SExI-FS: Spatially Explicit Individual-based Forest Simulator

SExI-FS: Spatially Explicit Individual-based Forest Simulator


The SExI Forest Simulator focuses on tree-tree interactions in a mixed multi-species agroforest. The high level of structural complexity of such traditional agroforestry systems defies classical forestry approaches when it comes to optimizing management practices. To cope with this complexity, farmers have adopted a tree-by-tree management approach, which is closer to gardening than to any usual tropical forestry or estate crop management model. Individual tree care and regular tending takes
the form of seedlings transplanting, selective cleaning and felling, adjusted harvesting intensity.

Farmers' approach appears to be in line with two basic tenets of biology: first, individuals are all different with behavior and physiology that result from a unique combination of genetic and environmental influence, and second, interactions are inherently local. Based on the same premises a computer model was developed to explore different management scenarios.

The model uses an object-oriented approach where each tree is represented by an instance of a generic class of tree. The simulated object trees, mimicking real trees, interact through
modifying their neighbors' environment. These modifications are mediated through two major resources: space and light. A 3D representation of a one-hectare plot of forest serves as the
grounds for the simulation of this competition.

What's new?


SExI-FS Documentation version 2 is available.


SExI-FS website is updated!
The updates including the new SExI-FS 1.0.200506  software, Documentations and User's


The first training on the SExI-FS model currently developed in ICRAF SEA. Participants came from various institutions and places (4 from ICRAF Jambi, 2 from ICRAF-Kalimantan, 1 from PSU Thailand, 3 ICRAF Bogor, 5 from IRRI Sembawa).


The new version of SExI-FS will be soon released with the new crown development model (STReTCH model). please contact us if you would need to be informed about the


The STReTCH Model Poster has been presented in the 4TH International Workshop on Functional-Structural Plant Models (FSPM), 07-11 June 2004, Montpellier, France.

The STReTCH model (Shape Transformation Response of Trees in Crowded Habitat) is a generic crown development model for multi-species forest stand modeling.more


SExI-FS 1.0 beta2 version is available for download! Bug Fixed : The trees which are loaded from a saved forest didn't show in 3D visualization.


3D Virtual Branch is available on the web. It's a tool for visualize tree branch data in 3D.

About SExI-FS

Result Examples

Rubber Monoculture plantation shows a predominantly regular distribution of tree size. The effect of border (more light) causing the tree to grow a bit faster.more






Rubber Agroforest shows a wide distribution of sizes due to dynamic competition of a mixed multi-species and species specific growth rates.



The parameters are divided into two categories, the plot level parameters and species sensitive parameters. Each species has its own set of growth parameters and morpho-physiological characteristics.

3D Visualization

The stand can be explored using a 3D viewer. Pseudo leaves (randomly oriented triangles) are spread over tree crown envelopes mimicking foliage. Broken or degraded crowns (CF < 5) may be identified as they show incomplete foliage coverage of crown envelope.


How does it's work?

Potential diameter increment of each tree is calculated using the first derivation of Chapman-Richards function (). Actual growth is then derived from this calculation after addition of other environmental effects and species sensitive response.




The STReTCH model (Shape Transformation Response of Trees in Crowded Habitat) is a generic crown development model for multi-species forest stand modeling.


Simple Light Interception Model (SLIM)

The purpose of the SLIM software is to compute canopy closure (an index of long term light level) at any height above the ground within a forest canopy. It was initially developed as a module of this dynamic forest growth model (SExI-FS).



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