Growth Model Users Group November 15, 2013 Greg Johnson Weyerhaeuser NR Company.
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Transcript of Growth Model Users Group November 15, 2013 Greg Johnson Weyerhaeuser NR Company.
![Page 1: Growth Model Users Group November 15, 2013 Greg Johnson Weyerhaeuser NR Company.](https://reader035.fdocuments.net/reader035/viewer/2022062221/56649f4f5503460f94c71751/html5/thumbnails/1.jpg)
MODEL VALIDATION USING THE SMC DATABASE
Growth Model Users GroupNovember 15, 2013
Greg JohnsonWeyerhaeuser NR Company
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Acknowledgements
Eric Turnblom (SMC) David Marshall (WY) Erin Smith-Mateja (USFS) Peter Gould (WA DNR)
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Objectives
Illustrate one of many potential valuable uses of the SMC Database.
Validate two commonly used and publically available growth models against the largest cooperative dataset on Douglas-fir and western hemlock growth and yield.
Spark a discussion.
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Approach
Use the SMC Database to extract complete growth records for untreated plots retaining the longest continuous period of remeasurement without treatment. Treatments excluded include: thinning and fertilization. Remeasurement intervals can be any length. There must be complete tree measurements (or a
sufficient sub-sample to impute missing measurements). Validate the growth models using a First-to-Last
validation scheme. Growth Models considered:
ORGANON v9.1 SMC Variant FVS PN Variant Region 612
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First-to-Last Validation
What is it? Passes initial plot measurements to the growth
model and projects the plot through time, periodically comparing the projected plot to remeasurement data without re-informing the model with new measurement data.
Why use it? Most challenging test for a growth model. Mimics many typical applications:
Harvest planning Appraisal
Test the SMC data set and uncover inconsistencies.
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ExampleFirst to Last Validation Example
Cumulative Years of Projection
Bas
al A
rea
per
Acr
e E
rror
(P
redi
cted
- A
ctua
l)
-50
0
50
100
5 10 15 20 25
Every plot starts here
Model gets progressivelyfurther off over time for thisplot.
Model stays relatively unbiased over time
Oops!
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The Data
“Control” Plots: 2,482 “Control” Plots after filtering for known
treatments: 1,770 Plots after merging with age, site index,
and location information: 485 Plots greater than 10 years old: 451 Plots that made it through the models (no
heavy in-growth, no unrecorded thinnings): 393
Growth Intervals to test: 2,532
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Initial Conditions
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Initial Conditions
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Initial Conditions
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Initial Conditions
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Initial Conditions
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The Models
Model variants tested: ORGANON v9.1 SMC Variant FVS PN Variant region 612 (compiled from Open-FVS
repository) Coded an R interface to each model and the SMC
database. Imputed height and height-to-live-crown for trees
with missing measurements. Plots with measurement records where no
heights or crowns were measured were dropped. Used elevation, slope, aspect, and Douglas-fir 50
year site index as needed for each model.
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Results
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Results – Basal Area
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Results – Trees per Acre
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Results - Height
Note that the ORGANON results use Lorey Height and FVS uses Mean Height
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Results – Dq
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Results – Total Cubic Volume
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Results – Total Cubic Volume
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Results – Total Cubic Volume
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Results – Stand Density Management Diagram
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Results – 10-Year Projection Errors
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Results – 10-Year Projection Errors
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Results – 10-Year Projection Errors
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Model Error Comparison
Do the models commit the same errors on the same plots?
Are the magnitude of the errors similar?
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Model Error Comparison
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Model Error Comparison
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Model Error Comparison
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Model Error Comparison
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Model Error Comparison
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Conclusions The SMC data base:
is a significant resource for Douglas-fir growth under management.
has a number of inconsistencies in treatment records, site index, and other details that should be fixed and would enhance the value of the data base.
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Conclusions The Models:
Both models are relatively stable over long projection periods, with ORGANON slightly more precise than FVS.
Biases in height growth are common to both models and may in part be a reflection of site index errors.
Mortality is low in managed Douglas-fir stands and is predicted well by both models, with FVS exhibiting a higher effective Max SDI.
Both models produced a under-estimate of volume growth over time with larger height growth errors in FVS balancing over-predictions of diameter growth.
The biases in both models argue for an new model-building effort based on currently available data.
Thinning and Fertilization need to be validated next!
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The End / What’s Next
To Infinity and Beyond!