3-PG - Process-based model
Approach for this model overview
3-PG Description- main characteristics- main modules- structure- inputs and outputs
3-PG Use sites for Pine - why and where has been used- Portuguese case study
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3-PG – Basic structure
Climate data
Initial stand
Site factors
Biomass production
Biomass allocation
Conversion into variables of
interest to forest managers
3-PG
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F F n F F
R R n R R
S S n
W P W
W P W
W P
NPP is partitioned into biomass pools (tDM ha-1): Foliage(WF), Above-ground woody tissue(WS) Roots (WR)
Partitioning rates (F, R and S) depend on growth conditions and stand dbh.
Litter-fall (F) and root-turnover (R) also taken into account. Thus:
3-PG – Biomass allocation (I)
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3-PG – Biomass allocation (II)
Increasing DBH decreases foliage partitioning and increases stem partitioning. Graphs show response when:
pFS(2) = 1, pFS(20) = 0.2
0.0
0.1
0.2
0.3
0.4
0.5
0.6
0 10 20 30
Stem diameter
Ab
ov
e-g
rou
nd
pa
rtit
ion
ing
Stem
Foliage
0.0
0.2
0.4
0.6
0.8
1.0
1.2
0 10 20 30
Stem diameter
Ra
tio
of
folia
ge
:sh
oo
t p
art
itio
nin
g
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State v ar iab les
Subs id iary v ar iab les
Climate & s ite Inputs
Los s es
Mater ia l f low s
Inf luenc es
Carbon
W ater
Trees
Ke y to colours & sha pe s
Subs id iary v ar iab les
+
H20 R ain
g C
Soil H20
E T
+
+
+
_
_
+
wS x
Deadtrees
Stocking+
+
_
wS +w S >w S x
_ _
N+
+
__
S tres s
VPD
T
FR
f
+
_
+
_
+
++
+
+
D BH
F /SR
L AIL UE
SL A
+
+
_
NPP
Stem
Foliage
Roots
GPP
CO2
C ,N
Litter
+
• Structure without the module for conversion into variables
of interest to forest managers
3-PG – Structure
• Climate data– Monthly data temperature, radiation, rainfall, VPD– Either observed values either means from several years
• Site and soils– Latitude– Soil texture & maximumASW– Fertility rating
• Stand data– Biomasses: Foliage, Above-ground woody tissue , Roots – N – number of trees per hectare
3-PG – Inputs
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There is a group of outputs useful for foresters and less common in process based models :
V, G, N, MAI, etc.
There is a group of outputs which are common in process based models :
GPP, NPP, allocated biomasses, etc.
3-PG – Outputs
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3-PG – Quick summary
Attribute Comments
Model type Dynamic; process-based & empirical relationships
Time frame Monthly
Processes NPP, biomass allocation, water usage & soil water balance, stem mortality, litterfall & root turnover
Inputs Monthly climate data, soil texture & water capacity, fertility
Outputs Biomass pools, stocking, available soil water, NPP & ET, DBH & standard stand attributes, and others
Strengths Fully dynamic, can be adapted for range of species, provides management-related outputs
Weaknesses Naïve treatment of soil nutrition, allocation based largely on size, poor predictor of canopy development & of mortality
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3-PG - Application
3-PG has been applied to many environments: Australia; New Zealand EUA Brazil; Chile South Africa United Kingdom; Sweden; Portugal; Finland China
3-PG has been applied to many species:
Eucalyptus globulus; E. pilularis; E. grandis; E. delagatensisPicea abies; P. sitchensisPinus radiata; P. taeda; P. patula; P. ponderosa; Pseudostuga menziesii
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3-PG – Application in Portugal (I)
3-PG Calibartion and validation for Eucalyptus globulus in Portugal
1.Initial test with 3-PG validated for Eucalyptus globulus in Australia (Sands & Landsberg 2002) with FER trial data:
Reasonable estimates for Ws and bad estimates for Wf2.SLA, wood density, allometric relationships3.3-PG calibration with FER trial4.Test of calibrated 3-PG with a stocking trial5.Validation with Eucalyptus globulus permanent sample plots
On going research is being carried out with Pinus pinaster.
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3-PG – Application in Portugal (II)
6 scenarios – Eucalyptus plantations in Aveiro region
1. To reduce by 30% the rainfall per year and concentrate the remaining by 15% in November and December2. To reduce by 30% the rainfall per year and concentrate the remaining by 15% in November, December and March3. To rise the mean monthly temperature by 1ºC4. To rise the mean monthly temperature by 3ºC5. To reduce by 30% the rainfall per year and to rise the mean monthly temperature by 1ºC 6. To reduce by 30% the rainfall per year and to rise the mean monthly temperature by 3ºC
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