Jari Perttunen1

Risto Sievänen1

Eero Nikinmaa2

1. The Finnish Forest Research Institute 2. University of Helsinki (Dept. of Forest Ecology)

LIGNUM: Towards Forest Scientist's Workbench

CONTENTS

The Model LIGNUM

Current Applications

Modeling Sugar Maple

The Design and Implementation of the Forest Scientist's Workbench

LIGNUM: General features

Simple structural units describe both structure and functioning of trees.

Carbon budget models the metabolism:

Annual net production is used to new growth.

Pipe model and functional balance steer growth.

Time step one growth period (one year).

LIGNUM: Structure

Capture the structure of a tree with simple structural units:

Tree Segment (TS)

Branching Point (BP)

Bud (B)

Axis (A)

LIGNUM: Tree Segment

Structure:

Dead heartwood (H)

Living sapwood (S)

Bark layer (BL)

Foliage (F)

Tree segment is the main functioning unit.

H S FBL

LIGNUM: Deciduous trees

Explicit leaves instead of cylindrical layer of foliage:

Leaf ellipse, use parameter to denote "degree of filling".

Track the 3D position of each leaf.

Dormant (suppressed) buds.

LIGNUM: Releasing suppressed buds

Maintain the structural integrityof the model:

Split the segment into two.

Insert a new branching point.

The released bud will become the terminating bud in the new axis.

LIGNUM: Implementation

LIGNUM: Carbon balance

LIGNUM: Segment length

LIGNUM: New buds

LIGNUM: Pipe model

LIGNUM: The Radiation Submodel

Standard overcast sky.

Divide the sky into sectors and assign each sector a radiant intensity.

Number of inclinations and azimuths can be defined by the user.

MJ

Y X

Z

LIGNUM: The Radiation SubmodelConiferous trees:

Compare segments to compute the distances light beams travel in foliage.

Compute attenuations of radiation.

Compute intercepted radiation.

Compute photosynthesis.

Deciduous trees:

Compare leaves.

Shading

Shaded

Voxel space: Alternative radiation model

LIGNUM: Applications

Gliricidia sepium

Sugar maple

Scots pine

Mountainbirch

Scots pine

Scots pine and Jack pine the first two tree species implemented.

Proved the modeling approach feasible.

Modeled (published) trees 10 years old.

Mountain birch

Structural analysis of mountain birch

Based on detailed measurements done in Finnish Lapland

Position and orientation of each segment known.

Position of leaves known.

Gliricidia sepium

Nitrogen fixing tropical tree species used in agroforestry.

Study the optimal management (frequency of cuttings).

Analysis of Daily Sapflow

Sugar mapleStudy the survival and growth of sugar maple saplings in forest gaps.

Long term goal to develop new cutting guidelines for natural regeneration of sugar maple:

Size of the canopy openings

Frequency of cuttings

Modeling Sugar maple in forest gapsSt-Hilaire, Quebec

Typically when modeling tree species with LIGNUM the following growth processes are assessed:

Metabolism:

Photosynthesis, respiration.

Structural Dynamics:

Birth, growth and senescence of tree compartments.

Tree Architecture:

Currently ad hoc descriptions.

Modeling Gaps in St-Hilaire

Field data: radiation measurements and fish-eye photographs from the gaps.

Analysis of field data resulted masks (Closed Gap and Open Gap) that can be superimposed on SOC.

INC RAD (MJ) CG% RZ% OG%0 456 96.4 96.4 961 598 90.4 90.4 77.32 622 77.7 77.7 67.83 507 84.9 84.9 60.4 4 270 76.9 0 51.2

Zenith 2 4 51.6 0 49SOC for St-Hilaire

Masks

Diameter Growth (Pipe model)

For newly created segments sapwood must support foliage.

For other segments match the sapwood coming above.

Asf

=A

f

SLA ´ U

Anew

= max[Asu

+ dAs + A

h, A

ts]

ParametersSearch, deduce and compile parameters from various sources (or make your best guess)

mf Respiration rate of a leaf. 0.26ms Respiration rate of sapwood. 0.040mr Respiration rate of roots. 0.240p0 Photosynthetic efficiency. 0.0010q Tree segment shortening factor. 0.40 Density of wood. 280.0 kg/m3

SLA Specific leaf area. 30.0 m2/kgrs Root senesence. 0.330ss Sapwood senesence. 0.070 Transmission coeffient of a leaf. 0.060Y Foliage mass supported by sapwood. 123.8 kg

Three 5 year old saplings in St-Hilaire

Closed Gap Released Zenith Open Gap

L = 1.37m

L = 2,43mL = 2.84m

LIGNUM: Scientist's Workbench

Class Hierarchy

TreeCompartment

Tree A BPTS B

CfTS HwTS

ScotsPine Birch

BirchBud

1.#include <Lignum> 2.using namespace Lignum; 3. 4. int main() 5.{ 6. Tree<ScotsPine> t1; 7. Tree<Birch> t2; 8. Tree<Birch,BirchBud> t3; 9. double p,m;10. 11. t1.growth(5);12. ForEach(t2,P<Birch>());13. ForEach(t2,M<Birch>());14. p = Accumulate(t2,0,CP<Birch>());15. m = Accumulate(t2,0,CM<Birch>());16. PropagateUp(t2,p-m,Allocate<Birch>());17. 18. exit(0);19.}

ScotsPine<TS,BUD>::P(){ p = Po*I;}

Birch<TS,BUD>::P(){ for_each(leaves,p());}

Sample Program

Concluding Remarks

To develop LIGNUM to a Forest Scientist's Workbench use simple, independent and easily customizable workbench components.

C++/OpenGL implementation is available on:

SGI IRIX, Linux, (Microsoft Windows NT).

Computer graphics aid understanding and presenting the results of simulations:

In the future the Virtual Reality can be used.

LIGNUM in HUTCAVE Virtual Room

www.metla.fi/projects/lignum