diameter-free growth modelling and other heresies oscar garcia university of northern british...
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Diameter-free Growth Modelling and other Heresies
Oscar Garcia
University of Northern
British Columbia
Themes
Resolution, science vs. technology Stem dbh as growth driver Stochastics
Model Uses
Decision-making (prediction) Research (understanding)
Prediction Precision Controllable variables Match:
Available input info Required output info
Management Decision-making
“Process models” Mechanistic, realistic Detailed Qualitative behavior Generate questions
Scientific Research
Science vs. Technology
N, S, W, E
Journal of
Applied Forestry
Science vs. Technology
N, S, W, E
Journal of
Applied Forestry
PredictionTree-level
modeltree list tree list
Prediction
Inventory
Tree-levelmodel
(B,N,H)
tree list tree list
Prediction
Inventory Application
Tree-levelmodel
(B,N,H)
tree list tree list
(B,N,H)
Prediction
Inventory Application
Tree-levelmodel
(B,N,H)
tree list tree list
(B,N,H)Stand-level
model
Complexity, Resolution Level
“Model at one level of detail below the level desired for prediction”
Complexity, Resolution Level
“Model at one level of detail below the level desired for prediction”
Understanding: Two levels higher? Prediction: Same level
Complexity, Resolution Level
“Model at one level of detail below the level desired for prediction”
Understanding: Two levels higher? Prediction: Same level
Links
Complexity, Resolution Level
Growth Drivers
v = f(age, dbh, site) ?
Growth Drivers
v = f( age , dbh, {site}) ?
height
Growth Drivers
v = f(height, dbh)
Growth driven by stem thickness?
Growth Drivers
v = f(height, dbh)
Growth driven by stem thickness??
v = f(height, resources captured)
TASSMitchell 1975
Stand-level
V / H = f(H, N, C) (Eichhorn 1904)
N / H = g(H, N, C)
C / H = h(H, N, C)
C vs. H
0
10
20
30
40
50
60
70
80
90
100
0 5 10 15 20 25 30
Cro
wn
co
ver
(%)
Top height (m)
'v9.prd'u 1:4
C vs. H
0
10
20
30
40
50
60
70
80
90
100
0 5 10 15 20 25 30
Cro
wn
co
ver
(%)
Top height (m)
dC/dH = a N Hb (1-C2)
'v9.prd'u 1:4''u 1:7
Stochastic Models
Convenient for the modeller Variability info? In practice, single realization
Gross Increment
0
20
40
60
80
100
120
140
160
180
200
0 10 20 30 40 50 60
3-m
etr
e g
ross
vo
lum
e in
cre
me
nt
(m3/h
a)
Top height (m)
Stochastic Models
Convenient for the modeller Variability info? In practice, single realization Worse of both worlds?
Mind the Users!
web.unbc.ca/~garcia