Stretch: a spatially explicit individual based forest simulator Montpellier, France L.Soler, D....

Stretch: a spatially Stretch: a spatially explicit individual based explicit individual based

forest simulatorforest simulator

Montpellier, France

L.Soler, D. Harja Asmara,M. Laurans, C.Madeleine, J.Dauzat,G. Vincent, F. de Coligny

Model portingModel porting From Sexi-FS (Degi Harja Asmara, From Sexi-FS (Degi Harja Asmara,

Grégoire Vincent)Grégoire Vincent) Increase the versatility/genericity of the Increase the versatility/genericity of the

modelmodel Modifications of processesModifications of processes Use functionalities of CapsisUse functionalities of Capsis TransferTransfer

Plasticity is one of the major axis of the Plasticity is one of the major axis of the laboratory AMAPlaboratory AMAP

Two Phd student work on this subjectTwo Phd student work on this subject

StretchStretch

Spatially explicitSpatially explicit Individual basedIndividual based Multi speciesMulti species 3D3D

Crown shape plasticityCrown shape plasticity LightLight Space limitationSpace limitation

The yearly simulation loopThe yearly simulation loop

mechanical constraints (BIOMECHANICS)

light availability (MMR,SLIM,Liebermann)

mortality

Regeneration

Tree overall dimension change, Crown deformation, phototropism, collision

Process Growth

Initialisation stepEnvironnement settingsScene initialisation (trees, terrain)Species initialisation (reference tree growth)

Legend:Red : additional options to the model with crownBlack : model without considering the crown

Current volume

Growth Reducer

New VolumePotential volume Increment

New dbh

Stem Growth algorithmStem Growth algorithm dbh function : Chapman Richards functiondbh function : Chapman Richards function Growth of stem volume :Growth of stem volume : Ln(vol(t)) = u + v*ln(dbh(t))+w*ln(h(t))Ln(vol(t)) = u + v*ln(dbh(t))+w*ln(h(t))

New height

Light

Crown growthCrown growth Depends on the stem growthDepends on the stem growth Virtual vectors of branchesVirtual vectors of branches PolygonesPolygones

LiebermanLieberman Calcul of the index of closure of the canopy : GCalcul of the index of closure of the canopy : G G caracterises the light environmentG caracterises the light environment

Δhi = hi - hhpi = √(d²i+Δh²i)sinΘi = Δhi /hpi

G = Σi sinΘ

M. Lieberman, D. Lieberman, R. Peralta, G.S. Hartshorn, 1995, « Canopy closure and the distribution of tropical forest tree species at La Selva, Costa rica »,Journal of Tropical Ecology, 11:161-178

Calcul of Light Growth Calcul of Light Growth ReducerReducer

The index G by interpolation will The index G by interpolation will determine the Light Growth Reducer (LGR)determine the Light Growth Reducer (LGR)

-0.2

0

0.2

0.4

0.6

0.8

1

1.2

-0.5 0 0.5 1 1.5

shade tolerant

light demanding

shade specialist

G

1-LGR

Mortality algorithmMortality algorithm

Primary mortalityPrimary mortality

- vigour (survival - vigour (survival probability, growth reducer, mortality probability, growth reducer, mortality function)function)

- senescence (dbhMax, - senescence (dbhMax, volumeMax, heightMax…)volumeMax, heightMax…)

Graphic interfaceGraphic interface

To doTo do

Alternative algorithm for dbh growthAlternative algorithm for dbh growth Alternative algorithm for height/dbh allometryAlternative algorithm for height/dbh allometry

Primary mortality (add biomecanics Primary mortality (add biomecanics constraints)constraints)

Secondary mortality Secondary mortality

RegenerationRegeneration 3D viewer3D viewer

To doTo do

Crown deformation moduleCrown deformation module- assymetric crown shape deformation- assymetric crown shape deformation- crown grow to reach the light- crown grow to reach the light

• Deformation can be local (radial anisotropy of light and available space)

• Local deformation is modeled via a set of independent vectors stemming from crown base subtending the crown envelope

SLIM and MMR

SExI-FS Scene

Simple Light Interception Model (SLIM)

A computed canopy openness compared to the real location in the forest.

This method is similar to hemispherical photographs, which are normally taken at ground level.

Shape transformation response of trees in

crowded habitats (STReTCH)

MMR

Ws, Wr Ts, Tr soil

W soil

measurementsmeasurementssimulatorsimulator

Micrometeo.Data Set

Light partitioning

PAR NIR TIR

Incident radiation

BRDFLIDAR

TIR Emittance

Cartography of soil irradiance, temperature and humidity

wind RHair Tair

E

H

Turbulent transfers

Air profiles

E H

RemoteSensing

RHair

Tair

irradiation

temperature

transpiration

photosynthesis leaf

sap

flow

MMR: one module in Archimed

MIRIncident radiation

MUSCMultiple scattering

RADBALRadiation balance

Meteo.

data

lightonsoil

plantIrradia-

tion

scenerad.

balance

Meteo.

details

Basic principle of MIR

All objects you can see when back to the sun are sunlit

Basic principle of MIR

Splitting skyhemisphere

with the"TURTLE"

model

Discretisation of incident radiation

The total leaf irradiation is

obtained by weighting

its partial irradiation

from each source

Mapping leaf irradiation

Échelles de modélisationmodèles numériques multi-échelles

SExI-FS Scene

Mir images

MMR

22

11

33

3322

11

The projections

of plants

are moved

modulo the

dimensions

of the scene

Virtual plot duplicationVirtual plot duplication

Altitude first hitAltitude first hit

Nb hits in layer 1Nb hits in layer 1

LAYERSLAYERS

00

11

22

33

Nb hitsNb hits in layer 2in layer 2

Nb hitsNb hits in layer 3in layer 3

Information for each pixelInformation for each pixel

The MUSCmodel isbased on

lightinterceptionprobabilities

output bythe MIRmodel

MuSc : calcul des "MUltiple SCattering

Daily irradiation