GLI light

For more on what GLI is and how it is calculated, see here.

Parameters for this behavior

Parameter name	Description
Height of Fisheye Photo	When a fish-eye photo is simulated for a tree, this positions the photo at either the top of the crown or at mid-crown. Seedlings always get fisheye photos at top-of-crown no matter what this value is.
Minimum Solar Angle for GLI Light, in rad	This is the minimum angle at which sunlight is seen, in radians. Below this value the sky is assumed to be dark due to shading neighbors.
Number of Altitude Sky Divisions for GLI Light Calculations	Number of grid cells into which the sky is divided from horizon to zenith, for the purpose of calculating light direction.
Number of Azimuth Sky Divisions for GLI Light Calculations	Number of grid cells into which the sky is divided around the horizon, for the purpose of calculating light direction.

General light parameters used by this behavior

Parameter name	Description
Beam Fraction of Global Radiation	The fraction of total solar radiation that is direct beam radiation (as opposed to diffuse). Expressed as a value between 0 and 1.
Clear Sky Transmission Coefficient	Used to determine the amount of solar radiation seen at the plot location.
First Day of Growing Season	The first day of the growing season, as a Julian day (number between 1 and 365). Trees only get light during the growing season.
Last Day of Growing Season	The last day of the growing season, as a Julian day (number between 1 and 365). Trees only get light during the growing season.
Amount Canopy Light Transmission (0-1)	Fraction of light transmitted through the tree crown for each species. Expressed as a fraction between 0 and 1. A value must be provided for all species, even if they don't all use light.
Snag Age Class 1 Amount Canopy Light Transmission (0-1)	Fraction of light transmitted through the snag tree crown for each species. Applies to those snags whose age is less than or equal to "Upper Age (Yrs) of Snag Light Transmission Class 1". Expressed as a fraction between 0 and 1. If your run does not work with snags, you can ignore this. Otherwise, a value must be provided for all species.
Snag Age Class 2 Amount Canopy Light Transmission (0-1)	Fraction of light transmitted through the snag tree crown for each species. Applies to those snags whose age is greater than "Upper Age (Yrs) of Snag Light Transmission Class 1", but is less than or equal to "Upper Age (Yrs) of Snag Light Transmission Class 2". Expressed as a fraction between 0 and 1. If your run does not work with snags, you can ignore this. Otherwise, a value must be provided for all species.
Snag Age Class 3 Amount Canopy Light Transmission (0-1)	Fraction of light transmitted through the snag tree crown for each species. Applies to those snags whose age is greater than "Upper Age (Yrs) of Snag Light Transmission Class 2". Expressed as a fraction between 0 and 1. If your run does not work with snags, you can ignore this. Otherwise, a value must be provided for all species.
Upper Age (Yrs) of Snag Light Transmission Class 1	The upper age limit, in years, defining the first age class of snag light transmission. Snags with an age less than or equal to this age have a light transmission coefficient matching "Snag Age Class 1 Light Transmission Coefficient". If your run does not work with snags, you can ignore this.
Upper Age (Yrs) of Snag Light Transmission Class 2	The upper age limit, in years, defining the second age class of snag light transmission. Snags with an age greater than the upper limit for size class 1, but less than or equal to this age, have a light transmission coefficient matching "Snag Age Class 2 Light Transmission Coefficient". Snags with an age greater than this value are in age class three. If your run does not work with snags, you can ignore this.

How it works

This behavior calculates a Global Light Index (GLI) value for each individual of each tree type to which it is assigned. GLI values range from 0 (no sun) to 100 (full sun).

How to apply it

This behavior may be applied to seedlings, saplings, and adults of any species.