SORTIE-ND
Software for spatially-explicit simulation of forest dynamics

# Linear growth w/ exponential shade reduction

This behavior does either diameter or height growth as a function of GLI.

### Parameters for this behavior

Parameter nameDescription
Shaded Linear - Diam Intercept in mm/yr (a)Intercept of the size dependent growth potential, in mm/yr, for diameter growth.
Shaded Linear - Diam Shade Exponent (c)Effect of shading, for diameter growth.
Shaded Linear - Diam Slope (b)Slope of the size dependent annual growth potential, for diameter growth.
Shaded Linear - Height Intercept in cm/yr (a)Intercept of the size dependent growth potential, in cm/yr, for height growth.
Shaded Linear - Height Shade Exponent (c)Effect of shading, for height growth.
Shaded Linear - Height Slope (b)Slope of the size dependent annual growth potential, for height growth.

### How it works

This behavior calculates an amount of diameter or height growth as:

Y = (a + (b * diam)) * (GLI/100)c * T

where

• Y = amount of diameter increase, in mm; or the amount of height increase, in cm
• a = Shaded Linear - Diam Intercept in mm/yr (a) parameter (for diameter growth) or the Shaded Linear - Height Intercept in cm/yr (a) parameter (for height growth)
• b = Shaded Linear - Diam Slope (b) parameter (for diameter growth) or the Shaded Linear - Height Slope (b) parameter (for height growth)
• c = Shaded Linear - Diam Shade Exponent (c) parameter (for diameter growth) or the Shaded Linear - Height Shade Exponent (c) parameter (for height growth)
• diam = diameter (diameter at 10 cm for seedlings and saplings, DBH for adults)
• GLI = global light index, as a percentage between 0 and 100, calculated by a light behavior
• T = number of years per timestep

If calculating height growth: In order to find the total amount of height increase for a timestep, the behavior takes as an input the amount of diameter growth increase. Assume that the number of years per timestep is X. The amount of diameter increase is divided by X. Then the logistic growth equation is calculated X times, with the diameter incremented by the amount of diameter increase per timestep each time. The total height increment is the sum of the X individual height increments.

### How to apply it

This behavior can be applied to seedlings, saplings, and adults of any species. Any tree species/type combination to which it is applied must also have a light behavior applied. You can choose either a diam with auto height, diam only, or height only version.