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Hybrid modelling of plantation crops. Euan Mason University of Canterbury. Outline. Hybrid models Current hybrid modelling projects at the School of Forestry Stand level hybrid growth and yield Hybrid initial growth models. Potential for hybrid models. Geographic Information Systems

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Hybrid modelling of plantation crops

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Hybrid modelling of plantation crops

Hybrid modelling of plantation crops

Euan Mason

University of Canterbury



  • Hybrid models

  • Current hybrid modelling projects at the School of Forestry

  • Stand level hybrid growth and yield

  • Hybrid initial growth models

Potential for hybrid models

Potential for hybrid models

  • Geographic Information Systems

    • More known about each site and stand

  • Variation in growth pattern from site to site

    • Less need for regional models

  • Variation in weather from year to year

    • Predicting the past

  • Variation in monthly climate offers monthly predictions

  • Climate change may affect growth patterns

  • Kyoto protocol

    • Carbon storage explicit in some models

An example hybrid model

An example “hybrid” model

3-PG Model (Landsberg & Waring 1997)

Allocation varies with fertility

Application of 3 pg 25 year old experiment

Application of 3-PG 25-year old experiment

Potential issues with 3 pg

Potential issues with 3-PG

  • Allocation of C is derived from allometry

  • Recursiveness, compounded errors

  • Over parametarisation

  • Fertility is inadequately represented

  • Stand and stem geometry are not modelled

  • Circularity

    • DBH->Carbon, Carbon->DBH

    • Measurement of LAI may partially solve this

Current hm projects at sof

Current HM projects at SoF

  • Physiological hybrid Initial Growth Model

  • Comparisons between hybrid and traditional G & Y models

  • Modelling effects of nutrition

  • Modelling effects of spacing and genotype on corewood properties

  • National hybrid model for P. radiata

  • Modelling clonal stands

Physiological hybrid igm

Physiological hybrid IGM

Comparisons of hybrid models

Comparisons of hybrid models

  • Guy Pinjuv, PhD candidate

  • Canterbury estate, highly variable sites

  • Comparison of a range of hybrids

    • Traditional growth and yield

    • 3-PG

    • Several alternatives in between

  • Evaluate fit and utility

    • Two types of validation required

Modelling effects of nutrition

Modelling effects of nutrition

  • Horacio Bown, PhD candidate

  • Development of fertility modifier for hybrid models

    • Long-term goal

  • Controlled environment

  • Field experiments

Corewood stiffness vs actual stocking clone j p lasserre

Corewood stiffness vs actual stocking & clone – J.P. Lasserre

Modelling clonal stands

Modelling clonal stands

  • Rajesh Sharma

  • What changes are needed when modelling for clonal forest management?

  • Potential for hybrid modelling to provide genotype-specific models

  • Large plot clonal experiment - SPBL

    • 10 clones, pure and mixed clone blocks

    • Planted 1993

    • Variation in growth, form, wood quality

    • Interchange in dominance

    • Competition with self or other genotypes

    • Local genotype-dependent individual tree model

    • Risk

National hybrid model for radiata pine

National hybrid model for radiata pine

  • Postdoctoral Fellow

    • Dr Helge Dzierzon

  • Can hybrid modelling remove need for regions?

  • Are hybrids more effective that traditional methods within regions?

  • How much local sensitivity do we lose by adopting a national hybrid model?

  • PSP data from 13 companies

  • Monthly weather data from climate stations, with local offsets

  • Elevation and soils from GIS

Weather stations used

Weather stations used

  • Reasonable data coverage from 1960 to 2005

  • Stations over all New Zealand

  • Data availability for each station is heterogeneous

Landcare research soil layer

Landcare Research Soil Layer

  • Aim: Investigate growth patterns over New Zealand

  • Format:

    • ESRI polygon layer

  • 8 Soil Classes (NZSCORD)

  • 67 Subclasses (NZSC) covered by PSPs

Results for mth using lcr layer the ultimate regional approach

Results for MTH using LCR Layer – the ultimate regional approach

  • Regression for SC:

    • MSE=2.03

    • N: 3202

    • N classes: 26

  • Residuals for SC

    • From 20955 to 13182

Results for g using lcr layer

Results for G using LCR Layer

  • Regression of SC:

    • MSE=9.70

    • N: 3202

    • N classes: 26

      Residuals for SC

    • From 360825 to 302916

  • Residuals of Simulation run

    • Mean: 356021

    • Std: 9154

An idea among many

An idea among many

  • Time = accumulated light

  • Use 3-PG type quantum efficiency modifiers to accumulate potentiallyused light

  • Use sigmoidal difference equations as usual, fitted to PSP data

  • Avoids some of 3-PG’s problems

    • Compounded errors

    • Allocation of C

    • Overparametarisation

    • Lack of stand geometry

An idea among many1

An idea among many

  • Estimate genetic components of seasonal variations in primary and secondary growth

  • Different radiation sums for primary and secondary growth

Seasonal growth in dbh red height yellow and 3 pg predictions blue tennent 1986

Seasonal growth in dbh (red), height (yellow) and 3-PG predictions (blue). (Tennent 1986)

An idea among many2

An idea among many

  • Climatic variables as well as stocking and radiation sum estimates in mortality model

  • To what extent can temporal variation in climatic influences inform us about influences on crop growth and mortality of spatial variation in climate?

An idea among many3

An idea among many

  • Compatible stand, distribution & individual tree projection systems

  • Models that represent height vs basal area growth as functions of site variables

  • Models that respond to climatic and local weather variation

  • Models specific to each site

  • Models that naturally provide growth estimates within years

Preliminary example p radiata in central north island

Preliminary Example – P. radiata in Central North Island


Daytime temp, VPD modifiers

Schumacher, daytime

temperature modifier

Mth results using light sum models dzierzon

MTH: Results using light sum models - Dzierzon

  • Regression example

    • MSE: 1.40

    • N: 2146

  • Residuals:

    • From 4427.0 to 4118

G results using light sum models dzierzon

G: Results using light sum models - Dzierzon

  • Regression Example

    • MSE: 5.05

    • N: 2146

  • Residuals:

    • From 57796 to 54822

Light sum initial growth model competition for light in r1835 2

Light sum initial growth model: Competition for light in R1835/2

Future directions

Future directions

  • Two fertile strands for forest modelling research

    • Internal qualities of stems

    • Physiological hybrids

  • The University of Canterbury contributes to both

  • Challenge is to bring the two strands together

Future directions1

Future directions

  • Hybrids may obviate a regional approach to growth and yield

  • Hybrids may provide an alternative or be complementary to 300 (500) index/Site index approach

  • Climatic and silvicultural effects may be more easily integrated in hybrid models than in traditional G & Y models

    • Site conditions mediate use of light



  • Several key studies in hybrid modelling

  • Hybrid modelling

    • More sensitive to local site conditions

    • Seasonal (monthly) predictions

    • Reduced need for regions?

    • Better estimates of growth since last inventory?

    • Carbon sequestration explicit?

    • Linkages between mensuration, silviculture and physiology

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