large fluctuations Cost “spike”; growth model dep.

12 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

13 Update Strategy Simulator - Defining the true inventory over time - Acres Beginning volume/acre PNW GMUG Portland, OR 9/11/03

14 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

15 Update Strategy Simulator - Defining growth model errors - PNW GMUG Portland, OR 9/11/03

16 Update Strategy Simulator - Defining the proposed update strategy - Precision Forestry Seattle, WA 6/17/03

17 Simulation Results - $ 64,765 PNW GMUG Portland, OR 9/11/03

18 Simulation Results replications $ 64,765 PNW GMUG Portland, OR 9/11/03

19 Simulation Results replications $ 64,765 PNW GMUG Portland, OR 9/11/03

20 Simulation Results replications $ 64,765 PNW GMUG Portland, OR 9/11/03

21 Simulation Results - $ 6,614 PNW GMUG Portland, OR 9/11/03

22 Simulation Results reps (No growth error) $ 6,614 PNW GMUG Portland, OR 9/11/03

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

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

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

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

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

28 A New Wrinkle - Growth Modeling Errors - PNW GMUG Portland, OR 9/11/03

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

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

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

32 “Update Strategies for Stand-Based Forest Inventories” Steve Fairweather Forest Inventory Systems Manager Mason, Bruce & Girard, Inc. Portland, Oregon PNW GMUG Portland, OR 9/11/03


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