Diameter-free Growth Modelling and other Heresies Oscar Garcia University of Northern British...

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