| LITE and SLIM Programs for Estimating Light Levels Beneath Tree Canopies |
Phil Comeau (University of Alberta, Dept. of Renewable Resources),
Peter Fielder (B.C. Ministry of Forests and Range, Research Branch)
Robert MacDonald (Ramsoft Systems)
and
Robert Bryce (Ramsoft Systems).
April 15, 2008LITE is a program developed to provide estimates of both instantaneous (hourly average) and seasonal photosynthetic photon flux density beneath tree canopies. The model provides utilities for estimating the leaf area contained in each cubic metre of canopy space from either a grid of Plant Canopy Analyzer (PCA) measurements, a grid of hemispherical photographs or from tree list data (including tree location, lean, height, height to crown base, crown extent, diameter at breast height and leaf area [if available]), or using a combination of methods. Directional PCA measurements are taken using either view restrictors supplied with an LAI-2000 instrument (a common approach is to take a reading in each of four cardinal directions using a 90° view restrictor). This input data must be already preprocessed into a GFR file by the SLIM computer program. When using PCA data or digitized hemispherical photographs, the user provides information on the location of each grid point (x, y, and z coordinates) and the height to the top and the base of the canopy.
The model calculates the location of the sun, partitions open sky total PPFD into diffuse and direct components, and estimates the penetration of each through the canopy to the selected point of interest. Direct PPFD is assumed to come from the location of the sun; diffuse PPFD is assumed to be evenly distributed across 480 equal-area segments of the sky.
LITE provides maps of LAI and PPFD across the study site and provides information on the light regime at selected locations. Routines for entering, merging, and editing data are also provided. The model is written for use with MS-WindowTM
SLIM (Spot Light Interception Model) is a program designed to estimate LAI, gap fraction, and fractional transmittance from hemispherical photographs or LICOR LAI-2000 Plant Canopy Analyzer data. In addition, SLIM prepares LAI-2000 data or hemispherical photos for use by the LITE model. The April 2008 release of SLIM includes the automatic thresholding and batch processing capabilities.
LITE and SLIM are designed to work with WindowsNT (version 4.0 or higher), and Windows XP and compatible operating systems.
As with any software, the user must accept all responsibility for interpretation and application of the results that are provided by these programs.
A brief overview of these models is provided in: Modeling light using SLIM & LITE.htm
Detailed documentation is provided in the help files included with both SLIM and LITE.
Please report problems and send comments or questions to: Phil.Comeau@UAlberta.CA or Peter.Fielder@gov.bc.ca
Installation of light modeling software
To install SLIM and LITE, first download and save the file LITESLIM.exe. To install, run the executable program file: liteslim.exe (by either clicking on it or by using run from the START menu). Appropriate drivers and software will be installed. Information on how to use these programs, and on the underlying algorithms used, is provided in the help files.
To download LITESLIM.exe click here: lite_slim.EXE
To download the tutorial on batch processing in SLIM click here and save this file:SLIM - Instructions for Batch Processing.pdf
Sample data files are included in the zip file labeled “Sample data files for SLIM & LITE.zip”. You should save this file on your hard-disk, then you will need to use WINZIP to unzip the contents of this file to an appropriate folder on your hard-disk. To download the sample data files (and description) click here and save this file: Sample data files for SLIM & LITE.zip
Acknowledgements: Support for development of these light modeling tools has been provided by a number of sources. These include: B.C. Ministry of Forests and Range, University of Alberta, Forest Renewal B.C., B.C. Forest Science Program, and the Natural Sciences and Engineering Research Council of Canada.