Simple Light Interception Model (SLIM)

Simple Light Interception Model
(SLIM)

What's new?
22-05-2003 : Documentation updated (click here) 25-07-2002 : SLIM 2 Full Version is available for download. (More simple installation)
About 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 the dynamic forest growth model, SExI Forest Simulator.
A simplified 3D description of the trees composing the stand is used	Specific crown porosity is estimated by photograph analysis.
	An elevation grid allows to interpolate individual tree altitude
From this information and the elevation grid, the software then computes the canopy openness either at regular grid points or at irregular spacing defined by the user or else for each tree of the stand.
Aerial view of a one-hectare stand of Damar agroforest in Sumatra	Map of Canopy Closure of stand
The amount of light received at any point in space is calculated by exploring a range of directions (combination of azimuth and zenith angles). Each time a beam originating from that point intercepts a crown envelop of a given porosity it reduces its contribution correspondingly. Total canopy openness at that point is obtained by summing up results for elementary beams. Weight of each beam is determined by the relative surface of the associated sky vault fraction.
A set of hemispherical photograph was used to test the model predictions. Left picture was taken by camera and right picture was generated by SLIM at same point in a real forest (left) and forest data inputted to SLIM (right).
3D Forest Visualization show more realistic view of a forest
3D View of a one-hectare stand of Damar agroforest in Sumatra generated by SLIM

Comments and questions send to : dharja@cgiar.org

Update: 22 May 2003